/*
** 2002 February 23
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement various SQL
** functions of SQLite.  
**
** There is only one exported symbol in this file - the function
** sqliteRegisterBuildinFunctions() found at the bottom of the file.
** All other code has file scope.
**
** $Id: func.c,v 1.203 2008/09/03 17:11:16 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include "vdbeInt.h"

/*
** Return the collating function associated with a function.
*/
static CollSeq *sqlite3GetFuncCollSeq(sqlite3_context *context){
  return context->pColl;
}

/*
** Implementation of the non-aggregate min() and max() functions
*/
static void minmaxFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  int i;
  int mask;    /* 0 for min() or 0xffffffff for max() */
  int iBest;
  CollSeq *pColl;

  if( argc==0 ) return;
  mask = sqlite3_user_data(context)==0 ? 0 : -1;
  pColl = sqlite3GetFuncCollSeq(context);
  assert( pColl );
  assert( mask==-1 || mask==0 );
  iBest = 0;
  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
  for(i=1; i<argc; i++){
    if( sqlite3_value_type(argv[i])==SQLITE_NULL ) return;
    if( (sqlite3MemCompare(argv[iBest], argv[i], pColl)^mask)>=0 ){
      iBest = i;
    }
  }
  sqlite3_result_value(context, argv[iBest]);
}

/*
** Return the type of the argument.
*/
static void typeofFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  const char *z = 0;
  switch( sqlite3_value_type(argv[0]) ){
    case SQLITE_NULL:    z = "null";    break;
    case SQLITE_INTEGER: z = "integer"; break;
    case SQLITE_TEXT:    z = "text";    break;
    case SQLITE_FLOAT:   z = "real";    break;
    case SQLITE_BLOB:    z = "blob";    break;
  }
  sqlite3_result_text(context, z, -1, SQLITE_STATIC);
}


/*
** Implementation of the length() function
*/
static void lengthFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  int len;

  assert( argc==1 );
  switch( sqlite3_value_type(argv[0]) ){
    case SQLITE_BLOB:
    case SQLITE_INTEGER:
    case SQLITE_FLOAT: {
      sqlite3_result_int(context, sqlite3_value_bytes(argv[0]));
      break;
    }
    case SQLITE_TEXT: {
      const unsigned char *z = sqlite3_value_text(argv[0]);
      if( z==0 ) return;
      len = 0;
      while( *z ){
        len++;
        SQLITE_SKIP_UTF8(z);
      }
      sqlite3_result_int(context, len);
      break;
    }
    default: {
      sqlite3_result_null(context);
      break;
    }
  }
}

/*
** Implementation of the abs() function
*/
static void absFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
  assert( argc==1 );
  switch( sqlite3_value_type(argv[0]) ){
    case SQLITE_INTEGER: {
      i64 iVal = sqlite3_value_int64(argv[0]);
      if( iVal<0 ){
        if( (iVal<<1)==0 ){
          sqlite3_result_error(context, "integer overflow", -1);
          return;
        }
        iVal = -iVal;
      } 
      sqlite3_result_int64(context, iVal);
      break;
    }
    case SQLITE_NULL: {
      sqlite3_result_null(context);
      break;
    }
    default: {
      double rVal = sqlite3_value_double(argv[0]);
      if( rVal<0 ) rVal = -rVal;
      sqlite3_result_double(context, rVal);
      break;
    }
  }
}

/*
** Implementation of the substr() function.
**
** substr(x,p1,p2)  returns p2 characters of x[] beginning with p1.
** p1 is 1-indexed.  So substr(x,1,1) returns the first character
** of x.  If x is text, then we actually count UTF-8 characters.
** If x is a blob, then we count bytes.
**
** If p1 is negative, then we begin abs(p1) from the end of x[].
*/
static void substrFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  const unsigned char *z;
  const unsigned char *z2;
  int len;
  int p0type;
  i64 p1, p2;

  assert( argc==3 || argc==2 );
  p0type = sqlite3_value_type(argv[0]);
  if( p0type==SQLITE_BLOB ){
    len = sqlite3_value_bytes(argv[0]);
    z = sqlite3_value_blob(argv[0]);
    if( z==0 ) return;
    assert( len==sqlite3_value_bytes(argv[0]) );
  }else{
    z = sqlite3_value_text(argv[0]);
    if( z==0 ) return;
    len = 0;
    for(z2=z; *z2; len++){
      SQLITE_SKIP_UTF8(z2);
    }
  }
  p1 = sqlite3_value_int(argv[1]);
  if( argc==3 ){
    p2 = sqlite3_value_int(argv[2]);
  }else{
    p2 = sqlite3_context_db_handle(context)->aLimit[SQLITE_LIMIT_LENGTH];
  }
  if( p1<0 ){
    p1 += len;
    if( p1<0 ){
      p2 += p1;
      p1 = 0;
    }
  }else if( p1>0 ){
    p1--;
  }
  if( p1+p2>len ){
    p2 = len-p1;
  }
  if( p0type!=SQLITE_BLOB ){
    while( *z && p1 ){
      SQLITE_SKIP_UTF8(z);
      p1--;
    }
    for(z2=z; *z2 && p2; p2--){
      SQLITE_SKIP_UTF8(z2);
    }
    sqlite3_result_text(context, (char*)z, z2-z, SQLITE_TRANSIENT);
  }else{
    if( p2<0 ) p2 = 0;
    sqlite3_result_blob(context, (char*)&z[p1], p2, SQLITE_TRANSIENT);
  }
}

/*
** Implementation of the round() function
*/
static void roundFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
  int n = 0;
  double r;
  char zBuf[500];  /* larger than the %f representation of the largest double */
  assert( argc==1 || argc==2 );
  if( argc==2 ){
    if( SQLITE_NULL==sqlite3_value_type(argv[1]) ) return;
    n = sqlite3_value_int(argv[1]);
    if( n>30 ) n = 30;
    if( n<0 ) n = 0;
  }
  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
  r = sqlite3_value_double(argv[0]);
  sqlite3_snprintf(sizeof(zBuf),zBuf,"%.*f",n,r);
  sqlite3AtoF(zBuf, &r);
  sqlite3_result_double(context, r);
}

