func.c

sqlite数据库管理系统开放源码

/*
** 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 1.43.2.3 2004/07/18 23:03:11 drh Exp $
*/
#include <ctype.h>
#include <math.h>
#include <stdlib.h>
#include <assert.h>
#include "sqliteInt.h"
#include "os.h"

/*
** Implementation of the non-aggregate min() and max() functions
*/
static void minmaxFunc(sqlite_func *context, int argc, const char **argv){
  const char *zBest; 
  int i;
  int (*xCompare)(const char*, const char*);
  int mask;    /* 0 for min() or 0xffffffff for max() */

  if( argc==0 ) return;
  mask = (int)sqlite_user_data(context);
  zBest = argv[0];
  if( zBest==0 ) return;
  if( argv[1][0]=='n' ){
    xCompare = sqliteCompare;
  }else{
    xCompare = strcmp;
  }
  for(i=2; i<argc; i+=2){
    if( argv[i]==0 ) return;
    if( (xCompare(argv[i], zBest)^mask)<0 ){
      zBest = argv[i];
    }
  }
  sqlite_set_result_string(context, zBest, -1);
}

/*
** Return the type of the argument.
*/
static void typeofFunc(sqlite_func *context, int argc, const char **argv){
  assert( argc==2 );
  sqlite_set_result_string(context, argv[1], -1);
}

/*
** Implementation of the length() function
*/
static void lengthFunc(sqlite_func *context, int argc, const char **argv){
  const char *z;
  int len;

  assert( argc==1 );
  z = argv[0];
  if( z==0 ) return;
#ifdef SQLITE_UTF8
  for(len=0; *z; z++){ if( (0xc0&*z)!=0x80 ) len++; }
#else
  len = strlen(z);
#endif
  sqlite_set_result_int(context, len);
}

/*
** Implementation of the abs() function
*/
static void absFunc(sqlite_func *context, int argc, const char **argv){
  const char *z;
  assert( argc==1 );
  z = argv[0];
  if( z==0 ) return;
  if( z[0]=='-' && isdigit(z[1]) ) z++;
  sqlite_set_result_string(context, z, -1);
}

/*
** Implementation of the substr() function
*/
static void substrFunc(sqlite_func *context, int argc, const char **argv){
  const char *z;
#ifdef SQLITE_UTF8
  const char *z2;
  int i;
#endif
  int p1, p2, len;
  assert( argc==3 );
  z = argv[0];
  if( z==0 ) return;
  p1 = atoi(argv[1]?argv[1]:0);
  p2 = atoi(argv[2]?argv[2]:0);
#ifdef SQLITE_UTF8
  for(len=0, z2=z; *z2; z2++){ if( (0xc0&*z2)!=0x80 ) len++; }
#else
  len = strlen(z);
#endif
  if( p1<0 ){
    p1 += len;
    if( p1<0 ){
      p2 += p1;
      p1 = 0;
    }
  }else if( p1>0 ){
    p1--;
  }
  if( p1+p2>len ){
    p2 = len-p1;
  }
#ifdef SQLITE_UTF8
  for(i=0; i<p1 && z[i]; i++){
    if( (z[i]&0xc0)==0x80 ) p1++;
  }
  while( z[i] && (z[i]&0xc0)==0x80 ){ i++; p1++; }
  for(; i<p1+p2 && z[i]; i++){
    if( (z[i]&0xc0)==0x80 ) p2++;
  }
  while( z[i] && (z[i]&0xc0)==0x80 ){ i++; p2++; }
#endif
  if( p2<0 ) p2 = 0;
  sqlite_set_result_string(context, &z[p1], p2);
}

/*
** Implementation of the round() function
*/
static void roundFunc(sqlite_func *context, int argc, const char **argv){
  int n;
  double r;
  char zBuf[100];
  assert( argc==1 || argc==2 );
  if( argv[0]==0 || (argc==2 && argv[1]==0) ) return;
  n = argc==2 ? atoi(argv[1]) : 0;
  if( n>30 ) n = 30;
  if( n<0 ) n = 0;
  r = sqliteAtoF(argv[0], 0);
  sprintf(zBuf,"%.*f",n,r);
  sqlite_set_result_string(context, zBuf, -1);
}

/*
** Implementation of the upper() and lower() SQL functions.
*/
static void upperFunc(sqlite_func *context, int argc, const char **argv){
  unsigned char *z;
  int i;
  if( argc<1 || argv[0]==0 ) return;
  z = (unsigned char*)sqlite_set_result_string(context, argv[0], -1);
  if( z==0 ) return;
  for(i=0; z[i]; i++){
    if( islower(z[i]) ) z[i] = toupper(z[i]);
  }
}
static void lowerFunc(sqlite_func *context, int argc, const char **argv){
  unsigned char *z;
  int i;
  if( argc<1 || argv[0]==0 ) return;
  z = (unsigned char*)sqlite_set_result_string(context, argv[0], -1);
  if( z==0 ) return;
  for(i=0; z[i]; i++){
    if( isupper(z[i]) ) z[i] = tolower(z[i]);
  }
}

