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FileOperations: Add Windows implementation for FileDescriptor.resize(to:) #89

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Merged
milseman merged 3 commits into from
Jun 9, 2022
Merged

FileOperations: Add Windows implementation for FileDescriptor.resize(to:) #89

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7e4c4ea
FileOperations: Add Windows implementation for FileDescriptor.resize(…
simonjbeaumont Jun 6, 2022
91d61b2
fixup: Replace _chsize with _chsize_s on Windows
simonjbeaumont Jun 7, 2022
7c0abfc
Merge branch 'main' into sb/resize-windows
milseman Jun 9, 2022
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2 changes: 0 additions & 2 deletions Sources/System/FileOperations.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -401,7 +401,6 @@ extension FileDescriptor {
}
#endif

#if !os(Windows)
/*System 1.2.0, @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)*/
extension FileDescriptor {
/// Truncate or extend the file referenced by this file descriptor.
Expand Down Expand Up @@ -447,4 +446,3 @@ extension FileDescriptor {
}
}
}
#endif
7 changes: 7 additions & 0 deletions Sources/System/Internals/WindowsSyscallAdapters.swift
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Expand Up @@ -105,4 +105,11 @@ internal func pwrite(
return Int(nNumberOfBytesWritten)
}

@inline(__always)
internal func ftruncate(
_ fd: Int32,
_ length: off_t
) -> Int32 {
_chsize(fd, numericCast(length))
}
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@simonjbeaumont simonjbeaumont Jun 6, 2022

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@compnerd do you have any opinions on this? Do you think that _chsize is the right choice for Windows or should we be using implementing this in terms of other APIs? You mentioned something about SetFilePointerEx and SetEndOfFile?

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@compnerd compnerd Jun 6, 2022 •
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In general, using the windows API is better. It tends to be more flexible and integrates better by covering more cases (e.g. file descriptors are really a lookup table in the C library to the underlying kernel handle, and that may be created bypassing the registration by using the Windows API).

At the very least please use _chsize_s (which in fact I have a pending patch for NIO) as that uses a __int64 for the offset rather than a long which is 32-bit. It effectively is the behavioral change of _FILE_OFFSET_BITS=64 on GNU. I don’t see a reason for modern code to use the 32-bit offset even under register pressure on 32-bit platforms in a library.

For keeping the signature the same, we can use _get_osf_handle to get the kernel handle from the file descriptor (as +0! do not free, aka CloseHandle). We should expose the handle variant of the API, but that can be done subsequently.

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@simonjbeaumont simonjbeaumont Jun 7, 2022

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@compnerd for now I replaced the use of _chsize with _chsize_s in 91d61b2.

I'd hate to break the Windows build again. Are there any useful docs for getting cross-compilation up and running?

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@compnerd compnerd Jun 7, 2022

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I do have some updated docs at https://github.com/compnerd/swift-build/blob/master/docs/WindowsQuickStart.md. I’m working on some more options for building.

#endif