| Message ID | 20230913094557.451463-1-andriy.shevchenko@linux.intel.com (mailing list archive) |
|---|---|
| State | Rejected |
| Headers | show |
| Series | [v1,1/1] lib/string_helpers: Don't copy a tail in kstrdup_and_replace() if 'new' is \0 | expand |
On Wed, Sep 13, 2023 at 12:45:57PM +0300, Andy Shevchenko wrote: > The kstrdup_and_replace() takes two characters, old and new, to replace > former with latter after the copying of the original string. But in case > when new is a NUL, there is no point to copy the rest of the string, > the contract with the callers is that that the function returns a > NUL-terminated string and not a buffer of the size filled with a given > data. With this we can optimize the memory consumption by copying only > meaningful part of the original string and drop the rest. Thinking about this more, I self NAK this. If the caller knows the size of the original message it can be handy to make a copy and replace all occurrences of old by NUL. This will be an optimized implementation of strsep(str, "$OLD").
diff --git a/lib/string_helpers.c b/lib/string_helpers.c index 7713f73e66b0..e385bf3cc2de 100644 --- a/lib/string_helpers.c +++ b/lib/string_helpers.c @@ -723,11 +723,17 @@ EXPORT_SYMBOL_GPL(kstrdup_quotable_file); /* * Returns duplicate string in which the @old characters are replaced by @new. + * + * If @new is NUL, copy the string up to the first occurrence of @old, which + * will be replaced by a NUL. */ char *kstrdup_and_replace(const char *src, char old, char new, gfp_t gfp) { char *dst; + if (new == '\0') + return kmemdup_nul(src, strchrnul(src, old) - src, gfp); + dst = kstrdup(src, gfp); if (!dst) return NULL;
The kstrdup_and_replace() takes two characters, old and new, to replace former with latter after the copying of the original string. But in case when new is a NUL, there is no point to copy the rest of the string, the contract with the callers is that that the function returns a NUL-terminated string and not a buffer of the size filled with a given data. With this we can optimize the memory consumption by copying only meaningful part of the original string and drop the rest. Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> --- The first user of this is pending: https://lore.kernel.org/platform-driver-x86/20230913092701.440959-1-andriy.shevchenko@linux.intel.com/ lib/string_helpers.c | 6 ++++++ 1 file changed, 6 insertions(+)