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Overview
Comment:Fix some bugs and other code issues in the session module.
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SHA1: f2930840e4af3d7d9cb199d316502932fcbbb867
User & Date: dan 2011-03-15 16:37:28
Context
2011-03-16
09:49
Remove the sqlite3_transaction_hook() API. check-in: b0015a1c user: dan tags: sessions
2011-03-15
16:37
Fix some bugs and other code issues in the session module. check-in: f2930840 user: dan tags: sessions
2011-03-14
19:49
Fix handling of return values from the conflict handler. Document the conflict handler arguments and return codes in sqlite3session.h. check-in: cbbb274e user: dan tags: sessions
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#include "sqliteInt.h"
#include "vdbeInt.h"

typedef struct RowChange RowChange;
typedef struct SessionTable SessionTable;
typedef struct SessionChange SessionChange;


#if 0
#ifndef SQLITE_AMALGAMATION

typedef unsigned char u8;
typedef unsigned long u32;
typedef sqlite3_uint64 u64;
#endif
#endif


struct sqlite3_session {
  sqlite3 *db;                    /* Database handle session is attached to */
  char *zDb;                      /* Name of database session is attached to */

  int rc;                         /* Non-zero if an error has occurred */
  sqlite3_session *pNext;         /* Next session object on same db. */
  SessionTable *pTable;           /* List of attached tables */
};
















/*
** Each session object maintains a set of the following structures, one
** for each table the session object is monitoring. The structures are
** stored in a linked list starting at sqlite3_session.pTable.
**
** The keys of the SessionTable.aChange[] hash table are all rows that have
................................................................................
** a subset of the initial values that the modified row contained at the
** start of the session. Or no initial values if the row was inserted.
*/
struct SessionTable {
  SessionTable *pNext;
  char *zName;                    /* Local name of table */
  int nCol;                       /* Number of columns in table zName */

  /* Hash table of modified rows */
  int nEntry;                     /* NUmber of entries in hash table */
  int nChange;                    /* Size of apChange[] array */
  SessionChange **apChange;       /* Hash table buckets */
};

/* 
** RECORD FORMAT:
**
................................................................................
struct SessionChange {
  sqlite3_int64 iKey;             /* Key value */
  int nRecord;                    /* Number of bytes in buffer aRecord[] */
  u8 *aRecord;                    /* Buffer containing old.* record */
  SessionChange *pNext;           /* For hash-table collisions */
};



static int sessionVarintPut(u8 *aBuf, u32 iVal){
  if( (iVal & ~0x7F)==0 ){

    if( aBuf ){
      aBuf[0] = (u8)iVal;


    }
    return 1;
  }
  if( (iVal & ~0x3FFF)==0 ){
    if( aBuf ){

      aBuf[0] = ((iVal >> 7) & 0x7F) | 0x80;
      aBuf[1] = iVal & 0x7F;



    }
    return 2;
  }
  if( aBuf ){
    aBuf[0] = ((iVal >> 28) & 0x7F) | 0x80;
    aBuf[1] = ((iVal >> 21) & 0x7F) | 0x80;

    aBuf[2] = ((iVal >> 14) & 0x7F) | 0x80;
    aBuf[3] = ((iVal >>  7) & 0x7F) | 0x80;

    aBuf[4] = iVal & 0x7F;
  }
  return 5;
}





static int sessionVarintGet(u8 *aBuf, int *piVal){
  int ret;
  u64 v;
  ret = (int)sqlite3GetVarint(aBuf, &v);
  *piVal = (int)v;
  return ret;
}





static sqlite3_int64 sessionGetI64(u8 *aRec){
  return (((sqlite3_int64)aRec[0]) << 56)
       + (((sqlite3_int64)aRec[1]) << 48)
       + (((sqlite3_int64)aRec[2]) << 40)
       + (((sqlite3_int64)aRec[3]) << 32)
       + (((sqlite3_int64)aRec[4]) << 24)
       + (((sqlite3_int64)aRec[5]) << 16)
       + (((sqlite3_int64)aRec[6]) <<  8)
       + (((sqlite3_int64)aRec[7]) <<  0);
}















/*
** This function is used to serialize the contents of value pValue (see
** comment titled "RECORD FORMAT" above).
**
** If it is non-NULL, the serialized form of the value is written to 
** buffer aBuf. *pnWrite is set to the number of bytes written before
................................................................................
** SQLITE_NOMEM is returned.
*/
static int sessionSerializeValue(
  u8 *aBuf,                       /* If non-NULL, write serialized value here */
  sqlite3_value *pValue,          /* Value to serialize */
  int *pnWrite                    /* IN/OUT: Increment by bytes written */
){
  int eType; 
  int nByte;

  eType = sqlite3_value_type(pValue);
  if( aBuf ) aBuf[0] = eType;

  switch( eType ){
    case SQLITE_NULL: 
      nByte = 1;
................................................................................
          i = (u64)sqlite3_value_int64(pValue);
        }else{
          double r;
          assert( sizeof(double)==8 && sizeof(u64)==8 );
          r = sqlite3_value_double(pValue);
          memcpy(&i, &r, 8);
        }
        aBuf[1] = (i>>56) & 0xFF;
        aBuf[2] = (i>>48) & 0xFF;
        aBuf[3] = (i>>40) & 0xFF;
        aBuf[4] = (i>>32) & 0xFF;
        aBuf[5] = (i>>24) & 0xFF;
        aBuf[6] = (i>>16) & 0xFF;
        aBuf[7] = (i>> 8) & 0xFF;
        aBuf[8] = (i>> 0) & 0xFF;
      }
      nByte = 9; 
      break;

    case SQLITE_TEXT: 
    case SQLITE_BLOB: {
      int n = sqlite3_value_bytes(pValue);
      int nVarint = sessionVarintPut(0, n);
      if( aBuf ){
        sessionVarintPut(&aBuf[1], n);
        memcpy(&aBuf[nVarint + 1], eType==SQLITE_TEXT ? 
            sqlite3_value_text(pValue) : sqlite3_value_blob(pValue), n
        );
      }

................................................................................
    pTab->nChange = nNew;
    pTab->apChange = apNew;
  }

  return SQLITE_OK;
}

















static int sessionInitTable(sqlite3_session *pSession, SessionTable *pTab){
  if( pTab->nCol==0 ){
    pTab->nCol = sqlite3_preupdate_count(pSession->db);
  }

  if( pTab->nCol!=sqlite3_preupdate_count(pSession->db) ){
    pSession->rc = SQLITE_SCHEMA;
    return SQLITE_ERROR;
  }

  return SQLITE_OK;
}

/*
** The 'pre-update' hook registered by this module with SQLite databases.
*/
static void xPreUpdate(
................................................................................
){
  sqlite3_session *pSession;
  int nDb = strlen(zDb);
  int nName = strlen(zDb);
 
  for(pSession=(sqlite3_session *)pCtx; pSession; pSession=pSession->pNext){
    SessionTable *pTab;






    if( pSession->rc ) continue;
    if( sqlite3_strnicmp(zDb, pSession->zDb, nDb+1) ) continue;

    for(pTab=pSession->pTable; pTab; pTab=pTab->pNext){
      if( 0==sqlite3_strnicmp(pTab->zName, zName, nName+1) ){
        SessionChange *pChange;
        SessionChange *pC;
        int iHash; 
        int rc = SQLITE_OK;

................................................................................
          pChange = (SessionChange *)sqlite3_malloc(sizeof(SessionChange));
          if( pChange ){
            memset(pChange, 0, sizeof(SessionChange));
          }
        }else{
          int nByte;            /* Number of bytes to allocate */
          int i;                /* Used to iterate through columns */
          sqlite3_value *pValue;

          /* Figure out how large an allocation is required */
          nByte = sizeof(SessionChange);
          for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){

            rc = sqlite3_preupdate_old(pSession->db, i, &pValue);
            if( rc==SQLITE_OK ){
              rc = sessionSerializeValue(0, pValue, &nByte);
            }
          }

          /* Allocate the change object */
          pChange = (SessionChange *)sqlite3_malloc(nByte);
          if( !pChange ){
            rc = SQLITE_NOMEM;
................................................................................
            memset(pChange, 0, sizeof(SessionChange));
            pChange->aRecord = (u8 *)&pChange[1];
          }

          /* Populate the change object */
          nByte = 0;
          for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){

            rc = sqlite3_preupdate_old(pSession->db, i, &pValue);
            if( rc==SQLITE_OK ){
              rc = sessionSerializeValue(
                  &pChange->aRecord[nByte], pValue, &nByte);
            }
          }
          pChange->nRecord = nByte;
        }

        /* If an error has occurred, mark the session object as failed. */
        if( rc!=SQLITE_OK ){
................................................................................
          return;
        }

        /* Add the change back to the hash-table */
        pChange->iKey = iKey2;
        pChange->pNext = pTab->apChange[iHash];
        pTab->apChange[iHash] = pChange;
      }
      break;

    }
  }
}

/*
** Create a session object. This session object will record changes to
** database zDb attached to connection db.
*/
int sqlite3session_create(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Name of db (e.g. "main") */
  sqlite3_session **ppSession     /* OUT: New session object */
){
  sqlite3_session *pNew;
  sqlite3_session *pOld;
  int nDb = strlen(zDb);          /* Length of zDb in bytes */


  *ppSession = 0;

  /* Allocate and populate the new session object. */
  pNew = (sqlite3_session *)sqlite3_malloc(sizeof(sqlite3_session) + nDb + 1);
  if( !pNew ) return SQLITE_NOMEM;
  memset(pNew, 0, sizeof(sqlite3_session));
  pNew->db = db;
  pNew->zDb = (char *)&pNew[1];

  memcpy(pNew->zDb, zDb, nDb+1);

