SQLite

  int rc = sqlite3changeset_start_strm(&pIter, xInput, pIn);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetApply(db, pIter, xFilter, xConflict, pCtx);
  }
  return rc;
}

/*
** sqlite3_changegroup handle.
*/
struct sqlite3_changegroup {
  int rc;                         /* Error code */
  int bPatch;                     /* True to accumulate patchsets */
  SessionTable *pList;            /* List of tables in current patch */
};

/*
** This function is called to merge two changes to the same row together as
** part of an sqlite3changeset_concat() operation. A new change object is
** allocated and a pointer to it stored in *ppNew.
*/
static int sessionChangeMerge(
  SessionTable *pTab,             /* Table structure */

  }

  *ppNew = pNew;
  return SQLITE_OK;
}

/*
** Add all changes in the changeset traversed by the iterator passed as
** the first argument to the changegroup hash tables.
*/
static int sessionChangesetToHash(
  sqlite3_changeset_iter *pIter,   /* Iterator to read from */
  sqlite3_changegroup *pGrp        /* Changegroup object to add changeset to */
){
  u8 *aRec;
  int nRec;
  int rc = SQLITE_OK;
  SessionTable *pTab = 0;


  while( SQLITE_ROW==sessionChangesetNext(pIter, &aRec, &nRec) ){
    const char *zNew;
    int nCol;
    int op;
    int iHash;
    int bIndirect;
    SessionChange *pChange;
    SessionChange *pExist = 0;
    SessionChange **pp;

    if( pGrp->pList==0 ){
      pGrp->bPatch = pIter->bPatchset;
    }else if( pIter->bPatchset!=pGrp->bPatch ){
      rc = SQLITE_ERROR;
      break;
    }

    sqlite3changeset_op(pIter, &zNew, &nCol, &op, &bIndirect);
    if( !pTab || sqlite3_stricmp(zNew, pTab->zName) ){
      /* Search the list for a matching table */
      int nNew = (int)strlen(zNew);
      u8 *abPK;

      sqlite3changeset_pk(pIter, &abPK, 0);
      for(pTab = pGrp->pList; pTab; pTab=pTab->pNext){
        if( 0==sqlite3_strnicmp(pTab->zName, zNew, nNew+1) ) break;
      }
      if( !pTab ){
        pTab = sqlite3_malloc(sizeof(SessionTable) + nCol + nNew+1);
        if( !pTab ){
          rc = SQLITE_NOMEM;
          break;
        }
        memset(pTab, 0, sizeof(SessionTable));
        pTab->pNext = pGrp->pList;
        pTab->nCol = nCol;
        pTab->abPK = (u8*)&pTab[1];
        memcpy(pTab->abPK, abPK, nCol);
        pTab->zName = (char*)&pTab->abPK[nCol];
        memcpy(pTab->zName, zNew, nNew+1);
        pGrp->pList = pTab;
      }else if( pTab->nCol!=nCol || memcmp(pTab->abPK, abPK, nCol) ){
        rc = SQLITE_SCHEMA;
        break;
      }
    }

    if( sessionGrowHash(pIter->bPatchset, pTab) ){

      pTab->nEntry++;
    }
  }

  if( rc==SQLITE_OK ) rc = pIter->rc;
  return rc;
}

/*
** Serialize a changeset (or patchset) based on all changesets (or patchsets)

** added to the changegroup object passed as the first argument.
**
** If xOutput is not NULL, then the changeset/patchset is returned to the

** user via one or more calls to xOutput, as with the other streaming
** interfaces. 
**
** Or, if xOutput is NULL, then (*ppOut) is populated with a pointer to a
** buffer containing the output changeset before this function returns. In
** this case (*pnOut) is set to the size of the output buffer in bytes. It
** is the responsibility of the caller to free the output buffer using
** sqlite3_free() when it is no longer required.
**
** If successful, SQLITE_OK is returned. Or, if an error occurs, an SQLite
** error code. If an error occurs and xOutput is NULL, (*ppOut) and (*pnOut)
** are both set to 0 before returning.
*/
static int sessionChangegroupOutput(
  sqlite3_changegroup *pGrp,

  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut,
  int *pnOut,
  void **ppOut
){

  int rc = SQLITE_OK;


