88 lines
2.6 KiB
C#
88 lines
2.6 KiB
C#
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using System;
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using System.IO;
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namespace NetVips;
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/// <summary>
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/// An source connected to a readable <see cref="Stream"/>.
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/// </summary>
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internal class SourceStream : SourceCustom
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{
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/// <summary>
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/// Read from this stream.
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/// </summary>
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private readonly Stream _stream;
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/// <summary>
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/// The start position within the stream.
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/// </summary>
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private readonly long _startPosition;
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/// <inheritdoc cref="SourceCustom"/>
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internal SourceStream(Stream stream)
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{
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var seekable = stream.CanSeek;
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_stream = stream;
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_startPosition = seekable ? _stream.Position : 0;
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OnRead += Read;
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if (seekable)
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{
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OnSeek += Seek;
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}
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}
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/// <summary>
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/// Create a <see cref="SourceStream"/> attached to an <see cref="Stream"/>.
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/// </summary>
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/// <param name="stream">Read from this stream.</param>
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/// <returns>A new <see cref="SourceStream"/>.</returns>
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/// <exception cref="T:System.ArgumentException">If <paramref name="stream"/> is not readable.</exception>
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internal static SourceStream NewFromStream(Stream stream)
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{
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if (!stream.CanRead)
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{
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throw new ArgumentException("The stream should be readable.", nameof(stream));
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}
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return new SourceStream(stream);
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}
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/// <summary>
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/// Attach a read handler.
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/// </summary>
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/// <param name="buffer">An array of bytes.</param>
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/// <param name="length">The maximum number of bytes to be read.</param>
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/// <returns>The total number of bytes read into the buffer.</returns>
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public int Read(byte[] buffer, int length)
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{
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return _stream.Read(buffer, 0, length);
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}
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/// <summary>
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/// Attach a seek handler.
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/// </summary>
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/// <param name="offset">A byte offset relative to the <paramref name="origin"/>
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/// parameter.</param>
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/// <param name="origin">A value of type <see cref="SeekOrigin"/> indicating the
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/// reference point used to obtain the new position.</param>
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/// <returns>The new position within the current stream.</returns>
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public long Seek(long offset, SeekOrigin origin)
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{
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try
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{
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return origin switch
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{
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SeekOrigin.Begin => _stream.Seek(_startPosition + offset, SeekOrigin.Begin) - _startPosition,
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SeekOrigin.Current => _stream.Seek(offset, SeekOrigin.Current) - _startPosition,
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SeekOrigin.End => _stream.Seek(offset, SeekOrigin.End) - _startPosition,
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_ => -1
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};
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}
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catch
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{
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return -1;
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}
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}
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}
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