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It focuses on low memory usage
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,42 @@ | ||
| namespace OpenMcdf | ||
| { | ||
| class ByteArrayPool : IByteArrayPool | ||
| { | ||
| public byte[] Rent(int minimumLength) | ||
| { | ||
| for (var i = 0; i < _bufferList.Length; i++) | ||
| { | ||
| var buffer = _bufferList[i]; | ||
|
|
||
| if (buffer != null && buffer.Length >= minimumLength) | ||
| { | ||
| _bufferList[i] = null; | ||
| return buffer; | ||
| } | ||
| } | ||
|
|
||
| return new byte[minimumLength]; | ||
| } | ||
|
|
||
| public void Return(byte[] byteList) | ||
| { | ||
| if (byteList == null || byteList.Length >= MaxBufferLength) | ||
| { | ||
| return; | ||
| } | ||
|
|
||
| for (var i = 0; i < _bufferList.Length; i++) | ||
| { | ||
| var buffer = _bufferList[i]; | ||
| if (buffer is null || byteList.Length > buffer.Length) | ||
| { | ||
| buffer = byteList; | ||
| _bufferList[i] = buffer; | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private readonly byte[][] _bufferList = new byte[4][]; | ||
| private const int MaxBufferLength = 8 * 1024; | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,89 @@ | ||
| using System; | ||
| using System.Diagnostics; | ||
| using System.IO; | ||
|
|
||
| namespace OpenMcdf | ||
| { | ||
| class ForwardSeekStream : Stream | ||
| { | ||
| public ForwardSeekStream(Stream sourceStream, IByteArrayPool byteArrayPool) | ||
| { | ||
| _sourceStream = sourceStream; | ||
| _byteArrayPool = byteArrayPool; | ||
| } | ||
|
|
||
| public override void Flush() | ||
| { | ||
| _sourceStream.Flush(); | ||
| } | ||
|
|
||
| public long CurrentPosition { private set; get; } | ||
|
|
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| public override int Read(byte[] buffer, int offset, int count) | ||
| { | ||
| var n = _sourceStream.Read(buffer, offset, count); | ||
| CurrentPosition += n; | ||
| return n; | ||
| } | ||
|
|
||
| public override long Seek(long offset, SeekOrigin origin) | ||
| { | ||
| if (offset == 0 && origin == SeekOrigin.Begin) | ||
| { | ||
| return CurrentPosition; | ||
| } | ||
|
|
||
| if (offset == CurrentPosition) return CurrentPosition; | ||
| if (offset > CurrentPosition) | ||
| { | ||
| int length = (int) (offset - CurrentPosition); | ||
|
|
||
| var currentReadCount = 0; | ||
| const int defaultMaxBufferLength = 4096; | ||
| var bufferLength = Math.Min(length, defaultMaxBufferLength); | ||
| var byteList = _byteArrayPool.Rent(bufferLength); | ||
| while (currentReadCount < length) | ||
| { | ||
| var size = length - currentReadCount; | ||
| size = Math.Min(size, bufferLength); | ||
|
|
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| currentReadCount += Read(byteList, 0, size); | ||
| } | ||
|
|
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| _byteArrayPool.Return(byteList); | ||
|
|
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| Debug.Assert(offset == CurrentPosition); | ||
| return CurrentPosition; | ||
| } | ||
|
|
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| throw new NotSupportedException(); | ||
| } | ||
|
|
||
| public override void SetLength(long value) | ||
| { | ||
| _sourceStream.SetLength(value); | ||
| } | ||
|
|
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| public override void Write(byte[] buffer, int offset, int count) | ||
| { | ||
| _sourceStream.Write(buffer, offset, count); | ||
| } | ||
|
|
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| public override bool CanRead => _sourceStream.CanRead; | ||
|
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| public override bool CanSeek => true; | ||
|
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| public override bool CanWrite => _sourceStream.CanWrite; | ||
|
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| public override long Length => _sourceStream.Length; | ||
|
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| public override long Position | ||
| { | ||
| get => _sourceStream.Position; | ||
| set => _sourceStream.Position = value; | ||
| } | ||
|
|
||
| private readonly Stream _sourceStream; | ||
| private readonly IByteArrayPool _byteArrayPool; | ||
| } | ||
| } |
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