SQLite

}

proc rbudiff_cksum {db1} {
  set txt ""

  sqlite3 dbtmp $db1
  foreach tbl [dbtmp eval {SELECT name FROM sqlite_master WHERE type='table'}] {
    set cols [list]
    dbtmp eval "PRAGMA table_info = $tbl" { lappend cols "quote( $name )" }
    append txt [dbtmp eval \
      "SELECT [join $cols {||'.'||}] FROM $tbl ORDER BY 1"
    ]
  }
  dbtmp close

  md5 $txt
}

    INSERT INTO t1 VALUES('u', 'v', 'w');
    INSERT INTO t1 VALUES('x', 'y', 'z');
  } {
    DELETE FROM t1 WHERE a='u';
    INSERT INTO t1 VALUES('a', 'b', 'c');
  }

  3 {
    CREATE TABLE t1(i INTEGER PRIMARY KEY, x);
    INSERT INTO t1 VALUES(1,
      X'0000000000000000111111111111111122222222222222223333333333333333'
    );
    CREATE TABLE t2(y INTEGER PRIMARY KEY, x);
    INSERT INTO t2 VALUES(1,
        X'0000000000000000111111111111111122222222222222223333333333333333'
    );
} {
    DELETE FROM t1;
    INSERT INTO t1 VALUES(1,
      X'0000000000000000111111111111111122222555555552223333333333333333'
    );
    DELETE FROM t2;
    INSERT INTO t2 VALUES(1,
        X'0000000000000000111111111111111122222222222222223333333FFF333333'
    );
  }

} {
  catch { db close }

  forcedelete test.db test.db2
  sqlite3 db test.db
  db eval "$init"
  sqlite3 db test.db2
  db eval "$init ; $mod"

  char *zDel;                     /* Delete this when closing file */

  const char *zWal;               /* Wal filename for this main db file */
  rbu_file *pWalFd;               /* Wal file descriptor for this main db */
  rbu_file *pMainNext;            /* Next MAIN_DB file */
};


/*************************************************************************
** The following three functions, found below:
**
**   rbuDeltaGetInt()
**   rbuDeltaChecksum()
**   rbuDeltaApply()
**
** are lifted from the fossil source code (http://fossil-scm.org). They
** are used to implement the scalar SQL function rbu_fossil_delta().
*/

/*
** Read bytes from *pz and convert them into a positive integer.  When
** finished, leave *pz pointing to the first character past the end of
** the integer.  The *pLen parameter holds the length of the string
** in *pz and is decremented once for each character in the integer.
*/
static unsigned int rbuDeltaGetInt(const char **pz, int *pLen){
  static const signed char zValue[] = {
    -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
     0,  1,  2,  3,  4,  5,  6,  7,    8,  9, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, 16,   17, 18, 19, 20, 21, 22, 23, 24,
    25, 26, 27, 28, 29, 30, 31, 32,   33, 34, 35, -1, -1, -1, -1, 36,
    -1, 37, 38, 39, 40, 41, 42, 43,   44, 45, 46, 47, 48, 49, 50, 51,
    52, 53, 54, 55, 56, 57, 58, 59,   60, 61, 62, -1, -1, -1, 63, -1,
  };
  unsigned int v = 0;
  int c;
  unsigned char *z = (unsigned char*)*pz;
  unsigned char *zStart = z;
  while( (c = zValue[0x7f&*(z++)])>=0 ){
     v = (v<<6) + c;
  }
  z--;
  *pLen -= z - zStart;
  *pz = (char*)z;
  return v;
}

/*
** Compute a 32-bit checksum on the N-byte buffer.  Return the result.
*/
static unsigned int rbuDeltaChecksum(const char *zIn, size_t N){
  const unsigned char *z = (const unsigned char *)zIn;
  unsigned sum0 = 0;
  unsigned sum1 = 0;
  unsigned sum2 = 0;
  unsigned sum3 = 0;
  while(N >= 16){
    sum0 += ((unsigned)z[0] + z[4] + z[8] + z[12]);
    sum1 += ((unsigned)z[1] + z[5] + z[9] + z[13]);
    sum2 += ((unsigned)z[2] + z[6] + z[10]+ z[14]);
    sum3 += ((unsigned)z[3] + z[7] + z[11]+ z[15]);
    z += 16;
    N -= 16;
  }
  while(N >= 4){
    sum0 += z[0];
    sum1 += z[1];
    sum2 += z[2];
    sum3 += z[3];
    z += 4;
    N -= 4;
  }
  sum3 += (sum2 << 8) + (sum1 << 16) + (sum0 << 24);
  switch(N){
    case 3:   sum3 += (z[2] << 8);
    case 2:   sum3 += (z[1] << 16);
    case 1:   sum3 += (z[0] << 24);
    default:  ;
  }
  return sum3;
}

