Add File extensions: WriteAllZeroes, ReadAllBytes(offset), ReadAllBytes(offset, length), ReadAllBytesAsync(offset), ReadAllBytesAsync(offset, length)

[Copilot]

Ports the File static-class extensions from GitHubActionsTestLogger, adding an async counterpart for the read operation.

New extensions

• File.WriteAllZeroes(path, count) — creates/overwrites a file of exactly count zero bytes via SetLength (no async; it's a metadata-only syscall)
• File.ReadAllBytes(path, offset) — reads all bytes from offset (a long) to EOF; returns an empty array when offset >= file length
• File.ReadAllBytes(path, offset, length) — reads exactly length bytes starting at offset
• File.ReadAllBytesAsync(path, offset, cancellationToken) — same as the offset-only sync version, using ReadExactlyAsync
• File.ReadAllBytesAsync(path, offset, length, cancellationToken) — same as the offset+length sync version, using ReadExactlyAsync

The length parameter in the offset+length overloads is int (matching the array size constraint), and offset is long to support large files.

File.WriteAllZeroes(path, count: 1024);

byte[] tail = File.ReadAllBytes(path, offset: 512L);
byte[] slice = File.ReadAllBytes(path, offset: 512L, length: 256);

byte[] tail = await File.ReadAllBytesAsync(path, offset: 512L);
byte[] slice = await File.ReadAllBytesAsync(path, offset: 512L, length: 256);

[Copilot]

Pull request overview

Ports a small set of System.IO.File extension members into PowerKit to support creating zero-filled files and reading a file tail from a given offset (sync + async), with accompanying unit tests.

Changes:

• Added File.WriteAllZeroes(path, count) to create/truncate a file to a specific length.
• Added File.ReadAllBytes(path, offset) and File.ReadAllBytesAsync(path, offset, cancellationToken) to read from an offset to EOF.
• Added xUnit coverage for the new extensions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
PowerKit/Extensions/FileExtensions.cs	Introduces the new File extension members (write-zeroes + read-from-offset sync/async).
PowerKit.Tests/FileExtensionsTests.cs	Adds tests validating zero-fill size/content and read-from-offset behavior for both sync and async APIs.

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[Tyrrrz]

@copilot try to fix the build errors

[Copilot]

@copilot try to fix the build errors

Fixed in 1663629. Two issues were causing the build failures:

1. FileStreamOptions isn't available in netstandard2.0 — replaced with the 6-parameter FileStream constructor that accepts FileOptions.Asynchronous directly.
2. stream.Length - offset produces a long which can't be used as an array length implicitly — wrapped in checked((int)(...)) so it converts safely and throws OverflowException if the remaining length exceeds int.MaxValue.

[Tyrrrz]

@copilot let's make length an int so it fits into an array?

[Copilot]

@copilot let's make length an int so it fits into an array?

Done in 7312aff. Both ReadAllBytes(path, offset, length) and ReadAllBytesAsync(path, offset, length, …) now take int length. The guard is simplified to just length < 0, and the buffer allocation is new byte[length] directly (no cast needed).

[Tyrrrz]

@copilot use the newly introduced TempFile/TestDirectory where needed

[Copilot]

@copilot use the newly introduced TempFile/TestDirectory where needed

Done in 33caa32. All nine tests now use using var tempFile = TempFile.Create() instead of Path.GetTempFileName() + try/finally blocks.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

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