add check to see if we need to seek before hand

[adamhathcock]

Related to findings on #1105 by @julianxhokaxhiu

This pull request improves memory efficiency and stream handling in BufferedSubStream by using pooled buffers and optimizing seek operations. It also updates the test suite to better simulate forward-only stream scenarios.

Memory Management Improvements:

• Switched _cache allocation in BufferedSubStream to use ArrayPool<byte>.Shared.Rent for buffer pooling, and ensured the buffer is returned to the pool in Dispose for reduced GC pressure. [1] [2]

Performance and Stream Handling Enhancements:

• Updated RefillCache and RefillCacheAsync to avoid unnecessary seek operations by checking the current stream position before seeking, improving performance for sequential reads. [1] [2]

Testing Improvements:

• Modified BufferReadAndSeekTest to wrap the memory stream with ForwardOnlyStream, better simulating streams that do not support seeking. [1] [2]

[Copilot]

Pull request overview

This pull request aims to improve performance and memory efficiency for buffered/forward-only stream scenarios (per issue #1105) by reducing unnecessary seek operations, pooling buffers, and adjusting tests to better represent non-seekable streams.

Changes:

• Update BufferedSubStream to rent its internal cache from ArrayPool<byte>.Shared and return it on dispose.
• Optimize cache refill logic to avoid unnecessary seeks when already at the correct position.
• Update BufferReadAndSeekTest to use a forward-only stream wrapper.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
tests/SharpCompress.Test/Streams/SharpCompressStreamTest.cs	Adjusts a test to wrap the base stream in ForwardOnlyStream to simulate non-seekable behavior.
src/SharpCompress/IO/SharpCompressStream.cs	Removes an unused local variable in Seek.
src/SharpCompress/IO/BufferedSubStream.cs	Introduces pooled buffer usage and conditional seeking in cache refill paths.

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[Copilot]

@adamhathcock I've opened a new pull request, #1161, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

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