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@ -5,6 +5,7 @@ using System; |
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using System.Buffers; |
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using System.IO; |
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using SixLabors.ImageSharp.Formats.Gif; |
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using SixLabors.ImageSharp.Memory; |
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namespace SixLabors.ImageSharp.Formats.Tiff |
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{ |
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@ -19,7 +20,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff |
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/// byte indicating the length of the sub-block. In TIFF the data is written as a single block
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/// with no length indicator (this can be determined from the 'StripByteCounts' entry).
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/// </remarks>
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internal sealed class TiffLzwDecoder : IDisposable |
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internal sealed class TiffLzwDecoder |
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{ |
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/// <summary>
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/// The max decoder pixel stack size.
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@ -37,52 +38,23 @@ namespace SixLabors.ImageSharp.Formats.Tiff |
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private readonly Stream stream; |
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/// <summary>
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/// The prefix buffer.
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/// The memory allocator.
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/// </summary>
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private readonly int[] prefix; |
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private readonly MemoryAllocator allocator; |
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/// <summary>
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/// The suffix buffer.
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/// </summary>
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private readonly int[] suffix; |
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/// <summary>
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/// The pixel stack buffer.
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/// </summary>
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private readonly int[] pixelStack; |
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/// <summary>
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/// A value indicating whether this instance of the given entity has been disposed.
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/// </summary>
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/// <value><see langword="true"/> if this instance has been disposed; otherwise, <see langword="false"/>.</value>
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/// <remarks>
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/// If the entity is disposed, it must not be disposed a second
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/// time. The isDisposed field is set the first time the entity
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/// is disposed. If the isDisposed field is true, then the Dispose()
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/// method will not dispose again. This help not to prolong the entity's
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/// life in the Garbage Collector.
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/// </remarks>
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private bool isDisposed; |
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/// <summary>
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/// Initializes a new instance of the <see cref="TiffLzwDecoder"/> class
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/// Initializes a new instance of the <see cref="TiffLzwDecoder" /> class
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/// and sets the stream, where the compressed data should be read from.
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/// </summary>
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/// <param name="stream">The stream to read from.</param>
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/// <exception cref="System.ArgumentNullException"><paramref name="stream"/> is null.</exception>
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public TiffLzwDecoder(Stream stream) |
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/// <param name="allocator">The memory allocator.</param>
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/// <exception cref="System.ArgumentNullException"><paramref name="stream" /> is null.</exception>
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public TiffLzwDecoder(Stream stream, MemoryAllocator allocator) |
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{ |
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Guard.NotNull(stream, nameof(stream)); |
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this.stream = stream; |
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this.prefix = ArrayPool<int>.Shared.Rent(MaxStackSize); |
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this.suffix = ArrayPool<int>.Shared.Rent(MaxStackSize); |
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this.pixelStack = ArrayPool<int>.Shared.Rent(MaxStackSize + 1); |
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Array.Clear(this.prefix, 0, MaxStackSize); |
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Array.Clear(this.suffix, 0, MaxStackSize); |
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Array.Clear(this.pixelStack, 0, MaxStackSize + 1); |
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this.allocator = allocator; |
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} |
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/// <summary>
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@ -95,6 +67,15 @@ namespace SixLabors.ImageSharp.Formats.Tiff |
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{ |
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Guard.MustBeLessThan(dataSize, int.MaxValue, nameof(dataSize)); |
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// Initialize buffers
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using IMemoryOwner<int> prefixMemory = this.allocator.Allocate<int>(MaxStackSize, AllocationOptions.Clean); |
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using IMemoryOwner<int> suffixMemory = this.allocator.Allocate<int>(MaxStackSize, AllocationOptions.Clean); |
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using IMemoryOwner<int> pixelStackMemory = this.allocator.Allocate<int>(MaxStackSize + 1, AllocationOptions.Clean); |
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Span<int> prefix = prefixMemory.GetSpan(); |
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Span<int> suffix = suffixMemory.GetSpan(); |
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Span<int> pixelStack = pixelStackMemory.GetSpan(); |
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// Calculate the clear code. The value of the clear code is 2 ^ dataSize
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int clearCode = 1 << dataSize; |
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@ -111,54 +92,39 @@ namespace SixLabors.ImageSharp.Formats.Tiff |
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int code; |
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int oldCode = NullCode; |
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int codeMask = (1 << codeSize) - 1; |
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int inputByte = 0; |
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int bits = 0; |
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int top = 0; |
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int count = 0; |
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int bi = 0; |
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int xyz = 0; |
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int data = 0; |
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int first = 0; |
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for (code = 0; code < clearCode; code++) |
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{ |
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this.prefix[code] = 0; |
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this.suffix[code] = (byte)code; |
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prefix[code] = 0; |
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suffix[code] = (byte)code; |
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} |
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byte[] buffer = new byte[255]; |
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// Decoding process
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while (xyz < length) |
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{ |
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if (top == 0) |
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{ |
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if (bits < codeSize) |
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{ |
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// Load bytes until there are enough bits for a code.
