1 files changed, 20 insertions, 3 deletions

diff --git a/libbb/compare_string_array.c b/libbb/compare_string_array.c
index 4b10cc138..e24815a03 100644
--- a/libbb/compare_string_array.c
+++ b/libbb/compare_string_array.c
@@ -5,6 +5,24 @@
 
 #include "libbb.h"
 
+char* FAST_FUNC is_prefixed_with(const char *string, const char *key)
+{
+#if 0   /* Two passes over key - probably slower */
+        int len = strlen(key);
+        if (strncmp(string, key, len) == 0)
+                return string + len;
+        return NULL;
+#else   /* Open-coded */
+        while (*key != '\0') {
+                if (*key != *string)
+                        return NULL;
+                key++;
+                string++;
+        }
+        return (char*)string;
+#endif
+}
+
 /* returns the array index of the string */
 /* (index of first match is returned, or -1) */
 int FAST_FUNC index_in_str_array(const char *const string_array[], const char *key)
@@ -39,10 +57,9 @@ int FAST_FUNC index_in_strings(const char *strings, const char *key)
 int FAST_FUNC index_in_substr_array(const char *const string_array[], const char *key)
 {
         int i;
-        int len = strlen(key);
-        if (len) {
+        if (key[0]) {
                 for (i = 0; string_array[i] != 0; i++) {
-                        if (strncmp(string_array[i], key, len) == 0) {
+                        if (is_prefixed_with(string_array[i], key)) {
                                 return i;
                         }
                 }