/*
** Apply a delta.
**
** The output buffer should be big enough to hold the whole output
** file and a NUL terminator at the end.  The delta_output_size()
** routine will determine this size for you.
**
** The delta string should be null-terminated.  But the delta string
** may contain embedded NUL characters (if the input and output are
** binary files) so we also have to pass in the length of the delta in
** the lenDelta parameter.
**
** This function returns the size of the output file in bytes (excluding
** the final NUL terminator character).  Except, if the delta string is
** malformed or intended for use with a source file other than zSrc,
** then this routine returns -1.
**
** Refer to the delta_create() documentation above for a description
** of the delta file format.
*/
static int rbuDeltaApply(
  const char *zSrc,      /* The source or pattern file */
  int lenSrc,            /* Length of the source file */
  const char *zDelta,    /* Delta to apply to the pattern */
  int lenDelta,          /* Length of the delta */
  char *zOut             /* Write the output into this preallocated buffer */
){
  unsigned int limit;
  unsigned int total = 0;
#ifndef FOSSIL_OMIT_DELTA_CKSUM_TEST
  char *zOrigOut = zOut;
#endif

  limit = rbuDeltaGetInt(&zDelta, &lenDelta);
  if( *zDelta!='\n' ){
    /* ERROR: size integer not terminated by "\n" */
    return -1;
  }
  zDelta++; lenDelta--;
  while( *zDelta && lenDelta>0 ){
    unsigned int cnt, ofst;
    cnt = rbuDeltaGetInt(&zDelta, &lenDelta);
    switch( zDelta[0] ){
      case '@': {
        zDelta++; lenDelta--;
        ofst = rbuDeltaGetInt(&zDelta, &lenDelta);
        if( lenDelta>0 && zDelta[0]!=',' ){
          /* ERROR: copy command not terminated by ',' */
          return -1;
        }
        zDelta++; lenDelta--;
        total += cnt;
        if( total>limit ){
          /* ERROR: copy exceeds output file size */
          return -1;
        }
        if( ofst+cnt > lenSrc ){
          /* ERROR: copy extends past end of input */
          return -1;
        }
        memcpy(zOut, &zSrc[ofst], cnt);
        zOut += cnt;
        break;
      }
      case ':': {
        zDelta++; lenDelta--;
        total += cnt;
        if( total>limit ){
          /* ERROR:  insert command gives an output larger than predicted */
          return -1;
        }
        if( cnt>lenDelta ){
          /* ERROR: insert count exceeds size of delta */
          return -1;
        }
        memcpy(zOut, zDelta, cnt);
        zOut += cnt;
        zDelta += cnt;
        lenDelta -= cnt;
        break;
      }
      case ';': {
        zDelta++; lenDelta--;
        zOut[0] = 0;
#ifndef FOSSIL_OMIT_DELTA_CKSUM_TEST
        if( cnt!=rbuDeltaChecksum(zOrigOut, total) ){
          /* ERROR:  bad checksum */
          return -1;
        }
#endif
        if( total!=limit ){
          /* ERROR: generated size does not match predicted size */
          return -1;
        }
        return total;
      }
      default: {
        /* ERROR: unknown delta operator */
        return -1;
      }
    }
  }
  /* ERROR: unterminated delta */
  return -1;
}

static int rbuDeltaOutputSize(const char *zDelta, int lenDelta){
  int size;
  size = rbuDeltaGetInt(&zDelta, &lenDelta);
  if( *zDelta!='\n' ){
    /* ERROR: size integer not terminated by "\n" */
    return -1;
  }
  return size;
}

/*
** End of code taken from fossil.
*************************************************************************/

