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Implementation of the INSTR() SQL function, as found in SQL Server, MySQL,

Browse Source 
and Oracle.

FossilOrigin-Name: 49ccae964f3a8ae5aab87f56503121e09424545f
This commit is contained in:
drh
2012-10-25 03:07:29 +00:00
parent 8749c1831a
commit d55e07296b
4 changed files with 271 additions and 7 deletions
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src/func.c
+50
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@@ -168,6 +168,55 @@ static void absFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
}
}
/*
** Implementation of the instr() function.
**
** instr(haystack,needle) finds the first occurrence of needle
** in haystack and returns the number of previous characters plus 1,
** or 0 if needle does not occur within haystack.
**
** If both haystack and needle are BLOBs, then the result is one more than
** the number of bytes in haystack prior to the first occurrence of needle,
** or 0 if needle never occurs in haystack.
*/
static void instrFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
const unsigned char *zHaystack;
const unsigned char *zNeedle;
int nHaystack;
int nNeedle;
int typeHaystack, typeNeedle;
int N = 1;
int isText;
typeHaystack = sqlite3_value_type(argv[0]);
typeNeedle = sqlite3_value_type(argv[1]);
if( typeHaystack==SQLITE_NULL || typeNeedle==SQLITE_NULL ) return;
nHaystack = sqlite3_value_bytes(argv[0]);
nNeedle = sqlite3_value_bytes(argv[1]);
if( typeHaystack==SQLITE_BLOB && typeNeedle==SQLITE_BLOB ){
zHaystack = sqlite3_value_blob(argv[0]);
zNeedle = sqlite3_value_blob(argv[1]);
isText = 0;
}else{
zHaystack = sqlite3_value_text(argv[0]);
zNeedle = sqlite3_value_text(argv[1]);
isText = 1;
}
while( nNeedle<=nHaystack && memcmp(zHaystack, zNeedle, nNeedle)!=0 ){
N++;
do{
nHaystack--;
zHaystack++;
}while( isText && (zHaystack[0]&0xc0)==0x80 );
}
if( nNeedle>nHaystack ) N = 0;
sqlite3_result_int(context, N);
}
/*
** Implementation of the substr() function.
**
@@ -1536,6 +1585,7 @@ void sqlite3RegisterGlobalFunctions(void){
AGGREGATE(max, 1, 1, 1, minmaxStep, minMaxFinalize ),
FUNCTION2(typeof, 1, 0, 0, typeofFunc, SQLITE_FUNC_TYPEOF),
FUNCTION2(length, 1, 0, 0, lengthFunc, SQLITE_FUNC_LENGTH),
FUNCTION(instr, 2, 0, 0, instrFunc ),
FUNCTION(substr, 2, 0, 0, substrFunc ),
FUNCTION(substr, 3, 0, 0, substrFunc ),
FUNCTION(abs, 1, 0, 0, absFunc ),