[libc] Add strncasecmp()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/string.c

@@ -27,6 +27,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <ctype.h>
 
 /** @file
@@ -205,11 +206,24 @@ int strncmp ( const char *first, const char *second, size_t max ) {
  * @ret diff		Difference
  */
 int strcasecmp ( const char *first, const char *second ) {
+
+	return strncasecmp ( first, second, ~( ( size_t ) 0 ) );
+}
+
+/**
+ * Compare case-insensitive strings
+ *
+ * @v first		First string
+ * @v second		Second string
+ * @v max		Maximum length to compare
+ * @ret diff		Difference
+ */
+int strncasecmp ( const char *first, const char *second, size_t max ) {
 	const uint8_t *first_bytes = ( ( const uint8_t * ) first );
 	const uint8_t *second_bytes = ( ( const uint8_t * ) second );
 	int diff;
 
-	for ( ; ; first_bytes++, second_bytes++ ) {
+	for ( ; max-- ; first_bytes++, second_bytes++ ) {
 		diff = ( toupper ( *first_bytes ) -
 			 toupper ( *second_bytes ) );
 		if ( diff )
@@ -217,6 +231,7 @@ int strcasecmp ( const char *first, const char *second ) {
 		if ( ! *first_bytes )
 			return 0;
 	}
+	return 0;
 }
 
 /**

src/include/strings.h

@@ -189,5 +189,7 @@ bzero ( void *dest, size_t len ) {
 }
 
 int __pure strcasecmp ( const char *first, const char *second ) __nonnull;
+int __pure strncasecmp ( const char *first, const char *second,
+			 size_t max ) __nonnull;
 
 #endif /* _STRINGS_H */

src/tests/string_test.c

@@ -105,6 +105,14 @@ static void string_test_exec ( void ) {
 	ok ( strcasecmp ( "Uncle", "Uncle Jack" ) != 0 );
 	ok ( strcasecmp ( "not", "equal" ) != 0 );
 
+	/* Test strncasecmp() */
+	ok ( strncasecmp ( "", "", 0 ) == 0 );
+	ok ( strncasecmp ( "", "", 73 ) == 0 );
+	ok ( strncasecmp ( "Uncle Jack", "Uncle jack", 47 ) == 0 );
+	ok ( strncasecmp ( "Uncle Jack", "Uncle jake", 47 ) != 0 );
+	ok ( strncasecmp ( "Uncle Jack", "Uncle jake", 9 ) != 0 );
+	ok ( strncasecmp ( "Uncle Jack", "Uncle jake", 8 ) == 0 );
+
 	/* Test memcmp() */
 	ok ( memcmp ( "", "", 0 ) == 0 );
 	ok ( memcmp ( "Foo", "Foo", 3 ) == 0 );