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authorDenys Vlasenko2010-09-04 21:21:07 +0200
committerDenys Vlasenko2010-09-04 21:21:07 +0200
commit701e127f7d892909a58c6f3333e23588ccef9e22 (patch)
tree9d756fca6a1ef496dbf02529e090f2f711a6c261 /shell/match.c
parente298ce69baef029f3951dd1d5ed50fdbc6c55c80 (diff)
downloadbusybox-701e127f7d892909a58c6f3333e23588ccef9e22.zip
busybox-701e127f7d892909a58c6f3333e23588ccef9e22.tar.gz
hush: optimize #[#] and %[%] for speed. size -2 bytes.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Diffstat (limited to 'shell/match.c')
-rw-r--r--shell/match.c106
1 files changed, 62 insertions, 44 deletions
diff --git a/shell/match.c b/shell/match.c
index 01b8439..e77c5d7 100644
--- a/shell/match.c
+++ b/shell/match.c
@@ -18,6 +18,9 @@
# include <stdlib.h>
# include <string.h>
# include <unistd.h>
+# define FAST_FUNC /* nothing */
+# define PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN /* nothing */
+# define POP_SAVED_FUNCTION_VISIBILITY /* nothing */
#else
# include "libbb.h"
#endif
@@ -26,16 +29,48 @@
#define pmatch(a, b) !fnmatch((a), (b), 0)
-char *scanleft(char *string, char *pattern, bool match_at_left)
+char* FAST_FUNC scan_and_match(char *string, const char *pattern, unsigned flags)
{
- char c;
- char *loc = string;
+ char *loc;
+ char *end;
+ unsigned len = strlen(string);
+ int early_exit;
+
+ /* We can stop the scan early only if the string part
+ * we are matching against is shrinking, and the pattern has
+ * an unquoted "star" at the corresponding end. There are two cases.
+ * Case 1:
+ * "qwerty" does not match against pattern "*zy",
+ * no point in trying to match "werty", "erty" etc:
+ */
+ early_exit = (flags == (SCAN_MOVE_FROM_LEFT + SCAN_MATCH_RIGHT_HALF) && pattern[0] == '*');
+
+ if (flags & SCAN_MOVE_FROM_LEFT) {
+ loc = string;
+ end = string + len + 1;
+ } else {
+ loc = string + len;
+ end = string - 1;
+ if (flags == (SCAN_MOVE_FROM_RIGHT + SCAN_MATCH_LEFT_HALF)) {
+ /* Case 2:
+ * "qwerty" does not match against pattern "qz*",
+ * no point in trying to match "qwert", "qwer" etc:
+ */
+ const char *p = pattern + strlen(pattern);
+ if (--p >= pattern && *p == '*') {
+ early_exit = 1;
+ while (--p >= pattern && *p == '\\')
+ early_exit ^= 1;
+ }
+ }
+ }
- while (1) {
+ while (loc != end) {
+ char c;
int match;
c = *loc;
- if (match_at_left) {
+ if (flags & SCAN_MATCH_LEFT_HALF) {
*loc = '\0';
match = pmatch(pattern, string);
*loc = c;
@@ -44,33 +79,19 @@ char *scanleft(char *string, char *pattern, bool match_at_left)
}
if (match)
return loc;
- if (!c)
- return NULL;
- loc++;
- }
-}
-
-char *scanright(char *string, char *pattern, bool match_at_left)
-{
- char c;
- char *loc = string + strlen(string);
-
- while (loc >= string) {
- int match;
+ if (early_exit) {
+#ifdef STANDALONE
+ printf("(early exit) ");
+#endif
+ break;
+ }
- c = *loc;
- if (match_at_left) {
- *loc = '\0';
- match = pmatch(pattern, string);
- *loc = c;
+ if (flags & SCAN_MOVE_FROM_LEFT) {
+ loc++;
} else {
- match = pmatch(pattern, loc);
+ loc--;
}
- if (match)
- return loc;
- loc--;
}
-
return NULL;
}
@@ -80,12 +101,11 @@ int main(int argc, char *argv[])
char *string;
char *op;
char *pattern;
- bool match_at_left;
char *loc;
- int i;
+ setvbuf(stdout, NULL, _IONBF, 0);
- if (argc == 1) {
+ if (!argv[1]) {
puts(
"Usage: match <test> [test...]\n\n"
"Where a <test> is the form: <string><op><match>\n"
@@ -95,36 +115,34 @@ int main(int argc, char *argv[])
return 1;
}
- for (i = 1; i < argc; ++i) {
+ while (*++argv) {
size_t off;
- scan_t scan;
-
- printf("'%s': ", argv[i]);
+ unsigned scan_flags;
- string = strdup(argv[i]);
+ string = *argv;
off = strcspn(string, "#%");
if (!off) {
printf("invalid format\n");
- free(string);
continue;
}
op = string + off;
- scan = pick_scan(op[0], op[1], &match_at_left);
+ scan_flags = pick_scan(op[0], op[1]);
+
+ printf("'%s': flags:%x, ", string, scan_flags);
pattern = op + 1;
if (op[0] == op[1])
- op[1] = '\0', ++pattern;
+ pattern++;
op[0] = '\0';
- loc = scan(string, pattern, match_at_left);
+ loc = scan_and_match(string, pattern, scan_flags);
- if (match_at_left) {
+ if (scan_flags & SCAN_MATCH_LEFT_HALF) {
printf("'%s'\n", loc);
} else {
- *loc = '\0';
+ if (loc)
+ *loc = '\0';
printf("'%s'\n", string);
}
-
- free(string);
}
return 0;