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Optimize BufferedSubStream.ReadByte

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This commit is contained in:
J.D. Purcell
2025-03-24 21:28:08 -04:00
parent ec21253af9
commit a7918d7b11
1 changed files with 27 additions and 27 deletions
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54
src/SharpCompress/IO/BufferedSubStream.cs Normal file → Executable file
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@@ -20,7 +20,7 @@ internal class BufferedSubStream(Stream stream, long origin, long bytesToRead)
public override void Flush() { }
public override long Length => BytesLeftToRead;
public override long Length => BytesLeftToRead + _cacheLength - _cacheOffset;
public override long Position
{
@@ -28,21 +28,33 @@ internal class BufferedSubStream(Stream stream, long origin, long bytesToRead)
set => throw new NotSupportedException();
}
private void RefillCache()
{
var count = (int)Math.Min(BytesLeftToRead, _cache.Length);
_cacheOffset = 0;
if (count == 0)
{
_cacheLength = 0;
return;
}
Stream.Position = origin;
_cacheLength = Stream.Read(_cache, 0, count);
origin += _cacheLength;
BytesLeftToRead -= _cacheLength;
}
public override int Read(byte[] buffer, int offset, int count)
{
if (count > BytesLeftToRead)
if (count > Length)
{
count = (int)BytesLeftToRead;
count = (int)Length;
}
if (count > 0)
{
if (_cacheLength == 0)
if (_cacheOffset == _cacheLength)
{
_cacheOffset = 0;
Stream.Position = origin;
_cacheLength = Stream.Read(_cache, 0, _cache.Length);
origin += _cacheLength;
RefillCache();
}
if (count > _cacheLength)
@@ -52,8 +64,6 @@ internal class BufferedSubStream(Stream stream, long origin, long bytesToRead)
Buffer.BlockCopy(_cache, _cacheOffset, buffer, offset, count);
_cacheOffset += count;
_cacheLength -= count;
BytesLeftToRead -= count;
}
return count;
@@ -61,26 +71,16 @@ internal class BufferedSubStream(Stream stream, long origin, long bytesToRead)
public override int ReadByte()
{
if (BytesLeftToRead == 0)
if (_cacheOffset == _cacheLength)
{
return -1;
RefillCache();
if (_cacheLength == 0)
{
return -1;
}
}
if (_cacheLength == 0)
{
_cacheOffset = 0;
Stream.Position = origin;
_cacheLength = Stream.Read(_cache, 0, _cache.Length);
origin += _cacheLength;
}
int value = _cache[_cacheOffset];
_cacheOffset++;
_cacheLength--;
BytesLeftToRead--;
return value;
return _cache[_cacheOffset++];
}
public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();