1310d7b1d
Denys Vlasenko
2021-07-22
Subject
ash: speed up ${v//pattern/repl} if !ASH_OPTIMIZE_FOR_SIZE
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shell/ash.c+27 -3
| @@ -6970,7 +6970,8 @@ scanright(char *startp, char *rmesc, char *rmescend, | |
| * Logic: | |
| * loc starts at NUL at the end of startp, loc2 starts at the end of rmesc, | |
| * and on each iteration they go back two/one char until they reach the beginning. | |
| - | * We try to find a match in "raw_value_of_v", "raw_value_of_", "raw_value_of" etc. |
| + | * We try to match "raw_value_of_v", "raw_value_of_", "raw_value_of" etc. |
| + | * If one of these matches, return pointer past last matched char in startp. |
| */ | |
| /* TODO: document in what other circumstances we are called. */ | |
| @@ -7258,6 +7259,7 @@ subevalvar(char *start, char *str, int strloc, | |
| #if BASH_PATTERN_SUBST | |
| workloc = expdest - (char *)stackblock(); | |
| if (subtype == VSREPLACE || subtype == VSREPLACEALL) { | |
| + | size_t no_meta_len; |
| int len; | |
| char *idx, *end; | |
| @@ -7275,16 +7277,38 @@ subevalvar(char *start, char *str, int strloc, | |
| if (str[0] == '\0') | |
| goto out1; | |
| + | no_meta_len = (ENABLE_ASH_OPTIMIZE_FOR_SIZE || strpbrk(str, "*?[\\")) ? 0 : strlen(str); |
| len = 0; | |
| idx = startp; | |
| end = str - 1; | |
| while (idx <= end) { | |
| try_to_match: | |
| - | loc = scanright(idx, rmesc, rmescend, str, quotes, 1); |
| + | if (no_meta_len == 0) { |
| + | /* pattern has meta chars, have to glob; or ENABLE_ASH_OPTIMIZE_FOR_SIZE */ |
| + | loc = scanright(idx, rmesc, rmescend, str, quotes, /*match_at_start:*/ 1); |
| + | } else { |
| + | /* Testcase for very slow replace (performs about 22k replaces): |
| + | * x=:::::::::::::::::::::: |
| + | * x=$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; | |