+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