X-Git-Url: https://pd.if.org/git/?p=pdclib;a=blobdiff_plain;f=functions%2Fstring%2Fstrstr.c;h=5c97a750c076400c90bf61520c1f26b9c24e880a;hp=b2494234b23df4944ef119071c7e04ed40e3be8f;hb=da0f3f353d417fed71f358a48d5d5394145e460d;hpb=34893ecc2200dc7017c36a54cb6c5f4c2378b5ec

diff --git a/functions/string/strstr.c b/functions/string/strstr.c
index b249423..5c97a75 100644
--- a/functions/string/strstr.c
+++ b/functions/string/strstr.c
@@ -1,17 +1,49 @@
-// ----------------------------------------------------------------------------
-// $Id$
-// ----------------------------------------------------------------------------
-// Public Domain C Library - http://pdclib.sourceforge.net
-// This code is Public Domain. Use, modify, and redistribute at will.
-// ----------------------------------------------------------------------------
+/* strstr( const char *, const char * )
 
-// ----------------------------------------------------------------------------
-// C++
+   This file is part of the Public Domain C Library (PDCLib).
+   Permission is granted to use, modify, and / or redistribute at will.
+*/
 
-const char * strstr( const char * s1, const char * s2 ) { /* TODO */ };
-char * strstr( char * s1, const char * s2 ) { /* TODO */ };
+#include <string.h>
 
-// ----------------------------------------------------------------------------
-// Standard C
+#ifndef REGTEST
 
-char * strstr( const char * s1, const char * s2 ) { /* TODO */ };
+char * strstr( const char * s1, const char * s2 )
+{
+    const char * p1 = s1;
+    const char * p2;
+    while ( *s1 )
+    {
+        p2 = s2;
+        while ( *p2 && ( *p1 == *p2 ) )
+        {
+            ++p1;
+            ++p2;
+        }
+        if ( ! *p2 )
+        {
+            return (char *) s1;
+        }
+        ++s1;
+        p1 = s1;
+    }
+    return NULL;
+}
+
+#endif
+
+#ifdef TEST
+#include "_PDCLIB_test.h"
+
+int main( void )
+{
+    char s[] = "abcabcabcdabcde";
+    TESTCASE( strstr( s, "x" ) == NULL );
+    TESTCASE( strstr( s, "xyz" ) == NULL );
+    TESTCASE( strstr( s, "a" ) == &s[0] );
+    TESTCASE( strstr( s, "abc" ) == &s[0] );
+    TESTCASE( strstr( s, "abcd" ) == &s[6] );
+    TESTCASE( strstr( s, "abcde" ) == &s[10] );
+    return TEST_RESULTS;
+}
+#endif