  /* Add the new session object to the linked list of session objects 
  ** attached to database handle $db. Do this under the cover of the db
  ** handle mutex.  */
  sqlite3_mutex_enter(sqlite3_db_mutex(db));
  pOld = (sqlite3_session*)sqlite3_preupdate_hook(db, xPreUpdate, (void*)pNew);
................................................................................
** Delete a session object previously allocated using sqlite3session_create().
*/
void sqlite3session_delete(sqlite3_session *pSession){
  sqlite3 *db = pSession->db;
  sqlite3_session *pHead;
  sqlite3_session **pp;



  sqlite3_mutex_enter(sqlite3_db_mutex(db));
  pHead = (sqlite3_session*)sqlite3_preupdate_hook(db, 0, 0);
  for(pp=&pHead; (*pp)!=pSession; pp=&((*pp)->pNext));
  *pp = (*pp)->pNext;
  if( pHead ) sqlite3_preupdate_hook(db, xPreUpdate, (void *)pHead);
  sqlite3_mutex_leave(sqlite3_db_mutex(db));



  while( pSession->pTable ){
    int i;
    SessionTable *pTab = pSession->pTable;
    pSession->pTable = pTab->pNext;
    for(i=0; i<pTab->nChange; i++){
      SessionChange *p;
      SessionChange *pNext;
................................................................................
        sqlite3_free(p);
      }
    }
    sqlite3_free(pTab->apChange);
    sqlite3_free(pTab);
  }


  sqlite3_free(pSession);
}

/*
** Attach a table to a session. All subsequent changes made to the table
** while the session object is enabled will be recorded.
**
................................................................................
** not matter if the PRIMARY KEY is an "INTEGER PRIMARY KEY" (rowid alias)
** or not.
*/
int sqlite3session_attach(
  sqlite3_session *pSession,      /* Session object */
  const char *zName               /* Table name */
){
  SessionTable *pTab;
  int nName;

  /* First search for an existing entry. If one is found, this call is
  ** a no-op. Return early. */
  nName = strlen(zName);
  for(pTab=pSession->pTable; pTab; pTab=pTab->pNext){
    if( 0==sqlite3_strnicmp(pTab->zName, zName, nName+1) ){
      return SQLITE_OK;
................................................................................
  memcpy(pTab->zName, zName, nName+1);
  pTab->pNext = pSession->pTable;
  pSession->pTable = pTab;

  return SQLITE_OK;
}

typedef struct SessionBuffer SessionBuffer;
struct SessionBuffer {
  u8 *aBuf;                       /* Pointer to changeset buffer */
  int nBuf;                       /* Size of buffer aBuf */
  int nAlloc;                     /* Size of allocation containing aBuf */
};

static int sessionBufferGrow(SessionBuffer *p, int nByte, int *pRc){
  if( p->nAlloc-p->nBuf<nByte ){
    u8 *aNew;
    int nNew = p->nAlloc ? p->nAlloc : 128;
    do {
      nNew = nNew*2;
    }while( nNew<(p->nAlloc+nByte) );
................................................................................
    }
    p->aBuf = aNew;
    p->nAlloc = nNew;
  }
  return 0;
}








static void sessionAppendByte(SessionBuffer *p, u8 v, int *pRc){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, 1, pRc) ){
    p->aBuf[p->nBuf++] = v;
  }
}








static void sessionAppendVarint(SessionBuffer *p, sqlite3_int64 v, int *pRc){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, 9, pRc) ){
    p->nBuf += sessionVarintPut(&p->aBuf[p->nBuf], v);
  }
}








static void sessionAppendBlob(
  SessionBuffer *p, 
  const u8 *aBlob, 
  int nBlob, 
  int *pRc
){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nBlob, pRc) ){
    memcpy(&p->aBuf[p->nBuf], aBlob, nBlob);
    p->nBuf += nBlob;
  }
}









static void sessionAppendStr(
  SessionBuffer *p, 
  const char *zStr, 
  int *pRc
){
  int nStr = strlen(zStr);
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nStr, pRc) ){
    memcpy(&p->aBuf[p->nBuf], zStr, nStr);
    p->nBuf += nStr;
  }
}









static void sessionAppendInteger(
  SessionBuffer *p, 
  int iVal,
  int *pRc


){
  char aBuf[24];
  sqlite3_snprintf(sizeof(aBuf)-1, aBuf, "%d", iVal);
  sessionAppendStr(p, aBuf, pRc);
}










static void sessionAppendIdent(
  SessionBuffer *p, 
  const char *zStr, 
  int *pRc

){
  int nStr = strlen(zStr)*2 + 2 + 1;
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nStr, pRc) ){
    char *zOut = (char *)&p->aBuf[p->nBuf];
    const char *zIn = zStr;
    *zOut++ = '"';
    while( *zIn ){
................................................................................
      *zOut++ = *(zIn++);
    }
    *zOut++ = '"';
    p->nBuf = ((u8 *)zOut - p->aBuf);
  }
}







static void sessionAppendCol(
  SessionBuffer *p, 
  sqlite3_stmt *pStmt, 
  int iCol,
  int *pRc


){
  if( *pRc==SQLITE_OK ){
    int eType = sqlite3_column_type(pStmt, iCol);
    sessionAppendByte(p, (u8)eType, pRc);
    if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
      sqlite3_int64 i;
      u8 aBuf[8];
      if( eType==SQLITE_INTEGER ){
        i = sqlite3_column_int64(pStmt, iCol);
      }else{
        double r = sqlite3_column_double(pStmt, iCol);
        memcpy(&i, &r, 8);
      }
      aBuf[0] = (i>>56) & 0xFF;
      aBuf[1] = (i>>48) & 0xFF;
      aBuf[2] = (i>>40) & 0xFF;
      aBuf[3] = (i>>32) & 0xFF;
      aBuf[4] = (i>>24) & 0xFF;
      aBuf[5] = (i>>16) & 0xFF;
      aBuf[6] = (i>> 8) & 0xFF;
      aBuf[7] = (i>> 0) & 0xFF;
      sessionAppendBlob(p, aBuf, 8, pRc);
    }
    if( eType==SQLITE_BLOB || eType==SQLITE_TEXT ){
      int nByte = sqlite3_column_bytes(pStmt, iCol);
      sessionAppendVarint(p, nByte, pRc);
      sessionAppendBlob(p, eType==SQLITE_BLOB ? 
        sqlite3_column_blob(pStmt, iCol) : sqlite3_column_text(pStmt, iCol),
        nByte, pRc
      );
    }
  }
}

























static void sessionAppendUpdate(
  sqlite3_stmt *pStmt, 
  SessionBuffer *pBuf,

  SessionChange *p,
  u8 *abPK,
  int *pRc


){
  if( *pRc==SQLITE_OK ){
    SessionBuffer buf2 = {0, 0, 0};
    int bNoop = 1;
    int i;


    u8 *pCsr = p->aRecord;

    sessionAppendByte(pBuf, SQLITE_UPDATE, pRc);
    for(i=0; i<sqlite3_column_count(pStmt); i++){
      int bChanged = 0;
      int nAdvance;
      int eType = *pCsr;
      switch( eType ){
        case SQLITE_NULL:
................................................................................
    }else{
      sessionAppendBlob(pBuf, buf2.aBuf, buf2.nBuf, pRc);
      sqlite3_free(buf2.aBuf);
    }
  }
}




























static int sessionTableInfo(
  sqlite3 *db,                    /* Database connection */

  const char *zThis,              /* Table name */
  int nCol,                       /* Expected number of columns */
  const char **pzTab,             /* OUT: Copy of zThis */
  const char ***pazCol,           /* OUT: Array of column names for table */
  u8 **pabPK                      /* OUT: Array of booleans - true for PK col */
){
  char *zPragma;
................................................................................
  int rc;
  int nByte;
  int nDbCol = 0;
  int nThis;
  int i;
  u8 *pAlloc;
  u8 *pFree = 0;

  char **azCol;
  u8 *abPK;



  nThis = strlen(zThis);
  zPragma = sqlite3_mprintf("PRAGMA main.table_info('%q')", zThis);
  if( !zPragma ) return SQLITE_NOMEM;

  rc = sqlite3_prepare_v2(db, zPragma, -1, &pStmt, 0);
  sqlite3_free(zPragma);
  if( rc!=SQLITE_OK ) return rc;

  nByte = nThis + 1;
................................................................................
      }
      if( pabPK ) abPK[i] = sqlite3_column_int(pStmt, 5);
      i++;
    }
    rc = sqlite3_reset(pStmt);
  
  }




  if( rc==SQLITE_OK ){
    if( pazCol ) *pazCol = (const char **)azCol;
    if( pabPK ) *pabPK = abPK;
  }else{
    if( pazCol ) *pazCol = 0;
    if( pabPK ) *pabPK = 0;
    if( pzTab ) *pzTab = 0;
    sqlite3_free(pFree);
  }

  sqlite3_finalize(pStmt);
  return rc;
}

/*
** Obtain a changeset object containing all changes recorded by the 
** session object passed as the first argument.
................................................................................
** using sqlite3_free().
*/
int sqlite3session_changeset(
  sqlite3_session *pSession,      /* Session object */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
){
  sqlite3 *db = pSession->db;
  SessionTable *pTab;
  SessionBuffer buf = {0, 0, 0};
  int rc;




  *pnChangeset = 0;
  *ppChangeset = 0;
  rc = pSession->rc;

  for(pTab=pSession->pTable; rc==SQLITE_OK && pTab; pTab=pTab->pNext){
    if( pTab->nEntry ){
      int i;
................................................................................
      }

      if( rc==SQLITE_OK && pTab->nCol!=sqlite3_column_count(pStmt) ){
        rc = SQLITE_SCHEMA;
      }

      if( rc==SQLITE_OK ){

        rc = sessionTableInfo(db, pTab->zName, pTab->nCol, 0, 0, &abPK);
      }

      for(i=0; i<pTab->nChange; i++){
        SessionChange *p;
        for(p=pTab->apChange[i]; rc==SQLITE_OK && p; p=p->pNext){
          sqlite3_bind_int64(pStmt, 1, p->iKey);
          if( sqlite3_step(pStmt)==SQLITE_ROW ){
            int iCol;
            if( p->aRecord ){
              sessionAppendUpdate(pStmt, &buf, p, abPK, &rc);
            }else{
              sessionAppendByte(&buf, SQLITE_INSERT, &rc);
              for(iCol=0; iCol<pTab->nCol; iCol++){
                sessionAppendCol(&buf, pStmt, iCol, &rc);
              }
            }
            bNoop = 0;
................................................................................

  if( rc==SQLITE_OK ){
    *pnChangeset = buf.nBuf;
    *ppChangeset = buf.aBuf;
  }else{
    sqlite3_free(buf.aBuf);
  }

  return rc;
}




int sqlite3session_enable(sqlite3_session *pSession, int bEnable){
  return bEnable;

