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Add a version of the LIKE operator to the icu extension. Requires optimisation. (CVS 3939)

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FossilOrigin-Name: 3e96105c1f084a4ab4dad4de6f4759e43fc497f7
This commit is contained in:
danielk1977
2007-05-07 16:58:02 +00:00
parent a393c03686
commit 7de68a097e
4 changed files with 150 additions and 22 deletions
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ext/icu/icu.c
+136 -10
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@@ -5,14 +5,14 @@
** for handling unicode data) and SQLite. The integration uses
** ICU to provide the following to SQLite:
**
** * An implementation of the SQL regexp() function (and hence REGEXP
** operator) using the ICU uregex_XX() APIs.
**
** * Implementations of the SQL scalar upper() and lower()
** functions for case mapping,
** functions for case mapping.
**
** * Collation sequences
**
** * Implementation of the SQL regexp() function (and hence REGEXP
** operator) using the ICU uregex_XX() APIs.
**
** * LIKE
*/
@@ -47,10 +47,130 @@ static void xFree(void *p){
}
/*
** LIKE operator.
**
** http://unicode.org/reports/tr21/tr21-5.html#Caseless_Matching
** Compare two UTF-8 strings for equality where the first string is
** a "LIKE" expression. Return true (1) if they are the same and
** false (0) if they are different.
*/
static int icuLikeCompare(
const uint8_t *zPattern, /* The UTF-8 LIKE pattern */
const uint8_t *zString, /* The UTF-8 string to compare against */
const UChar32 uEsc /* The escape character */
){
static const int MATCH_ONE = (UChar32)'_';
static const int MATCH_ALL = (UChar32)'%';
int iPattern = 0; /* Current byte index in zPattern */
int iString = 0; /* Current byte index in zString */
int prevEscape = 0; /* True if the previous character was uEsc */
while( zPattern[iPattern]!=0 ){
/* Read (and consume) the next character from the input pattern. */
UChar32 uPattern;
U8_NEXT_UNSAFE(zPattern, iPattern, uPattern);
assert(uPattern!=0);
/* There are now 4 possibilities:
**
** 1. uPattern is an unescaped match-all character "%",
** 2. uPattern is an unescaped match-one character "_",
** 3. uPattern is an unescaped escape character, or
** 4. uPattern is to be handled as an ordinary character
*/
if( !prevEscape && uPattern==MATCH_ALL ){
/* Case 1. */
uint8_t c;
/* Skip any MATCH_ALL or MATCH_ONE characters that follow a
** MATCH_ALL. For each MATCH_ONE, skip one character in the
** test string.
*/
while( (c=zPattern[iPattern]) == MATCH_ALL || c == MATCH_ONE ){
if( c==MATCH_ONE ){
if( zString[iString]==0 ) return 0;
U8_FWD_1_UNSAFE(zString, iString);
}
iPattern++;
}
if( zPattern[iPattern]==0 ) return 1;
while( zString[iString] ){
if( icuLikeCompare(&zPattern[iPattern], &zString[iString], uEsc) ){
return 1;
}
U8_FWD_1_UNSAFE(zString, iString);
}
return 0;
}else if( !prevEscape && uPattern==MATCH_ONE ){
/* Case 2. */
if( zString[iString]==0 ) return 0;
U8_FWD_1_UNSAFE(zString, iString);
}else if( !prevEscape && uPattern==uEsc){
/* Case 3. */
prevEscape = 1;
}else{
/* Case 4. */
UChar32 uString;
U8_NEXT_UNSAFE(zString, iString, uString);
uString = u_foldCase(uString, U_FOLD_CASE_DEFAULT);
uPattern = u_foldCase(uPattern, U_FOLD_CASE_DEFAULT);
if( uString!=uPattern ){
return 0;
}
prevEscape = 0;
}
}
return zString[iString]==0;
}
/*
** 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). If there is an escape character E,
**
** A LIKE B ESCAPE E
**
** is mapped to like(B, A, E).
*/
static void icuLikeFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
const unsigned char *zA = sqlite3_value_text(argv[0]);
const unsigned char *zB = sqlite3_value_text(argv[1]);
UChar32 uEsc = 0;
if( argc==3 ){
/* The escape character string must consist of a single UTF-8 character.
** Otherwise, return an error.
*/
int nE= sqlite3_value_bytes(argv[2]);
const unsigned char *zE = sqlite3_value_text(argv[2]);
int i = 0;
if( zE==0 ) return;
U8_NEXT(zE, i, nE, uEsc);
if( i!=nE){
sqlite3_result_error(context,
"ESCAPE expression must be a single character", -1);
return;
}
}
if( zA && zB ){
sqlite3_result_int(context, icuLikeCompare(zA, zB, uEsc));
}
}
/*
** This function is called when an ICU function called from within
@@ -194,6 +314,9 @@ static void icuCaseFunc16(sqlite3_context *p, int nArg, sqlite3_value **apArg){
}
zInput = sqlite3_value_text16(apArg[0]);
if( !zInput ){
return;
}
nInput = sqlite3_value_bytes16(apArg[0]);
nOutput = nInput * 2 + 2;
@@ -244,7 +367,7 @@ static int icuCollationColl(
case UCOL_GREATER: return +1;
case UCOL_EQUAL: return 0;
}
assert(!"Bad return value from ucol_strcoll()");
assert(!"Unexpected return value from ucol_strcoll()");
return 0;
}
@@ -288,7 +411,7 @@ static void icuLoadCollation(
}
assert(p);
rc = sqlite3_create_collation_x(db, zName, SQLITE_UTF16, (void *)pUCollator,
rc = sqlite3_create_collation_v2(db, zName, SQLITE_UTF16, (void *)pUCollator,
icuCollationColl, icuCollationDel
);
if( rc!=SQLITE_OK ){
@@ -308,7 +431,7 @@ int sqlite3IcuInit(sqlite3 *db){
void *pContext; /* sqlite3_user_data() context */
void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
} scalars[] = {
{"regexp", 2, SQLITE_ANY, 0, icuRegexpFunc},
{"regexp",-1, SQLITE_ANY, 0, icuRegexpFunc},
{"lower", 1, SQLITE_UTF16, 0, icuCaseFunc16},
{"lower", 2, SQLITE_UTF16, 0, icuCaseFunc16},
@@ -320,6 +443,9 @@ int sqlite3IcuInit(sqlite3 *db){
{"upper", 1, SQLITE_UTF8, (void*)1, icuCaseFunc16},
{"upper", 2, SQLITE_UTF8, (void*)1, icuCaseFunc16},
{"like", 2, SQLITE_UTF8, 0, icuLikeFunc},
{"like", 3, SQLITE_UTF8, 0, icuLikeFunc},
{"icu_load_collation", 2, SQLITE_UTF8, (void*)db, icuLoadCollation},
};