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#include "regexp.h"
#define MAX_SUBST_STRING 4095
typedef struct subst_string
{
char s[MAX_SUBST_STRING+1];
int len;
} subst_string;
static void
subst_string_init( subst_string* string,
const char* source )
{
int len = 0;
if (source)
{
len = strlen(source);
if (len > MAX_SUBST_STRING)
len = MAX_SUBST_STRING;
if (len > 0)
memcpy( string->s, source, len );
}
string->s[len] = 0;
string->len = len;
}
static void
subst_string_add( subst_string* string,
const char* source,
int src_len )
{
int delta;
delta = string->len + src_len - MAX_SUBST_STRING;
if (delta > 0)
src_len -= delta;
if ( src_len > 0 )
{
memcpy( string->s + string->len, source, src_len );
string->len += src_len;
string->s[ string->len ] = 0;
}
}
static void
subst_string_add_char( subst_string* string,
const char c )
{
int len = string->len;
if ( len < MAX_SUBST_STRING )
{
string->s[len++] = c;
string->s[len] = 0;
string->len = len;
}
}
static void
subst_string_setsub( subst_string* string,
int offset,
int len,
const char* replacement )
{
subst_string temp;
int end;
subst_string_init( &temp, 0 );
subst_string_add( &temp, string->s, offset );
if (replacement)
subst_string_add( &temp, replacement, strlen(replacement) );
offset += len;
subst_string_add( &temp, string->s + offset, string->len - offset );
*string = temp;
}
void substitute( const char* source,
const char* pattern,
const char* replacement,
char* target )
{
regexp* repat;
target[0] = '\0';
repat = regcomp( (char*)pattern );
if (repat)
{
if ( regexec( repat, (char*)source ) )
{
subst_string targ;
/* a match was found */
if ( !strchr( replacement, '$' ) )
{
/* fast, simple replacement */
subst_string_init( &targ, source );
subst_string_setsub( &targ, repat->startp[0] - source,
repat->endp[0] - repat->startp[0],
replacement );
}
else
{
/* perform sub-expression replacement */
subst_string temp;
const char* src = replacement;
char c;
subst_string_init( &targ, 0 );
subst_string_init( &temp, 0 );
for (;;)
{
c = *src++;
if (!c) break;
if ( c == '$' )
{
if ( *src == '&' || (*src - '0') <= 9 )
{
int n = (*src++ - '0');
if ( (unsigned int)n > 9)
n = 0;
subst_string_add( &temp, repat->startp[n],
repat->endp[n] - repat->startp[n] );
continue;
}
}
/* ordinary character */
if ( c == '\\' && ( *src == '\\' || *src == '$' ) )
c = *src++;
subst_string_add_char( &temp, c );
}
subst_string_setsub( &targ, repat->startp[0] - source,
repat->endp[0] - repat->startp[0],
temp.s );
}
/* now copy the content of "targ" to the target */
strcpy( target, targ.s );
}
else
{
/* no match, simply copy source into target */
strcpy( target, source );
}
free( repat );
}
}
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