  SessionBuffer buf = {0, 0, 0};
  SessionTable *pTab;
  assert( xOutput==0 || (ppOut==0 && pnOut==0) );













  /* Create the serialized output changeset based on the contents of the
  ** hash tables attached to the SessionTable objects in list p->pList. 
  */
  for(pTab=pGrp->pList; rc==SQLITE_OK && pTab; pTab=pTab->pNext){
    int i;
    if( pTab->nEntry==0 ) continue;

    sessionAppendTableHdr(&buf, pGrp->bPatch, pTab, &rc);
    for(i=0; i<pTab->nChange; i++){
      SessionChange *p;
      for(p=pTab->apChange[i]; p; p=p->pNext){
        sessionAppendByte(&buf, p->op, &rc);
        sessionAppendByte(&buf, p->bIndirect, &rc);
        sessionAppendBlob(&buf, p->aRecord, p->nRecord, &rc);
      }

      *ppOut = buf.aBuf;
      *pnOut = buf.nBuf;
      buf.aBuf = 0;
    }
  }
  sqlite3_free(buf.aBuf);

  return rc;
}

/*
** Allocate a new, empty, sqlite3_changegroup.
*/
int sqlite3changegroup_new(sqlite3_changegroup **pp){
  int rc = SQLITE_OK;             /* Return code */
  sqlite3_changegroup *p;         /* New object */
  p = (sqlite3_changegroup*)sqlite3_malloc(sizeof(sqlite3_changegroup));
  if( p==0 ){
    rc = SQLITE_NOMEM;
  }else{
    memset(p, 0, sizeof(sqlite3_changegroup));
  }
  *pp = p;
  return rc;
}

/*
** Add the changeset currently stored in buffer pData, size nData bytes,
** to changeset-group p.
*/
int sqlite3changegroup_add(sqlite3_changegroup *pGrp, int nData, void *pData){
  sqlite3_changeset_iter *pIter;  /* Iterator opened on pData/nData */
  int rc;                         /* Return code */

  rc = sqlite3changeset_start(&pIter, nData, pData);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetToHash(pIter, pGrp);
  }
  sqlite3changeset_finalize(pIter);
  return rc;
}

/*
** Obtain a buffer containing a changeset representing the concatenation
** of all changesets added to the group so far.
*/
int sqlite3changegroup_output(
    sqlite3_changegroup *pGrp,
    int *pnData,
    void **ppData
){
  return sessionChangegroupOutput(pGrp, 0, 0, pnData, ppData);
}

/*
** Streaming versions of changegroup_add().
*/
int sqlite3changegroup_add_strm(
  sqlite3_changegroup *pGrp,
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn
){
  sqlite3_changeset_iter *pIter;  /* Iterator opened on pData/nData */
  int rc;                         /* Return code */

  rc = sqlite3changeset_start_strm(&pIter, xInput, pIn);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetToHash(pIter, pGrp);
  }
  sqlite3changeset_finalize(pIter);
  return rc;
}

/*
** Streaming versions of changegroup_output().
*/
int sqlite3changegroup_output_strm(
  sqlite3_changegroup *pGrp,
  int (*xOutput)(void *pOut, const void *pData, int nData), 
  void *pOut
){
  return sessionChangegroupOutput(pGrp, xOutput, pOut, 0, 0);
}

/*
** Delete a changegroup object.
*/
void sqlite3changegroup_delete(sqlite3_changegroup *pGrp){
  if( pGrp ){
    sessionDeleteTable(pGrp->pList);
    sqlite3_free(pGrp);
  }
}

/* 
** Combine two changesets together.
*/
int sqlite3changeset_concat(
  int nLeft,                      /* Number of bytes in lhs input */
  void *pLeft,                    /* Lhs input changeset */
  int nRight                      /* Number of bytes in rhs input */,
  void *pRight,                   /* Rhs input changeset */
  int *pnOut,                     /* OUT: Number of bytes in output changeset */
  void **ppOut                    /* OUT: changeset (left <concat> right) */
){
  sqlite3_changegroup *pGrp;

  int rc;



  rc = sqlite3changegroup_new(&pGrp);
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add(pGrp, nLeft, pLeft);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add(pGrp, nRight, pRight);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_output(pGrp, pnOut, ppOut);
  }
  sqlite3changegroup_delete(pGrp);