}


/************************************************************************/
/************************************************************************/
/************************************************************************/

struct sqlite3_changeset_iter {
  u8 *aChangeset;                 /* Pointer to buffer containing changeset */
  int nChangeset;                 /* Number of bytes in aChangeset */
  u8 *pNext;                      /* Pointer to next change within aChangeset */
  int rc;

  sqlite3_stmt *pConflict;        /* Conflicting row, if any */
  char *zTab;                     /* Current table */
  int nCol;                       /* Number of columns in zTab */
  int op;                         /* Current operation */
  sqlite3_value **apValue;        /* old.* and new.* values */
};

/*
** Create an iterator used to iterate through the contents of a changeset.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **ppIter,
  int nChangeset, 
  void *pChangeset
){
  sqlite3_changeset_iter *pRet;   /* Iterator to return */
  int nByte;                      /* Number of bytes to allocate for iterator */


  *ppIter = 0;


  nByte = sizeof(sqlite3_changeset_iter);
  pRet = (sqlite3_changeset_iter *)sqlite3_malloc(nByte);
  if( !pRet ) return SQLITE_NOMEM;
  memset(pRet, 0, sizeof(sqlite3_changeset_iter));

  pRet->aChangeset = (u8 *)pChangeset;
  pRet->nChangeset = nChangeset;
  pRet->pNext = pRet->aChangeset;


  *ppIter = pRet;
  return SQLITE_OK;
}






















static int sessionReadRecord(
  u8 **paChange,                  /* IN/OUT: Pointer to binary record */
  int nCol,                       /* Number of values in record */
  sqlite3_value **apOut           /* Write values to this array */
){
  int i;
  u8 *aRec = *paChange;

  for(i=0; i<nCol; i++){
    int eType = *aRec++;
    assert( !apOut || apOut[i]==0 );
    if( eType ){
      if( apOut ){
        apOut[i] = sqlite3ValueNew(0);
        if( !apOut[i] ) return SQLITE_NOMEM;
      }

................................................................................
** callback by changeset_apply().
*/
int sqlite3changeset_next(sqlite3_changeset_iter *p){
  u8 *aChange;
  int i;
  u8 c;


  if( p->rc!=SQLITE_OK ) return p->rc;


  if( p->apValue ){
    for(i=0; i<p->nCol*2; i++){
      sqlite3ValueFree(p->apValue[i]);
    }
    memset(p->apValue, 0, sizeof(sqlite3_value*)*p->nCol*2);
  }

................................................................................

/*
** The following three functions extract information on the current change
** from a changeset iterator. They may only be called after changeset_next()
** has returned SQLITE_ROW.
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp                        /* OUT: SQLITE_INSERT, DELETE or UPDATE */
){
  *pOp = pIter->op;
  *pnCol = pIter->nCol;
  *pzTab = pIter->zTab;
  return SQLITE_OK;
}














int sqlite3changeset_old(
  sqlite3_changeset_iter *pIter,
  int iVal,

  sqlite3_value **ppValue         /* OUT: Old value (or NULL pointer) */
){
  if( pIter->op!=SQLITE_UPDATE && pIter->op!=SQLITE_DELETE ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[iVal];
  return SQLITE_OK;
}














int sqlite3changeset_new(
  sqlite3_changeset_iter *pIter,
  int iVal,

  sqlite3_value **ppValue         /* OUT: New value (or NULL pointer) */
){
  if( pIter->op!=SQLITE_UPDATE && pIter->op!=SQLITE_INSERT ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[pIter->nCol+iVal];
  return SQLITE_OK;
}












int sqlite3changeset_conflict(
  sqlite3_changeset_iter *pIter,
  int iVal,

  sqlite3_value **ppValue         /* OUT: Value from conflicting row */
){
  if( !pIter->pConflict ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=sqlite3_column_count(pIter->pConflict) ){
    return SQLITE_RANGE;
................................................................................
/*
** Finalize an iterator allocated with sqlite3changeset_start().
**
** This function may not be called on iterators passed to a conflict handler
** callback by changeset_apply().
*/
int sqlite3changeset_finalize(sqlite3_changeset_iter *p){
  int i;
  int rc = p->rc;
  for(i=0; i<p->nCol*2; i++) sqlite3ValueFree(p->apValue[i]);
  sqlite3_free(p->apValue);
  sqlite3_free(p);
  return rc;
}

/*
................................................................................
    }
  }

  *pnInverted = nChangeset;
  *ppInverted = (void *)aOut;
  return SQLITE_OK;
}

static void sessionUpdateDeleteWhere(
  SessionBuffer *pBuf,            /* Buffer to append to */
  int nCol,                       /* Number of entries in azCol and abPK */
  const char **azCol,             /* Column names */
  u8 *abPK,                       /* True for PK columns */ 
  int *pRc                        /* IN/OUT: Error code */
){
  if( *pRc==SQLITE_OK ){
    int i;
    const char *zSep = "";

    sessionAppendStr(pBuf, " WHERE ", pRc);

    for(i=0; i<nCol; i++){
      if( abPK[i] ){
        sessionAppendStr(pBuf, zSep, pRc);
        sessionAppendIdent(pBuf, azCol[i], pRc);
        sessionAppendStr(pBuf, " = ?", pRc);
        sessionAppendInteger(pBuf, i+1, pRc);
        zSep = "AND ";
      }
    }

    sessionAppendStr(pBuf, " AND (?", pRc);
    sessionAppendInteger(pBuf, nCol+1, pRc);
    sessionAppendStr(pBuf, " OR ", pRc);

    zSep = "";
    for(i=0; i<nCol; i++){
      if( !abPK[i] ){
        sessionAppendStr(pBuf, zSep, pRc);
        sessionAppendIdent(pBuf, azCol[i], pRc);
        sessionAppendStr(pBuf, " IS ?", pRc);
        sessionAppendInteger(pBuf, i+1, pRc);
        zSep = "AND ";
      }
    }
    sessionAppendStr(pBuf, ")", pRc);
  }
}


typedef struct SessionApplyCtx SessionApplyCtx;
struct SessionApplyCtx {
  sqlite3 *db;
  sqlite3_stmt *pDelete;          /* DELETE statement */
  sqlite3_stmt *pUpdate;          /* DELETE statement */
  sqlite3_stmt *pInsert;          /* INSERT statement */
................................................................................
** The DELETE statement looks like this:
**
**     DELETE FROM x WHERE a = :1 AND c = :3 AND :5 OR (b IS :2 AND d IS :4)
**
** Variable :5 (nCol+1) is a boolean. It should be set to 0 if we require
** matching b and d values, or 1 otherwise. The second case comes up if the
** conflict handler is invoked with NOTFOUND and returns CHANGESET_REPLACE.



*/
static int sessionDeleteRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){


  int rc = SQLITE_OK;
  SessionBuffer buf = {0, 0, 0};

  sessionAppendStr(&buf, "DELETE FROM ", &rc);
  sessionAppendIdent(&buf, zTab, &rc);
  sessionUpdateDeleteWhere(&buf, p->nCol, p->azCol, p->abPK, &rc);



























  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pDelete, 0);
  }
  sqlite3_free(buf.aBuf);

  return rc;
................................................................................
**     ?(i*3+3)    The new.* value of the column, if any.
**
** Also, a boolean flag that, if set to true, causes the statement to update
** a row even if the non-PK values do not match. This is required if the
** conflict-handler is invoked with CHANGESET_DATA and returns
** CHANGESET_REPLACE. This is variable "?(nCol*3+1)".
**


*/
static int sessionUpdateRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
................................................................................
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pUpdate, 0);
  }
  sqlite3_free(buf.aBuf);

  return rc;
}














static int sessionSelectRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
  int i;
................................................................................
  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pSelect, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}










static int sessionInsertRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
  int i;
................................................................................
  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pInsert, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}
















static int sessionSeekToRow(
  sqlite3 *db,                    /* Database handle */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  u8 *abPK,                       /* Primary key flags array */
  sqlite3_stmt *pSelect           /* SELECT statement from sessionSelectRow() */
){
  int rc = SQLITE_OK;


  int i;
  int nCol;
  int op;
  const char *zDummy;

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);

  for(i=0; rc==SQLITE_OK && i<nCol; i++){
    if( abPK[i] ){
      sqlite3_value *pVal = 0;
      if( op!=SQLITE_DELETE ){
................................................................................
    rc = sqlite3_step(pSelect);
    if( rc!=SQLITE_ROW ) rc = sqlite3_reset(pSelect);
  }

  return rc;
}




































static int sessionConflictHandler(
  int eType,

  SessionApplyCtx *p,
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int(*xConflict)(void *, int, sqlite3_changeset_iter*),
  void *pCtx,
  int *pbReplace


){
  int res;

  int rc;
  int nCol;
  int op;
  const char *zDummy;

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);

................................................................................
        break;
    }
  }

  return rc;
}

























static int sessionApplyOneOp(
  sqlite3_changeset_iter *pIter,
  SessionApplyCtx *p,
  int(*xConflict)(void *, int, sqlite3_changeset_iter *),
  void *pCtx,
  int *pbReplace,
  int *pbRetry



){
  const char *zDummy;
  int op;
  int nCol;
  int rc = SQLITE_OK;

  assert( p->pDelete && p->pUpdate && p->pInsert && p->pSelect );
................................................................................
      );
    }
  }

  return rc;
}






int sqlite3changeset_apply(
  sqlite3 *db,

  int nChangeset,
  void *pChangeset,
  int(*xConflict)(
    void *pCtx,                   /* Copy of fifth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx
){
  sqlite3_changeset_iter *pIter = 0;
  int rc;
  int rc2;

  const char *zTab = 0;           /* Name of current table */
  int nTab = 0;                   /* Result of strlen(zTab) */


  SessionApplyCtx sApply;
  memset(&sApply, 0, sizeof(sApply));

  sqlite3changeset_start(&pIter, nChangeset, pChangeset);

  rc = sqlite3_exec(db, "SAVEPOINT changeset_apply", 0, 0, 0);
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int nCol;
    int op;
    int bReplace = 0;
................................................................................
      sqlite3_finalize(sApply.pUpdate); 
      sqlite3_finalize(sApply.pInsert);
      sqlite3_finalize(sApply.pSelect);
      memset(&sApply, 0, sizeof(sApply));
      sApply.db = db;
      sApply.nCol = nCol;


      rc = sessionTableInfo(db, zNew, nCol, &zTab, &sApply.azCol, &sApply.abPK);

      if( rc!=SQLITE_OK 
       || (rc = sessionSelectRow(db, zTab, &sApply))
       || (rc = sessionUpdateRow(db, zTab, &sApply))
       || (rc = sessionDeleteRow(db, zTab, &sApply))
       || (rc = sessionInsertRow(db, zTab, &sApply))
      ){
................................................................................
      }
      if( rc==SQLITE_OK ){
        rc = sqlite3_exec(db, "RELEASE replace_op", 0, 0, 0);
      }
    }
  }


  rc2 = sqlite3changeset_finalize(pIter);
  if( rc==SQLITE_OK ) rc = rc2;




  if( rc==SQLITE_OK ){
    rc = sqlite3_exec(db, "RELEASE changeset_apply", 0, 0, 0);
  }else{
    sqlite3_exec(db, "ROLLBACK TO changeset_apply", 0, 0, 0);
    sqlite3_exec(db, "RELEASE changeset_apply", 0, 0, 0);
  }







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#include "sqliteInt.h"
#include "vdbeInt.h"

typedef struct RowChange RowChange;
typedef struct SessionTable SessionTable;
typedef struct SessionChange SessionChange;
typedef struct SessionBuffer SessionBuffer;



/*
** Session handle structure.





