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Archive   : REGEXG11.ZIP
Filename : MATCH.C

/*
EPSHeader

File: match.c
Author: J. Kercheval
Created: Sat, 01/05/1991 22:21:49
*/
/*
EPSRevision History

J. Kercheval Wed, 02/20/1991 22:29:01 Released to Public Domain
J. Kercheval Fri, 02/22/1991 15:29:01 fix '\' bugs (two 🙁 of them)
J. Kercheval Sun, 03/10/1991 19:31:29 add error return to matche()
J. Kercheval Sun, 03/10/1991 20:11:11 add is_valid_pattern code
J. Kercheval Sun, 03/10/1991 20:37:11 beef up main()
J. Kercheval Tue, 03/12/1991 22:25:10 Released as V1.1 to Public Domain
*/

/*
Wildcard Pattern Matching
*/


#include "match.h"

int matche_after_star (register char *pattern, register char *text);
int fast_match_after_star (register char *pattern, register char *text);

/*----------------------------------------------------------------------------
*
* Return TRUE if PATTERN has any special wildcard characters
*
----------------------------------------------------------------------------*/

BOOLEAN is_pattern (char *p)
{
while ( *p ) {
switch ( *p++ ) {
case '?':
case '*':
case '[':
case '\\':
return TRUE;
}
}
return FALSE;
}


/*----------------------------------------------------------------------------
*
* Return TRUE if PATTERN has is a well formed regular expression according
* to the above syntax
*
* error_type is a return code based on the type of pattern error. Zero is
* returned in error_type if the pattern is a valid one. error_type return
* values are as follows:
*
* PATTERN_VALID - pattern is well formed
* PATTERN_ESC - pattern has invalid escape ('\' at end of pattern)
* PATTERN_RANGE - [..] construct has a no end range in a '-' pair (ie [a-])
* PATTERN_CLOSE - [..] construct has no end bracket (ie [abc-g )
* PATTERN_EMPTY - [..] construct is empty (ie [])
*
----------------------------------------------------------------------------*/

BOOLEAN is_valid_pattern (char *p, int *error_type)
{

/* init error_type */
*error_type = PATTERN_VALID;

/* loop through pattern to EOS */
while( *p ) {

/* determine pattern type */
switch( *p ) {

/* check literal escape, it cannot be at end of pattern */
case '\\':
if( !*++p ) {
*error_type = PATTERN_ESC;
return FALSE;
}
p++;
break;

/* the [..] construct must be well formed */
case '[':
p++;

/* if the next character is ']' then bad pattern */
if ( *p == ']' ) {
*error_type = PATTERN_EMPTY;
return FALSE;
}

/* if end of pattern here then bad pattern */
if ( !*p ) {
*error_type = PATTERN_CLOSE;
return FALSE;
}

/* loop to end of [..] construct */
while( *p != ']' ) {

/* check for literal escape */
if( *p == '\\' ) {
p++;

/* if end of pattern here then bad pattern */
if ( !*p++ ) {
*error_type = PATTERN_ESC;
return FALSE;
}
}
else
p++;

/* if end of pattern here then bad pattern */
if ( !*p ) {
*error_type = PATTERN_CLOSE;
return FALSE;
}

/* if this a range */
if( *p == '-' ) {

/* we must have an end of range */
if ( !*++p || *p == ']' ) {
*error_type = PATTERN_RANGE;
return FALSE;
}
else {

/* check for literal escape */
if( *p == '\\' )
p++;

/* if end of pattern here then bad pattern */
if ( !*p++ ) {
*error_type = PATTERN_ESC;
return FALSE;
}
}
}
}
break;

