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Overview
Comment:Changes to spellfix to try to get it to use stack space instead of heap space in cases where that makes sense.
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SHA1: dfcebc7393a3a780ee9c4f257723c303bb633064
User & Date: drh 2016-01-23 18:24:52
Context
2016-01-23
22:55
Add the SQLITE_SPELLFIX_STACKALLOC_SZ compile-time option to control how much stack space is available for use as the Wagner matrix in editDest3 of the spellfix extension. check-in: dd0100dd user: drh tags: trunk
18:24
Changes to spellfix to try to get it to use stack space instead of heap space in cases where that makes sense. check-in: dfcebc73 user: drh tags: trunk
15:57
Fix some signed/unsigned comparison compiler warnings in fts5. check-in: 3be336aa user: dan tags: trunk
Changes
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Changes to ext/misc/spellfix.c.

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  char cAnext, cBnext;   /* Next character in zA and zB */
  int d;                 /* North-west cost value */
  int dc = 0;            /* North-west character value */
  int res;               /* Final result */
  int *m;                /* The cost matrix */
  char *cx;              /* Corresponding character values */
  int *toFree = 0;       /* Malloced space */
  int mStack[60+15];     /* Stack space to use if not too much is needed */
  int nMatch = 0;


  /* Early out if either input is NULL */
  if( zA==0 || zB==0 ) return -1;

  /* Skip any common prefix */
  while( zA[0] && zA[0]==zB[0] ){ dc = zA[0]; zA++; zB++; nMatch++; }
  if( pnMatch ) *pnMatch = nMatch;
................................................................................
){
  int k, n;
  int i1, b1;
  int i2, b2;
  EditDist3FromString f = *pFrom;
  EditDist3To *a2;
  unsigned int *m;

  int szRow;
  EditDist3Cost *p;
  int res;



  /* allocate the Wagner matrix and the aTo[] array for the TO string */
  n = (f.n+1)*(n2+1);
  n = (n+1)&~1;
  m = sqlite3_malloc( n*sizeof(m[0]) + sizeof(a2[0])*n2 );





  if( m==0 ) return -1;            /* Out of memory */

  a2 = (EditDist3To*)&m[n];
  memset(a2, 0, sizeof(a2[0])*n2);

  /* Fill in the a1[] matrix for all characters of the TO string */
  for(i2=0; i2<n2; i2++){
    a2[i2].nByte = utf8Len((unsigned char)z2[i2], n2-i2);
    for(p=pLang->pCost; p; p=p->pNext){
................................................................................
      if( (z2[k] & 0xc0)==0x80 ) nExtra++;
    }
    *pnMatch = n - nExtra;
  }

editDist3Abort:
  for(i2=0; i2<n2; i2++) sqlite3_free(a2[i2].apIns);
  sqlite3_free(m);
  return res;
}

/*
** Get an appropriate EditDist3Lang object.
*/
static const EditDist3Lang *editDist3FindLang(







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901
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  char cAnext, cBnext;   /* Next character in zA and zB */
  int d;                 /* North-west cost value */
  int dc = 0;            /* North-west character value */
  int res;               /* Final result */
  int *m;                /* The cost matrix */
  char *cx;              /* Corresponding character values */
  int *toFree = 0;       /* Malloced space */

  int nMatch = 0;
  int mStack[60+15];     /* Stack space to use if not too much is needed */

  /* Early out if either input is NULL */
  if( zA==0 || zB==0 ) return -1;

  /* Skip any common prefix */
  while( zA[0] && zA[0]==zB[0] ){ dc = zA[0]; zA++; zB++; nMatch++; }
  if( pnMatch ) *pnMatch = nMatch;
................................................................................
){
  int k, n;
  int i1, b1;
  int i2, b2;
  EditDist3FromString f = *pFrom;
  EditDist3To *a2;
  unsigned int *m;
  unsigned int *pToFree;
  int szRow;
  EditDist3Cost *p;
  int res;
  sqlite3_uint64 nByte;
  unsigned int stackSpace[16*1024];

  /* allocate the Wagner matrix and the aTo[] array for the TO string */
  n = (f.n+1)*(n2+1);
  n = (n+1)&~1;
  nByte = n*sizeof(m[0]) + sizeof(a2[0])*n2;
  if( nByte<=sizeof(stackSpace) ){
    m = stackSpace;
    pToFree = 0;
  }else{
    m = pToFree = sqlite3_malloc( nByte );
    if( m==0 ) return -1;            /* Out of memory */
  }
  a2 = (EditDist3To*)&m[n];
  memset(a2, 0, sizeof(a2[0])*n2);

  /* Fill in the a1[] matrix for all characters of the TO string */
  for(i2=0; i2<n2; i2++){
    a2[i2].nByte = utf8Len((unsigned char)z2[i2], n2-i2);
    for(p=pLang->pCost; p; p=p->pNext){
................................................................................
      if( (z2[k] & 0xc0)==0x80 ) nExtra++;
    }
    *pnMatch = n - nExtra;
  }

editDist3Abort:
  for(i2=0; i2<n2; i2++) sqlite3_free(a2[i2].apIns);
  sqlite3_free(pToFree);
  return res;
}

/*
** Get an appropriate EditDist3Lang object.
*/
static const EditDist3Lang *editDist3FindLang(