/*
** Implementation of SQL scalar function rbu_fossil_delta().
**
** This function applies a fossil delta patch to a blob. Exactly two
** arguments must be passed to this function. The first is the blob to
** patch and the second the patch to apply. If no error occurs, this
** function returns the patched blob.
*/
static void rbuFossilDeltaFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  const char *aDelta;
  int nDelta;
  const char *aOrig;
  int nOrig;

  int nOut;
  int nOut2;
  char *aOut;

  assert( argc==2 );

  nOrig = sqlite3_value_bytes(argv[0]);
  aOrig = (const char*)sqlite3_value_blob(argv[0]);
  nDelta = sqlite3_value_bytes(argv[1]);
  aDelta = (const char*)sqlite3_value_blob(argv[1]);

  /* Figure out the size of the output */
  nOut = rbuDeltaOutputSize(aDelta, nDelta);
  if( nOut<0 ){
    sqlite3_result_error(context, "corrupt fossil delta", -1);
    return;
  }

  aOut = sqlite3_malloc(nOut+1);
  if( aOut==0 ){
    sqlite3_result_error_nomem(context);
  }else{
    int nOut2 = rbuDeltaApply(aOrig, nOrig, aDelta, nDelta, aOut);
    if( nOut2!=nOut ){
      sqlite3_result_error(context, "corrupt fossil delta", -1);
    }else{
      sqlite3_result_blob(context, aOut, nOut, sqlite3_free);
    }
  }
}


/*
** Prepare the SQL statement in buffer zSql against database handle db.
** If successful, set *ppStmt to point to the new statement and return
** SQLITE_OK. 
**
** Otherwise, if an error does occur, set *ppStmt to NULL and return

        char c = zMask[pIter->aiSrcOrder[i]];
        if( c=='x' ){
          zList = rbuMPrintf(p, "%z%s\"%w\"=?%d", 
              zList, zSep, pIter->azTblCol[i], i+1
          );
          zSep = ", ";
        }
        else if( c=='d' ){
          zList = rbuMPrintf(p, "%z%s\"%w\"=rbu_delta(\"%w\", ?%d)", 
              zList, zSep, pIter->azTblCol[i], pIter->azTblCol[i], i+1
          );
          zSep = ", ";
        }
        else if( c=='f' ){
          zList = rbuMPrintf(p, "%z%s\"%w\"=rbu_fossil_delta(\"%w\", ?%d)", 
              zList, zSep, pIter->azTblCol[i], pIter->azTblCol[i], i+1
          );
          zSep = ", ";
        }
      }
    }
  }
  return zList;
}

  }

  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_create_function(p->dbMain, 
        "rbu_tmp_insert", -1, SQLITE_UTF8, (void*)p, rbuTmpInsertFunc, 0, 0
    );
  }

  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_create_function(p->dbMain, 
        "rbu_fossil_delta", 2, SQLITE_UTF8, 0, rbuFossilDeltaFunc, 0, 0
    );
  }

  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_create_function(p->dbRbu, 
        "rbu_target_name", 1, SQLITE_UTF8, (void*)p, rbuTargetNameFunc, 0, 0
    );
  }

      sqlite3_stmt *pUpdate = 0;
      assert( eType==RBU_UPDATE );
      rbuGetUpdateStmt(p, pIter, zMask, &pUpdate);
      if( pUpdate ){
        for(i=0; p->rc==SQLITE_OK && i<pIter->nCol; i++){
          char c = zMask[pIter->aiSrcOrder[i]];
          pVal = sqlite3_column_value(pIter->pSelect, i);
          if( pIter->abTblPk[i] || c!='.' ){
            p->rc = sqlite3_bind_value(pUpdate, i+1, pVal);
          }
        }
        if( p->rc==SQLITE_OK 
         && (pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE) 
        ){
          /* Bind the rbu_rowid value to column _rowid_ */

** For example, this row:
**
**   INSERT INTO data_t1(a, b, c, rbu_control) VALUES(4, NULL, 'usa', '..d');
**
** is similar to an UPDATE statement such as: 
**
**   UPDATE t1 SET c = rbu_delta(c, 'usa') WHERE a = 4;
**
** Finally, if an 'f' character appears in place of a 'd' or 's' in an 
** ota_control string, the contents of the data_xxx table column is assumed
** to be a "fossil delta" - a patch to be applied to a blob value in the
** format used by the fossil source-code management system. In this case
** the existing value within the target database table must be of type BLOB. 
** It is replaced by the result of applying the specified fossil delta to
** itself.
**
** If the target database table is a virtual table or a table with no PRIMARY
** KEY, the rbu_control value should not include a character corresponding 
** to the rbu_rowid value. For example, this:
**
**   INSERT INTO data_ft1(a, b, rbu_rowid, rbu_control) 
**       VALUES(NULL, 'usa', 12, '.x');