/*
** Allocate nByte bytes of space using sqlite3_malloc(). If the
** allocation fails, call sqlite3_result_error_nomem() to notify
** the database handle that malloc() has failed.
*/
static void *contextMalloc(sqlite3_context *context, i64 nByte){
  char *z;
  if( nByte>sqlite3_context_db_handle(context)->aLimit[SQLITE_LIMIT_LENGTH] ){
    sqlite3_result_error_toobig(context);
    z = 0;
  }else{
    z = sqlite3Malloc(nByte);
    if( !z && nByte>0 ){
      sqlite3_result_error_nomem(context);
    }
  }
  return z;
}

/*
** Implementation of the upper() and lower() SQL functions.
*/
static void upperFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
  char *z1;
  const char *z2;
  int i, n;
  if( argc<1 || SQLITE_NULL==sqlite3_value_type(argv[0]) ) return;
  z2 = (char*)sqlite3_value_text(argv[0]);
  n = sqlite3_value_bytes(argv[0]);
  /* Verify that the call to _bytes() does not invalidate the _text() pointer */
  assert( z2==(char*)sqlite3_value_text(argv[0]) );
  if( z2 ){
    z1 = contextMalloc(context, ((i64)n)+1);
    if( z1 ){
      memcpy(z1, z2, n+1);
      for(i=0; z1[i]; i++){
        z1[i] = toupper(z1[i]);
      }
      sqlite3_result_text(context, z1, -1, sqlite3_free);
    }
  }
}
static void lowerFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
  char *z1;
  const char *z2;
  int i, n;
  if( argc<1 || SQLITE_NULL==sqlite3_value_type(argv[0]) ) return;
  z2 = (char*)sqlite3_value_text(argv[0]);
  n = sqlite3_value_bytes(argv[0]);
  /* Verify that the call to _bytes() does not invalidate the _text() pointer */
  assert( z2==(char*)sqlite3_value_text(argv[0]) );
  if( z2 ){
    z1 = contextMalloc(context, ((i64)n)+1);
    if( z1 ){
      memcpy(z1, z2, n+1);
      for(i=0; z1[i]; i++){
        z1[i] = tolower(z1[i]);
      }
      sqlite3_result_text(context, z1, -1, sqlite3_free);
    }
  }
}

/*
** Implementation of the IFNULL(), NVL(), and COALESCE() functions.  
** All three do the same thing.  They return the first non-NULL
** argument.
*/
static void ifnullFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  int i;
  for(i=0; i<argc; i++){
    if( SQLITE_NULL!=sqlite3_value_type(argv[i]) ){
      sqlite3_result_value(context, argv[i]);
      break;
    }
  }
}

/*
** Implementation of random().  Return a random integer.  
*/
static void randomFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  sqlite_int64 r;
  sqlite3_randomness(sizeof(r), &r);
  if( (r<<1)==0 ) r = 0;  /* Prevent 0x8000.... as the result so that we */
                          /* can always do abs() of the result */
  sqlite3_result_int64(context, r);
}

/*
** Implementation of randomblob(N).  Return a random blob
** that is N bytes long.
*/
static void randomBlob(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  int n;
  unsigned char *p;
  assert( argc==1 );
  n = sqlite3_value_int(argv[0]);
  if( n<1 ){
    n = 1;
  }
  p = contextMalloc(context, n);
  if( p ){
    sqlite3_randomness(n, p);
    sqlite3_result_blob(context, (char*)p, n, sqlite3_free);
  }
}

/*
** Implementation of the last_insert_rowid() SQL function.  The return
** value is the same as the sqlite3_last_insert_rowid() API function.
*/
static void last_insert_rowid(
  sqlite3_context *context, 
  int arg, 
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  sqlite3_result_int64(context, sqlite3_last_insert_rowid(db));
}

/*
** Implementation of the changes() SQL function.  The return value is the
** same as the sqlite3_changes() API function.
*/
static void changes(
  sqlite3_context *context,
  int arg,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  sqlite3_result_int(context, sqlite3_changes(db));
}

/*
** Implementation of the total_changes() SQL function.  The return value is
** the same as the sqlite3_total_changes() API function.
*/
static void total_changes(
  sqlite3_context *context,
  int arg,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  sqlite3_result_int(context, sqlite3_total_changes(db));
}

/*
** A structure defining how to do GLOB-style comparisons.
*/
struct compareInfo {
  u8 matchAll;
  u8 matchOne;
  u8 matchSet;
  u8 noCase;
};

/*
** For LIKE and GLOB matching on EBCDIC machines, assume that every
** character is exactly one byte in size.  Also, all characters are
** able to participate in upper-case-to-lower-case mappings in EBCDIC
** whereas only characters less than 0x80 do in ASCII.
*/
#if defined(SQLITE_EBCDIC)
# define sqlite3Utf8Read(A,B,C)  (*(A++))
# define GlogUpperToLower(A)     A = sqlite3UpperToLower[A]
#else
# define GlogUpperToLower(A)     if( A<0x80 ){ A = sqlite3UpperToLower[A]; }
#endif

static const struct compareInfo globInfo = { '*', '?', '[', 0 };
/* The correct SQL-92 behavior is for the LIKE operator to ignore
** case.  Thus  'a' LIKE 'A' would be true. */
static const struct compareInfo likeInfoNorm = { '%', '_',   0, 1 };
/* If SQLITE_CASE_SENSITIVE_LIKE is defined, then the LIKE operator
** is case sensitive causing 'a' LIKE 'A' to be false */
static const struct compareInfo likeInfoAlt = { '%', '_',   0, 0 };

