speed up base64 decode character lookup

Author: kaidokert

Base64.cpp

@@ -122,12 +122,10 @@ inline void a4_to_a3(unsigned char * a3, unsigned char * a4) {
 }
 
 inline unsigned char b64_lookup(char c) {
-	int i;
-	for(i = 0; i < 64; i++) {
-		if(b64_alphabet[i] == c) {
-			return i;
-		}
-	}
-
+	if(c >='A' && c <='Z') return c - 'A';
+	if(c >='a' && c <='z') return c - 71;
+	if(c >='0' && c <='9') return c + 4;
+	if(c == '+') return 62;
+	if(c == '/') return 63;
 	return -1;
 }