Add hex encoding/decoding

1 files changed, 58 insertions, 1 deletions

diff --git a/src/Encoding.php b/src/Encoding.php
index 3324b34..81983c2 100644
--- a/src/Encoding.php
+++ b/src/Encoding.php
@@ -336,6 +336,63 @@ class Encoding
     }
 
     /**
+     * Convert a binary string into a hexadecimal string without cache-timing
+     * leaks
+     *
+     * @param string $bin_string (raw binary)
+     * @return string
+     */
+    public static function hexEncode($bin_string)
+    {
+        $hex = '';
+        $len = self::safeStrlen($bin_string);
+        for ($i = 0; $i < $len; ++$i) {
+            $c = \ord($bin_string[$i]) & 0xf;
+            $b = \ord($bin_string[$i]) >> 4;
+            $hex .= \chr(87 + $b + ((($b - 10) >> 8) & ~38));
+            $hex .= \chr(87 + $c + ((($c - 10) >> 8) & ~38));
+        }
+        return $hex;
+    }
+
+    /**
+     * Convert a hexadecimal string into a binary string without cache-timing
+     * leaks
+     *
+     * @param string $hex_string
+     * @return string (raw binary)
+     */
+    public static function hexDecode($hex_string)
+    {
+        $hex_pos = 0;
+        $bin = '';
+        $hex_len = self::safeStrlen($hex_string);
+        $state = 0;
+
+        while ($hex_pos < $hex_len) {
+            $c = \ord($hex_string[$hex_pos]);
+            $c_num = $c ^ 48;
+            $c_num0 = ($c_num - 10) >> 8;
+            $c_alpha = ($c & ~32) - 55;
+            $c_alpha0 = (($c_alpha - 10) ^ ($c_alpha - 16)) >> 8;
+            if (($c_num0 | $c_alpha0) === 0) {
+                throw new \RangeException(
+                    'hexEncode() only expects hexadecimal characters'
+                );
+            }
+            $c_val = ($c_num0 & $c_num) | ($c_alpha & $c_alpha0);
+            if ($state === 0) {
+                $c_acc = $c_val * 16;
+            } else {
+                $bin .= \chr($c_acc | $c_val);
+            }
+            $state = $state ? 0 : 1;
+            ++$hex_pos;
+        }
+        return $bin;
+    }
+
+    /**
      *
      * Base64 character set:
      * [A-Z]      [a-z]      [0-9]      +     /
@@ -487,7 +544,7 @@ class Encoding
      * @param string $str
      * @return int
      */
-    public static function safeStrlen($str)
+    protected static function safeStrlen($str)
     {
         if (\function_exists('mb_strlen')) {
             return \mb_strlen($str, '8bit');