/*
** Compare two UTF-8 strings for equality where the first string can
** potentially be a "glob" expression.  Return true (1) if they
** are the same and false (0) if they are different.
**
** Globbing rules:
**
**      '*'       Matches any sequence of zero or more characters.
**
**      '?'       Matches exactly one character.
**
**     [...]      Matches one character from the enclosed list of
**                characters.
**
**     [^...]     Matches one character not in the enclosed list.
**
** With the [...] and [^...] matching, a ']' character can be included
** in the list by making it the first character after '[' or '^'.  A
** range of characters can be specified using '-'.  Example:
** "[a-z]" matches any single lower-case letter.  To match a '-', make
** it the last character in the list.
**
** This routine is usually quick, but can be N**2 in the worst case.
**
** Hints: to match '*' or '?', put them in "[]".  Like this:
**
**         abc[*]xyz        Matches "abc*xyz" only
*/
static int patternCompare(
  const u8 *zPattern,              /* The glob pattern */
  const u8 *zString,               /* The string to compare against the glob */
  const struct compareInfo *pInfo, /* Information about how to do the compare */
  const int esc                    /* The escape character */
){
  int c, c2;
  int invert;
  int seen;
  u8 matchOne = pInfo->matchOne;
  u8 matchAll = pInfo->matchAll;
  u8 matchSet = pInfo->matchSet;
  u8 noCase = pInfo->noCase; 
  int prevEscape = 0;     /* True if the previous character was 'escape' */

  while( (c = sqlite3Utf8Read(zPattern,0,&zPattern))!=0 ){
    if( !prevEscape && c==matchAll ){
      while( (c=sqlite3Utf8Read(zPattern,0,&zPattern)) == matchAll
               || c == matchOne ){
        if( c==matchOne && sqlite3Utf8Read(zString, 0, &zString)==0 ){
          return 0;
        }
      }
      if( c==0 ){
        return 1;
      }else if( c==esc ){
        c = sqlite3Utf8Read(zPattern, 0, &zPattern);
        if( c==0 ){
          return 0;
        }
      }else if( c==matchSet ){
        assert( esc==0 );         /* This is GLOB, not LIKE */
        assert( matchSet<0x80 );  /* '[' is a single-byte character */
        while( *zString && patternCompare(&zPattern[-1],zString,pInfo,esc)==0 ){
          SQLITE_SKIP_UTF8(zString);
        }
        return *zString!=0;
      }
      while( (c2 = sqlite3Utf8Read(zString,0,&zString))!=0 ){
        if( noCase ){
          GlogUpperToLower(c2);
          GlogUpperToLower(c);
          while( c2 != 0 && c2 != c ){
            c2 = sqlite3Utf8Read(zString, 0, &zString);
            GlogUpperToLower(c2);
          }
        }else{
          while( c2 != 0 && c2 != c ){
            c2 = sqlite3Utf8Read(zString, 0, &zString);
          }
        }
        if( c2==0 ) return 0;
        if( patternCompare(zPattern,zString,pInfo,esc) ) return 1;
      }
      return 0;
    }else if( !prevEscape && c==matchOne ){
      if( sqlite3Utf8Read(zString, 0, &zString)==0 ){
        return 0;
      }
    }else if( c==matchSet ){
      int prior_c = 0;
      assert( esc==0 );    /* This only occurs for GLOB, not LIKE */
      seen = 0;
      invert = 0;
      c = sqlite3Utf8Read(zString, 0, &zString);
      if( c==0 ) return 0;
      c2 = sqlite3Utf8Read(zPattern, 0, &zPattern);
      if( c2=='^' ){
        invert = 1;
        c2 = sqlite3Utf8Read(zPattern, 0, &zPattern);
      }
      if( c2==']' ){
        if( c==']' ) seen = 1;
        c2 = sqlite3Utf8Read(zPattern, 0, &zPattern);
      }
      while( c2 && c2!=']' ){
        if( c2=='-' && zPattern[0]!=']' && zPattern[0]!=0 && prior_c>0 ){
          c2 = sqlite3Utf8Read(zPattern, 0, &zPattern);
          if( c>=prior_c && c<=c2 ) seen = 1;
          prior_c = 0;
        }else{
          if( c==c2 ){
            seen = 1;
          }
          prior_c = c2;
        }
        c2 = sqlite3Utf8Read(zPattern, 0, &zPattern);
      }
      if( c2==0 || (seen ^ invert)==0 ){
        return 0;
      }
    }else if( esc==c && !prevEscape ){
      prevEscape = 1;
    }else{
      c2 = sqlite3Utf8Read(zString, 0, &zString);
      if( noCase ){
        GlogUpperToLower(c);
        GlogUpperToLower(c2);
      }
      if( c!=c2 ){
        return 0;
      }
      prevEscape = 0;
    }
  }
  return *zString==0;
}

/*
** Count the number of times that the LIKE operator (or GLOB which is
** just a variation of LIKE) gets called.  This is used for testing
** only.
*/
#ifdef SQLITE_TEST
int sqlite3_like_count = 0;
#endif


/*
** Implementation of the like() SQL function.  This function implements
** the build-in LIKE operator.  The first argument to the function is the
** pattern and the second argument is the string.  So, the SQL statements:
**
**       A LIKE B
**
** is implemented as like(B,A).
**
** This same function (with a different compareInfo structure) computes
** the GLOB operator.
*/
static void likeFunc(
  sqlite3_context *context, 
  int argc, 
  sqlite3_value **argv
){
  const unsigned char *zA, *zB;
  int escape = 0;
  sqlite3 *db = sqlite3_context_db_handle(context);

  zB = sqlite3_value_text(argv[0]);
  zA = sqlite3_value_text(argv[1]);