/*
** Implementation of the IFNULL(), NVL(), and COALESCE() functions.  
** All three do the same thing.  They return the first non-NULL
** argument.
*/
static void ifnullFunc(sqlite_func *context, int argc, const char **argv){
  int i;
  for(i=0; i<argc; i++){
    if( argv[i] ){
      sqlite_set_result_string(context, argv[i], -1);
      break;
    }
  }
}

/*
** Implementation of random().  Return a random integer.  
*/
static void randomFunc(sqlite_func *context, int argc, const char **argv){
  int r;
  sqliteRandomness(sizeof(r), &r);
  sqlite_set_result_int(context, r);
}

/*
** Implementation of the last_insert_rowid() SQL function.  The return
** value is the same as the sqlite_last_insert_rowid() API function.
*/
static void last_insert_rowid(sqlite_func *context, int arg, const char **argv){
  sqlite *db = sqlite_user_data(context);
  sqlite_set_result_int(context, sqlite_last_insert_rowid(db));
}

/*
** Implementation of the change_count() SQL function.  The return
** value is the same as the sqlite_changes() API function.
*/
static void change_count(sqlite_func *context, int arg, const char **argv){
  sqlite *db = sqlite_user_data(context);
  sqlite_set_result_int(context, sqlite_changes(db));
}

/*
** Implementation of the last_statement_change_count() SQL function.  The
** return value is the same as the sqlite_last_statement_changes() API function.
*/
static void last_statement_change_count(sqlite_func *context, int arg,
                                        const char **argv){
  sqlite *db = sqlite_user_data(context);
  sqlite_set_result_int(context, sqlite_last_statement_changes(db));
}

/*
** Implementation of the like() SQL function.  This function implements
** the build-in LIKE operator.  The first argument to the function is the
** string and the second argument is the pattern.  So, the SQL statements:
**
**       A LIKE B
**
** is implemented as like(A,B).
*/
static void likeFunc(sqlite_func *context, int arg, const char **argv){
  if( argv[0]==0 || argv[1]==0 ) return;
  sqlite_set_result_int(context, 
    sqliteLikeCompare((const unsigned char*)argv[0],
                      (const unsigned char*)argv[1]));
}

/*
** Implementation of the glob() SQL function.  This function implements
** the build-in GLOB operator.  The first argument to the function is the
** string and the second argument is the pattern.  So, the SQL statements:
**
**       A GLOB B
**
** is implemented as glob(A,B).
*/
static void globFunc(sqlite_func *context, int arg, const char **argv){
  if( argv[0]==0 || argv[1]==0 ) return;
  sqlite_set_result_int(context,
    sqliteGlobCompare((const unsigned char*)argv[0],
                      (const unsigned char*)argv[1]));
}

/*
** 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(sqlite_func *context, int argc, const char **argv){
  if( argv[0]!=0 && sqliteCompare(argv[0],argv[1])!=0 ){
    sqlite_set_result_string(context, argv[0], -1);
  }
}

/*
** Implementation of the VERSION(*) function.  The result is the version
** of the SQLite library that is running.
*/
static void versionFunc(sqlite_func *context, int argc, const char **argv){
  sqlite_set_result_string(context, sqlite_version, -1);
}

/*
** 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(sqlite_func *context, int argc, const char **argv){
  if( argc<1 ) return;
  if( argv[0]==0 ){
    sqlite_set_result_string(context, "NULL", 4);
  }else if( sqliteIsNumber(argv[0]) ){
    sqlite_set_result_string(context, argv[0], -1);
  }else{
    int i,j,n;
    char *z;
    for(i=n=0; argv[0][i]; i++){ if( argv[0][i]=='\'' ) n++; }
    z = sqliteMalloc( i+n+3 );
    if( z==0 ) return;
    z[0] = '\'';
    for(i=0, j=1; argv[0][i]; i++){
      z[j++] = argv[0][i];
      if( argv[0][i]=='\'' ){
        z[j++] = '\'';
      }
    }
    z[j++] = '\'';
    z[j] = 0;
    sqlite_set_result_string(context, z, j);
    sqliteFree(z);
  }
}

#ifdef SQLITE_SOUNDEX
/*
** Compute the soundex encoding of a word.
*/
static void soundexFunc(sqlite_func *context, int argc, const char **argv){
  char zResult[8];
  const char *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,