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if (count == 0) |
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{ |
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// Read a new data block.
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count = this.ReadBlock(buffer); |
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if (count == 0) |
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{ |
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break; |
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} |
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bi = 0; |
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} |
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data += buffer[bi] << bits; |
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// Get the next code
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int data = inputByte & ((1 << bits) - 1); |
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while (bits < codeSize) |
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{ |
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inputByte = this.stream.ReadByte(); |
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data = (data << 8) | inputByte; |
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bits += 8; |
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bi++; |
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count--; |
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continue; |
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} |
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// Get the next code
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code = data & codeMask; |
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data >>= codeSize; |
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data >>= bits - codeSize; |
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bits -= codeSize; |
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code = data & codeMask; |
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// Interpret the code
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if (code > availableCode || code == endCode) |
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@ -178,7 +144,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff |
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if (oldCode == NullCode) |
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{ |
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this.pixelStack[top++] = this.suffix[code]; |
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pixelStack[top++] = suffix[code]; |
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oldCode = code; |
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first = code; |
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continue; |
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@ -187,27 +153,27 @@ namespace SixLabors.ImageSharp.Formats.Tiff |
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int inCode = code; |
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if (code == availableCode) |
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{ |
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this.pixelStack[top++] = (byte)first; |
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pixelStack[top++] = (byte)first; |
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code = oldCode; |
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} |
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while (code > clearCode) |
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{ |
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this.pixelStack[top++] = this.suffix[code]; |
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code = this.prefix[code]; |
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pixelStack[top++] = suffix[code]; |
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code = prefix[code]; |
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} |
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first = this.suffix[code]; |
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first = suffix[code]; |
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this.pixelStack[top++] = this.suffix[code]; |
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pixelStack[top++] = suffix[code]; |
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// Fix for Gifs that have "deferred clear code" as per here :
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// https://bugzilla.mozilla.org/show_bug.cgi?id=55918
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if (availableCode < MaxStackSize) |
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{ |
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this.prefix[availableCode] = oldCode; |
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this.suffix[availableCode] = first; |
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prefix[availableCode] = oldCode; |
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suffix[availableCode] = first; |
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availableCode++; |
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if (availableCode == codeMask + 1 && availableCode < MaxStackSize) |
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{ |
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@ -223,49 +189,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff |
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top--; |
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// Clear missing pixels
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pixels[xyz++] = (byte)this.pixelStack[top]; |
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pixels[xyz++] = (byte)pixelStack[top]; |
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} |
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} |
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/// <inheritdoc />
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public void Dispose() |
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{ |
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// Do not change this code. Put cleanup code in Dispose(bool disposing) above.
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this.Dispose(true); |
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} |
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/// <summary>
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/// Reads the next data block from the stream. For consistency with the GIF decoder,
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/// the image is read in blocks - For TIFF this is always a maximum of 255
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/// </summary>
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/// <param name="buffer">The buffer to store the block in.</param>
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/// <returns>
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/// The <see cref="T:byte[]"/>.
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/// </returns>
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private int ReadBlock(byte[] buffer) |
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{ |
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return this.stream.Read(buffer, 0, 255); |
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} |
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/// <summary>
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/// Disposes the object and frees resources for the Garbage Collector.
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/// </summary>
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/// <param name="disposing">If true, the object gets disposed.</param>
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private void Dispose(bool disposing) |
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{ |
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if (this.isDisposed) |
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{ |
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return; |
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} |
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if (disposing) |
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{ |
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ArrayPool<int>.Shared.Return(this.prefix); |
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ArrayPool<int>.Shared.Return(this.suffix); |
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ArrayPool<int>.Shared.Return(this.pixelStack); |
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} |
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this.isDisposed = true; |
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} |
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} |
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} |
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Ildar Khayrutdinov
6 years ago
