From 1310d7b1d106d7ab0ec84ce88c12302cca934230 Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Thu, 22 Jul 2021 18:15:59 +0200
Subject: ash: speed up ${v//pattern/repl} if !ASH_OPTIMIZE_FOR_SIZE
function old new delta
subevalvar 1353 1447 +94
.rodata 104179 104184 +5
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 99/0) Total: 99 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
shell/ash.c | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)
diff --git a/shell/ash.c b/shell/ash.c
index 2eac6e113..092f3bcc7 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6970,7 +6970,8 @@ scanright(char *startp, char *rmesc, char *rmescend,
* Logic:
* loc starts at NUL at the end of startp, loc2 starts at the end of rmesc,
* and on each iteration they go back two/one char until they reach the beginning.
- * We try to find a match in "raw_value_of_v", "raw_value_of_", "raw_value_of" etc.
+ * We try to match "raw_value_of_v", "raw_value_of_", "raw_value_of" etc.
+ * If one of these matches, return pointer past last matched char in startp.
*/
/* TODO: document in what other circumstances we are called. */
@@ -7258,6 +7259,7 @@ subevalvar(char *start, char *str, int strloc,
#if BASH_PATTERN_SUBST
workloc = expdest - (char *)stackblock();
if (subtype == VSREPLACE || subtype == VSREPLACEALL) {
+ size_t no_meta_len;
int len;
char *idx, *end;
@@ -7275,16 +7277,38 @@ subevalvar(char *start, char *str, int strloc,
if (str[0] == '\0')
goto out1;
+ no_meta_len = (ENABLE_ASH_OPTIMIZE_FOR_SIZE || strpbrk(str, "*?[\\")) ? 0 : strlen(str);
len = 0;
idx = startp;
end = str - 1;
while (idx <= end) {
try_to_match:
- loc = scanright(idx, rmesc, rmescend, str, quotes, 1);
+ if (no_meta_len == 0) {
+ /* pattern has meta chars, have to glob; or ENABLE_ASH_OPTIMIZE_FOR_SIZE */
+ loc = scanright(idx, rmesc, rmescend, str, quotes, /*match_at_start:*/ 1);
+ } else {
+ /* Testcase for very slow replace (performs about 22k replaces):
+ * x=::::::::::::::::::::::
+ * x=$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//:/|}"
+ */
+ size_t n;
+ if (strncmp(rmesc, str, no_meta_len) != 0)
+ goto no_match;
+ n = no_meta_len;
+ loc = idx;
+ do {
+ if (quotes && (unsigned char)*loc == CTLESC)
+ loc++;
+ loc++;
+ } while (--n != 0);
+ }
//bb_error_msg("scanright('%s'):'%s'", str, loc);
if (!loc) {
+ char *restart_detect;
+ no_match:
/* No match, advance */
- char *restart_detect = stackblock();
+ restart_detect = stackblock();
skip_matching:
if (idx >= end)
break;
--
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