fileSetLength

fn fileSetLength(userdata: ?*anyopaque, file: File, length: u64) File.SetLengthError!void {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;

    const signed_len: i64 = @bitCast(length);
    if (signed_len < 0) return error.FileTooBig; // Avoid ambiguous EINVAL errors.

    if (is_windows) {
        var io_status_block: windows.IO_STATUS_BLOCK = undefined;
        var eof_info: windows.FILE.END_OF_FILE_INFORMATION = .{
            .EndOfFile = signed_len,
        };

        const syscall: Syscall = try .start();
        while (true) switch (windows.ntdll.NtSetInformationFile(
            file.handle,
            &io_status_block,
            &eof_info,
            @sizeOf(windows.FILE.END_OF_FILE_INFORMATION),
            .EndOfFile,
        )) {
            .SUCCESS => return syscall.finish(),
            .CANCELLED => {
                try syscall.checkCancel();
                continue;
            },
            .INVALID_HANDLE => |err| return syscall.ntstatusBug(err), // Handle not open for writing.
            .ACCESS_DENIED => return syscall.fail(error.AccessDenied),
            .USER_MAPPED_FILE => return syscall.fail(error.AccessDenied),
            .INVALID_PARAMETER => return syscall.fail(error.FileTooBig),
            else => |status| return syscall.unexpectedNtstatus(status),
        };
    }

    if (native_os == .wasi and !builtin.link_libc) {
        const syscall: Syscall = try .start();
        while (true) {
            switch (std.os.wasi.fd_filestat_set_size(file.handle, length)) {
                .SUCCESS => return syscall.finish(),
                .INTR => {
                    try syscall.checkCancel();
                    continue;
                },
                else => |e| {
                    syscall.finish();
                    switch (e) {
                        .FBIG => return error.FileTooBig,
                        .IO => return error.InputOutput,
                        .PERM => return error.PermissionDenied,
                        .TXTBSY => return error.FileBusy,
                        .BADF => |err| return errnoBug(err), // Handle not open for writing
                        .INVAL => return error.NonResizable,
                        .NOTCAPABLE => return error.AccessDenied,
                        else => |err| return posix.unexpectedErrno(err),
                    }
                },
            }
        }
    }

    const syscall: Syscall = try .start();
    while (true) {
        switch (posix.errno(ftruncate_sym(file.handle, signed_len))) {
            .SUCCESS => return syscall.finish(),
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .FBIG => return error.FileTooBig,
                    .IO => return error.InputOutput,
                    .PERM => return error.PermissionDenied,
                    .TXTBSY => return error.FileBusy,
                    .BADF => |err| return errnoBug(err), // Handle not open for writing.
                    .INVAL => return error.NonResizable, // This is returned for /dev/null for example.
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }
}