** run the utility.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <ctype.h>
#include <string.h>
#include <assert.h>
#include "sqlite3.h"

/*
** All global variables are gathered into the "g" singleton.
*/
struct GlobalVars {
  const char *zArgv0;       /* Name of program */

    }
  }else{
    runtimeError("table %s missing from one or both databases", safeId(zTab));
  }
  sqlite3_finalize(pStmt);
}

/**************************************************************************
** The following code is copied from fossil. It is used to generate the
** fossil delta blobs sometimes used in RBU update records.
*/

typedef unsigned short u16;
typedef unsigned int u32;
typedef unsigned char u8;

/*
** The width of a hash window in bytes.  The algorithm only works if this
** is a power of 2.
*/
#define NHASH 16

/*
** The current state of the rolling hash.
**
** z[] holds the values that have been hashed.  z[] is a circular buffer.
** z[i] is the first entry and z[(i+NHASH-1)%NHASH] is the last entry of
** the window.
**
** Hash.a is the sum of all elements of hash.z[].  Hash.b is a weighted
** sum.  Hash.b is z[i]*NHASH + z[i+1]*(NHASH-1) + ... + z[i+NHASH-1]*1.
** (Each index for z[] should be module NHASH, of course.  The %NHASH operator
** is omitted in the prior expression for brevity.)
*/
typedef struct hash hash;
struct hash {
  u16 a, b;         /* Hash values */
  u16 i;            /* Start of the hash window */
  char z[NHASH];    /* The values that have been hashed */
};

/*
** Initialize the rolling hash using the first NHASH characters of z[]
*/
static void hash_init(hash *pHash, const char *z){
  u16 a, b, i;
  a = b = 0;
  for(i=0; i<NHASH; i++){
    a += z[i];
    b += (NHASH-i)*z[i];
    pHash->z[i] = z[i];
  }
  pHash->a = a & 0xffff;
  pHash->b = b & 0xffff;
  pHash->i = 0;
}

/*
** Advance the rolling hash by a single character "c"
*/
static void hash_next(hash *pHash, int c){
  u16 old = pHash->z[pHash->i];
  pHash->z[pHash->i] = c;
  pHash->i = (pHash->i+1)&(NHASH-1);
  pHash->a = pHash->a - old + c;
  pHash->b = pHash->b - NHASH*old + pHash->a;
}

/*
** Return a 32-bit hash value
*/
static u32 hash_32bit(hash *pHash){
  return (pHash->a & 0xffff) | (((u32)(pHash->b & 0xffff))<<16);
}

/*
** Write an base-64 integer into the given buffer.
*/
static void putInt(unsigned int v, char **pz){
  static const char zDigits[] =
    "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz~";
  /*  123456789 123456789 123456789 123456789 123456789 123456789 123 */
  int i, j;
  char zBuf[20];
  if( v==0 ){
    *(*pz)++ = '0';
    return;
  }
  for(i=0; v>0; i++, v>>=6){
    zBuf[i] = zDigits[v&0x3f];
  }
  for(j=i-1; j>=0; j--){
    *(*pz)++ = zBuf[j];
  }
}

/*
** Read bytes from *pz and convert them into a positive integer.  When
** finished, leave *pz pointing to the first character past the end of
** the integer.  The *pLen parameter holds the length of the string
** in *pz and is decremented once for each character in the integer.
*/
static unsigned int getInt(const char **pz, int *pLen){
  static const signed char zValue[] = {
    -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
     0,  1,  2,  3,  4,  5,  6,  7,    8,  9, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, 16,   17, 18, 19, 20, 21, 22, 23, 24,
    25, 26, 27, 28, 29, 30, 31, 32,   33, 34, 35, -1, -1, -1, -1, 36,
    -1, 37, 38, 39, 40, 41, 42, 43,   44, 45, 46, 47, 48, 49, 50, 51,
    52, 53, 54, 55, 56, 57, 58, 59,   60, 61, 62, -1, -1, -1, 63, -1,
  };
  unsigned int v = 0;
  int c;
  unsigned char *z = (unsigned char*)*pz;
  unsigned char *zStart = z;
  while( (c = zValue[0x7f&*(z++)])>=0 ){
     v = (v<<6) + c;
  }
  z--;
  *pLen -= z - zStart;
  *pz = (char*)z;
  return v;
}