*/
struct sqlite3_session {
  sqlite3 *db;                    /* Database handle session is attached to */
  char *zDb;                      /* Name of database session is attached to */
  int bEnable;                    /* True if currently recording */
  int rc;                         /* Non-zero if an error has occurred */
  sqlite3_session *pNext;         /* Next session object on same db. */
  SessionTable *pTable;           /* List of attached tables */
};

/*
** Structure for changeset iterators.
*/
struct sqlite3_changeset_iter {
  u8 *aChangeset;                 /* Pointer to buffer containing changeset */
  int nChangeset;                 /* Number of bytes in aChangeset */
  u8 *pNext;                      /* Pointer to next change within aChangeset */
  int rc;                         /* Iterator error code */
  sqlite3_stmt *pConflict;        /* Points to conflicting row, if any */
  char *zTab;                     /* Current table */
  int nCol;                       /* Number of columns in zTab */
  int op;                         /* Current operation */
  sqlite3_value **apValue;        /* old.* and new.* values */
};

/*
** Each session object maintains a set of the following structures, one
** for each table the session object is monitoring. The structures are
** stored in a linked list starting at sqlite3_session.pTable.
**
** The keys of the SessionTable.aChange[] hash table are all rows that have
................................................................................
** a subset of the initial values that the modified row contained at the
** start of the session. Or no initial values if the row was inserted.
*/
struct SessionTable {
  SessionTable *pNext;
  char *zName;                    /* Local name of table */
  int nCol;                       /* Number of columns in table zName */


  int nEntry;                     /* Total number of entries in hash table */
  int nChange;                    /* Size of apChange[] array */
  SessionChange **apChange;       /* Hash table buckets */
};

/* 
** RECORD FORMAT:
**
................................................................................
struct SessionChange {
  sqlite3_int64 iKey;             /* Key value */
  int nRecord;                    /* Number of bytes in buffer aRecord[] */
  u8 *aRecord;                    /* Buffer containing old.* record */
  SessionChange *pNext;           /* For hash-table collisions */
};


/*
** Instances of this structure are used to build strings or binary records.

*/
struct SessionBuffer {
  u8 *aBuf;                       /* Pointer to changeset buffer */
  int nBuf;                       /* Size of buffer aBuf */
  int nAlloc;                     /* Size of allocation containing aBuf */
};




/*
** Write a varint with value iVal into the buffer at aBuf. Return the 
** number of bytes written.
*/
static int sessionVarintPut(u8 *aBuf, int iVal){
  return putVarint32(aBuf, iVal);
}





/*
** Return the number of bytes required to store value iVal as a varint.

*/
static int sessionVarintLen(int iVal){

  return sqlite3VarintLen(iVal);
}

/*
** Read a varint value from aBuf[] into *piVal. Return the number of 
** bytes read.
*/
static int sessionVarintGet(u8 *aBuf, int *piVal){



  return getVarint32(aBuf, *piVal);

}

/*
** Read a 64-bit big-endian integer value from buffer aRec[]. Return
** the value read.
*/
static sqlite3_int64 sessionGetI64(u8 *aRec){
  return (((sqlite3_int64)aRec[0]) << 56)
       + (((sqlite3_int64)aRec[1]) << 48)
       + (((sqlite3_int64)aRec[2]) << 40)
       + (((sqlite3_int64)aRec[3]) << 32)
       + (((sqlite3_int64)aRec[4]) << 24)
       + (((sqlite3_int64)aRec[5]) << 16)
       + (((sqlite3_int64)aRec[6]) <<  8)
       + (((sqlite3_int64)aRec[7]) <<  0);
}

/*
** Write a 64-bit big-endian integer value to the buffer aBuf[].
*/
static void sessionPutI64(u8 *aBuf, sqlite3_int64 i){
  aBuf[0] = (i>>56) & 0xFF;
  aBuf[1] = (i>>48) & 0xFF;
  aBuf[2] = (i>>40) & 0xFF;
  aBuf[3] = (i>>32) & 0xFF;
  aBuf[4] = (i>>24) & 0xFF;
  aBuf[5] = (i>>16) & 0xFF;
  aBuf[6] = (i>> 8) & 0xFF;
  aBuf[7] = (i>> 0) & 0xFF;
}

/*
** This function is used to serialize the contents of value pValue (see
** comment titled "RECORD FORMAT" above).
**
** If it is non-NULL, the serialized form of the value is written to 
** buffer aBuf. *pnWrite is set to the number of bytes written before
................................................................................
** SQLITE_NOMEM is returned.
*/
static int sessionSerializeValue(
  u8 *aBuf,                       /* If non-NULL, write serialized value here */
  sqlite3_value *pValue,          /* Value to serialize */
  int *pnWrite                    /* IN/OUT: Increment by bytes written */
){
  int eType;                      /* Value type (SQLITE_NULL, TEXT etc.) */
  int nByte;                      /* Size of serialized value in bytes */

  eType = sqlite3_value_type(pValue);
  if( aBuf ) aBuf[0] = eType;

  switch( eType ){
    case SQLITE_NULL: 
      nByte = 1;
................................................................................
          i = (u64)sqlite3_value_int64(pValue);
        }else{
          double r;
          assert( sizeof(double)==8 && sizeof(u64)==8 );
          r = sqlite3_value_double(pValue);
          memcpy(&i, &r, 8);
        }
        sessionPutI64(&aBuf[1], i);







      }
      nByte = 9; 
      break;

    case SQLITE_TEXT: 
    case SQLITE_BLOB: {
      int n = sqlite3_value_bytes(pValue);
      int nVarint = sessionVarintLen(n);
      if( aBuf ){
        sessionVarintPut(&aBuf[1], n);
        memcpy(&aBuf[nVarint + 1], eType==SQLITE_TEXT ? 
            sqlite3_value_text(pValue) : sqlite3_value_blob(pValue), n
        );
      }

................................................................................
    pTab->nChange = nNew;
    pTab->apChange = apNew;
  }

  return SQLITE_OK;
}

/*
** This function is only called from within a pre-update handler for a
** write to table pTab, part of session pSession. If this is the first
** write to this table, set the SessionTable.nCol variable to the number
** of columns in the table.
**
** Otherwise, if this is not the first time this table has been written
** to, check that the number of columns in the table has not changed. If
** it has not, return zero.
**
** If the number of columns in the table has changed since the last write
** was recorded, set the session error-code to SQLITE_SCHEMA and return
** non-zero. Users are not allowed to change the number of columns in a table
** for which changes are being recorded by the session module. If they do so, 
** it is an error.
*/
static int sessionInitTable(sqlite3_session *pSession, SessionTable *pTab){
  if( pTab->nCol==0 ){
    pTab->nCol = sqlite3_preupdate_count(pSession->db);


  }else if( pTab->nCol!=sqlite3_preupdate_count(pSession->db) ){
    pSession->rc = SQLITE_SCHEMA;
    return SQLITE_ERROR;
  }

  return SQLITE_OK;
}

/*
** The 'pre-update' hook registered by this module with SQLite databases.
*/
static void xPreUpdate(
................................................................................
){
  sqlite3_session *pSession;
  int nDb = strlen(zDb);
  int nName = strlen(zDb);
 
  for(pSession=(sqlite3_session *)pCtx; pSession; pSession=pSession->pNext){
    SessionTable *pTab;

    /* If this session is already in the error-state, or if it is attached
    ** to a different database ("main", "temp" etc.), or if it is not 
    ** currently enabled, there is nothing to do. Skip to the next session
    ** object attached to this database. */
    if( pSession->bEnable==0 ) continue;
    if( pSession->rc ) continue;
    if( sqlite3_strnicmp(zDb, pSession->zDb, nDb+1) ) continue;

    for(pTab=pSession->pTable; pTab; pTab=pTab->pNext){
      if( 0==sqlite3_strnicmp(pTab->zName, zName, nName+1) ){
        SessionChange *pChange;
        SessionChange *pC;
        int iHash; 
        int rc = SQLITE_OK;

................................................................................
          pChange = (SessionChange *)sqlite3_malloc(sizeof(SessionChange));
          if( pChange ){
            memset(pChange, 0, sizeof(SessionChange));
          }
        }else{
          int nByte;              /* Number of bytes to allocate */
          int i;                  /* Used to iterate through columns */


          /* Figure out how large an allocation is required */
          nByte = sizeof(SessionChange);
          for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){
            sqlite3_value *p;     /* old.* value */
            rc = sqlite3_preupdate_old(pSession->db, i, &p);
            if( rc==SQLITE_OK ){
              rc = sessionSerializeValue(0, p, &nByte);
            }
          }

          /* Allocate the change object */
          pChange = (SessionChange *)sqlite3_malloc(nByte);
          if( !pChange ){
            rc = SQLITE_NOMEM;
................................................................................
            memset(pChange, 0, sizeof(SessionChange));
            pChange->aRecord = (u8 *)&pChange[1];
          }

          /* Populate the change object */
          nByte = 0;
          for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){
            sqlite3_value *p;     /* old.* value */
            rc = sqlite3_preupdate_old(pSession->db, i, &p);
            if( rc==SQLITE_OK ){
              rc = sessionSerializeValue(&pChange->aRecord[nByte], p, &nByte);

