Merge remote-tracking branch 'upstream/master' into random

1 files changed, 94 insertions, 0 deletions

diff --git a/MediaBrowser.Common/Hex.cs b/MediaBrowser.Common/Hex.cs
new file mode 100644
index 000000000..b2d9aea3a
--- /dev/null
+++ b/MediaBrowser.Common/Hex.cs
@@ -0,0 +1,94 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+namespace MediaBrowser.Common
+{
+    /// <summary>
+    /// Encoding and decoding hex strings.
+    /// </summary>
+    public static class Hex
+    {
+        internal const string HexCharsLower = "0123456789abcdef";
+        internal const string HexCharsUpper = "0123456789ABCDEF";
+
+        internal const int LastHexSymbol = 0x66; // 102: f
+
+        /// <summary>
+        /// Map from an ASCII char to its hex value shifted,
+        /// e.g. <c>b</c> -> 11. 0xFF means it's not a hex symbol.
+        /// </summary>
+        /// <value></value>
+        internal static ReadOnlySpan<byte> HexLookup => new byte[] {
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+            0xFF, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
+        };
+
+        /// <summary>
+        /// Encodes <c>bytes</c> as a hex string.
+        /// </summary>
+        /// <param name="bytes"></param>
+        /// <param name="lowercase"></param>
+        /// <returns><c>bytes</c> as a hex string.</returns>
+        public static string Encode(ReadOnlySpan<byte> bytes, bool lowercase = true)
+        {
+            var hexChars = lowercase ? HexCharsLower : HexCharsUpper;
+
+            // TODO: use string.Create when it's supports spans
+            // Ref: https://github.com/dotnet/corefx/issues/29120
+            char[] s = new char[bytes.Length * 2];
+            int j = 0;
+            for (int i = 0; i < bytes.Length; i++)
+            {
+                s[j++] = hexChars[bytes[i] >> 4];
+                s[j++] = hexChars[bytes[i] & 0x0f];
+            }
+
+            return new string(s);
+        }
+
+        /// <summary>
+        /// Decodes a hex string into bytes.
+        /// </summary>
+        /// <param name="str">The <see cref="string" />.</param>
+        /// <returns>The decoded bytes.</returns>
+        public static byte[] Decode(ReadOnlySpan<char> str)
+        {
+            if (str.Length == 0)
+            {
+                return Array.Empty<byte>();
+            }
+
+            var unHex = HexLookup;
+
+            int byteLen = str.Length / 2;
+            byte[] bytes = new byte[byteLen];
+            int i = 0;
+            for (int j = 0; j < byteLen; j++)
+            {
+                byte a;
+                byte b;
+                if (str[i] > LastHexSymbol
+                    || (a = unHex[str[i++]]) == 0xFF
+                    || str[i] > LastHexSymbol
+                    || (b = unHex[str[i++]]) == 0xFF)
+                {
+                    ThrowArgumentException(nameof(str));
+                    break; // Unreachable
+                }
+
+                bytes[j] = (byte)((a * 16) | b);
+            }
+
+            return bytes;
+        }
+
+        [DoesNotReturn]
+        private static void ThrowArgumentException(string paramName)
+            => throw new ArgumentException("Character is not a hex symbol.", paramName);
+    }
+}