linux-kernel - [RFC/PATCH 1/8] lib: string: Introduce strreplace

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Message-Id: <1433410636-26812-2-git-send-email-linux@rasmusvillemoes.dk>
Date:	Thu,  4 Jun 2015 11:37:08 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-kernel@...r.kernel.org
Subject: [RFC/PATCH 1/8] lib: string: Introduce strreplace

Strings are sometimes sanitized by replacing a certain character
(often '/') by another (often '!'). In a few places, this is done the
same way Schlemiel the Painter would do it. Others are slightly
smarter but still do multiple strchr() calls. Introduce strreplace()
to do this using a single function call and a single pass over the
string.

One would expect the return value to be one of three things: void, s,
or the number of replacements made. I chose the fourth, returning a
pointer to the end of the string. This is more likely to be useful
(for example allowing the caller to avoid a strlen call).

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 include/linux/string.h |  1 +
 lib/string.c           | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index e40099e585c9..4f09e41c7169 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -111,6 +111,7 @@ extern int memcmp(const void *,const void *,__kernel_size_t);
 extern void * memchr(const void *,int,__kernel_size_t);
 #endif
 void *memchr_inv(const void *s, int c, size_t n);
+extern char *strreplace(char *s, char bad, char good);
 
 extern void kfree_const(const void *x);
 
diff --git a/lib/string.c b/lib/string.c
index bb3d4b6993c4..ef52e86f6b87 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -849,3 +849,20 @@ void *memchr_inv(const void *start, int c, size_t bytes)
 	return check_bytes8(start, value, bytes % 8);
 }
 EXPORT_SYMBOL(memchr_inv);
+
+/**
+ * strreplace - Replace all occurences of character in string
+ * @s: The string to operate on
+ * @bad: The character being replaced
+ * @good: The character @bad is replaced with.
+ *
+ * Returns pointer to the nul byte at the end of @s.
+ */
+char *strreplace(char *s, char bad, char good)
+{
+	for (; *s; ++s)
+		if (*s == bad)
+			*s = good;
+	return s;
+}
+EXPORT_SYMBOL(strreplace);
-- 
2.1.3

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