Function writeStruct [src]

The function is inline to avoid the dead code in case endian is comptime-known and matches host endianness.

Prototype

pub inline fn writeStruct(w: *Writer, value: anytype, endian: std.builtin.Endian) Error!void

Parameters

w: *Writerendian: std.builtin.Endian

Possible Errors

WriteFailed

See the Writer implementation for detailed diagnostics.

Example

 test writeStruct {
    var buffer: [16]u8 = undefined;
    const S = extern struct { a: u64, b: u32, c: u32 };
    const s: S = .{ .a = 1, .b = 2, .c = 3 };
    {
        var w: Writer = .fixed(&buffer);
        try w.writeStruct(s, .little);
        try testing.expectEqualSlices(u8, &.{
            1, 0, 0, 0, 0, 0, 0, 0, //
            2, 0, 0, 0, //
            3, 0, 0, 0, //
        }, &buffer);
    }
    {
        var w: Writer = .fixed(&buffer);
        try w.writeStruct(s, .big);
        try testing.expectEqualSlices(u8, &.{
            0, 0, 0, 0, 0, 0, 0, 1, //
            0, 0, 0, 2, //
            0, 0, 0, 3, //
        }, &buffer);
    }
}

Source

  pub inline fn writeStruct(w: *Writer, value: anytype, endian: std.builtin.Endian) Error!void {
    switch (@typeInfo(@TypeOf(value))) {
        .@"struct" => |info| switch (info.layout) {
            .auto => @compileError("ill-defined memory layout"),
            .@"extern" => {
                if (native_endian == endian) {
                    return w.writeAll(@ptrCast((&value)[0..1]));
                } else {
                    var copy = value;
                    std.mem.byteSwapAllFields(@TypeOf(value), ©);
                    return w.writeAll(@ptrCast((©)[0..1]));
                }
            },
            .@"packed" => {
                return writeInt(w, info.backing_integer.?, @bitCast(value), endian);
            },
        },
        else => @compileError("not a struct"),
    }
}  