  /* Limit the length of the LIKE or GLOB pattern to avoid problems
  ** of deep recursion and N*N behavior in patternCompare().
  */
  if( sqlite3_value_bytes(argv[0]) >
        db->aLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH] ){
    sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
    return;
  }
  assert( zB==sqlite3_value_text(argv[0]) );  /* Encoding did not change */

  if( argc==3 ){
    /* The escape character string must consist of a single UTF-8 character.
    ** Otherwise, return an error.
    */
    const unsigned char *zEsc = sqlite3_value_text(argv[2]);
    if( zEsc==0 ) return;
    if( sqlite3Utf8CharLen((char*)zEsc, -1)!=1 ){
      sqlite3_result_error(context, 
          "ESCAPE expression must be a single character", -1);
      return;
    }
    escape = sqlite3Utf8Read(zEsc, 0, &zEsc);
  }
  if( zA && zB ){
    struct compareInfo *pInfo = sqlite3_user_data(context);
#ifdef SQLITE_TEST
    sqlite3_like_count++;
#endif
    
    sqlite3_result_int(context, patternCompare(zB, zA, pInfo, escape));
  }
}

/*
** Implementation of the NULLIF(x,y) function.  The result is the first
** argument if the arguments are different.  The result is NULL if the
** arguments are equal to each other.
*/
static void nullifFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  CollSeq *pColl = sqlite3GetFuncCollSeq(context);
  if( sqlite3MemCompare(argv[0], argv[1], pColl)!=0 ){
    sqlite3_result_value(context, argv[0]);
  }
}

/*
** Implementation of the VERSION(*) function.  The result is the version
** of the SQLite library that is running.
*/
static void versionFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  sqlite3_result_text(context, sqlite3_version, -1, SQLITE_STATIC);
}

/* Array for converting from half-bytes (nybbles) into ASCII hex
** digits. */
static const char hexdigits[] = {
  '0', '1', '2', '3', '4', '5', '6', '7',
  '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' 
};

/*
** EXPERIMENTAL - This is not an official function.  The interface may
** change.  This function may disappear.  Do not write code that depends
** on this function.
**
** Implementation of the QUOTE() function.  This function takes a single
** argument.  If the argument is numeric, the return value is the same as
** the argument.  If the argument is NULL, the return value is the string
** "NULL".  Otherwise, the argument is enclosed in single quotes with
** single-quote escapes.
*/
static void quoteFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
  if( argc<1 ) return;
  switch( sqlite3_value_type(argv[0]) ){
    case SQLITE_NULL: {
      sqlite3_result_text(context, "NULL", 4, SQLITE_STATIC);
      break;
    }
    case SQLITE_INTEGER:
    case SQLITE_FLOAT: {
      sqlite3_result_value(context, argv[0]);
      break;
    }
    case SQLITE_BLOB: {
      char *zText = 0;
      char const *zBlob = sqlite3_value_blob(argv[0]);
      int nBlob = sqlite3_value_bytes(argv[0]);
      assert( zBlob==sqlite3_value_blob(argv[0]) ); /* No encoding change */
      zText = (char *)contextMalloc(context, (2*(i64)nBlob)+4); 
      if( zText ){
        int i;
        for(i=0; i<nBlob; i++){
          zText[(i*2)+2] = hexdigits[(zBlob[i]>>4)&0x0F];
          zText[(i*2)+3] = hexdigits[(zBlob[i])&0x0F];
        }
        zText[(nBlob*2)+2] = '\'';
        zText[(nBlob*2)+3] = '\0';
        zText[0] = 'X';
        zText[1] = '\'';
        sqlite3_result_text(context, zText, -1, SQLITE_TRANSIENT);
        sqlite3_free(zText);
      }
      break;
    }
    case SQLITE_TEXT: {
      int i,j;
      u64 n;
      const unsigned char *zArg = sqlite3_value_text(argv[0]);
      char *z;

      if( zArg==0 ) return;
      for(i=0, n=0; zArg[i]; i++){ if( zArg[i]=='\'' ) n++; }
      z = contextMalloc(context, ((i64)i)+((i64)n)+3);
      if( z ){
        z[0] = '\'';
        for(i=0, j=1; zArg[i]; i++){
          z[j++] = zArg[i];
          if( zArg[i]=='\'' ){
            z[j++] = '\'';
          }
        }
        z[j++] = '\'';
        z[j] = 0;
        sqlite3_result_text(context, z, j, sqlite3_free);
      }
    }
  }
}

/*
** The hex() function.  Interpret the argument as a blob.  Return
** a hexadecimal rendering as text.
*/
static void hexFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  int i, n;
  const unsigned char *pBlob;
  char *zHex, *z;
  assert( argc==1 );
  pBlob = sqlite3_value_blob(argv[0]);
  n = sqlite3_value_bytes(argv[0]);
  assert( pBlob==sqlite3_value_blob(argv[0]) );  /* No encoding change */
  z = zHex = contextMalloc(context, ((i64)n)*2 + 1);
  if( zHex ){
    for(i=0; i<n; i++, pBlob++){
      unsigned char c = *pBlob;
      *(z++) = hexdigits[(c>>4)&0xf];
      *(z++) = hexdigits[c&0xf];
    }
    *z = 0;
    sqlite3_result_text(context, zHex, n*2, sqlite3_free);
  }
}

/*
** The zeroblob(N) function returns a zero-filled blob of size N bytes.
*/
static void zeroblobFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  i64 n;
  assert( argc==1 );
  n = sqlite3_value_int64(argv[0]);
  if( n>SQLITE_MAX_LENGTH ){
    sqlite3_result_error_toobig(context);
  }else{
    sqlite3_result_zeroblob(context, n);
  }
}

