Implemented windows versions of seekTo and getPos #710
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std/io.zig
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| const err = system.GetLastError(); | ||
| return switch (err) { | ||
| system.ERROR.INVALID_PARAMETER => error.BadFd, | ||
| else => os.unexpectedErrorPosix(err), |
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I think this should be unexpectedErrorWindows
std/os/windows/index.zig
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| @@ -74,6 +74,9 @@ pub extern "kernel32" stdcallcc fn ReadFile(in_hFile: HANDLE, out_lpBuffer: LPVO | |||
| in_nNumberOfBytesToRead: DWORD, out_lpNumberOfBytesRead: &DWORD, | |||
| in_out_lpOverlapped: ?&OVERLAPPED) -> BOOL; | |||
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| pub extern "kernel32" stdcallcc fn SetFilePointerEx(in_fFile: HANDLE, in_liDistanceToMove: LARGE_INTEGER, | |||
| out_opt_ldNewFilePointer: ?PLARGE_INTEGER, in_dwMoveMethod: DWORD) -> BOOL; | |||
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The precedent here is to use ?&LARGE_INTEGER instead of PLARGE_INTEGER. The P naming by Microsoft is a bit of an anti-pattern.
std/io.zig
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| @@ -245,6 +263,18 @@ pub const File = struct { | |||
| } | |||
| return result; | |||
| }, | |||
| Os.windows => { | |||
| var pos : usize = undefined; | |||
| if (system.SetFilePointerEx(self.handle, 0, @ptrCast(system.PLARGE_INTEGER, &pos), system.FILE_CURRENT) == 0) { | |||
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LARGE_INTEGER is always an i64. usize is pointer-sized. These are not necessarily the same byte size. Also the signed-ness is different. So part of the job of this function is to get the i64 from Windows, and then convert it to a usize, making correct decisions about how to handle the following situations:
- when usize is smaller than i64 (probably return
error.FilePosLargerThanPointerRange, which is maybe a hint that we should actually return u64 instead of usize from getPos, but that's a separate issue, which could be fixed later) - when the i64 we get from microsoft is negative instead of positive (maybe we assert that it will not happen? maybe we return an error?)
Generally, @ptrCast should be avoided if possible, and this is a situation where I don't think we need one.
std/io.zig
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| @@ -224,6 +233,15 @@ pub const File = struct { | |||
| }; | |||
| } | |||
| }, | |||
| Os.windows => { | |||
| if (system.SetFilePointerEx(self.handle, @bitCast(isize, pos), null, system.FILE_BEGIN) == 0) { | |||
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bitcasting pos to isize could produce an invalid value if pos has a 1 for the highest-order bit. We should handle this edge case correctly. perhaps std.math.cast could be of use.
…e don't want to compare pos to @MaxValue(usize).
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