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 fd6e5d26b14fac318eacaf63ea17cca845755ca3..31602ec8a9fef4709ce87b2904c821fb6256d2f4 100644 (file)
--- a/functions/string/strncpy.c
+++ b/functions/string/strncpy.c
@@ -1,29 +1,50 @@
-// ----------------------------------------------------------------------------
-// $Id$
-// ----------------------------------------------------------------------------
-// Public Domain C Library - http://pdclib.sourceforge.net
-// This code is Public Domain. Use, modify, and redistribute at will.
-// ----------------------------------------------------------------------------
+/* $Id$ */
 
-char * strncpy( char * restrict s1, const char * restrict s2, size_t n ) { /* TODO */ };
+/* Release $Name$ */
 
-/* PDPC code - unreviewed
-char *strncpy(char *s1, const char *s2, size_t n)
+/* 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 *p = s1;
-    size_t x;
-    
-    for (x=0; x < n; x++)
+    char * rc = s1;
+    while ( ( n > 0 ) && ( *s1++ = *s2++ ) )
     {
-        *p = *s2;
-        if (*s2 == '\0') break;
-        p++;
-        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;
     }
-    for (; x < n; x++)
+    while ( --n )
     {
-        *p++ = '\0';
+        *s1++ = '\0';
     }
-    return (s1);
+    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;
 }
-*/
\ No newline at end of file
+#endif