/* all other characters are valid pattern elements */
case '*':
case '?':
default:
p++; /* "normal" character */
break;
}
}

return TRUE;
}


/*----------------------------------------------------------------------------
*
* Match the pattern PATTERN against the string TEXT;
*
* returns MATCH_VALID if pattern matches, or an errorcode as follows
* otherwise:
*
* MATCH_PATTERN - bad pattern
* MATCH_LITERAL - match failure on literal mismatch
* MATCH_RANGE - match failure on [..] construct
* MATCH_ABORT - premature end of text string
* MATCH_END - premature end of pattern string
* MATCH_VALID - valid match
*
*
* A match means the entire string TEXT is used up in matching.
*
* In the pattern string:
* `*' matches any sequence of characters (zero or more)
* `?' matches any character
* [SET] matches any character in the specified set,
* [!SET] or [^SET] matches any character not in the specified set.
*
* A set is composed of characters or ranges; a range looks like
* character hyphen character (as in 0-9 or A-Z). [0-9a-zA-Z_] is the
* minimal set of characters allowed in the [..] pattern construct.
* Other characters are allowed (ie. 8 bit characters) if your system
* will support them.
*
* To suppress the special syntactic significance of any of `[]*?!^-\',
* and match the character exactly, precede it with a `\'.
*
----------------------------------------------------------------------------*/

int matche ( register char *p, register char *t )
{
register char range_start, range_end; /* start and end in range */

BOOLEAN invert; /* is this [..] or [!..] */
BOOLEAN member_match; /* have I matched the [..] construct? */
BOOLEAN loop; /* should I terminate? */

for ( ; *p; p++, t++ ) {

/* if this is the end of the text then this is the end of the match */
if (!*t) {
return ( *p == '*' && *++p == '\0' ) ? MATCH_VALID : MATCH_ABORT;
}

/* determine and react to pattern type */
switch ( *p ) {

/* single any character match */
case '?':
break;

/* multiple any character match */
case '*':
return matche_after_star (p, t);

/* [..] construct, single member/exclusion character match */
case '[': {

/* move to beginning of range */
p++;

/* check if this is a member match or exclusion match */
invert = FALSE;
if ( *p == '!' || *p == '^') {
invert = TRUE;
p++;
}

/* if closing bracket here or at range start then we have a
malformed pattern */
if ( *p == ']' ) {
return MATCH_PATTERN;
}

member_match = FALSE;
loop = TRUE;

while ( loop ) {

/* if end of construct then loop is done */
if (*p == ']') {
loop = FALSE;
continue;
}

/* matching a '!', '^', '-', '\' or a ']' */
if ( *p == '\\' ) {
range_start = range_end = *++p;
}
else {
range_start = range_end = *p;
}

/* if end of pattern then bad pattern (Missing ']') */
if (!*p)
return MATCH_PATTERN;

/* check for range bar */
if (*++p == '-') {

/* get the range end */
range_end = *++p;

/* if end of pattern or construct then bad pattern */
if (range_end == '\0' || range_end == ']')
return MATCH_PATTERN;

/* special character range end */
if (range_end == '\\') {
range_end = *++p;

/* if end of text then we have a bad pattern */
if (!range_end)
return MATCH_PATTERN;
}

/* move just beyond this range */
p++;
}

/* if the text character is in range then match found.
make sure the range letters have the proper
relationship to one another before comparison */
if ( range_start < range_end ) {
if (*t >= range_start && *t <= range_end) {
member_match = TRUE;
loop = FALSE;
}
}
else {
if (*t >= range_end && *t <= range_start) {
member_match = TRUE;
loop = FALSE;
}
}
}

/* if there was a match in an exclusion set then no match */
/* if there was no match in a member set then no match */
if ((invert && member_match) ||
!(invert || member_match))
return MATCH_RANGE;

/* if this is not an exclusion then skip the rest of the [...]
construct that already matched. */
if (member_match) {
while (*p != ']') {

/* bad pattern (Missing ']') */
if (!*p)
return MATCH_PATTERN;

/* skip exact match */
if (*p == '\\') {
p++;

/* if end of text then we have a bad pattern */
if (!*p)
return MATCH_PATTERN;
}

/* move to next pattern char */
p++;
}
}

break;
}

/* next character is quoted and must match exactly */
case '\\':

/* move pattern pointer to quoted char and fall through */
p++;

