strcasestr optimize for speed and size

revisit this and shave a bit more off on code size

Change-Id: I90546b931780c6779960129619a41cc6592c44e1

1 files changed, 23 insertions, 25 deletions

diff --git a/firmware/common/strcasestr.c b/firmware/common/strcasestr.c
index a20951d877..44269b58ee 100644
--- a/firmware/common/strcasestr.c
+++ b/firmware/common/strcasestr.c
@@ -36,43 +36,41 @@ typedef unsigned chartype;
 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
 char* strcasestr (const char* haystack, const char* needle)
 {
-    chartype needle_ch = tolower(*needle++);
-    chartype needle_upch = toupper(needle_ch);
-    chartype ch_h;
-    char* match = (char*)haystack; /* if needle empty return haystack */
+    const char* match, *needle_search;
+    chartype needle_ch, needle_upch, ch_h;
 
-    if (needle_ch != 0) {
+    if (*needle == 0) /* if needle empty return haystack */
+        return (char*)haystack;
+
+    while(1)
+    {
+        needle_search = needle;
+        needle_ch = tolower(*needle_search++);
+        needle_upch = toupper(needle_ch);
         /* find the first matching character */
-        do {
+        do
+        {
             ch_h = *haystack++;
             if (ch_h == 0) /* end of haystack no match.. */
                 return NULL;
         } while (ch_h != needle_ch && ch_h != needle_upch);
+        match = haystack;
+        goto case_match;
 
-        match = (char*) haystack - 1;
         /* find the first non-matching character */
-lcase_match:
-        while (ch_h == needle_ch) {
-            ch_h = *haystack++;
-            needle_ch = tolower(*needle++);
+        while (ch_h == needle_ch)
+        {
+case_match:
+            ch_h = *match++;
+            needle_ch = tolower(*needle_search++);
             if (needle_ch == 0) /* end of needle, found match.. */
-                return match;
+                return (char*)haystack - 1;
         }
-/* lcase or ucase match */
         needle_upch = toupper(needle_ch);
-        while (ch_h == needle_upch || ch_h == needle_ch) {
-            ch_h = *haystack++;
-            needle_ch = tolower(*needle++);
-            if (needle_ch == 0) /* end of needle, found match.. */
-                return match;
-
-            if (ch_h == needle_ch)
-                goto lcase_match;
-            needle_upch = toupper(needle_ch);
-        }
-        match = NULL;
+        if (ch_h == needle_upch)
+            goto case_match;
+        haystack = match;
     }
-    return match;
 }
 #else
 char* strcasestr (const char* phaystack, const char* pneedle)