/*
** Return the number digits in the base-64 representation of a positive integer
*/
static int digit_count(int v){
  unsigned int i, x;
  for(i=1, x=64; v>=x; i++, x <<= 6){}
  return i;
}

/*
** Compute a 32-bit checksum on the N-byte buffer.  Return the result.
*/
static unsigned int checksum(const char *zIn, size_t N){
  const unsigned char *z = (const unsigned char *)zIn;
  unsigned sum0 = 0;
  unsigned sum1 = 0;
  unsigned sum2 = 0;
  unsigned sum3 = 0;
  while(N >= 16){
    sum0 += ((unsigned)z[0] + z[4] + z[8] + z[12]);
    sum1 += ((unsigned)z[1] + z[5] + z[9] + z[13]);
    sum2 += ((unsigned)z[2] + z[6] + z[10]+ z[14]);
    sum3 += ((unsigned)z[3] + z[7] + z[11]+ z[15]);
    z += 16;
    N -= 16;
  }
  while(N >= 4){
    sum0 += z[0];
    sum1 += z[1];
    sum2 += z[2];
    sum3 += z[3];
    z += 4;
    N -= 4;
  }
  sum3 += (sum2 << 8) + (sum1 << 16) + (sum0 << 24);
  switch(N){
    case 3:   sum3 += (z[2] << 8);
    case 2:   sum3 += (z[1] << 16);
    case 1:   sum3 += (z[0] << 24);
    default:  ;
  }
  return sum3;
}

/*
** Create a new delta.
**
** The delta is written into a preallocated buffer, zDelta, which
** should be at least 60 bytes longer than the target file, zOut.
** The delta string will be NUL-terminated, but it might also contain
** embedded NUL characters if either the zSrc or zOut files are
** binary.  This function returns the length of the delta string
** in bytes, excluding the final NUL terminator character.
**
** Output Format:
**
** The delta begins with a base64 number followed by a newline.  This
** number is the number of bytes in the TARGET file.  Thus, given a
** delta file z, a program can compute the size of the output file
** simply by reading the first line and decoding the base-64 number
** found there.  The delta_output_size() routine does exactly this.
**
** After the initial size number, the delta consists of a series of
** literal text segments and commands to copy from the SOURCE file.
** A copy command looks like this:
**
**     NNN@MMM,
**
** where NNN is the number of bytes to be copied and MMM is the offset
** into the source file of the first byte (both base-64).   If NNN is 0
** it means copy the rest of the input file.  Literal text is like this:
**
**     NNN:TTTTT
**
** where NNN is the number of bytes of text (base-64) and TTTTT is the text.
**
** The last term is of the form
**
**     NNN;
**
** In this case, NNN is a 32-bit bigendian checksum of the output file
** that can be used to verify that the delta applied correctly.  All
** numbers are in base-64.
**
** Pure text files generate a pure text delta.  Binary files generate a
** delta that may contain some binary data.
**
** Algorithm:
**
** The encoder first builds a hash table to help it find matching
** patterns in the source file.  16-byte chunks of the source file
** sampled at evenly spaced intervals are used to populate the hash
** table.
**
** Next we begin scanning the target file using a sliding 16-byte
** window.  The hash of the 16-byte window in the target is used to
** search for a matching section in the source file.  When a match
** is found, a copy command is added to the delta.  An effort is
** made to extend the matching section to regions that come before
** and after the 16-byte hash window.  A copy command is only issued
** if the result would use less space that just quoting the text
** literally. Literal text is added to the delta for sections that
** do not match or which can not be encoded efficiently using copy
** commands.
*/
static int rbuDeltaCreate(
  const char *zSrc,      /* The source or pattern file */
  unsigned int lenSrc,   /* Length of the source file */
  const char *zOut,      /* The target file */
  unsigned int lenOut,   /* Length of the target file */
  char *zDelta           /* Write the delta into this buffer */
){
  int i, base;
  char *zOrigDelta = zDelta;
  hash h;
  int nHash;                 /* Number of hash table entries */
  int *landmark;             /* Primary hash table */
  int *collide;              /* Collision chain */
  int lastRead = -1;         /* Last byte of zSrc read by a COPY command */

