The patch titled
Subject: lib/string: add strnchrnul()
has been added to the -mm tree. Its filename is
lib-string-add-strnchrnul.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-string-add-strnchrnul.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-string-add-strnchrnul.patch
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------------------------------------------------------
From: Yury Norov <ynorov@xxxxxxxxxxx>
Subject: lib/string: add strnchrnul()
Similarly to recently revisited bitmap_parselist() [1], bitmap_parse() is
ineffective and overcomplicated. This series reworks it, aligns its
interface with bitmap_parselist() and makes usage simpler.
The series also adds a test for the function and fixes usage of it in
cpumask_parse() according to new design - drops the calculating of length
of an input string.
The following users would also consider to drop the length argument,
if possible:
drivers/block/drbd/drbd_main.c:2608
kernel/padata.c:924
net/core/net-sysfs.c:726
net/core/net-sysfs.c:1309
net/core/net-sysfs.c:1391
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.
Tested on arm64 and BE mips.
[1] https://lkml.org/lkml/2019/4/16/66
This patch (of 7):
New function works like strchrnul() with a length limited string.
Link: http://lkml.kernel.org/r/20190501010636.30595-2-ynorov@xxxxxxxxxxx
Signed-off-by: Yury Norov <ynorov@xxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Amritha Nambiar <amritha.nambiar@xxxxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: "Tobin C . Harding" <tobin@xxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/string.h | 1 +
lib/string.c | 17 +++++++++++++++++
2 files changed, 18 insertions(+)
--- a/include/linux/string.h~lib-string-add-strnchrnul
+++ a/include/linux/string.h
@@ -62,6 +62,7 @@ extern char * strchr(const char *,int);
#ifndef __HAVE_ARCH_STRCHRNUL
extern char * strchrnul(const char *,int);
#endif
+extern char * strnchrnul(const char *, size_t, int);
#ifndef __HAVE_ARCH_STRNCHR
extern char * strnchr(const char *, size_t, int);
#endif
--- a/lib/string.c~lib-string-add-strnchrnul
+++ a/lib/string.c
@@ -432,6 +432,23 @@ 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
_
Patches currently in -mm which might be from ynorov@xxxxxxxxxxx are
lib-string-add-strnchrnul.patch
bitops-more-bits_to_-macros.patch
lib-add-test-for-bitmap_parse.patch
lib-make-bitmap_parse_user-a-wrapper-on-bitmap_parse.patch
lib-rework-bitmap_parse.patch
lib-new-testcases-for-bitmap_parse_user.patch
cpumask-dont-calculate-length-of-the-input-string.patch
