    const std = @import("../std.zig");
    const builtin = @import("builtin");
    const io = std.io;
    const testing = std.testing;
    const os = std.os;

    pub const CWriter = io.Writer(*std.c.FILE, std.fs.File.WriteError, cWriterWrite);

    pub fn cWriter(c_file: *std.c.FILE) CWriter {
        return .{ .context = c_file };
    }

    fn cWriterWrite(c_file: *std.c.FILE, bytes: []const u8) std.fs.File.WriteError!usize {
        const amt_written = std.c.fwrite(bytes.ptr, 1, bytes.len, c_file);
        if (amt_written >= 0) return amt_written;
        switch (@intToEnum(os.E, std.c._errno().*)) {
            .SUCCESS => unreachable,
            .INVAL => unreachable,
            .FAULT => unreachable,
            .AGAIN => unreachable, // this is a blocking API

            .BADF => unreachable, // always a race condition

            .DESTADDRREQ => unreachable, // connect was never called

            .DQUOT => return error.DiskQuota,
            .FBIG => return error.FileTooBig,
            .IO => return error.InputOutput,
            .NOSPC => return error.NoSpaceLeft,
            .PERM => return error.AccessDenied,
            .PIPE => return error.BrokenPipe,
            else => |err| return os.unexpectedErrno(err),
        }
    }

    test "C Writer" {
        if (!builtin.link_libc or builtin.os.tag == .wasi) return error.SkipZigTest;

        const filename = "tmp_io_test_file.txt";
        const out_file = std.c.fopen(filename, "w") orelse return error.UnableToOpenTestFile;
        defer {
            _ = std.c.fclose(out_file);
            std.fs.cwd().deleteFileZ(filename) catch {};
        }

        const writer = cWriter(out_file);
        try writer.print("hi: {}\n", .{@as(i32, 123)});
    }