  /* Add the target file size to the beginning of the delta
  */
  putInt(lenOut, &zDelta);
  *(zDelta++) = '\n';

  /* If the source file is very small, it means that we have no
  ** chance of ever doing a copy command.  Just output a single
  ** literal segment for the entire target and exit.
  */
  if( lenSrc<=NHASH ){
    putInt(lenOut, &zDelta);
    *(zDelta++) = ':';
    memcpy(zDelta, zOut, lenOut);
    zDelta += lenOut;
    putInt(checksum(zOut, lenOut), &zDelta);
    *(zDelta++) = ';';
    return zDelta - zOrigDelta;
  }

  /* Compute the hash table used to locate matching sections in the
  ** source file.
  */
  nHash = lenSrc/NHASH;
  collide = sqlite3_malloc( nHash*2*sizeof(int) );
  landmark = &collide[nHash];
  memset(landmark, -1, nHash*sizeof(int));
  memset(collide, -1, nHash*sizeof(int));
  for(i=0; i<lenSrc-NHASH; i+=NHASH){
    int hv;
    hash_init(&h, &zSrc[i]);
    hv = hash_32bit(&h) % nHash;
    collide[i/NHASH] = landmark[hv];
    landmark[hv] = i/NHASH;
  }

  /* Begin scanning the target file and generating copy commands and
  ** literal sections of the delta.
  */
  base = 0;    /* We have already generated everything before zOut[base] */
  while( base+NHASH<lenOut ){
    int iSrc, iBlock;
    unsigned int bestCnt, bestOfst=0, bestLitsz=0;
    hash_init(&h, &zOut[base]);
    i = 0;     /* Trying to match a landmark against zOut[base+i] */
    bestCnt = 0;
    while( 1 ){
      int hv;
      int limit = 250;

      hv = hash_32bit(&h) % nHash;
      iBlock = landmark[hv];
      while( iBlock>=0 && (limit--)>0 ){
        /*
        ** The hash window has identified a potential match against
        ** landmark block iBlock.  But we need to investigate further.
        **
        ** Look for a region in zOut that matches zSrc. Anchor the search
        ** at zSrc[iSrc] and zOut[base+i].  Do not include anything prior to
        ** zOut[base] or after zOut[outLen] nor anything after zSrc[srcLen].
        **
        ** Set cnt equal to the length of the match and set ofst so that
        ** zSrc[ofst] is the first element of the match.  litsz is the number
        ** of characters between zOut[base] and the beginning of the match.
        ** sz will be the overhead (in bytes) needed to encode the copy
        ** command.  Only generate copy command if the overhead of the
        ** copy command is less than the amount of literal text to be copied.
        */
        int cnt, ofst, litsz;
        int j, k, x, y;
        int sz;

        /* Beginning at iSrc, match forwards as far as we can.  j counts
        ** the number of characters that match */
        iSrc = iBlock*NHASH;
        for(j=0, x=iSrc, y=base+i; x<lenSrc && y<lenOut; j++, x++, y++){
          if( zSrc[x]!=zOut[y] ) break;
        }
        j--;

        /* Beginning at iSrc-1, match backwards as far as we can.  k counts
        ** the number of characters that match */
        for(k=1; k<iSrc && k<=i; k++){
          if( zSrc[iSrc-k]!=zOut[base+i-k] ) break;
        }
        k--;

        /* Compute the offset and size of the matching region */
        ofst = iSrc-k;
        cnt = j+k+1;
        litsz = i-k;  /* Number of bytes of literal text before the copy */
        /* sz will hold the number of bytes needed to encode the "insert"
        ** command and the copy command, not counting the "insert" text */
        sz = digit_count(i-k)+digit_count(cnt)+digit_count(ofst)+3;
        if( cnt>=sz && cnt>bestCnt ){
          /* Remember this match only if it is the best so far and it
          ** does not increase the file size */
          bestCnt = cnt;
          bestOfst = iSrc-k;
          bestLitsz = litsz;
        }

