X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=functions%2Fstring%2Fstrncpy.c;h=da1397a93caaf2a7a1b6b3ebf5499f941f1f8236;hb=d865c4403fc91d1f1ac95ba76febcee9f429bb97;hp=2d865d782b7f0601798aa0b84ba600a6d65fe1ff;hpb=34893ecc2200dc7017c36a54cb6c5f4c2378b5ec;p=pdclib

diff --git a/functions/string/strncpy.c b/functions/string/strncpy.c
index 2d865d7..da1397a 100644
--- a/functions/string/strncpy.c
+++ b/functions/string/strncpy.c
@@ -1,8 +1,56 @@
-// ----------------------------------------------------------------------------
-// $Id$
-// ----------------------------------------------------------------------------
-// Public Domain C Library - http://pdclib.sourceforge.net
-// This code is Public Domain. Use, modify, and redistribute at will.
-// ----------------------------------------------------------------------------
-
-char * strncpy( char * restrict s1, const char * restrict s2, size_t n ) { /* TODO */ };
+/* strncpy( char *, const char *, size_t )
+
+   This file is part of the Public Domain C Library (PDCLib).
+   Permission is granted to use, modify, and / or redistribute at will.
+*/
+
+#include <string.h>
+
+#ifndef REGTEST
+
+char * strncpy( char * _PDCLIB_restrict s1, const char * _PDCLIB_restrict s2, size_t n )
+{
+    char * rc = s1;
+    while ( ( n > 0 ) && ( *s1++ = *s2++ ) )
+    {
+        /* Cannot do "n--" in the conditional as size_t is unsigned and we have
+           to check it again for >0 in the next loop below, so we must not risk
+           underflow.
+        */
+        --n;
+    }
+    /* Checking against 1 as we missed the last --n in the loop above. */
+    while ( n-- > 1 )
+    {
+        *s1++ = '\0';
+    }
+    return rc;
+}
+
+#endif
+
+#ifdef TEST
+
+#include "_PDCLIB_test.h"
+
+int main( void )
+{
+    char s[] = "xxxxxxx";
+    TESTCASE( strncpy( s, "", 1 ) == s );
+    TESTCASE( s[0] == '\0' );
+    TESTCASE( s[1] == 'x' );
+    TESTCASE( strncpy( s, abcde, 6 ) == s );
+    TESTCASE( s[0] == 'a' );
+    TESTCASE( s[4] == 'e' );
+    TESTCASE( s[5] == '\0' );
+    TESTCASE( s[6] == 'x' );
+    TESTCASE( strncpy( s, abcde, 7 ) == s );
+    TESTCASE( s[6] == '\0' );
+    TESTCASE( strncpy( s, "xxxx", 3 ) == s );
+    TESTCASE( s[0] == 'x' );
+    TESTCASE( s[2] == 'x' );
+    TESTCASE( s[3] == 'd' );
+    return TEST_RESULTS;
+}
+
+#endif