            }
          }
          pChange->nRecord = nByte;
        }

        /* If an error has occurred, mark the session object as failed. */
        if( rc!=SQLITE_OK ){
................................................................................
          return;
        }

        /* Add the change back to the hash-table */
        pChange->iKey = iKey2;
        pChange->pNext = pTab->apChange[iHash];
        pTab->apChange[iHash] = pChange;

        break;
      }
    }
  }
}

/*
** Create a session object. This session object will record changes to
** database zDb attached to connection db.
*/
int sqlite3session_create(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Name of db (e.g. "main") */
  sqlite3_session **ppSession     /* OUT: New session object */
){
  sqlite3_session *pNew;          /* Newly allocated session object */
  sqlite3_session *pOld;          /* Session object already attached to db */
  int nDb = strlen(zDb);          /* Length of zDb in bytes */

  /* Zero the output value in case an error occurs. */
  *ppSession = 0;

  /* Allocate and populate the new session object. */
  pNew = (sqlite3_session *)sqlite3_malloc(sizeof(sqlite3_session) + nDb + 1);
  if( !pNew ) return SQLITE_NOMEM;
  memset(pNew, 0, sizeof(sqlite3_session));
  pNew->db = db;
  pNew->zDb = (char *)&pNew[1];
  pNew->bEnable = 1;
  memcpy(pNew->zDb, zDb, nDb+1);

  /* Add the new session object to the linked list of session objects 
  ** attached to database handle $db. Do this under the cover of the db
  ** handle mutex.  */
  sqlite3_mutex_enter(sqlite3_db_mutex(db));
  pOld = (sqlite3_session*)sqlite3_preupdate_hook(db, xPreUpdate, (void*)pNew);
................................................................................
** Delete a session object previously allocated using sqlite3session_create().
*/
void sqlite3session_delete(sqlite3_session *pSession){
  sqlite3 *db = pSession->db;
  sqlite3_session *pHead;
  sqlite3_session **pp;

  /* Unlink the session from the linked list of sessions attached to the
  ** database handle. Hold the db mutex while doing so.  */
  sqlite3_mutex_enter(sqlite3_db_mutex(db));
  pHead = (sqlite3_session*)sqlite3_preupdate_hook(db, 0, 0);
  for(pp=&pHead; (*pp)!=pSession; pp=&((*pp)->pNext));
  *pp = (*pp)->pNext;
  if( pHead ) sqlite3_preupdate_hook(db, xPreUpdate, (void *)pHead);
  sqlite3_mutex_leave(sqlite3_db_mutex(db));

  /* Delete all attached table objects. And the contents of their 
  ** associated hash-tables. */
  while( pSession->pTable ){
    int i;
    SessionTable *pTab = pSession->pTable;
    pSession->pTable = pTab->pNext;
    for(i=0; i<pTab->nChange; i++){
      SessionChange *p;
      SessionChange *pNext;
................................................................................
        sqlite3_free(p);
      }
    }
    sqlite3_free(pTab->apChange);
    sqlite3_free(pTab);
  }

  /* Free the session object itself. */
  sqlite3_free(pSession);
}

/*
** Attach a table to a session. All subsequent changes made to the table
** while the session object is enabled will be recorded.
**
................................................................................
** not matter if the PRIMARY KEY is an "INTEGER PRIMARY KEY" (rowid alias)
** or not.
*/
int sqlite3session_attach(
  sqlite3_session *pSession,      /* Session object */
  const char *zName               /* Table name */
){
  SessionTable *pTab;             /* New table object (if required) */
  int nName;                      /* Number of bytes in string zName */

  /* First search for an existing entry. If one is found, this call is
  ** a no-op. Return early. */
  nName = strlen(zName);
  for(pTab=pSession->pTable; pTab; pTab=pTab->pNext){
    if( 0==sqlite3_strnicmp(pTab->zName, zName, nName+1) ){
      return SQLITE_OK;
................................................................................
  memcpy(pTab->zName, zName, nName+1);
  pTab->pNext = pSession->pTable;
  pSession->pTable = pTab;

  return SQLITE_OK;
}

/*
** Ensure that there is room in the buffer to append nByte bytes of data.
** If not, use sqlite3_realloc() to grow the buffer so that there is.
**
** If successful, return zero. Otherwise, if an OOM condition is encountered,
** set *pRc to SQLITE_NOMEM and return non-zero.
*/
static int sessionBufferGrow(SessionBuffer *p, int nByte, int *pRc){
  if( p->nAlloc-p->nBuf<nByte ){
    u8 *aNew;
    int nNew = p->nAlloc ? p->nAlloc : 128;
    do {
      nNew = nNew*2;
    }while( nNew<(p->nAlloc+nByte) );
................................................................................
    }
    p->aBuf = aNew;
    p->nAlloc = nNew;
  }
  return 0;
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single byte to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendByte(SessionBuffer *p, u8 v, int *pRc){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, 1, pRc) ){
    p->aBuf[p->nBuf++] = v;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single varint to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendVarint(SessionBuffer *p, sqlite3_int64 v, int *pRc){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, 9, pRc) ){
    p->nBuf += sessionVarintPut(&p->aBuf[p->nBuf], v);
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a blob of data to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendBlob(
  SessionBuffer *p, 
  const u8 *aBlob, 
  int nBlob, 
  int *pRc
){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nBlob, pRc) ){
    memcpy(&p->aBuf[p->nBuf], aBlob, nBlob);
    p->nBuf += nBlob;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a string to the buffer. All bytes in the string
** up to (but not including) the nul-terminator are written to the buffer.
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendStr(
  SessionBuffer *p, 
  const char *zStr, 
  int *pRc
){
  int nStr = strlen(zStr);
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nStr, pRc) ){
    memcpy(&p->aBuf[p->nBuf], zStr, nStr);
    p->nBuf += nStr;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append the string representation of integer iVal
** to the buffer. No nul-terminator is written.
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendInteger(
  SessionBuffer *p,               /* Buffer to append to */


  int iVal,                       /* Value to write the string rep. of */
  int *pRc                        /* IN/OUT: Error code */
){
  char aBuf[24];
  sqlite3_snprintf(sizeof(aBuf)-1, aBuf, "%d", iVal);
  sessionAppendStr(p, aBuf, pRc);
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append the string zStr enclosed in quotes (") and
** with any embedded quote characters escaped to the buffer. No 
** nul-terminator byte is written.
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendIdent(
  SessionBuffer *p,               /* Buffer to a append to */
  const char *zStr,               /* String to quote, escape and append */

  int *pRc                        /* IN/OUT: Error code */
){
  int nStr = strlen(zStr)*2 + 2 + 1;
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nStr, pRc) ){
    char *zOut = (char *)&p->aBuf[p->nBuf];
    const char *zIn = zStr;
    *zOut++ = '"';
    while( *zIn ){
................................................................................
      *zOut++ = *(zIn++);
    }
    *zOut++ = '"';
    p->nBuf = ((u8 *)zOut - p->aBuf);
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is
** called. Otherwse, it appends the serialized version of the value stored
** in column iCol of the row that SQL statement pStmt currently points
** to to the buffer.
*/
static void sessionAppendCol(
  SessionBuffer *p,               /* Buffer to append to */
  sqlite3_stmt *pStmt,            /* Handle pointing to row containing value */


  int iCol,                       /* Column to read value from */
  int *pRc                        /* IN/OUT: Error code */
){
  if( *pRc==SQLITE_OK ){
    int eType = sqlite3_column_type(pStmt, iCol);
    sessionAppendByte(p, (u8)eType, pRc);
    if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
      sqlite3_int64 i;
      u8 aBuf[8];
      if( eType==SQLITE_INTEGER ){
        i = sqlite3_column_int64(pStmt, iCol);
      }else{
        double r = sqlite3_column_double(pStmt, iCol);
        memcpy(&i, &r, 8);
      }
      sessionPutI64(aBuf, i);







      sessionAppendBlob(p, aBuf, 8, pRc);
    }
    if( eType==SQLITE_BLOB || eType==SQLITE_TEXT ){
      int nByte = sqlite3_column_bytes(pStmt, iCol);
      sessionAppendVarint(p, nByte, pRc);
      sessionAppendBlob(p, eType==SQLITE_BLOB ? 
        sqlite3_column_blob(pStmt, iCol) : sqlite3_column_text(pStmt, iCol),
        nByte, pRc
      );
    }
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is
** called. 
**
** Otherwse, if *pRc is SQLITE_OK, then it appends an update change to
** the buffer (see the comments under "CHANGESET FORMAT" at the top of the
** file). An update change consists of:
**
**   1 byte:  SQLITE_UPDATE (0x17)
**   n bytes: old.* record (see RECORD FORMAT)
**   m bytes: new.* record (see RECORD FORMAT)
**
** The SessionChange object passed as the third argument contains the
** values that were stored in the row when the session began (the old.*
** values). The statement handle passed as the second argument points
** at the current version of the row (the new.* values).
**
** If all of the old.* values are equal to their corresponding new.* value
** (i.e. nothing has changed), then no data at all is appended to the buffer.
**
** Otherwise, the old.* record contains all primary key values and the 
** original values of any fields that have been modified. The new.* record 
** contains the new values of only those fields that have been modified.
*/ 
static void sessionAppendUpdate(

  SessionBuffer *pBuf,            /* Buffer to append to */
  sqlite3_stmt *pStmt,            /* Statement handle pointing at new row */
  SessionChange *p,               /* Object containing old values */


  u8 *abPK,                       /* Boolean array - true for PK columns */
  int *pRc                        /* IN/OUT: Error code */
){
  if( *pRc==SQLITE_OK ){
    SessionBuffer buf2 = {0,0,0}; /* Buffer to accumulate new.* record in */


    int bNoop = 1;                /* Set to zero if any values are modified */
    int i;                        /* Used to iterate through columns */
    u8 *pCsr = p->aRecord;        /* Used to iterate through old.* values */

    sessionAppendByte(pBuf, SQLITE_UPDATE, pRc);
    for(i=0; i<sqlite3_column_count(pStmt); i++){
      int bChanged = 0;
      int nAdvance;
      int eType = *pCsr;
      switch( eType ){
        case SQLITE_NULL:
................................................................................
    }else{
      sessionAppendBlob(pBuf, buf2.aBuf, buf2.nBuf, pRc);
      sqlite3_free(buf2.aBuf);
    }
  }
}

