}

/*
** 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 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){
................................................................................
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 */

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

  /* 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;

................................................................................
        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;

}

/*
** 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] = (char)c;
  pHash->i = (pHash->i+1)&(NHASH-1);
  pHash->a = pHash->a - old + (char)c;
  pHash->b = pHash->b - NHASH*old + pHash->a;
}

/*
** Return a 32-bit hash value
*/
static u32 hash_32bit(hash *pHash){
................................................................................
}

/*
** 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; (unsigned int)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){
................................................................................
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 */
){
  unsigned 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 */

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

  /* 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;
    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;

................................................................................
        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;
          (unsigned int)x<lenSrc && (unsigned int)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 && (unsigned int)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;