fileSeekBy

fn fileSeekBy(userdata: ?*anyopaque, file: File, offset: i64) File.SeekError!void

File

Code

fn fileSeekBy(userdata: ?*anyopaque, file: File, offset: i64) File.SeekError!void {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;

    if (is_windows) {
        var iosb: windows.IO_STATUS_BLOCK = undefined;
        var info: windows.FILE.POSITION_INFORMATION = undefined;
        const syscall: Syscall = try .start();
        while (true) switch (windows.ntdll.NtQueryInformationFile(
            file.handle,
            &iosb,
            &info,
            @sizeOf(windows.FILE.POSITION_INFORMATION),
            .Position,
        )) {
            .SUCCESS => break,
            .CANCELLED => try syscall.checkCancel(),
            .ACCESS_DENIED => return syscall.fail(error.AccessDenied),
            .PIPE_NOT_AVAILABLE => return syscall.fail(error.Unseekable),
            else => |status| return syscall.unexpectedNtstatus(status),
        };
        info.CurrentByteOffset = @bitCast((if (offset >= 0) std.math.add(
            u64,
            @bitCast(info.CurrentByteOffset),
            @intCast(offset),
        ) else std.math.sub(
            u64,
            @bitCast(info.CurrentByteOffset),
            @intCast(-offset),
        )) catch |err| switch (err) {
            error.Overflow => return syscall.fail(error.Unseekable),
        });
        while (true) switch (windows.ntdll.NtSetInformationFile(
            file.handle,
            &iosb,
            &info,
            @sizeOf(windows.FILE.POSITION_INFORMATION),
            .Position,
        )) {
            .SUCCESS => return syscall.finish(),
            .CANCELLED => try syscall.checkCancel(),
            .ACCESS_DENIED => return syscall.fail(error.AccessDenied),
            .PIPE_NOT_AVAILABLE => return syscall.fail(error.Unseekable),
            else => |status| return syscall.unexpectedNtstatus(status),
        };
    }

    if (native_os == .wasi and !builtin.link_libc) {
        var new_offset: std.os.wasi.filesize_t = undefined;
        const syscall: Syscall = try .start();
        while (true) {
            switch (std.os.wasi.fd_seek(file.handle, offset, .CUR, &new_offset)) {
                .SUCCESS => {
                    syscall.finish();
                    return;
                },
                .INTR => {
                    try syscall.checkCancel();
                    continue;
                },
                else => |e| {
                    syscall.finish();
                    switch (e) {
                        .BADF => |err| return errnoBug(err), // File descriptor used after closed.
                        .INVAL => return error.Unseekable,
                        .OVERFLOW => return error.Unseekable,
                        .SPIPE => return error.Unseekable,
                        .NXIO => return error.Unseekable,
                        .NOTCAPABLE => return error.AccessDenied,
                        else => |err| return posix.unexpectedErrno(err),
                    }
                },
            }
        }
    }

    if (posix.SEEK == void) return error.Unseekable;

    if (native_os == .linux and !builtin.link_libc and @sizeOf(posix.system.syscall_arg_t) == 4) {
        var result: i64 = undefined;
        const syscall: Syscall = try .start();
        while (true) {
            switch (posix.errno(posix.system.llseek(file.handle, offset, &result, posix.SEEK.CUR))) {
                .SUCCESS => {
                    syscall.finish();
                    return;
                },
                .INTR => {
                    try syscall.checkCancel();
                    continue;
                },
                else => |e| {
                    syscall.finish();
                    switch (e) {
                        .BADF => |err| return errnoBug(err), // File descriptor used after closed.
                        .INVAL => return error.Unseekable,
                        .OVERFLOW => return error.Unseekable,
                        .SPIPE => return error.Unseekable,
                        .NXIO => return error.Unseekable,
                        else => |err| return posix.unexpectedErrno(err),
                    }
                },
            }
        }
    }

    const syscall: Syscall = try .start();
    while (true) {
        switch (posix.errno(lseek_sym(file.handle, offset, posix.SEEK.CUR))) {
            .SUCCESS => {
                syscall.finish();
                return;
            },
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .BADF => |err| return errnoBug(err), // File descriptor used after closed.
                    .INVAL => return error.Unseekable,
                    .OVERFLOW => return error.Unseekable,
                    .SPIPE => return error.Unseekable,
                    .NXIO => return error.Unseekable,
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }
}