linux-kernel - [PATCH 1/1] lib: small update for strlen, strnlen, use less cpu instructions

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Message-ID: <55806FE8.9030302@gmail.com>
Date:	Tue, 16 Jun 2015 13:50:16 -0500
From:	Orestes Leal Rodriguez <lukes357@...il.com>
To:	linux-kernel@...r.kernel.org
CC:	mihai.dontu@...il.com
Subject: [PATCH 1/1] lib: small update for strlen, strnlen, use less
 cpu instructions

Very small update to strlen and strnlen that now use less cpu 
instructions by using a counter to avoid the memory addresses 
substraction to find the length of the string.

Signed-off-by: Orestes Leal Rodriguez <lukes357@...il.com>
---

diff --git a/lib/string.c" "b/lib/string.c
index 992bf30..c873436 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -17,6 +17,10 @@
   * * Sat Feb 09 2002, Jason Thomas <jason@...ic.com.au>,
   *                    Matthew Hawkins <matt@...dropbear.id.au>
   * -  Kissed strtok() goodbye
+ *
+ * * Tuesday June 16 2015, Orestes Leal Rodriguez <lukes357@...il.com>
+ * - strlen, strnlen: by using a single counter we use less cpu 
instructions
+ *   by avoiding substracting the memory addresses before return
   */

  #include <linux/types.h>
@@ -401,11 +405,11 @@ EXPORT_SYMBOL(strim);
   */
  size_t strlen(const char *s)
  {
-	const char *sc;
+	size_t sz = 0;

-	for (sc = s; *sc != '\0'; ++sc)
-		/* nothing */;
-	return sc - s;
+	for (; *s++ != '\0'; sz++)
+		/* empty */;
+	return sz;
  }
  EXPORT_SYMBOL(strlen);
  #endif
@@ -418,12 +422,13 @@ EXPORT_SYMBOL(strlen);
   */
  size_t strnlen(const char *s, size_t count)
  {
-	const char *sc;
+	size_t sz = 0;

-	for (sc = s; count-- && *sc != '\0'; ++sc)
-		/* nothing */;
-	return sc - s;
+	for (; count-- && *s++ != '\0'; sz++)
+		/* empty */;
+	return sz;
  }
+
  EXPORT_SYMBOL(strnlen);
  #endif


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