From 0bee0cece2a6a71ccc347fdc1d46cf638cd5fd1c Mon Sep 17 00:00:00 2001 From: Yury Norov Date: Mon, 3 Feb 2020 17:37:20 -0800 Subject: lib/string: add strnchrnul() Patch series "lib: rework bitmap_parse", v5. Similarl to the recently revisited bitmap_parselist(), bitmap_parse() is ineffective and overcomplicated. This series reworks it, aligns its interface with bitmap_parselist() and makes it simpler to use. The series also adds a test for the function and fixes usage of it in cpumask_parse() according to the new design - drops the calculating of length of an input string. bitmap_parse() takes the array of numbers to be put into the map in the BE order which is reversed to the natural LE order for bitmaps. For example, to construct bitmap containing a bit on the position 42, we have to put a line '400,0'. Current implementation reads chunk one by one from the beginning ('400' before '0') and makes bitmap shift after each successful parse. It makes the complexity of the whole process as O(n^2). We can do it in reverse direction ('0' before '400') and avoid shifting, but it requires reverse parsing helpers. This patch (of 7): New function works like strchrnul() with a length limited string. Link: http://lkml.kernel.org/r/20200102043031.30357-2-yury.norov@gmail.com Signed-off-by: Yury Norov Reviewed-by: Andy Shevchenko Cc: Rasmus Villemoes Cc: Amritha Nambiar Cc: Willem de Bruijn Cc: Kees Cook Cc: Matthew Wilcox Cc: "Tobin C . Harding" Cc: Will Deacon Cc: Miklos Szeredi Cc: Vineet Gupta Cc: Chris Wilson Cc: Arnaldo Carvalho de Melo Cc: Steffen Klassert Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/string.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'lib/string.c') diff --git a/lib/string.c b/lib/string.c index 08ec58cc673b..f607b967d978 100644 --- a/lib/string.c +++ b/lib/string.c @@ -434,6 +434,23 @@ char *strchrnul(const char *s, int c) EXPORT_SYMBOL(strchrnul); #endif +/** + * strnchrnul - Find and return a character in a length limited string, + * or end of string + * @s: The string to be searched + * @count: The number of characters to be searched + * @c: The character to search for + * + * Returns pointer to the first occurrence of 'c' in s. If c is not found, + * then return a pointer to the last character of the string. + */ +char *strnchrnul(const char *s, size_t count, int c) +{ + while (count-- && *s && *s != (char)c) + s++; + return (char *)s; +} + #ifndef __HAVE_ARCH_STRRCHR /** * strrchr - Find the last occurrence of a character in a string -- cgit v1.2.3 From c11d3fa0116a6bc832a9e387427caa16f8de5ef2 Mon Sep 17 00:00:00 2001 From: Alexandru Ardelean Date: Thu, 20 Feb 2020 20:04:21 -0800 Subject: lib/string.c: update match_string() doc-strings with correct behavior There were a few attempts at changing behavior of the match_string() helpers (i.e. 'match_string()' & 'sysfs_match_string()'), to change & extend the behavior according to the doc-string. But the simplest approach is to just fix the doc-strings. The current behavior is fine as-is, and some bugs were introduced trying to fix it. As for extending the behavior, new helpers can always be introduced if needed. The match_string() helpers behave more like 'strncmp()' in the sense that they go up to n elements or until the first NULL element in the array of strings. This change updates the doc-strings with this info. Link: http://lkml.kernel.org/r/20200213072722.8249-1-alexandru.ardelean@analog.com Signed-off-by: Alexandru Ardelean Acked-by: Andy Shevchenko Cc: Kees Cook Cc: "Tobin C . Harding" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/string.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'lib/string.c') diff --git a/lib/string.c b/lib/string.c index f607b967d978..6012c385fb31 100644 --- a/lib/string.c +++ b/lib/string.c @@ -699,6 +699,14 @@ EXPORT_SYMBOL(sysfs_streq); * @n: number of strings in the array or -1 for NULL terminated arrays * @string: string to match with * + * This routine will look for a string in an array of strings up to the + * n-th element in the array or until the first NULL element. + * + * Historically the value of -1 for @n, was used to search in arrays that + * are NULL terminated. However, the function does not make a distinction + * when finishing the search: either @n elements have been compared OR + * the first NULL element was found. + * * Return: * index of a @string in the @array if matches, or %-EINVAL otherwise. */ @@ -727,6 +735,14 @@ EXPORT_SYMBOL(match_string); * * Returns index of @str in the @array or -EINVAL, just like match_string(). * Uses sysfs_streq instead of strcmp for matching. + * + * This routine will look for a string in an array of strings up to the + * n-th element in the array or until the first NULL element. + * + * Historically the value of -1 for @n, was used to search in arrays that + * are NULL terminated. However, the function does not make a distinction + * when finishing the search: either @n elements have been compared OR + * the first NULL element was found. */ int __sysfs_match_string(const char * const *array, size_t n, const char *str) { -- cgit v1.2.3