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Posted to commits@nuttx.apache.org by GitBox <gi...@apache.org> on 2022/05/10 12:26:27 UTC
[GitHub] [incubator-nuttx] juniskane opened a new pull request, #6229: libc/string: simplify strrchr
juniskane opened a new pull request, #6229:
URL: https://github.com/apache/incubator-nuttx/pull/6229
## Summary
Do not call strlen() inside strrchr(). Old implementation iterated over string twice, if searched for position was at the beginning. This commit changes strrchr() to scan string only once, regardless of input.
At least my compiler with -O2 was not smart enough to get rid of strlen() call.
strrchr(s, 0) still works correctly with new implementation.
## Impact
Minor optimization / code simplification
## Testing
--
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[GitHub] [incubator-nuttx] juniskane commented on a diff in pull request #6229: libc/string: simplify strrchr
Posted by GitBox <gi...@apache.org>.
juniskane commented on code in PR #6229:
URL: https://github.com/apache/incubator-nuttx/pull/6229#discussion_r869267336
##########
libs/libc/string/lib_strrchr.c:
##########
@@ -37,15 +37,16 @@
#undef strrchr /* See mm/README.txt */
FAR char *strrchr(FAR const char *s, int c)
{
- FAR const char *p = &s[strlen(s)];
+ FAR const char *r = NULL;
- for (; p >= s; p--)
+ do
{
- if (*p == c)
+ if (*s == (char)c)
{
- return (FAR char *)p;
+ r = s;
}
}
+ while (*s++);
Review Comment:
done
##########
libs/libc/string/lib_strrchr.c:
##########
@@ -37,15 +37,16 @@
#undef strrchr /* See mm/README.txt */
FAR char *strrchr(FAR const char *s, int c)
{
- FAR const char *p = &s[strlen(s)];
+ FAR const char *r = NULL;
- for (; p >= s; p--)
+ do
{
- if (*p == c)
+ if (*s == (char)c)
Review Comment:
removed cast
--
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[GitHub] [incubator-nuttx] xiaoxiang781216 merged pull request #6229: libc/string: simplify strrchr
Posted by GitBox <gi...@apache.org>.
xiaoxiang781216 merged PR #6229:
URL: https://github.com/apache/incubator-nuttx/pull/6229
--
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[GitHub] [incubator-nuttx] pkarashchenko commented on a diff in pull request #6229: libc/string: simplify strrchr
Posted by GitBox <gi...@apache.org>.
pkarashchenko commented on code in PR #6229:
URL: https://github.com/apache/incubator-nuttx/pull/6229#discussion_r869177221
##########
libs/libc/string/lib_strrchr.c:
##########
@@ -37,15 +37,16 @@
#undef strrchr /* See mm/README.txt */
FAR char *strrchr(FAR const char *s, int c)
{
- FAR const char *p = &s[strlen(s)];
+ FAR const char *r = NULL;
- for (; p >= s; p--)
+ do
{
- if (*p == c)
+ if (*s == (char)c)
Review Comment:
I think the cast is redundant
##########
libs/libc/string/lib_strrchr.c:
##########
@@ -37,15 +37,16 @@
#undef strrchr /* See mm/README.txt */
FAR char *strrchr(FAR const char *s, int c)
{
- FAR const char *p = &s[strlen(s)];
+ FAR const char *r = NULL;
- for (; p >= s; p--)
+ do
{
- if (*p == c)
+ if (*s == (char)c)
{
- return (FAR char *)p;
+ r = s;
}
}
+ while (*s++);
Review Comment:
```suggestion
while (*s++ != '\0');
```
--
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[GitHub] [incubator-nuttx] xiaoxiang781216 commented on a diff in pull request #6229: libc/string: simplify strrchr
Posted by GitBox <gi...@apache.org>.
xiaoxiang781216 commented on code in PR #6229:
URL: https://github.com/apache/incubator-nuttx/pull/6229#discussion_r869179992
##########
libs/libc/string/lib_strrchr.c:
##########
@@ -37,15 +37,16 @@
#undef strrchr /* See mm/README.txt */
FAR char *strrchr(FAR const char *s, int c)
{
- FAR const char *p = &s[strlen(s)];
+ FAR const char *r = NULL;
- for (; p >= s; p--)
+ do
{
- if (*p == c)
+ if (*s == (char)c)
Review Comment:
don't need (char)
--
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