Faster unhexlify

[folly.git] / folly / String-inl.h

diff --git a/folly/String-inl.h b/folly/String-inl.h
index 2bf0104a6259f113b825f22cf484e2a4234b8392..1732b50ce3d42feaddc691f01c584ed2cd957dc9 100644 (file)
--- a/folly/String-inl.h
+++ b/folly/String-inl.h
@@ -587,17 +587,12 @@ bool unhexlify(const InputString& input, OutputString& output) {
   }
   output.resize(input.size() / 2);
   int j = 0;
-  auto unhex = [](char c) -> int {
-    return c >= '0' && c <= '9' ? c - '0' :
-           c >= 'A' && c <= 'F' ? c - 'A' + 10 :
-           c >= 'a' && c <= 'f' ? c - 'a' + 10 :
-           -1;
-  };
 
   for (size_t i = 0; i < input.size(); i += 2) {
-    int highBits = unhex(input[i]);
-    int lowBits = unhex(input[i + 1]);
-    if (highBits < 0 || lowBits < 0) {
+    int highBits = detail::hexTable[static_cast<uint8_t>(input[i])];
+    int lowBits = detail::hexTable[static_cast<uint8_t>(input[i + 1])];
+    if ((highBits | lowBits) & 0x10) {
+      // One of the characters wasn't a hex digit
       return false;
     }
     output[j++] = (highBits << 4) + lowBits;