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Fix the application-defined function logic so that functions with a variable

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number of parameters can be replaced or deleted correctly.  Also refactor
some of the function-finder code for clarity of presentation.

FossilOrigin-Name: 09d5581c81fb6a9bf6a369d0abf5ef6b54637576
This commit is contained in:
drh
2012-04-07 00:09:21 +00:00
parent 370026242a
commit 89d5d6a2a7
5 changed files with 65 additions and 46 deletions
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89
src/callback.c
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@@ -223,38 +223,57 @@ CollSeq *sqlite3FindCollSeq(
** that uses encoding enc. The value returned indicates how well the
** request is matched. A higher value indicates a better match.
**
** If nArg is -1 that means to only return a match (non-zero) if p->nArg
** is also -1. In other words, we are searching for a function that
** takes a variable number of arguments.
**
** If nArg is -2 that means that we are searching for any function
** regardless of the number of arguments it uses, so return a positive
** match score for any
**
** The returned value is always between 0 and 6, as follows:
**
** 0: Not a match, or if nArg<0 and the function is has no implementation.
** 1: A variable arguments function that prefers UTF-8 when a UTF-16
** encoding is requested, or vice versa.
** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is
** requested, or vice versa.
** 3: A variable arguments function using the same text encoding.
** 4: A function with the exact number of arguments requested that
** prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.
** 5: A function with the exact number of arguments requested that
** prefers UTF-16LE when UTF-16BE is requested, or vice versa.
** 6: An exact match.
** 0: Not a match.
** 1: UTF8/16 conversion required and function takes any number of arguments.
** 2: UTF16 byte order change required and function takes any number of args.
** 3: encoding matches and function takes any number of arguments
** 4: UTF8/16 conversion required - argument count matches exactly
** 5: UTF16 byte order conversion required - argument count matches exactly
** 6: Perfect match: encoding and argument count match exactly.
**
** If nArg==(-2) then any function with a non-null xStep or xFunc is
** a perfect match and any function with both xStep and xFunc NULL is
** a non-match.
*/
static int matchQuality(FuncDef *p, int nArg, u8 enc){
int match = 0;
if( p->nArg==-1 || p->nArg==nArg
|| (nArg==-1 && (p->xFunc!=0 || p->xStep!=0))
){
#define FUNC_PERFECT_MATCH 6 /* The score for a perfect match */
static int matchQuality(
FuncDef *p, /* The function we are evaluating for match quality */
int nArg, /* Desired number of arguments. (-1)==any */
u8 enc /* Desired text encoding */
){
int match;
/* nArg of -2 is a special case */
if( nArg==(-2) ) return (p->xFunc==0 && p->xStep==0) ? 0 : FUNC_PERFECT_MATCH;
/* Wrong number of arguments means "no match" */
if( p->nArg!=nArg && p->nArg>=0 ) return 0;
/* Give a better score to a function with a specific number of arguments
** than to function that accepts any number of arguments. */
if( p->nArg==nArg ){
match = 4;
}else{
match = 1;
if( p->nArg==nArg || nArg==-1 ){
match = 4;
}
if( enc==p->iPrefEnc ){
match += 2;
}
else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||
(enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){
match += 1;
}
}
/* Bonus points if the text encoding matches */
if( enc==p->iPrefEnc ){
match += 2; /* Exact encoding match */
}else if( (enc & p->iPrefEnc & 2)!=0 ){
match += 1; /* Both are UTF16, but with different byte orders */
}
return match;
}
@@ -310,13 +329,12 @@ void sqlite3FuncDefInsert(
**
** If the createFlag argument is true, then a new (blank) FuncDef
** structure is created and liked into the "db" structure if a
** no matching function previously existed. When createFlag is true
** and the nArg parameter is -1, then only a function that accepts
** any number of arguments will be returned.
** no matching function previously existed.
**
** If createFlag is false and nArg is -1, then the first valid
** function found is returned. A function is valid if either xFunc
** or xStep is non-zero.
** If nArg is -2, then the first valid function found is returned. A
** function is valid if either xFunc or xStep is non-zero. The nArg==(-2)
** case is used to see if zName is a valid function name for some number
** of arguments. If nArg is -2, then createFlag must be 0.
**
** If createFlag is false, then a function with the required name and
** number of arguments may be returned even if the eTextRep flag does not
@@ -328,14 +346,15 @@ FuncDef *sqlite3FindFunction(
int nName, /* Number of characters in the name */
int nArg, /* Number of arguments. -1 means any number */
u8 enc, /* Preferred text encoding */
int createFlag /* Create new entry if true and does not otherwise exist */
u8 createFlag /* Create new entry if true and does not otherwise exist */
){
FuncDef *p; /* Iterator variable */
FuncDef *pBest = 0; /* Best match found so far */
int bestScore = 0; /* Score of best match */
int h; /* Hash value */
assert( nArg>=(-2) );
assert( nArg>=(-1) || createFlag==0 );
assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
h = (sqlite3UpperToLower[(u8)zName[0]] + nName) % ArraySize(db->aFunc.a);
@@ -381,7 +400,7 @@ FuncDef *sqlite3FindFunction(
** exact match for the name, number of arguments and encoding, then add a
** new entry to the hash table and return it.
*/
if( createFlag && (bestScore<6 || pBest->nArg!=nArg) &&
if( createFlag && bestScore<FUNC_PERFECT_MATCH &&
(pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
pBest->zName = (char *)&pBest[1];
pBest->nArg = (u16)nArg;