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Moved HexStringToBytes into a SixLabors.ImageSharp.Common.Helpers.HexConverter.

pull/1877/head
WINDEV2110EVAL\User 4 years ago
parent
0409d9699a
commit
6dba6cf1f8
2 changed files with 101 additions and 89 deletions
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  1. 98
      src/ImageSharp/Common/Helpers/HexConverter.cs
  2. 92
      src/ImageSharp/Formats/Png/PngDecoderCore.cs

98
src/ImageSharp/Common/Helpers/HexConverter.cs
View File

@ -0,0 +1,98 @@
// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.
using System;
using System.Runtime.CompilerServices;
namespace SixLabors.ImageSharp.Common.Helpers
{
internal static class HexConverter
{
/// <summary>
/// Parses a hexadecimal string into a byte array without allocations. Throws on non-hexadecimal character.
/// Adapted from https://source.dot.net/#System.Private.CoreLib/Convert.cs,c9e4fbeaca708991.
/// </summary>
/// <param name="chars">The hexadecimal string to parse.</param>
/// <param name="bytes">The destination for the parsed bytes. Must be at least <paramref name="chars"/>.Length / 2 bytes long.</param>
/// <returns>The number of bytes written to <paramref name="bytes"/>.</returns>
public static int HexStringToBytes(ReadOnlySpan<char> chars, Span<byte> bytes)
{
if ((chars.Length % 2) != 0)
{
throw new ArgumentException("Input string length must be a multiple of 2", nameof(chars));
}
if ((bytes.Length * 2) < chars.Length)
{
throw new ArgumentException("Output span must be at least half the length of the input string");
}
else
{
// Slightly better performance in the loop below, allows us to skip a bounds check
// while still supporting output buffers that are larger than necessary
bytes = bytes.Slice(0, chars.Length / 2);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static int FromChar(int c)
{
// Map from an ASCII char to its hex value, e.g. arr['b'] == 11. 0xFF means it's not a hex digit.
// This doesn't actually allocate.
ReadOnlySpan<byte> charToHexLookup = new byte[]
{
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 15
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 31
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 47
0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 63
0xFF, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 79
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 95
0xFF, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 111
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 127
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 143
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 159
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 175
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 191
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 207
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 223
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 239
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 255
};
return c >= charToHexLookup.Length ? 0xFF : charToHexLookup[c];
}
// See https://source.dot.net/#System.Private.CoreLib/HexConverter.cs,4681d45a0aa0b361
int i = 0;
int j = 0;
int byteLo = 0;
int byteHi = 0;
while (j < bytes.Length)
{
byteLo = FromChar(chars[i + 1]);
byteHi = FromChar(chars[i]);
// byteHi hasn't been shifted to the high half yet, so the only way the bitwise or produces this pattern
// is if either byteHi or byteLo was not a hex character.
if ((byteLo | byteHi) == 0xFF)
{
break;
}
bytes[j++] = (byte)((byteHi << 4) | byteLo);
i += 2;
}
if (byteLo == 0xFF)
{
i++;
}
if ((byteLo | byteHi) == 0xFF)
{
throw new ArgumentException("Input string contained non-hexadecimal characters", nameof(chars));
}
return j;
}
}
}

92
src/ImageSharp/Formats/Png/PngDecoderCore.cs
View File

@ -11,6 +11,7 @@ using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using SixLabors.ImageSharp.Common.Helpers;
using SixLabors.ImageSharp.Compression.Zlib;
using SixLabors.ImageSharp.Formats.Png.Chunks;
using SixLabors.ImageSharp.Formats.Png.Filters;
@ -1093,7 +1094,7 @@ namespace SixLabors.ImageSharp.Formats.Png
tempExifBuf = new byte[exifHeader.Length];
}
HexStringToBytes(dataSpan.Slice(0, exifHeader.Length * 2), tempExifBuf);
HexConverter.HexStringToBytes(dataSpan.Slice(0, exifHeader.Length * 2), tempExifBuf);
if (!tempExifBuf.AsSpan().Slice(0, exifHeader.Length).SequenceEqual(exifHeader))
{
// Exif header in the hex data is not valid
@ -1115,7 +1116,7 @@ namespace SixLabors.ImageSharp.Formats.Png
lineSpan = dataSpan.Slice(0, newlineIndex);
}
i += HexStringToBytes(lineSpan, exifBlob.AsSpan().Slice(i));
i += HexConverter.HexStringToBytes(lineSpan, exifBlob.AsSpan().Slice(i));
dataSpan = dataSpan.Slice(newlineIndex + 1);
}
@ -1163,93 +1164,6 @@ namespace SixLabors.ImageSharp.Formats.Png
#pragma warning restore IDE0022 // Use expression body for methods
}
/// <summary>
/// Parses a hexadecimal string into a byte array without allocations. Throws on non-hexadecimal character.
/// Adapted from https://source.dot.net/#System.Private.CoreLib/Convert.cs,c9e4fbeaca708991.
/// </summary>
/// <param name="chars">The hexadecimal string to parse.</param>
/// <param name="bytes">The destination for the parsed bytes. Must be at least <paramref name="chars"/>.Length / 2 bytes long.</param>
/// <returns>The number of bytes written to <paramref name="bytes"/>.</returns>
private static int HexStringToBytes(ReadOnlySpan<char> chars, Span<byte> bytes)
{
if ((chars.Length % 2) != 0)
{
throw new ArgumentException("Input string length must be a multiple of 2", nameof(chars));
}
if ((bytes.Length * 2) < chars.Length)
{
throw new ArgumentException("Output span must be at least half the length of the input string");
}
else
{
// Slightly better performance in the loop below, allows us to skip a bounds check
// while still supporting output buffers that are larger than necessary
bytes = bytes.Slice(0, chars.Length / 2);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static int FromChar(int c)
{
// Map from an ASCII char to its hex value, e.g. arr['b'] == 11. 0xFF means it's not a hex digit.
// This doesn't actually allocate.
ReadOnlySpan<byte> charToHexLookup = new byte[]
{
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 15
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 31
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 47
0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 63
0xFF, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 79
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 95
0xFF, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 111
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 127
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 143
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 159
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 175
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 191
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 207
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 223
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 239
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 255
};
return c >= charToHexLookup.Length ? 0xFF : charToHexLookup[c];
}
// See https://source.dot.net/#System.Private.CoreLib/HexConverter.cs,4681d45a0aa0b361
int i = 0;
int j = 0;
int byteLo = 0;
int byteHi = 0;
while (j < bytes.Length)
{
byteLo = FromChar(chars[i + 1]);
byteHi = FromChar(chars[i]);
// byteHi hasn't been shifted to the high half yet, so the only way the bitwise or produces this pattern
// is if either byteHi or byteLo was not a hex character.
if ((byteLo | byteHi) == 0xFF)
{
break;
}
bytes[j++] = (byte)((byteHi << 4) | byteLo);
i += 2;
}
if (byteLo == 0xFF)
{
i++;
}
if ((byteLo | byteHi) == 0xFF)
{
throw new ArgumentException("Input string contained non-hexadecimal characters", nameof(chars));
}
return j;
}
/// <summary>
/// Sets the <see cref="ExifProfile"/> in <paramref name="metadata"/> to <paramref name="newProfile"/>,
/// or copies exif tags if <paramref name="metadata"/> already contains an <see cref="ExifProfile"/>.

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