        /* Check the next matching block */
        iBlock = collide[iBlock];
      }

      /* We have a copy command that does not cause the delta to be larger
      ** than a literal insert.  So add the copy command to the delta.
      */
      if( bestCnt>0 ){
        if( bestLitsz>0 ){
          /* Add an insert command before the copy */
          putInt(bestLitsz,&zDelta);
          *(zDelta++) = ':';
          memcpy(zDelta, &zOut[base], bestLitsz);
          zDelta += bestLitsz;
          base += bestLitsz;
        }
        base += bestCnt;
        putInt(bestCnt, &zDelta);
        *(zDelta++) = '@';
        putInt(bestOfst, &zDelta);
        *(zDelta++) = ',';
        if( bestOfst + bestCnt -1 > lastRead ){
          lastRead = bestOfst + bestCnt - 1;
        }
        bestCnt = 0;
        break;
      }

      /* If we reach this point, it means no match is found so far */
      if( base+i+NHASH>=lenOut ){
        /* We have reached the end of the file and have not found any
        ** matches.  Do an "insert" for everything that does not match */
        putInt(lenOut-base, &zDelta);
        *(zDelta++) = ':';
        memcpy(zDelta, &zOut[base], lenOut-base);
        zDelta += lenOut-base;
        base = lenOut;
        break;
      }

      /* Advance the hash by one character.  Keep looking for a match */
      hash_next(&h, zOut[base+i+NHASH]);
      i++;
    }
  }
  /* Output a final "insert" record to get all the text at the end of
  ** the file that does not match anything in the source file.
  */
  if( base<lenOut ){
    putInt(lenOut-base, &zDelta);
    *(zDelta++) = ':';
    memcpy(zDelta, &zOut[base], lenOut-base);
    zDelta += lenOut-base;
  }
  /* Output the final checksum record. */
  putInt(checksum(zOut, lenOut), &zDelta);
  *(zDelta++) = ';';
  sqlite3_free(collide);
  return zDelta - zOrigDelta;
}

/*
** End of code copied from fossil.
**************************************************************************/

static void strPrintfArray(
  Str *pStr,                      /* String object to append to */
  const char *zSep,               /* Separator string */
  const char *zFmt,               /* Format for each entry */
  char **az, int n                /* Array of strings & its size (or -1) */
){
  int i;

  Str *pSql
){
  int i;

  /* First the newly inserted rows: **/ 
  strPrintf(pSql, "SELECT ");
  strPrintfArray(pSql, ", ", "%s", azCol, -1);
  strPrintf(pSql, ", 0, ");       /* Set ota_control to 0 for an insert */
  strPrintfArray(pSql, ", ", "NULL", azCol, -1);
  strPrintf(pSql, " FROM aux.%Q AS n WHERE NOT EXISTS (\n", zTab);
  strPrintf(pSql, "    SELECT 1 FROM ", zTab);
  strPrintf(pSql, " main.%Q AS o WHERE ", zTab);
  strPrintfArray(pSql, " AND ", "(n.%Q IS o.%Q)", azCol, nPK);
  strPrintf(pSql, "\n)");

  /* Deleted rows: */
  strPrintf(pSql, "\nUNION ALL\nSELECT ");
  strPrintfArray(pSql, ", ", "%s", azCol, nPK);
  if( azCol[nPK] ){
    strPrintf(pSql, ", ");
    strPrintfArray(pSql, ", ", "NULL", &azCol[nPK], -1);
  }
  strPrintf(pSql, ", 1, ");       /* Set ota_control to 1 for a delete */
  strPrintfArray(pSql, ", ", "NULL", azCol, -1);
  strPrintf(pSql, " FROM main.%Q AS n WHERE NOT EXISTS (\n", zTab);
  strPrintf(pSql, "    SELECT 1 FROM ", zTab);
  strPrintf(pSql, " aux.%Q AS o WHERE ", zTab);
  strPrintfArray(pSql, " AND ", "(n.%Q IS o.%Q)", azCol, nPK);
  strPrintf(pSql, "\n) ");

  /* Updated rows. If all table columns are part of the primary key, there 

      strPrintf(pSql, "' ||\n");
    }else{
      strPrintf(pSql, ",\n");
    }
    strPrintfArray(pSql, " ||\n", 
        "    CASE WHEN n.%s IS o.%s THEN '.' ELSE 'x' END", &azCol[nPK], -1
    );
    strPrintf(pSql, "\nAS ota_control, ");
    strPrintfArray(pSql, ", ", "NULL", azCol, nPK);
    strPrintf(pSql, ",\n");
    strPrintfArray(pSql, " ,\n", 
        "    CASE WHEN n.%s IS o.%s THEN NULL ELSE o.%s END", &azCol[nPK], -1
    );

    strPrintf(pSql, "\nFROM main.%Q AS o, aux.%Q AS n\nWHERE ", zTab, zTab);
    strPrintfArray(pSql, " AND ", "(n.%Q IS o.%Q)", azCol, nPK);
    strPrintf(pSql, " AND ota_control LIKE '%%x%%'");
  }