/*
** This function queries the database for the names of the columns of table
** zThis, in schema zDb. It is expected that the table has nCol columns. If
** not, SQLITE_SCHEMA is returned and none of the output variables are
** populated.
**
** Otherwise, if it is not NULL, variable *pzTab is set to point to a
** nul-terminated copy of the table name. *pazCol (if not NULL) is set to
** point to an array of pointers to column names. And *pabPK (again, if not
** NULL) is set to point to an array of booleans - true if the corresponding
** column is part of the primary key.
**
** For example, if the table is declared as:
**
**     CREATE TABLE tbl1(w, x, y, z, PRIMARY KEY(w, z));
**
** Then the three output variables are populated as follows:
**
**     *pzTab  = "tbl1"
**     *pazCol = {"w", "x", "y", "z"}
**     *pabPK  = {1, 0, 0, 1}
**
** All returned buffers are part of the same single allocation, which must
** be freed using sqlite3_free() by the caller. If pazCol was not NULL, then
** pointer *pazCol should be freed to release all memory. Otherwise, pointer
** *pabPK. It is illegal for both pazCol and pabPK to be NULL.
*/
static int sessionTableInfo(
  sqlite3 *db,                    /* Database connection */
  const char *zDb,                /* Name of attached database (e.g. "main") */
  const char *zThis,              /* Table name */
  int nCol,                       /* Expected number of columns */
  const char **pzTab,             /* OUT: Copy of zThis */
  const char ***pazCol,           /* OUT: Array of column names for table */
  u8 **pabPK                      /* OUT: Array of booleans - true for PK col */
){
  char *zPragma;
................................................................................
  int rc;
  int nByte;
  int nDbCol = 0;
  int nThis;
  int i;
  u8 *pAlloc;
  u8 *pFree = 0;

  char **azCol;
  u8 *abPK;

  assert( pazCol || pabPK );

  nThis = strlen(zThis);
  zPragma = sqlite3_mprintf("PRAGMA '%q'.table_info('%q')", zDb, zThis);
  if( !zPragma ) return SQLITE_NOMEM;

  rc = sqlite3_prepare_v2(db, zPragma, -1, &pStmt, 0);
  sqlite3_free(zPragma);
  if( rc!=SQLITE_OK ) return rc;

  nByte = nThis + 1;
................................................................................
      }
      if( pabPK ) abPK[i] = sqlite3_column_int(pStmt, 5);
      i++;
    }
    rc = sqlite3_reset(pStmt);
  
  }

  /* If successful, populate the output variables. Otherwise, zero them and
  ** free any allocation made. An error code will be returned in this case.
  */
  if( rc==SQLITE_OK ){
    if( pazCol ) *pazCol = (const char **)azCol;
    if( pabPK ) *pabPK = abPK;
  }else{
    if( pazCol ) *pazCol = 0;
    if( pabPK ) *pabPK = 0;
    if( pzTab ) *pzTab = 0;
    sqlite3_free(pFree);
  }

  sqlite3_finalize(pStmt);
  return rc;
}

/*
** Obtain a changeset object containing all changes recorded by the 
** session object passed as the first argument.
................................................................................
** using sqlite3_free().
*/
int sqlite3session_changeset(
  sqlite3_session *pSession,      /* Session object */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
){
  sqlite3 *db = pSession->db;     /* Source database handle */
  SessionTable *pTab;             /* Used to iterate through attached tables */
  SessionBuffer buf = {0,0,0};    /* Buffer in which to accumlate changeset */
  int rc;                         /* Return code */

  /* Zero the output variables in case an error occurs. If this session
  ** object is already in the error state (sqlite3_session.rc != SQLITE_OK),
  ** this call will be a no-op.  */
  *pnChangeset = 0;
  *ppChangeset = 0;
  rc = pSession->rc;

  for(pTab=pSession->pTable; rc==SQLITE_OK && pTab; pTab=pTab->pNext){
    if( pTab->nEntry ){
      int i;
................................................................................
      }

      if( rc==SQLITE_OK && pTab->nCol!=sqlite3_column_count(pStmt) ){
        rc = SQLITE_SCHEMA;
      }

      if( rc==SQLITE_OK ){
        rc = sessionTableInfo(
            db, pSession->zDb, pTab->zName, pTab->nCol, 0, 0, &abPK);
      }

      for(i=0; i<pTab->nChange; i++){
        SessionChange *p;
        for(p=pTab->apChange[i]; rc==SQLITE_OK && p; p=p->pNext){
          sqlite3_bind_int64(pStmt, 1, p->iKey);
          if( sqlite3_step(pStmt)==SQLITE_ROW ){
            int iCol;
            if( p->aRecord ){
              sessionAppendUpdate(&buf, pStmt, p, abPK, &rc);
            }else{
              sessionAppendByte(&buf, SQLITE_INSERT, &rc);
              for(iCol=0; iCol<pTab->nCol; iCol++){
                sessionAppendCol(&buf, pStmt, iCol, &rc);
              }
            }
            bNoop = 0;
................................................................................

  if( rc==SQLITE_OK ){
    *pnChangeset = buf.nBuf;
    *ppChangeset = buf.aBuf;
  }else{
    sqlite3_free(buf.aBuf);
  }

  return rc;
}

/*
** Enable or disable the session object passed as the first argument.
*/
int sqlite3session_enable(sqlite3_session *pSession, int bEnable){
  if( bEnable>=0 ){
    pSession->bEnable = bEnable;
  }
  return pSession->bEnable;
}

















/*
** Create an iterator used to iterate through the contents of a changeset.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int nChangeset,                 /* Size of buffer pChangeset in bytes */
  void *pChangeset                /* Pointer to buffer containing changeset */
){
  sqlite3_changeset_iter *pRet;   /* Iterator to return */
  int nByte;                      /* Number of bytes to allocate for iterator */

  /* Zero the output variable in case an error occurs. */
  *pp = 0;

  /* Allocate and initialize the iterator structure. */
  nByte = sizeof(sqlite3_changeset_iter);
  pRet = (sqlite3_changeset_iter *)sqlite3_malloc(nByte);
  if( !pRet ) return SQLITE_NOMEM;
  memset(pRet, 0, sizeof(sqlite3_changeset_iter));

  pRet->aChangeset = (u8 *)pChangeset;
  pRet->nChangeset = nChangeset;
  pRet->pNext = pRet->aChangeset;

  /* Populate the output variable and return success. */
  *pp = pRet;
  return SQLITE_OK;
}

/*
** Deserialize a single record from a buffer in memory. See "RECORD FORMAT"
** for details.
**
** When this function is called, *paChange points to the start of the record
** to deserialize. Assuming no error occurs, *paChange is set to point to
** one byte after the end of the same record before this function returns.
**
** If successful, each element of the apOut[] array (allocated by the caller)
** is set to point to an sqlite3_value object containing the value read
** from the corresponding position in the record. If that value is not
** included in the record (i.e. because the record is part of an UPDATE change
** and the field was not modified), the corresponding element of apOut[] is
** set to NULL.
**
** It is the responsibility of the caller to free all sqlite_value structures
** using sqlite3_free().
**
** If an error occurs, an SQLite error code (e.g. SQLITE_NOMEM) is returned.
** The apOut[] array may have been partially populated in this case.
*/
static int sessionReadRecord(
  u8 **paChange,                  /* IN/OUT: Pointer to binary record */
  int nCol,                       /* Number of values in record */
  sqlite3_value **apOut           /* Write values to this array */
){
  int i;                          /* Used to iterate through columns */
  u8 *aRec = *paChange;           /* Cursor for the serialized record */

  for(i=0; i<nCol; i++){
    int eType = *aRec++;          /* Type of value (SQLITE_NULL, TEXT etc.) */
    assert( !apOut || apOut[i]==0 );
    if( eType ){
      if( apOut ){
        apOut[i] = sqlite3ValueNew(0);
        if( !apOut[i] ) return SQLITE_NOMEM;
      }

................................................................................
** callback by changeset_apply().
*/
int sqlite3changeset_next(sqlite3_changeset_iter *p){
  u8 *aChange;
  int i;
  u8 c;

  /* If the iterator is in the error-state, return immediately. */
  if( p->rc!=SQLITE_OK ) return p->rc;

  /* Free the current contents of p->apValue[]. */
  if( p->apValue ){
    for(i=0; i<p->nCol*2; i++){
      sqlite3ValueFree(p->apValue[i]);
    }
    memset(p->apValue, 0, sizeof(sqlite3_value*)*p->nCol*2);
  }

................................................................................

/*
** The following three functions extract information on the current change
** from a changeset iterator. They may only be called after changeset_next()
** has returned SQLITE_ROW.
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator handle */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp                        /* OUT: SQLITE_INSERT, DELETE or UPDATE */
){
  *pOp = pIter->op;
  *pnCol = pIter->nCol;
  *pzTab = pIter->zTab;
  return SQLITE_OK;
}

/*
** This function may only be called while the iterator is pointing to an
** SQLITE_UPDATE or SQLITE_DELETE change (see sqlite3changeset_op()).
** Otherwise, SQLITE_MISUSE is returned.
**
** It sets *ppValue to point to an sqlite3_value structure containing the
** iVal'th value in the old.* record. Or, if that particular value is not
** included in the record (because the change is an UPDATE and the field
** was not modified and is not a PK column), set *ppValue to NULL.
**
** If value iVal is out-of-range, SQLITE_RANGE is returned and *ppValue is
** not modified. Otherwise, SQLITE_OK.
*/
int sqlite3changeset_old(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */

  int iVal,                       /* Index of old.* value to retrieve */
  sqlite3_value **ppValue         /* OUT: Old value (or NULL pointer) */
){
  if( pIter->op!=SQLITE_UPDATE && pIter->op!=SQLITE_DELETE ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[iVal];
  return SQLITE_OK;
}

/*
** This function may only be called while the iterator is pointing to an
** SQLITE_UPDATE or SQLITE_INSERT change (see sqlite3changeset_op()).
** Otherwise, SQLITE_MISUSE is returned.
**
** It sets *ppValue to point to an sqlite3_value structure containing the
** iVal'th value in the new.* record. Or, if that particular value is not
** included in the record (because the change is an UPDATE and the field
** was not modified), set *ppValue to NULL.
**
** If value iVal is out-of-range, SQLITE_RANGE is returned and *ppValue is
** not modified. Otherwise, SQLITE_OK.
*/
int sqlite3changeset_new(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */

  int iVal,                       /* Index of new.* value to retrieve */
  sqlite3_value **ppValue         /* OUT: New value (or NULL pointer) */
){
  if( pIter->op!=SQLITE_UPDATE && pIter->op!=SQLITE_INSERT ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[pIter->nCol+iVal];
  return SQLITE_OK;
}

