Added test driver, fixed off-by-one bug.

[pdclib] / functions / string / strncpy.c

diff --git a/functions/string/strncpy.c b/functions/string/strncpy.c
index 2d865d782b7f0601798aa0b84ba600a6d65fe1ff..31602ec8a9fef4709ce87b2904c821fb6256d2f4 100644 (file)
--- a/functions/string/strncpy.c
+++ b/functions/string/strncpy.c
@@ -1,8 +1,50 @@
-// ----------------------------------------------------------------------------
-// $Id$
-// ----------------------------------------------------------------------------
-// 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 */ };
+/* $Id$ */
+
+/* Release $Name$ */
+
+/* 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 <_PDCLIB_aux.h>
+#include <string.h>
+
+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.
+        */
+        --n;
+    }
+    while ( --n )
+    {
+        *s1++ = '\0';
+    }
+    return rc;
+}
+
+#ifdef TEST
+#include <_PDCLIB_test.h>
+
+int main()
+{
+    char s[] = "xxxxxxx";
+    BEGIN_TESTS;
+    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' );
+    return TEST_RESULTS;
+}
+#endif