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authorRon Yorston <rmy@pobox.com>2021-01-29 13:23:27 +0000
committerDenys Vlasenko <vda.linux@googlemail.com>2021-02-02 14:37:37 +0100
commitbcf91d276047910538c5de0a45f3a4645e3ff471 (patch)
tree87feb6eb824d4fc2ee27918a559a03df28e15a99
parent59120c330330467c9e6aaec6d4ca8295baa653af (diff)
downloadbusybox-bcf91d276047910538c5de0a45f3a4645e3ff471.tar.gz
libbb: code shrink and speed up index_in_strings()
Rewrite index_in_strings() to replace calls to strcmp()/strlen(). With this change searching for valid names in the applet_names array (for example) is 40% faster. The code has to assume the strings aren't sorted, so will always scan the entire array when presented with an invalid name. function old new delta index_in_strings 63 56 -7 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-7) Total: -7 bytes Signed-off-by: Ron Yorston <rmy@pobox.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--libbb/compare_string_array.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/libbb/compare_string_array.c b/libbb/compare_string_array.c
index a06e57d3d..d8cd033a3 100644
--- a/libbb/compare_string_array.c
+++ b/libbb/compare_string_array.c
@@ -63,13 +63,19 @@ int FAST_FUNC index_in_str_array(const char *const string_array[], const char *k
int FAST_FUNC index_in_strings(const char *strings, const char *key)
{
- int idx = 0;
+ int j, idx = 0;
while (*strings) {
- if (strcmp(strings, key) == 0) {
- return idx;
+ /* Do we see "key\0" at current position in strings? */
+ for (j = 0; *strings == key[j]; ++j) {
+ if (*strings++ == '\0') {
+ //bb_error_msg("found:'%s' i:%u", key, idx);
+ return idx; /* yes */
+ }
}
- strings += strlen(strings) + 1; /* skip NUL */
+ /* No. Move to the start of the next string. */
+ while (*strings++ != '\0')
+ continue;
idx++;
}
return -1;