/*
** The replace() function.  Three arguments are all strings: call
** them A, B, and C. The result is also a string which is derived
** from A by replacing every occurance of B with C.  The match
** must be exact.  Collating sequences are not used.
*/
static void replaceFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  const unsigned char *zStr;        /* The input string A */
  const unsigned char *zPattern;    /* The pattern string B */
  const unsigned char *zRep;        /* The replacement string C */
  unsigned char *zOut;              /* The output */
  int nStr;                /* Size of zStr */
  int nPattern;            /* Size of zPattern */
  int nRep;                /* Size of zRep */
  i64 nOut;                /* Maximum size of zOut */
  int loopLimit;           /* Last zStr[] that might match zPattern[] */
  int i, j;                /* Loop counters */

  assert( argc==3 );
  zStr = sqlite3_value_text(argv[0]);
  if( zStr==0 ) return;
  nStr = sqlite3_value_bytes(argv[0]);
  assert( zStr==sqlite3_value_text(argv[0]) );  /* No encoding change */
  zPattern = sqlite3_value_text(argv[1]);
  if( zPattern==0 || zPattern[0]==0 ) return;
  nPattern = sqlite3_value_bytes(argv[1]);
  assert( zPattern==sqlite3_value_text(argv[1]) );  /* No encoding change */
  zRep = sqlite3_value_text(argv[2]);
  if( zRep==0 ) return;
  nRep = sqlite3_value_bytes(argv[2]);
  assert( zRep==sqlite3_value_text(argv[2]) );
  nOut = nStr + 1;
  assert( nOut<SQLITE_MAX_LENGTH );
  zOut = contextMalloc(context, (i64)nOut);
  if( zOut==0 ){
    return;
  }
  loopLimit = nStr - nPattern;  
  for(i=j=0; i<=loopLimit; i++){
    if( zStr[i]!=zPattern[0] || memcmp(&zStr[i], zPattern, nPattern) ){
      zOut[j++] = zStr[i];
    }else{
      u8 *zOld;
      sqlite3 *db = sqlite3_context_db_handle(context);
      nOut += nRep - nPattern;
      if( nOut>=db->aLimit[SQLITE_LIMIT_LENGTH] ){
        sqlite3_result_error_toobig(context);
        sqlite3DbFree(db, zOut);
        return;
      }
      zOld = zOut;
      zOut = sqlite3_realloc(zOut, (int)nOut);
      if( zOut==0 ){
        sqlite3_result_error_nomem(context);
        sqlite3DbFree(db, zOld);
        return;
      }
      memcpy(&zOut[j], zRep, nRep);
      j += nRep;
      i += nPattern-1;
    }
  }
  assert( j+nStr-i+1==nOut );
  memcpy(&zOut[j], &zStr[i], nStr-i);
  j += nStr - i;
  assert( j<=nOut );
  zOut[j] = 0;
  sqlite3_result_text(context, (char*)zOut, j, sqlite3_free);
}

/*
** Implementation of the TRIM(), LTRIM(), and RTRIM() functions.
** The userdata is 0x1 for left trim, 0x2 for right trim, 0x3 for both.
*/
static void trimFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  const unsigned char *zIn;         /* Input string */
  const unsigned char *zCharSet;    /* Set of characters to trim */
  int nIn;                          /* Number of bytes in input */
  int flags;                        /* 1: trimleft  2: trimright  3: trim */
  int i;                            /* Loop counter */
  unsigned char *aLen;              /* Length of each character in zCharSet */
  unsigned char **azChar;           /* Individual characters in zCharSet */
  int nChar;                        /* Number of characters in zCharSet */

  if( sqlite3_value_type(argv[0])==SQLITE_NULL ){
    return;
  }
  zIn = sqlite3_value_text(argv[0]);
  if( zIn==0 ) return;
  nIn = sqlite3_value_bytes(argv[0]);
  assert( zIn==sqlite3_value_text(argv[0]) );
  if( argc==1 ){
    static const unsigned char lenOne[] = { 1 };
    static unsigned char * const azOne[] = { (u8*)" " };
    nChar = 1;
    aLen = (u8*)lenOne;
    azChar = (unsigned char **)azOne;
    zCharSet = 0;
  }else if( (zCharSet = sqlite3_value_text(argv[1]))==0 ){
    return;
  }else{
    const unsigned char *z;
    for(z=zCharSet, nChar=0; *z; nChar++){
      SQLITE_SKIP_UTF8(z);
    }
    if( nChar>0 ){
      azChar = contextMalloc(context, ((i64)nChar)*(sizeof(char*)+1));
      if( azChar==0 ){
        return;
      }
      aLen = (unsigned char*)&azChar[nChar];
      for(z=zCharSet, nChar=0; *z; nChar++){
        azChar[nChar] = (unsigned char *)z;
        SQLITE_SKIP_UTF8(z);
        aLen[nChar] = z - azChar[nChar];
      }
    }
  }
  if( nChar>0 ){
    flags = SQLITE_PTR_TO_INT(sqlite3_user_data(context));
    if( flags & 1 ){
      while( nIn>0 ){
        int len;
        for(i=0; i<nChar; i++){
          len = aLen[i];
          if( memcmp(zIn, azChar[i], len)==0 ) break;
        }
        if( i>=nChar ) break;
        zIn += len;
        nIn -= len;
      }
    }
    if( flags & 2 ){
      while( nIn>0 ){
        int len;
        for(i=0; i<nChar; i++){
          len = aLen[i];
          if( len<=nIn && memcmp(&zIn[nIn-len],azChar[i],len)==0 ) break;
        }
        if( i>=nChar ) break;
        nIn -= len;
      }
    }
    if( zCharSet ){
      sqlite3_free(azChar);
    }
  }
  sqlite3_result_text(context, (char*)zIn, nIn, SQLITE_TRANSIENT);
}


