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hush: optimize ${var/pattern/repl} for trivial patterns

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function                                             old     new   delta
expand_one_var                                      2353    2507    +154

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-07-27 17:53:55 +02:00
parent c450437a4e
commit 49cc3cac30
2 changed files with 14 additions and 2 deletions
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13
shell/hush.c
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@ -6466,6 +6466,19 @@ static arith_t expand_and_evaluate_arith(const char *arg, const char **errmsg_p)
/* ${var/[/]pattern[/repl]} helpers */
static char *strstr_pattern(char *val, const char *pattern, int *size)
{
if (!strpbrk(pattern, "*?[\\")) {
/* Optimization for trivial patterns.
* Testcase for very slow replace (performs about 22k replaces):
* x=::::::::::::::::::::::
* x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;x=$x$x;echo ${#x}
* echo "${x//:/|}"
*/
char *found = strstr(val, pattern);
if (found)
*size = strlen(pattern);
return found;
}
while (1) {
char *end = scan_and_match(val, pattern, SCAN_MOVE_FROM_RIGHT + SCAN_MATCH_LEFT_HALF);
debug_printf_varexp("val:'%s' pattern:'%s' end:'%s'\n", val, pattern, end);

3
shell/match.c
View File

@ -64,11 +64,10 @@ char* FAST_FUNC scan_and_match(char *string, const char *pattern, unsigned flags
}
while (loc != end) {
char c;
int r;
c = *loc;
if (flags & SCAN_MATCH_LEFT_HALF) {
char c = *loc;
*loc = '\0';
r = fnmatch(pattern, string, 0);
//bb_error_msg("fnmatch('%s','%s',0):%d", pattern, string, r);