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