#ifdef SQLITE_SOUNDEX
/*
** Compute the soundex encoding of a word.
*/
static void soundexFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  char zResult[8];
  const u8 *zIn;
  int i, j;
  static const unsigned char iCode[] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 1, 2, 3, 0, 1, 2, 0, 0, 2, 2, 4, 5, 5, 0,
    1, 2, 6, 2, 3, 0, 1, 0, 2, 0, 2, 0, 0, 0, 0, 0,
    0, 0, 1, 2, 3, 0, 1, 2, 0, 0, 2, 2, 4, 5, 5, 0,
    1, 2, 6, 2, 3, 0, 1, 0, 2, 0, 2, 0, 0, 0, 0, 0,
  };
  assert( argc==1 );
  zIn = (u8*)sqlite3_value_text(argv[0]);
  if( zIn==0 ) zIn = (u8*)"";
  for(i=0; zIn[i] && !isalpha(zIn[i]); i++){}
  if( zIn[i] ){
    u8 prevcode = iCode[zIn[i]&0x7f];
    zResult[0] = toupper(zIn[i]);
    for(j=1; j<4 && zIn[i]; i++){
      int code = iCode[zIn[i]&0x7f];
      if( code>0 ){
        if( code!=prevcode ){
          prevcode = code;
          zResult[j++] = code + '0';
        }
      }else{
        prevcode = 0;
      }
    }
    while( j<4 ){
      zResult[j++] = '0';
    }
    zResult[j] = 0;
    sqlite3_result_text(context, zResult, 4, SQLITE_TRANSIENT);
  }else{
    sqlite3_result_text(context, "?000", 4, SQLITE_STATIC);
  }
}
#endif

#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** A function that loads a shared-library extension then returns NULL.
*/
static void loadExt(sqlite3_context *context, int argc, sqlite3_value **argv){
  const char *zFile = (const char *)sqlite3_value_text(argv[0]);
  const char *zProc;
  sqlite3 *db = sqlite3_context_db_handle(context);
  char *zErrMsg = 0;

  if( argc==2 ){
    zProc = (const char *)sqlite3_value_text(argv[1]);
  }else{
    zProc = 0;
  }
  if( zFile && sqlite3_load_extension(db, zFile, zProc, &zErrMsg) ){
    sqlite3_result_error(context, zErrMsg, -1);
    sqlite3_free(zErrMsg);
  }
}
#endif


/*
** An instance of the following structure holds the context of a
** sum() or avg() aggregate computation.
*/
typedef struct SumCtx SumCtx;
struct SumCtx {
  double rSum;      /* Floating point sum */
  i64 iSum;         /* Integer sum */   
  i64 cnt;          /* Number of elements summed */
  u8 overflow;      /* True if integer overflow seen */
  u8 approx;        /* True if non-integer value was input to the sum */
};

/*
** Routines used to compute the sum, average, and total.
**
** The SUM() function follows the (broken) SQL standard which means
** that it returns NULL if it sums over no inputs.  TOTAL returns
** 0.0 in that case.  In addition, TOTAL always returns a float where
** SUM might return an integer if it never encounters a floating point
** value.  TOTAL never fails, but SUM might through an exception if
** it overflows an integer.
*/
static void sumStep(sqlite3_context *context, int argc, sqlite3_value **argv){
  SumCtx *p;
  int type;
  assert( argc==1 );
  p = sqlite3_aggregate_context(context, sizeof(*p));
  type = sqlite3_value_numeric_type(argv[0]);
  if( p && type!=SQLITE_NULL ){
    p->cnt++;
    if( type==SQLITE_INTEGER ){
      i64 v = sqlite3_value_int64(argv[0]);
      p->rSum += v;
      if( (p->approx|p->overflow)==0 ){
        i64 iNewSum = p->iSum + v;
        int s1 = p->iSum >> (sizeof(i64)*8-1);
        int s2 = v       >> (sizeof(i64)*8-1);
        int s3 = iNewSum >> (sizeof(i64)*8-1);
        p->overflow = (s1&s2&~s3) | (~s1&~s2&s3);
        p->iSum = iNewSum;
      }
    }else{
      p->rSum += sqlite3_value_double(argv[0]);
      p->approx = 1;
    }
  }
}
static void sumFinalize(sqlite3_context *context){
  SumCtx *p;
  p = sqlite3_aggregate_context(context, 0);
  if( p && p->cnt>0 ){
    if( p->overflow ){
      sqlite3_result_error(context,"integer overflow",-1);
    }else if( p->approx ){
      sqlite3_result_double(context, p->rSum);
    }else{
      sqlite3_result_int64(context, p->iSum);
    }
  }
}
static void avgFinalize(sqlite3_context *context){
  SumCtx *p;
  p = sqlite3_aggregate_context(context, 0);
  if( p && p->cnt>0 ){
    sqlite3_result_double(context, p->rSum/(double)p->cnt);
  }
}
static void totalFinalize(sqlite3_context *context){
  SumCtx *p;
  p = sqlite3_aggregate_context(context, 0);
  sqlite3_result_double(context, p ? p->rSum : 0.0);
}

/*
** The following structure keeps track of state information for the
** count() aggregate function.
*/
typedef struct CountCtx CountCtx;
struct CountCtx {
  i64 n;
};

/*
** Routines to implement the count() aggregate function.
*/
static void countStep(sqlite3_context *context, int argc, sqlite3_value **argv){
  CountCtx *p;
  p = sqlite3_aggregate_context(context, sizeof(*p));
  if( (argc==0 || SQLITE_NULL!=sqlite3_value_type(argv[0])) && p ){
    p->n++;
  }
}   
static void countFinalize(sqlite3_context *context){
  CountCtx *p;
  p = sqlite3_aggregate_context(context, 0);
  sqlite3_result_int64(context, p ? p->n : 0);
}

/*
** Routines to implement min() and max() aggregate functions.
*/
static void minmaxStep(sqlite3_context *context, int argc, sqlite3_value **argv){
  Mem *pArg  = (Mem *)argv[0];
  Mem *pBest;