  /* Now add an ORDER BY clause to sort everything by PK. */

  /* Grab the column names and PK details for the table(s). If no usable PK
  ** columns are found, bail out early.  */
  azCol = columnNames("main", zTab, &nPK, &bOtaRowid);
  if( azCol==0 ){
    runtimeError("table %s has no usable PK columns", zTab);
  }
  for(nCol=0; azCol[nCol]; nCol++);

  /* Build and output the CREATE TABLE statement for the data_xxx table */
  strPrintf(&ct, "CREATE TABLE IF NOT EXISTS 'data_%q'(", zTab);
  if( bOtaRowid ) strPrintf(&ct, "rbu_rowid, ");
  strPrintfArray(&ct, ", ", "%s", &azCol[bOtaRowid], -1);
  strPrintf(&ct, ", rbu_control);");


  /* Get the SQL for the query to retrieve data from the two databases */
  getRbudiffQuery(zTab, azCol, nPK, bOtaRowid, &sql);

  /* Build the first part of the INSERT statement output for each row
  ** in the data_xxx table. */
  strPrintf(&insert, "INSERT INTO 'data_%q' (", zTab);
  if( bOtaRowid ) strPrintf(&insert, "rbu_rowid, ");
  strPrintfArray(&insert, ", ", "%s", &azCol[bOtaRowid], -1);
  strPrintf(&insert, ", rbu_control) VALUES(");

  pStmt = db_prepare("%s", sql.z);

  while( sqlite3_step(pStmt)==SQLITE_ROW ){
    
    /* If this is the first row output, print out the CREATE TABLE 
    ** statement first. And then set ct.z to NULL so that it is not 
    ** printed again.  */
    if( ct.z ){
      fprintf(out, "%s\n", ct.z);
      strFree(&ct);
    }

    /* Output the first part of the INSERT statement */
    fprintf(out, "%s", insert.z);

    if( sqlite3_column_type(pStmt, nCol)==SQLITE_INTEGER ){
      for(i=0; i<=nCol; i++){
        if( i>0 ) fprintf(out, ", ");
        printQuoted(out, sqlite3_column_value(pStmt, i));
      }
    }else{
      char *zOtaControl;
      int nOtaControl = sqlite3_column_bytes(pStmt, nCol);

      zOtaControl = (char*)sqlite3_malloc(nOtaControl);
      memcpy(zOtaControl, sqlite3_column_text(pStmt, nCol), nOtaControl+1);

    for(i=0; i<nCol; i++){
        int bDone = 0;
        if( i>=nPK 
            && sqlite3_column_type(pStmt, i)==SQLITE_BLOB
            && sqlite3_column_type(pStmt, nCol+1+i)==SQLITE_BLOB
        ){
          const char *aSrc = sqlite3_column_blob(pStmt, nCol+1+i);
          int nSrc = sqlite3_column_bytes(pStmt, nCol+1+i);
          const char *aFinal = sqlite3_column_blob(pStmt, i);
          int nFinal = sqlite3_column_bytes(pStmt, i);
          char *aDelta;
          int nDelta;

          aDelta = sqlite3_malloc(nFinal + 60);
          nDelta = rbuDeltaCreate(aSrc, nSrc, aFinal, nFinal, aDelta);
          if( nDelta<nFinal ){
            int j;
            fprintf(out, "x'");
            for(j=0; j<nDelta; j++) fprintf(out, "%02x", (u8)aDelta[j]);
            fprintf(out, "'");
            zOtaControl[i-bOtaRowid] = 'f';
            bDone = 1;
          }
          sqlite3_free(aDelta);
        }

        if( bDone==0 ){
      printQuoted(out, sqlite3_column_value(pStmt, i));
    }
        fprintf(out, ", ");
      }
      fprintf(out, "'%s'", zOtaControl);
      sqlite3_free(zOtaControl);
    }

    /* And the closing bracket of the insert statement */
    fprintf(out, ");\n");
  }

  sqlite3_finalize(pStmt);

  strFree(&ct);
  strFree(&sql);