/*
** 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;
/* 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])>SQLITE_MAX_LIKE_PATTERN_LENGTH ){
sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
return;
}
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));
}
}
/*
** 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, /* 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;
}
/*
** 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, /* 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 prevEscape = 0; /* True if the previous character was uEsc */
while( 1 ){
/* Read (and consume) the next character from the input pattern. */
UChar32 uPattern;
SQLITE_ICU_READ_UTF8(zPattern, uPattern);
if( uPattern==0 ) break;
/* 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) == MATCH_ALL || c == MATCH_ONE ){
if( c==MATCH_ONE ){
if( *zString==0 ) return 0;
SQLITE_ICU_SKIP_UTF8(zString);
}
zPattern++;
}
if( *zPattern==0 ) return 1;
while( *zString ){
if( icuLikeCompare(zPattern, zString, uEsc) ){
return 1;
}
SQLITE_ICU_SKIP_UTF8(zString);
}
return 0;
}else if( !prevEscape && uPattern==MATCH_ONE ){
/* Case 2. */
if( *zString==0 ) return 0;
SQLITE_ICU_SKIP_UTF8(zString);
}else if( !prevEscape && uPattern==uEsc){
/* Case 3. */
prevEscape = 1;
}else{
/* Case 4. */
UChar32 uString;
SQLITE_ICU_READ_UTF8(zString, 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==0;
}
