Add stpncpy() support

Imports Apple's stpncpy.c verbatim from Libc-825.24.

Removes 'restrict' qualifiers for pre-C99 compatibility.

Fixes whitespace; adds modification notice and proper build
conditional.

Updates the legacy-support headers.

Updates the README.

Closes: https://trac.macports.org/ticket/69571

TESTED:
Tested on 10.4-10.5 ppc, 10.4-10.6 i386, 10.5-10.6 ppc (i386 Rosetta),
10.5-12.x x86_64, 11.x-14.x arm64.
Passes all tests, including newly added stpncpy() tests.

README.md

@@ -86,7 +86,7 @@ Wrapped headers and replaced functions are:
   </tr>
   <tr>
     <td><code>string.h</code></td>
-    <td>Adds <code>strnlen</code>, <code>strndup</code> and <code>memmem</code> functions</td>
+    <td>Adds <code>stpncpy</code>, <code>strnlen</code>, <code>strndup</code> and <code>memmem</code> functions</td>
     <td>OSX10.6</td>
   </tr>
   <tr>

include/MacportsLegacySupport.h

@@ -69,6 +69,9 @@
 /* CMSG_DATA definition in <sys/socket.h> */
 #define __MP_LEGACY_SUPPORT_CMSG_DATA_FIX__  (__APPLE__ && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1060)
 
+/* stpncpy */
+#define __MP_LEGACY_SUPPORT_STPNCPY__         (__APPLE__ && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1070)
+
 /* strnlen */
 #define __MP_LEGACY_SUPPORT_STRNLEN__         (__APPLE__ && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1070)
 

include/string.h

@@ -24,6 +24,13 @@
 /* Include the primary system string.h */
 #include_next <string.h>
 
+/* stpncpy */
+#if __MP_LEGACY_SUPPORT_STPNCPY__
+__MP__BEGIN_DECLS
+extern char *stpncpy(char *dst, const char *src, size_t n);
+__MP__END_DECLS
+#endif
+
 /* strnlen */
 #if __MP_LEGACY_SUPPORT_STRNLEN__
 __MP__BEGIN_DECLS

src/stpncpy.c

@@ -0,0 +1,64 @@
+/*
+ * 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@
+ */
+
+ /*
+ * NOTICE: This file was modified in April 2024 to allow
+ * for use as a supporting file for MacPorts legacy support library. This notice
+ * is included in support of clause 2.2 (b) of the Apple Public License,
+ * Version 2.0.
+ *
+ * The code is almost verbatim from Apple except for the removal of the
+ * 'restrict' qualifiers for compatibility with pre-C99 compilers.
+ */
+
+/* MP support header */
+#include "MacportsLegacySupport.h"
+#if __MP_LEGACY_SUPPORT_STPNCPY__
+
+#include <string.h>
+
+char *
+stpncpy(char * dst, const char * src, size_t maxlen) {
+    const size_t srclen = strnlen(src, maxlen);
+    if (srclen < maxlen) {
+        //  The stpncpy() and strncpy() functions copy at most maxlen
+        //  characters from src into dst.
+        memcpy(dst, src, srclen);
+        //  If src is less than maxlen characters long, the remainder
+        //  of dst is filled with '\0' characters.
+        memset(dst+srclen, 0, maxlen-srclen);
+        //  The stpcpy() and stpncpy() functions return a pointer to the
+        //  terminating '\0' character of dst.
+        return dst+srclen;
+    } else {
+        //  The stpncpy() and strncpy() functions copy at most maxlen
+        //  characters from src into dst.
+        memcpy(dst, src, maxlen);
+        //  If stpncpy() does not terminate dst with a NUL character, it
+        //  instead returns a pointer to src[maxlen] (which does not
+        //  necessarily refer to a valid memory location.)
+        return dst+maxlen;
+    }
+}
+
+#endif /* __MP_LEGACY_SUPPORT_STPNCPY__ */