  return rc;
}

/*
** Streaming version of sqlite3changeset_concat().
*/
int sqlite3changeset_concat_strm(
  int (*xInputA)(void *pIn, void *pData, int *pnData),
  void *pInA,
  int (*xInputB)(void *pIn, void *pData, int *pnData),
  void *pInB,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
){
  sqlite3_changegroup *pGrp;

  int rc;

  rc = sqlite3changegroup_new(&pGrp);
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add_strm(pGrp, xInputA, pInA);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add_strm(pGrp, xInputB, pInB);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_output_strm(pGrp, xOutput, pOut);
  }
  sqlite3changegroup_delete(pGrp);

  return rc;
}

#endif /* SQLITE_ENABLE_SESSION && SQLITE_ENABLE_PREUPDATE_HOOK */

/*
** CAPI3REF: Concatenate Two Changeset Objects
**
** This function is used to concatenate two changesets, A and B, into a 
** single changeset. The result is a changeset equivalent to applying
** changeset A followed by changeset B. 
**





** This function combines the two input changesets using an 

** sqlite3_changegroup object. Calling it produces similar results as the
** following code fragment:
**







**   sqlite3_changegroup *pGrp;
**   rc = sqlite3_changegroup_new(&pGrp);



**   if( rc==SQLITE_OK ) rc = sqlite3changegroup_add(pGrp, nA, pA);

**   if( rc==SQLITE_OK ) rc = sqlite3changegroup_add(pGrp, nB, pB);


**   if( rc==SQLITE_OK ){



**     rc = sqlite3changegroup_output(pGrp, pnOut, ppOut);







**   }else{



**     *ppOut = 0;



**     *pnOut = 0;

**   }








**


** Refer to the sqlite3_changegroup documentation below for details.



*/
int sqlite3changeset_concat(
  int nA,                         /* Number of bytes in buffer pA */
  void *pA,                       /* Pointer to buffer containing changeset A */
  int nB,                         /* Number of bytes in buffer pB */
  void *pB,                       /* Pointer to buffer containing changeset B */
  int *pnOut,                     /* OUT: Number of bytes in output changeset */
  void **ppOut                    /* OUT: Buffer containing output changeset */
);


/*
** Changegroup handle.
*/
typedef struct sqlite3_changegroup sqlite3_changegroup;

/*
** CAPI3REF: Combine two or more changesets into a single changeset.
**
** An sqlite3_changegroup object is used to combine two or more changesets
** (or patchsets) into a single changeset (or patchset). A single changegroup
** object may combine changesets or patchsets, but not both. The output is
** always in the same format as the input.
**
** If successful, this function returns SQLITE_OK and populates (*pp) with
** a pointer to a new sqlite3_changegroup object before returning. The caller
** should eventually free the returned object using a call to 
** sqlite3changegroup_delete(). If an error occurs, an SQLite error code
** (i.e. SQLITE_NOMEM) is returned and *pp is set to NULL.
**
** The usual usage pattern for an sqlite3_changegroup object is as follows:
**
** <ul>
**   <li> It is created using a call to sqlite3changegroup_new().
**
**   <li> Zero or more changesets (or patchsets) are added to the object
**        by calling sqlite3changegroup_add().
**
**   <li> The result of combining all input changesets together is obtained 
**        by the application via a call to sqlite3changegroup_output().
**
**   <li> The object is deleted using a call to sqlite3changegroup_delete().
** </ul>
**
** Any number of calls to add() and output() may be made between the calls to
** new() and delete(), and in any order.
**
** As well as the regular sqlite3changegroup_add() and 
** sqlite3changegroup_output() functions, also available are the streaming
** versions sqlite3changegroup_add_strm() and sqlite3changegroup_output_strm().
*/
int sqlite3changegroup_new(sqlite3_changegroup **pp);

