Libc-825.24.tar.gz

[apple/libc.git] / arm / string / strchr.s

diff --git a/arm/string/strchr.s b/arm/string/strchr.s
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..229db7bad0884cdc68a4d562148e64509964b35f 100644 (file)
--- a/arm/string/strchr.s
+++ b/arm/string/strchr.s
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2010 Apple, Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ * 
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ * 
+ * @APPLE_LICENSE_HEADER_END@
+ */
+ 
+//  char * strchr(const char *s, int c);
+//
+//  The strchr( ) function locates the first occurence of c (converted to a
+//  char) in the string s.  If c is '\0', the function locates the terminating
+//  '\0' byte.
+
+.text
+.syntax unified
+.code 32
+.globl _strchr
+
+.align 3
+_strchr:
+//  Setup a frame and convert c to a char.
+    push   {r7,lr}
+    mov     r7,         sp
+    and     r1,     r1, #0xff
+
+//  Basic character-by-character search for c; on each pass through the loop
+//  we load a byte from s and increment s.  We then check if this byte is equal
+//  to either c or to '\0'; if not, we continue the loop.
+0:  ldrb    r2,    [r0],#1
+    cmp     r2,     r1
+    tstne   r2,     r2
+    bne     0b
+
+//  Either we have found a match, or we have reached the end of the string (or
+//  both, if c == '\0').  Because we incremented s after loading the last
+//  character, we need to decrement the pointer by one to get a pointer to
+//  either the matching or terminating character. 
+    sub     r0,     r0, #1
+    
+//  Now compare the last character we loaded to the character that we're
+//  searching for.  If they don't match, the character was not found in the
+//  string, so return NULL.
+    cmp     r2,     r1
+    movne   r0,     #0
+    pop    {r7,pc}