Libc-825.24.tar.gz

[apple/libc.git] / string / strncat.c

diff --git a/string/strncat.c b/string/strncat.c
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+++ b/string/strncat.c
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+/*
+ * Copyright (c) 2011 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@
+ */
+
+#include <string.h>
+
+char *
+strncat(char *restrict dst, const char *restrict src, size_t maxlen) {
+       const size_t dstlen = strlen(dst);
+       const size_t srclen = strnlen(src, maxlen);
+    //  The strcat() and strncat() functions append a copy of the null-
+    //  terminated string src to the end of the null-terminated string dst,
+    //  then add a terminating '\0'.  The string dst must have sufficient
+    //  space to hold the result.
+    //
+    //  The strncat() function appends not more than maxlen characters
+    //  from src, and then adds a terminating '\0'.
+    const size_t cpylen = srclen < maxlen ? srclen : maxlen;
+    memcpy(dst+dstlen, src, cpylen);
+    dst[dstlen+cpylen] = '\0';
+    //  The strcat() and strncat() functions return dst.
+    return dst;
+}