/*
** This function may only be called with a changeset iterator that has been
** passed to an SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT 
** conflict-handler function. Otherwise, SQLITE_MISUSE is returned.
**
** If successful, *ppValue is set to point to an sqlite3_value structure
** containing the iVal'th value of the conflicting record.
**
** If value iVal is out-of-range or some other error occurs, an SQLite error
** code is returned. Otherwise, SQLITE_OK.
*/
int sqlite3changeset_conflict(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */

  int iVal,                       /* Index of conflict record value to fetch */
  sqlite3_value **ppValue         /* OUT: Value from conflicting row */
){
  if( !pIter->pConflict ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=sqlite3_column_count(pIter->pConflict) ){
    return SQLITE_RANGE;
................................................................................
/*
** Finalize an iterator allocated with sqlite3changeset_start().
**
** This function may not be called on iterators passed to a conflict handler
** callback by changeset_apply().
*/
int sqlite3changeset_finalize(sqlite3_changeset_iter *p){
  int i;                          /* Used to iterate through p->apValue[] */
  int rc = p->rc;                 /* Return code */
  for(i=0; i<p->nCol*2; i++) sqlite3ValueFree(p->apValue[i]);
  sqlite3_free(p->apValue);
  sqlite3_free(p);
  return rc;
}

/*
................................................................................
    }
  }

  *pnInverted = nChangeset;
  *ppInverted = (void *)aOut;
  return SQLITE_OK;
}











































typedef struct SessionApplyCtx SessionApplyCtx;
struct SessionApplyCtx {
  sqlite3 *db;
  sqlite3_stmt *pDelete;          /* DELETE statement */
  sqlite3_stmt *pUpdate;          /* DELETE statement */
  sqlite3_stmt *pInsert;          /* INSERT statement */
................................................................................
** The DELETE statement looks like this:
**
**     DELETE FROM x WHERE a = :1 AND c = :3 AND :5 OR (b IS :2 AND d IS :4)
**
** Variable :5 (nCol+1) is a boolean. It should be set to 0 if we require
** matching b and d values, or 1 otherwise. The second case comes up if the
** conflict handler is invoked with NOTFOUND and returns CHANGESET_REPLACE.
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pDelete is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionDeleteRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int i;
  const char *zSep = "";
  int rc = SQLITE_OK;
  SessionBuffer buf = {0, 0, 0};

  sessionAppendStr(&buf, "DELETE FROM ", &rc);
  sessionAppendIdent(&buf, zTab, &rc);
  sessionAppendStr(&buf, " WHERE ", &rc);

  for(i=0; i<p->nCol; i++){
    if( p->abPK[i] ){
      sessionAppendStr(&buf, zSep, &rc);
      sessionAppendIdent(&buf, p->azCol[i], &rc);
      sessionAppendStr(&buf, " = ?", &rc);
      sessionAppendInteger(&buf, i+1, &rc);
      zSep = "AND ";
    }
  }

  sessionAppendStr(&buf, " AND (?", &rc);
  sessionAppendInteger(&buf, p->nCol+1, &rc);
  sessionAppendStr(&buf, " OR ", &rc);

  zSep = "";
  for(i=0; i<p->nCol; i++){
    if( !p->abPK[i] ){
      sessionAppendStr(&buf, zSep, &rc);
      sessionAppendIdent(&buf, p->azCol[i], &rc);
      sessionAppendStr(&buf, " IS ?", &rc);
      sessionAppendInteger(&buf, i+1, &rc);
      zSep = "AND ";
    }
  }
  sessionAppendStr(&buf, ")", &rc);

  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pDelete, 0);
  }
  sqlite3_free(buf.aBuf);

  return rc;
................................................................................
**     ?(i*3+3)    The new.* value of the column, if any.
**
** Also, a boolean flag that, if set to true, causes the statement to update
** a row even if the non-PK values do not match. This is required if the
** conflict-handler is invoked with CHANGESET_DATA and returns
** CHANGESET_REPLACE. This is variable "?(nCol*3+1)".
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pUpdate is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionUpdateRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
................................................................................
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pUpdate, 0);
  }
  sqlite3_free(buf.aBuf);

  return rc;
}

/*
** Formulate and prepare an SQL statement to query table zTab by primary
** key. Assuming the following table structure:
**
**     CREATE TABLE x(a, b, c, d, PRIMARY KEY(a, c));
**
** The SELECT statement looks like this:
**
**     SELECT * FROM x WHERE a = ?1 AND c = ?3
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pSelect is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionSelectRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
  int i;
................................................................................
  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pSelect, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}

/*
** Formulate and prepare an INSERT statement to add a record to table zTab.
** For example:
**
**     INSERT INTO main."zTab" VALUES(?1, ?2, ?3 ...);
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pInsert is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionInsertRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
  int i;
................................................................................
  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pInsert, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}

/*
** SQL statement pSelect is as generated by the sessionSelectRow() function.
** This function binds the primary key values from the change that changeset
** iterator pIter points to to the SELECT and attempts to seek to the table
** entry. If a row is found, the SELECT statement left pointing at the row 
** and SQLITE_ROW is returned. Otherwise, if no row is found and no error
** has occured, the statement is reset and SQLITE_OK is returned. If an
** error occurs, an SQLite error code is returned.
**
** If the iterator currently points to an INSERT record, bind values from the
** new.* record to the SELECT statement. Or, if it points to a DELETE, bind
** values from the old.* record. If the changeset iterator points to an
** UPDATE, bind values from the new.* record, but use old.* values in place
** of any undefined new.* values.
*/
static int sessionSeekToRow(
  sqlite3 *db,                    /* Database handle */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  u8 *abPK,                       /* Primary key flags array */
  sqlite3_stmt *pSelect           /* SELECT statement from sessionSelectRow() */
){
  int rc = SQLITE_OK;             /* Return code */

  int i;                          /* Used to iterate through table columns */
  int nCol;                       /* Number of columns in table */
  int op;                         /* Changset operation (SQLITE_UPDATE etc.) */

  const char *zDummy;             /* Unused */

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);

  for(i=0; rc==SQLITE_OK && i<nCol; i++){
    if( abPK[i] ){
      sqlite3_value *pVal = 0;
      if( op!=SQLITE_DELETE ){
................................................................................
    rc = sqlite3_step(pSelect);
    if( rc!=SQLITE_ROW ) rc = sqlite3_reset(pSelect);
  }

  return rc;
}

/*
** Invoke the conflict handler for the change that the changeset iterator
** currently points to.
**
** Argument eType must be either CHANGESET_DATA or CHANGESET_CONFLICT.
** If argument pbReplace is NULL, then the type of conflict handler invoked
** depends solely on eType, as follows:
**
**    eType value                 Value passed to xConflict
**    -------------------------------------------------
**    CHANGESET_DATA              CHANGESET_NOTFOUND
**    CHANGESET_CONFLICT          CHANGESET_CONSTRAINT
**
** Or, if pbReplace is not NULL, then an attempt is made to find an existing
** record with the same primary key as the record about to be deleted, updated
** or inserted. If such a record can be found, it is available to the conflict
** handler as the "conflicting" record. In this case the type of conflict
** handler invoked is as follows:
**
**    eType value         PK Record found?   Value passed to xConflict
**    ----------------------------------------------------------------
**    CHANGESET_DATA      Yes                CHANGESET_DATA
**    CHANGESET_DATA      No                 CHANGESET_NOTFOUND
**    CHANGESET_CONFLICT  Yes                CHANGESET_CONFLICT
**    CHANGESET_CONFLICT  No                 CHANGESET_CONSTRAINT
**
** If pbReplace is not NULL, and a record with a matching PK is found, and
** the conflict handler function returns SQLITE_CHANGESET_REPLACE, *pbReplace
** is set to non-zero before returning SQLITE_OK.
**
** If the conflict handler returns SQLITE_CHANGESET_ABORT, SQLITE_ABORT is
** returned. Or, if the conflict handler returns an invalid value, 
** SQLITE_MISUSE. If the conflict handler returns SQLITE_CHANGESET_OMIT,
** this function returns SQLITE_OK.
*/
static int sessionConflictHandler(

  int eType,                      /* Either CHANGESET_DATA or CONFLICT */
  SessionApplyCtx *p,             /* changeset_apply() context */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int(*xConflict)(void *, int, sqlite3_changeset_iter*),


  void *pCtx,                     /* First argument for conflict handler */
  int *pbReplace                  /* OUT: Set to true if PK row is found */
){

  int res;                        /* Value returned by conflict handler */
  int rc;
  int nCol;
  int op;
  const char *zDummy;

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);

................................................................................
        break;
    }
  }

  return rc;
}

/*
** Attempt to apply the change that the iterator passed as the first argument
** currently points to to the database. If a conflict is encountered, invoke
** the conflict handler callback.
**
** If argument pbRetry is NULL, then ignore any CHANGESET_DATA conflict. If
** one is encountered, update or delete the row with the matching primary key
** instead. Or, if pbRetry is not NULL and a CHANGESET_DATA conflict occurs,
** invoke the conflict handler. If it returns CHANGESET_REPLACE, set *pbRetry
** to true before returning. In this case the caller will invoke this function
** again, this time with pbRetry set to NULL.
**
** If argument pbReplace is NULL and a CHANGESET_CONFLICT conflict is 
** encountered invoke the conflict handler with CHANGESET_CONSTRAINT instead.
** Or, if pbReplace is not NULL, invoke it with CHANGESET_CONFLICT. If such
** an invocation returns SQLITE_CHANGESET_REPLACE, set *pbReplace to true
** before retrying. In this case the caller attempts to remove the conflicting
** row before invoking this function again, this time with pbReplace set 
** to NULL.
**
** If any conflict handler returns SQLITE_CHANGESET_ABORT, this function
** returns SQLITE_ABORT. Otherwise, if no error occurs, SQLITE_OK is 
** returned.
*/
static int sessionApplyOneOp(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  SessionApplyCtx *p,             /* changeset_apply() context */
  int(*xConflict)(void *, int, sqlite3_changeset_iter *),



  void *pCtx,                     /* First argument for the conflict handler */
  int *pbReplace,                 /* OUT: True to remove PK row and retry */
  int *pbRetry                    /* OUT: True to retry. */
){
  const char *zDummy;
  int op;
  int nCol;
  int rc = SQLITE_OK;

  assert( p->pDelete && p->pUpdate && p->pInsert && p->pSelect );
................................................................................
      );
    }
  }

  return rc;
}

/*
** Apply the changeset passed via pChangeset/nChangeset to the main database
** attached to handle "db". Invoke the supplied conflict handler callback
** to resolve any conflicts encountered while applying the change.
*/
int sqlite3changeset_apply(