/* if end of text then we have a bad pattern */
if (!*p)
return MATCH_PATTERN;

/* must match this character exactly */
default:
if (*p != *t)
return MATCH_LITERAL;
}
}

/* if end of text not reached then the pattern fails */
if ( *t )
return MATCH_END;
else
return MATCH_VALID;
}


/*----------------------------------------------------------------------------
*
* recursively call matche() with final segment of PATTERN and of TEXT.
*
----------------------------------------------------------------------------*/

int matche_after_star (register char *p, register char *t)
{
register int match = 0;
register nextp;

/* pass over existing ? and * in pattern */
while ( *p == '?' || *p == '*' ) {

/* take one char for each ? and + */
if ( *p == '?' ) {

/* if end of text then no match */
if ( !*t++ ) {
return MATCH_ABORT;
}
}

/* move to next char in pattern */
p++;
}

/* if end of pattern we have matched regardless of text left */
if ( !*p ) {
return MATCH_VALID;
}

/* get the next character to match which must be a literal or '[' */
nextp = *p;
if ( nextp == '\\' ) {
nextp = p[1];

/* if end of text then we have a bad pattern */
if (!nextp)
return MATCH_PATTERN;
}

/* Continue until we run out of text or definite result seen */
do {

/* a precondition for matching is that the next character
in the pattern match the next character in the text or that
the next pattern char is the beginning of a range. Increment
text pointer as we go here */
if ( nextp == *t || nextp == '[' ) {
match = matche(p, t);
}

/* if the end of text is reached then no match */
if ( !*t++ ) match = MATCH_ABORT;

} while ( match != MATCH_VALID &&
match != MATCH_ABORT &&
match != MATCH_PATTERN);

/* return result */
return match;
}


/*----------------------------------------------------------------------------
*
* match() is a shell to matche() to return only BOOLEAN values.
*
----------------------------------------------------------------------------*/

BOOLEAN match( char *p, char *t )
{
int error_type;
error_type = matche(p,t);
return (error_type == MATCH_VALID ) ? TRUE : FALSE;
}


#ifdef TEST

/*
* This test main expects as first arg the pattern and as second arg
* the match string. Output is yaeh or nay on match. If nay on
* match then the error code is parsed and written.
*/

#include

int main(int argc, char *argv[])
{
int error;
int is_valid_error;

if (argc != 3) {
printf("Usage: MATCH Pattern Text\n");
}
else {
printf("Pattern: %s\n", argv[1]);
printf("Text : %s\n", argv[2]);

if (!is_pattern(argv[1])) {
printf(" First Argument Is Not A Pattern\n");
}
else {
error = matche(argv[1],argv[2]);
is_valid_pattern(argv[1],&is_valid_error);

switch ( error ) {
case MATCH_VALID:
printf(" Match Successful");
if (is_valid_error != PATTERN_VALID)
printf(" -- is_valid_pattern() is complaining\n");
else
printf("\n");
break;
case MATCH_LITERAL:
printf(" Match Failed on Literal\n");
break;
case MATCH_RANGE:
printf(" Match Failed on [..]\n");
break;
case MATCH_ABORT:
printf(" Match Failed on Early Text Termination\n");
break;
case MATCH_END:
printf(" Match Failed on Early Pattern Termination\n");
break;
case MATCH_PATTERN:
switch ( is_valid_error ) {
case PATTERN_VALID:
printf(" Internal Disagreement On Pattern\n");
break;
case PATTERN_ESC:
printf(" Literal Escape at End of Pattern\n");
break;
case PATTERN_RANGE:
printf(" No End of Range in [..] Construct\n");
break;
case PATTERN_CLOSE:
printf(" [..] Construct is Open\n");
break;
case PATTERN_EMPTY:
printf(" [..] Construct is Empty\n");
break;
default:
printf(" Internal Error in is_valid_pattern()\n");
}
break;
default:
printf(" Internal Error in matche()\n");
break;
}
}

}
return(0);
}

#endif