  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
  pBest = (Mem *)sqlite3_aggregate_context(context, sizeof(*pBest));
  if( !pBest ) return;

  if( pBest->flags ){
    int max;
    int cmp;
    CollSeq *pColl = sqlite3GetFuncCollSeq(context);
    /* This step function is used for both the min() and max() aggregates,
    ** the only difference between the two being that the sense of the
    ** comparison is inverted. For the max() aggregate, the
    ** sqlite3_user_data() function returns (void *)-1. For min() it
    ** returns (void *)db, where db is the sqlite3* database pointer.
    ** Therefore the next statement sets variable 'max' to 1 for the max()
    ** aggregate, or 0 for min().
    */
    max = sqlite3_user_data(context)!=0;
    cmp = sqlite3MemCompare(pBest, pArg, pColl);
    if( (max && cmp<0) || (!max && cmp>0) ){
      sqlite3VdbeMemCopy(pBest, pArg);
    }
  }else{
    sqlite3VdbeMemCopy(pBest, pArg);
  }
}
static void minMaxFinalize(sqlite3_context *context){
  sqlite3_value *pRes;
  pRes = (sqlite3_value *)sqlite3_aggregate_context(context, 0);
  if( pRes ){
    if( pRes->flags ){
      sqlite3_result_value(context, pRes);
    }
    sqlite3VdbeMemRelease(pRes);
  }
}

/*
** group_concat(EXPR, ?SEPARATOR?)
*/
static void groupConcatStep(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  const char *zVal;
  StrAccum *pAccum;
  const char *zSep;
  int nVal, nSep, i;
  if( argc==0 || sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
  pAccum = (StrAccum*)sqlite3_aggregate_context(context, sizeof(*pAccum));

  if( pAccum ){
    sqlite3 *db = sqlite3_context_db_handle(context);
    pAccum->useMalloc = 1;
    pAccum->mxAlloc = db->aLimit[SQLITE_LIMIT_LENGTH];
    if( pAccum->nChar ){
      if( argc>1 ){
        zSep = (char*)sqlite3_value_text(argv[argc-1]);
        nSep = sqlite3_value_bytes(argv[argc-1]);
      }else{
        zSep = ",";
        nSep = 1;
      }
      sqlite3StrAccumAppend(pAccum, zSep, nSep);
    }
    i = 0;
    do{
      zVal = (char*)sqlite3_value_text(argv[i]);
      nVal = sqlite3_value_bytes(argv[i]);
      sqlite3StrAccumAppend(pAccum, zVal, nVal);
      i++;
    }while( i<argc-1 );
  }
}
static void groupConcatFinalize(sqlite3_context *context){
  StrAccum *pAccum;
  pAccum = sqlite3_aggregate_context(context, 0);
  if( pAccum ){
    if( pAccum->tooBig ){
      sqlite3_result_error_toobig(context);
    }else if( pAccum->mallocFailed ){
      sqlite3_result_error_nomem(context);
    }else{    
      sqlite3_result_text(context, sqlite3StrAccumFinish(pAccum), -1, 
                          sqlite3_free);
    }
  }
}

/*
** This function registered all of the above C functions as SQL
** functions.  This should be the only routine in this file with
** external linkage.
*/
void sqlite3RegisterBuiltinFunctions(sqlite3 *db){
#ifndef SQLITE_OMIT_ALTERTABLE
  sqlite3AlterFunctions(db);
#endif
#ifndef SQLITE_OMIT_PARSER
  sqlite3AttachFunctions(db);
#endif
  if( !db->mallocFailed ){
    int rc = sqlite3_overload_function(db, "MATCH", 2);
    assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
    if( rc==SQLITE_NOMEM ){
      db->mallocFailed = 1;
    }
  }
#ifdef SQLITE_SSE
  (void)sqlite3SseFunctions(db);
#endif
}

/*
** Set the LIKEOPT flag on the 2-argument function with the given name.
*/
static void setLikeOptFlag(sqlite3 *db, const char *zName, int flagVal){
  FuncDef *pDef;
  pDef = sqlite3FindFunction(db, zName, strlen(zName), 2, SQLITE_UTF8, 0);
  if( pDef ){
    pDef->flags = flagVal;
  }
}

/*
** Register the built-in LIKE and GLOB functions.  The caseSensitive
** parameter determines whether or not the LIKE operator is case
** sensitive.  GLOB is always case sensitive.
*/
void sqlite3RegisterLikeFunctions(sqlite3 *db, int caseSensitive){
  struct compareInfo *pInfo;
  if( caseSensitive ){
    pInfo = (struct compareInfo*)&likeInfoAlt;
  }else{
    pInfo = (struct compareInfo*)&likeInfoNorm;
  }
  sqlite3CreateFunc(db, "like", 2, SQLITE_UTF8, pInfo, likeFunc, 0, 0);
  sqlite3CreateFunc(db, "like", 3, SQLITE_UTF8, pInfo, likeFunc, 0, 0);
  sqlite3CreateFunc(db, "glob", 2, SQLITE_UTF8, 
      (struct compareInfo*)&globInfo, likeFunc, 0,0);
  setLikeOptFlag(db, "glob", SQLITE_FUNC_LIKE | SQLITE_FUNC_CASE);
  setLikeOptFlag(db, "like", 
      caseSensitive ? (SQLITE_FUNC_LIKE | SQLITE_FUNC_CASE) : SQLITE_FUNC_LIKE);
}

/*
** pExpr points to an expression which implements a function.  If
** it is appropriate to apply the LIKE optimization to that function
** then set aWc[0] through aWc[2] to the wildcard characters and
** return TRUE.  If the function is not a LIKE-style function then
** return FALSE.
*/
int sqlite3IsLikeFunction(sqlite3 *db, Expr *pExpr, int *pIsNocase, char *aWc){
  FuncDef *pDef;
  if( pExpr->op!=TK_FUNCTION || !pExpr->pList ){
    return 0;
  }
  if( pExpr->pList->nExpr!=2 ){
    return 0;
  }
  pDef = sqlite3FindFunction(db, (char*)pExpr->token.z, pExpr->token.n, 2,
                             SQLITE_UTF8, 0);
  if( pDef==0 || (pDef->flags & SQLITE_FUNC_LIKE)==0 ){
    return 0;
  }