/*
** Add all changes within the changeset (or patchset) in buffer pData (size
** nData bytes) to the changegroup. 
**
** If the buffer contains a patchset, then all prior calls to this function
** on the same changegroup object must also have specified patchsets. Or, if
** the buffer contains a changeset, so must have the earlier calls to this
** function. Otherwise, SQLITE_ERROR is returned and no changes are added
** to the changegroup.
**
** Rows within the changeset and changegroup are identified by the values in
** their PRIMARY KEY columns. A change in the changeset is considered to
** apply to the same row as a change already present in the changegroup if
** the two rows have the same primary key.
**
** Changes to rows that that do not already appear in the changegroup are
** simply copied into it. Or, if both the new changeset and the changegroup
** contain changes that apply to a single row, the final contents of the
** changegroup depends on the type of each change, as follows:
**
** <table border=1 style="margin-left:8ex;margin-right:8ex">
**   <tr><th style="white-space:pre">Existing Change  </th>
**       <th style="white-space:pre">New Change       </th>
**       <th>Output Change
**   <tr><td>INSERT <td>INSERT <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
**   <tr><td>INSERT <td>UPDATE <td>
**       The INSERT change remains in the changegroup. The values in the 
**       INSERT change are modified as if the row was inserted by the
**       existing change and then updated according to the new change.
**   <tr><td>INSERT <td>DELETE <td>
**       The existing INSERT is removed from the changegroup. The DELETE is
**       not added.
**   <tr><td>UPDATE <td>INSERT <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
**   <tr><td>UPDATE <td>UPDATE <td>
**       The existing UPDATE remains within the changegroup. It is amended 
**       so that the accompanying values are as if the row was updated once 
**       by the existing change and then again by the new change.
**   <tr><td>UPDATE <td>DELETE <td>
**       The existing UPDATE is replaced by the new DELETE within the
**       changegroup.
**   <tr><td>DELETE <td>INSERT <td>
**       If one or more of the column values in the row inserted by the
**       new change differ from those in the row deleted by the existing 
**       change, the existing DELETE is replaced by an UPDATE within the
**       changegroup. Otherwise, if the inserted row is exactly the same 
**       as the deleted row, the existing DELETE is simply discarded.
**   <tr><td>DELETE <td>UPDATE <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
**   <tr><td>DELETE <td>DELETE <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
** </table>
**
** If the new changeset contains changes to a table that is already present
** in the changegroup, then the number of columns and the position of the
** primary key columns for the table must be consistent. If this is not the
** case, this function fails with SQLITE_SCHEMA. If the input changeset
** appears to be corrupt and the corruption is detected, SQLITE_CORRUPT is
** returned. Or, if an out-of-memory condition occurs during processing, this
** function returns SQLITE_NOMEM. In all cases, if an error occurs the
** final contents of the changegroup is undefined.
**
** If no error occurs, SQLITE_OK is returned.
*/
int sqlite3changegroup_add(sqlite3_changegroup*, int nData, void *pData);

/*
** Obtain a buffer containing a changeset (or patchset) representing the
** current contents of the changegroup. If the inputs to the changegroup
** were themselves changesets, the output is a changeset. Or, if the
** inputs were patchsets, the output is also a patchset.
**
** If an error occurs, an SQLite error code is returned and the output
** variables (*pnData) and (*ppData) are set to 0. Otherwise, SQLITE_OK
** is returned and the output variables are set to the size of and a 
** pointer to the output buffer, respectively. In this case it is the
** responsibility of the caller to eventually free the buffer using a
** call to sqlite3_free().
*/
int sqlite3changegroup_output(
  sqlite3_changegroup*,
  int *pnData,                    /* OUT: Size of output buffer in bytes */
  void **ppData                   /* OUT: Pointer to output buffer */
);

/*
** Delete a changegroup object.
*/
void sqlite3changegroup_delete(sqlite3_changegroup*);

/*
** CAPI3REF: Apply A Changeset To A Database
**
** Apply a changeset to a database. This function attempts to update the
** "main" database attached to handle db with the changes found in the
** changeset passed via the second and third arguments.
**

  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3session_patchset_strm(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3changegroup_add_strm(sqlite3_changegroup*, 
    int (*xInput)(void *pIn, void *pData, int *pnData),
    void *pIn
);
int sqlite3changegroup_output_strm(sqlite3_changegroup*,
    int (*xOutput)(void *pOut, const void *pData, int nData), 
    void *pOut
);


/*
** Make sure we can call this stuff from C++.
*/
#ifdef __cplusplus
}
#endif

#endif  /* SQLITE_ENABLE_SESSION && SQLITE_ENABLE_PREUPDATE_HOOK */