  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  int nChangeset,                 /* Size of changeset in bytes */
  void *pChangeset,               /* Changeset blob */
  int(*xConflict)(
    void *pCtx,                   /* Copy of fifth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
){
  sqlite3_changeset_iter *pIter;  /* Iterator to skip through changeset */  
  int rc;                         /* Return code */


  const char *zTab = 0;           /* Name of current table */
  int nTab = 0;                   /* Result of strlen(zTab) */
  SessionApplyCtx sApply;         /* changeset_apply() context object */


  memset(&sApply, 0, sizeof(sApply));

  sqlite3changeset_start(&pIter, nChangeset, pChangeset);

  rc = sqlite3_exec(db, "SAVEPOINT changeset_apply", 0, 0, 0);
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int nCol;
    int op;
    int bReplace = 0;
................................................................................
      sqlite3_finalize(sApply.pUpdate); 
      sqlite3_finalize(sApply.pInsert);
      sqlite3_finalize(sApply.pSelect);
      memset(&sApply, 0, sizeof(sApply));
      sApply.db = db;
      sApply.nCol = nCol;

      rc = sessionTableInfo(
          db, "main", zNew, nCol, &zTab, &sApply.azCol, &sApply.abPK);

      if( rc!=SQLITE_OK 
       || (rc = sessionSelectRow(db, zTab, &sApply))
       || (rc = sessionUpdateRow(db, zTab, &sApply))
       || (rc = sessionDeleteRow(db, zTab, &sApply))
       || (rc = sessionInsertRow(db, zTab, &sApply))
      ){
................................................................................
      }
      if( rc==SQLITE_OK ){
        rc = sqlite3_exec(db, "RELEASE replace_op", 0, 0, 0);
      }
    }
  }

  if( rc==SQLITE_OK ){
    rc = sqlite3changeset_finalize(pIter);

  }else{
    sqlite3changeset_finalize(pIter);
  }

  if( rc==SQLITE_OK ){
    rc = sqlite3_exec(db, "RELEASE changeset_apply", 0, 0, 0);
  }else{
    sqlite3_exec(db, "ROLLBACK TO changeset_apply", 0, 0, 0);
    sqlite3_exec(db, "RELEASE changeset_apply", 0, 0, 0);
  }

Changes to ext/session/sqlite3session.h.

65
66
67
68
69
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73
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77
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79
..
96
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107
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113
114

115
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...
149
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153
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160
161
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163
164
165
166
167
168
169
170
171
);

/*
** Delete a session object previously allocated using sqlite3session_create().
*/
void sqlite3session_delete(sqlite3_session *pSession);


/*
** Create an iterator used to iterate through the contents of a changeset.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **ppIter,
  int nChangeset, 
  void *pChangeset
................................................................................
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,      /* Iterator object */
  const char **pzTab,                 /* OUT: Pointer to table name */
  int *pnCol,                         /* OUT: Number of columns in table */
  int *pOp                            /* OUT: SQLITE_INSERT, DELETE or UPDATE */
);

int sqlite3changeset_old(
  sqlite3_changeset_iter *pIter,
  int iVal,

  sqlite3_value **ppValue             /* OUT: Old value (or NULL pointer) */
);

int sqlite3changeset_new(
  sqlite3_changeset_iter *pIter,
  int iVal,

  sqlite3_value **ppValue             /* OUT: New value (or NULL pointer) */
);

/*
** This function is only usable with sqlite3_changeset_iter objects passed
** to the xConflict callback by sqlite3changeset_apply(). It cannot be used
** with iterators created using sqlite3changeset_start().
**
** It is used to access the "conflicting row" information available to the
** conflict handler if the second argument is either SQLITE_CHANGESET_DATA
** or SQLITE_CHANGESET_CONFLICT.
*/
int sqlite3changeset_conflict(
  sqlite3_changeset_iter *pIter,
  int iVal,
  sqlite3_value **ppValue         /* OUT: Value from conflicting row */
);


/*
** Finalize an iterator allocated with sqlite3changeset_start().
**
................................................................................
**
** It is safe to execute SQL statements, including those that write to the
** table that the callback related to, from within the xConflict callback.
** This can be used to further customize the applications conflict
** resolution strategy.
*/
int sqlite3changeset_apply(
  sqlite3 *db,
  int nChangeset,
  void *pChangeset,
  int(*xConflict)(
    void *pCtx,                   /* Copy of fifth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx
);

/* 
** Values passed as the second argument to a conflict-handler.
**
** SQLITE_CHANGESET_DATA:
**   The conflict handler is invoked with CHANGESET_DATA as the second argument







<







 







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65
66
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68
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72
73
74
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..
95
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98
99
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101

102
103

104
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107
108

109
110
111
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113
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116
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147
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152
153
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155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
);

/*
** Delete a session object previously allocated using sqlite3session_create().
*/
void sqlite3session_delete(sqlite3_session *pSession);


/*
** Create an iterator used to iterate through the contents of a changeset.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **ppIter,
  int nChangeset, 
  void *pChangeset
................................................................................
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator object */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp                        /* OUT: SQLITE_INSERT, DELETE or UPDATE */
);

int sqlite3changeset_old(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */

  int iVal,                       /* Column number */
  sqlite3_value **ppValue         /* OUT: Old value (or NULL pointer) */
);

int sqlite3changeset_new(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */

  int iVal,                       /* Column number */
  sqlite3_value **ppValue         /* OUT: New value (or NULL pointer) */
);

/*
** This function is only usable with sqlite3_changeset_iter objects passed
** to the xConflict callback by sqlite3changeset_apply(). It cannot be used
** with iterators created using sqlite3changeset_start().
**
** It is used to access the "conflicting row" information available to the
** conflict handler if the second argument is either SQLITE_CHANGESET_DATA
** or SQLITE_CHANGESET_CONFLICT.
*/
int sqlite3changeset_conflict(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int iVal,                       /* Column number */
  sqlite3_value **ppValue         /* OUT: Value from conflicting row */
);


/*
** Finalize an iterator allocated with sqlite3changeset_start().
**
................................................................................
**
** It is safe to execute SQL statements, including those that write to the
** table that the callback related to, from within the xConflict callback.
** This can be used to further customize the applications conflict
** resolution strategy.
*/
int sqlite3changeset_apply(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  int nChangeset,                 /* Size of changeset in bytes */
  void *pChangeset,               /* Changeset blob */
  int(*xConflict)(
    void *pCtx,                   /* Copy of fifth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
);

/* 
** Values passed as the second argument to a conflict-handler.
**
** SQLITE_CHANGESET_DATA:
**   The conflict handler is invoked with CHANGESET_DATA as the second argument

Changes to test/session1.test.

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409
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412
  {UPDATE t4 CONSTRAINT {i 7 i 8 i 9} {n {} {} {} {} {}}}
}
do_db2_test     3.3.4 { SELECT * FROM t4 } {0 2 3 4 5 7 7 8 9 x 11 12}
do_execsql_test 3.3.5 { SELECT * FROM t4 } {-1 2 3 -1 5 6 {} 8 9 x 11 12}

#-------------------------------------------------------------------------
# This next block of tests verifies that values returned by the conflict
# handler are intepreted correctly. The following cases are tested:
#
#     Test case   Operation   Conflict   Return Code
#                 UPDATE      DATA       OMIT
#                 UPDATE      DATA       REPLACE
#

proc test_reset {} {
  db close
  db2 close
  forcedelete test.db test.db2
  sqlite3 db test.db
................................................................................
    {DELETE d1 DATA {i 2 t two} {i 2 t TWO}}
  }

  set res(REPLACE) {1 one}
  set res(OMIT)    {1 one 2 TWO}
  do_db2_test 5.$tn.3 "SELECT * FROM d1" $res($conflict_return)
}






























catch { db2 close }
finish_test








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295
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  {UPDATE t4 CONSTRAINT {i 7 i 8 i 9} {n {} {} {} {} {}}}
}
do_db2_test     3.3.4 { SELECT * FROM t4 } {0 2 3 4 5 7 7 8 9 x 11 12}
do_execsql_test 3.3.5 { SELECT * FROM t4 } {-1 2 3 -1 5 6 {} 8 9 x 11 12}

#-------------------------------------------------------------------------
# This next block of tests verifies that values returned by the conflict
# handler are intepreted correctly.




#

proc test_reset {} {
  db close
  db2 close
  forcedelete test.db test.db2
  sqlite3 db test.db
................................................................................
    {DELETE d1 DATA {i 2 t two} {i 2 t TWO}}
  }

  set res(REPLACE) {1 one}
  set res(OMIT)    {1 one 2 TWO}
  do_db2_test 5.$tn.3 "SELECT * FROM d1" $res($conflict_return)
}

#-------------------------------------------------------------------------
# Test that two tables can be monitored by a single session object.
#
test_reset
set schema {
  CREATE TABLE t1(a COLLATE nocase PRIMARY KEY, b);
  CREATE TABLE t2(a, b PRIMARY KEY);
}
do_test 6.0 {
  execsql $schema db
  execsql $schema db2
  execsql {
    INSERT INTO t1 VALUES('a', 'b');
    INSERT INTO t2 VALUES('a', 'b');
  } db2
} {}

set conflict_return ""
do_conflict_test 6.1 -tables {t1 t2} -sql {
  INSERT INTO t1 VALUES('1', '2');
  INSERT INTO t1 VALUES('A', 'B');
  INSERT INTO t2 VALUES('A', 'B');
} -conflicts {
  {INSERT t1 CONFLICT {t A t B} {t a t b}}
}

do_db2_test 6.2 "SELECT * FROM t1" {a b 1 2}
do_db2_test 6.3 "SELECT * FROM t2" {a b A B}

catch { db2 close }
finish_test