  /* The memcpy() statement assumes that the wildcard characters are
  ** the first three statements in the compareInfo structure.  The
  ** asserts() that follow verify that assumption
  */
  memcpy(aWc, pDef->pUserData, 3);
  assert( (char*)&likeInfoAlt == (char*)&likeInfoAlt.matchAll );
  assert( &((char*)&likeInfoAlt)[1] == (char*)&likeInfoAlt.matchOne );
  assert( &((char*)&likeInfoAlt)[2] == (char*)&likeInfoAlt.matchSet );
  *pIsNocase = (pDef->flags & SQLITE_FUNC_CASE)==0;
  return 1;
}

/*
** All all of the FuncDef structures in the aBuiltinFunc[] array above
** to the global function hash table.  This occurs at start-time (as
** a consequence of calling sqlite3_initialize()).
**
** After this routine runs
*/
void sqlite3RegisterGlobalFunctions(void){
  /*
  ** The following array holds FuncDef structures for all of the functions
  ** defined in this file.
  **
  ** The array cannot be constant since changes are made to the
  ** FuncDef.pHash elements at start-time.  The elements of this array
  ** are read-only after initialization is complete.
  */
  static SQLITE_WSD FuncDef aBuiltinFunc[] = {
    FUNCTION(ltrim,              1, 1, 0, trimFunc         ),
    FUNCTION(ltrim,              2, 1, 0, trimFunc         ),
    FUNCTION(rtrim,              1, 2, 0, trimFunc         ),
    FUNCTION(rtrim,              2, 2, 0, trimFunc         ),
    FUNCTION(trim,               1, 3, 0, trimFunc         ),
    FUNCTION(trim,               2, 3, 0, trimFunc         ),
    FUNCTION(min,               -1, 0, 1, minmaxFunc       ),
    FUNCTION(min,                0, 0, 1, 0                ),
    AGGREGATE(min,               1, 0, 1, minmaxStep,      minMaxFinalize ),
    FUNCTION(max,               -1, 1, 1, minmaxFunc       ),
    FUNCTION(max,                0, 1, 1, 0                ),
    AGGREGATE(max,               1, 1, 1, minmaxStep,      minMaxFinalize ),
    FUNCTION(typeof,             1, 0, 0, typeofFunc       ),
    FUNCTION(length,             1, 0, 0, lengthFunc       ),
    FUNCTION(substr,             2, 0, 0, substrFunc       ),
    FUNCTION(substr,             3, 0, 0, substrFunc       ),
    FUNCTION(abs,                1, 0, 0, absFunc          ),
    FUNCTION(round,              1, 0, 0, roundFunc        ),
    FUNCTION(round,              2, 0, 0, roundFunc        ),
    FUNCTION(upper,              1, 0, 0, upperFunc        ),
    FUNCTION(lower,              1, 0, 0, lowerFunc        ),
    FUNCTION(coalesce,           1, 0, 0, 0                ),
    FUNCTION(coalesce,          -1, 0, 0, ifnullFunc       ),
    FUNCTION(coalesce,           0, 0, 0, 0                ),
    FUNCTION(hex,                1, 0, 0, hexFunc          ),
    FUNCTION(ifnull,             2, 0, 1, ifnullFunc       ),
    FUNCTION(random,            -1, 0, 0, randomFunc       ),
    FUNCTION(randomblob,         1, 0, 0, randomBlob       ),
    FUNCTION(nullif,             2, 0, 1, nullifFunc       ),
    FUNCTION(sqlite_version,     0, 0, 0, versionFunc      ),
    FUNCTION(quote,              1, 0, 0, quoteFunc        ),
    FUNCTION(last_insert_rowid,  0, 0, 0, last_insert_rowid),
    FUNCTION(changes,            0, 0, 0, changes          ),
    FUNCTION(total_changes,      0, 0, 0, total_changes    ),
    FUNCTION(replace,            3, 0, 0, replaceFunc      ),
    FUNCTION(zeroblob,           1, 0, 0, zeroblobFunc     ),
  #ifdef SQLITE_SOUNDEX
    FUNCTION(soundex,            1, 0, 0, soundexFunc      ),
  #endif
  #ifndef SQLITE_OMIT_LOAD_EXTENSION
    FUNCTION(load_extension,     1, 0, 0, loadExt          ),
    FUNCTION(load_extension,     2, 0, 0, loadExt          ),
  #endif
    AGGREGATE(sum,               1, 0, 0, sumStep,         sumFinalize    ),
    AGGREGATE(total,             1, 0, 0, sumStep,         totalFinalize    ),
    AGGREGATE(avg,               1, 0, 0, sumStep,         avgFinalize    ),
    AGGREGATE(count,             0, 0, 0, countStep,       countFinalize  ),
    AGGREGATE(count,             1, 0, 0, countStep,       countFinalize  ),
    AGGREGATE(group_concat,     -1, 0, 0, groupConcatStep, groupConcatFinalize),
  
    LIKEFUNC(glob, 2, &globInfo, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
  #ifdef SQLITE_CASE_SENSITIVE_LIKE
    LIKEFUNC(like, 2, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
    LIKEFUNC(like, 3, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
  #else
    LIKEFUNC(like, 2, &likeInfoNorm, SQLITE_FUNC_LIKE),
    LIKEFUNC(like, 3, &likeInfoNorm, SQLITE_FUNC_LIKE),
  #endif
  };

  int i;
  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aBuiltinFunc);

  for(i=0; i<ArraySize(aBuiltinFunc); i++){
    sqlite3FuncDefInsert(pHash, &aFunc[i]);
  }
  sqlite3RegisterDateTimeFunctions();
}
