From dd6422c56fbd251976691b13ea0796db0cda4e85 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Mon, 30 Nov 2015 19:57:59 +0200
Subject: [PATCH] Optimized hexbyte2int

---
 bytesconv.go | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/bytesconv.go b/bytesconv.go
index a956247..6d8326a 100644
--- a/bytesconv.go
+++ b/bytesconv.go
@@ -195,17 +195,24 @@ func hexCharUpper(c byte) byte {
 	return c - 10 + 'A'
 }
 
+var hex2intTable = func() []byte {
+	b := make([]byte, 255)
+	for i := byte(0); i < 255; i++ {
+		c := byte(0)
+		if i >= '0' && i <= '9' {
+			c = 1 + i - '0'
+		} else if i >= 'a' && i <= 'f' {
+			c = 1 + i - 'a' + 10
+		} else if i >= 'A' && i <= 'F' {
+			c = 1 + i - 'A' + 10
+		}
+		b[i] = c
+	}
+	return b
+}()
+
 func hexbyte2int(c byte) int {
-	if c >= '0' && c <= '9' {
-		return int(c - '0')
-	}
-	if c >= 'a' && c <= 'f' {
-		return int(c - 'a' + 10)
-	}
-	if c >= 'A' && c <= 'F' {
-		return int(c - 'A' + 10)
-	}
-	return -1
+	return int(hex2intTable[c]) - 1
 }
 
 const toLower = 'a' - 'A'