Function byteSwapAllFields [src]

Swap the byte order of all the members of the fields of a struct (Changing their endianness)

Prototype

pub fn byteSwapAllFields(comptime S: type, ptr: *S) void

Parameters

S: typeptr: *S

Example

 test byteSwapAllFields {
    const T = extern struct {
        f0: u8,
        f1: u16,
        f2: u32,
        f3: [1]u8,
        f4: bool,
        f5: f32,
        f6: extern union { f0: u16, f1: u16 },
    };
    const K = extern struct {
        f0: u8,
        f1: T,
        f2: u16,
        f3: [1]u8,
        f4: bool,
        f5: f32,
    };
    var s = T{
        .f0 = 0x12,
        .f1 = 0x1234,
        .f2 = 0x12345678,
        .f3 = .{0x12},
        .f4 = true,
        .f5 = @as(f32, @bitCast(@as(u32, 0x4640e400))),
        .f6 = .{ .f0 = 0x1234 },
    };
    var k = K{
        .f0 = 0x12,
        .f1 = s,
        .f2 = 0x1234,
        .f3 = .{0x12},
        .f4 = false,
        .f5 = @as(f32, @bitCast(@as(u32, 0x45d42800))),
    };
    byteSwapAllFields(T, &s);
    byteSwapAllFields(K, &k);
    try std.testing.expectEqual(T{
        .f0 = 0x12,
        .f1 = 0x3412,
        .f2 = 0x78563412,
        .f3 = .{0x12},
        .f4 = true,
        .f5 = @as(f32, @bitCast(@as(u32, 0x00e44046))),
        .f6 = .{ .f0 = 0x3412 },
    }, s);
    try std.testing.expectEqual(K{
        .f0 = 0x12,
        .f1 = s,
        .f2 = 0x3412,
        .f3 = .{0x12},
        .f4 = false,
        .f5 = @as(f32, @bitCast(@as(u32, 0x0028d445))),
    }, k);
}

Source

  pub fn byteSwapAllFields(comptime S: type, ptr: *S) void {
    switch (@typeInfo(S)) {
        .@"struct" => {
            inline for (std.meta.fields(S)) |f| {
                switch (@typeInfo(f.type)) {
                    .@"struct" => |struct_info| if (struct_info.backing_integer) |Int| {
                        @field(ptr, f.name) = @bitCast(@byteSwap(@as(Int, @bitCast(@field(ptr, f.name)))));
                    } else {
                        byteSwapAllFields(f.type, &@field(ptr, f.name));
                    },
                    .@"union", .array => byteSwapAllFields(f.type, &@field(ptr, f.name)),
                    .@"enum" => {
                        @field(ptr, f.name) = @enumFromInt(@byteSwap(@intFromEnum(@field(ptr, f.name))));
                    },
                    .bool => {},
                    .float => |float_info| {
                        @field(ptr, f.name) = @bitCast(@byteSwap(@as(std.meta.Int(.unsigned, float_info.bits), @bitCast(@field(ptr, f.name)))));
                    },
                    else => {
                        @field(ptr, f.name) = @byteSwap(@field(ptr, f.name));
                    },
                }
            }
        },
        .@"union" => |union_info| {
            if (union_info.tag_type != null) {
                @compileError("byteSwapAllFields expects an untagged union");
            }

            const first_size = @bitSizeOf(union_info.fields[0].type);
            inline for (union_info.fields) |field| {
                if (@bitSizeOf(field.type) != first_size) {
                    @compileError("Unable to byte-swap unions with varying field sizes");
                }
            }

            const BackingInt = std.meta.Int(.unsigned, @bitSizeOf(S));
            ptr.* = @bitCast(@byteSwap(@as(BackingInt, @bitCast(ptr.*))));
        },
        .array => |info| {
            byteSwapAllElements(info.child, ptr);
        },
        else => {
            ptr.* = @byteSwap(ptr.*);
        },
    }
}  