Move Filesystem APIs to std.Io

[andrewrk]

Extracted from #25592.

All of std.fs, std.fs.File, and std.fs.Dir should be deprecated and implementations moved to std.Io.File and std.Io.Dir.

To close the issue std.Io.Threaded must implement all the APIs, including these which currently have @panic stubs:

• dirStat
• fileSeekBy
• dirMakePath
• openSelfExe
• fileWritePositional
• fileWriteStreaming

[leroycep]

I made a table comparing the functions from std.fs.Dir with the std.Io.VTable fields:

fs.Dir fn	Io.VTable field	Variants	Notes
iterate			accompanying Iterator struct
iterateAssumeFirstIteration			accompanying Iterator struct
walkSelectively			accompanying SelectiveWalker struct
walk			accompanying Walker struct
close	dirClose
openFile	dirOpenFile
createFile	dirCreateFile
makeDir	dirMake	Z, W	Z and W variants deprecated
makePath	dirMakePath		Io.Dir.makePath does not use the Io.VTable field
makePathStatus			Should this be part of the VTable?
makeOpenPath	dirMakeOpenPath
realpath		Z, W, W2, Alloc	#19353
setAsCwd
openDir	dirOpenDir
deleteFile		Z, W
deleteDir		Z, W
rename		Z, W
symLink		Z, W, Wasi
atomicSymLink
readLink		Z, W, Wasi
readFile		Alloc, AllocOptions	implemented in terms of VTable
deleteTree
deleteTreeMinStackSize
writeFile
access	dirAccess
copyFile
atomicFile
stat	dirStat
statFile	dirStatPath
chmod
chown
setPermissions

Here's a similar table for std.fs.File:

fs.File fn	Io.VTable field	Notes
stdout
stderr
stdin
close	fileClose
sync
isTty
isCygwinPty
getOrEnableAnsiEscapeSupport
supportsAnsiEscapeCodes
setEndPos
seekBy	fileSeekBy
seekFromEnd
seekTo	fileSeekTo
getPos
getEndPos
mode
stat	fileStat
chmod
chown
setPermissions
updateTimes
read		deprecated in favor of fileReadStreaming, I assume
pread		deprecated in favor of fileReadPositional, I assume
preadAll		/// Deprecated in favor of Reader.
readv	fileReadStreaming	#7699
preadv	fileReadPositional	#7699
write		deprecated in favor of fileWriteStreaming, I assume
writeAll		deprecated in favor of fileWriteStreaming, I assume
pwriteAll		/// Deprecated in favor of Writer.
pwrite		deprecated in favor of fileWritePositional, I assume
writev	fileWriteStreaming	#7699
pwritev	fileWritePositional	#7699
copyRange		/// Deprecated in favor of Writer.
copyRangeAll		/// Deprecated in favor of Writer.
lock
unlock
tryLock
downgradeLock

• Should std.Io.Dir.cwd() be part of the Io interface?
• std.fs.File.Writer needs to be moved into std.Io.File.

[francisqureshi]

FYI: I am sure you all know, but I think currently std.Io.File.readPositional’s fn signature is borked and expects a buffer []u8 vs the vtable which takes a data: [][]u8 ?

😙

[hugomano]

@leroycep on Should std.Io.Dir.cwd() be part of the Io interface? : it's a big yes for us because this unlock the implementation of virtual filesystems on top of the IO interface.

[andrewrk]

Discussion continues at https://codeberg.org/ziglang/zig/pulls/30232