tiny.wayland.wire

1pub const wire = @import("wire.zig");

1const std = @import("std");2const builtin = @import("builtin");34pub const header_size = 8;5pub const maximum_message_size = std.math.maxInt(u16) & ~@as(u16, 3);67pub const Error = error{8    IncompleteHeader,9    InvalidObject,10    InvalidSize,11    MessageTooLarge,12};1314pub const Header = struct {15    object_id: u32,16    opcode: u16,17    size: u16,1819    pub fn init(object_id: u32, opcode: u16, payload_size: usize) Error!Header {20        if (object_id == 0) return error.InvalidObject;21        if (payload_size % 4 != 0) return error.InvalidSize;22        if (payload_size > maximum_message_size - header_size) return error.MessageTooLarge;23        const size = header_size + payload_size;24        return .{25            .object_id = object_id,26            .opcode = opcode,27            .size = @intCast(size),28        };29    }3031    pub fn encode(self: Header, destination: *[header_size]u8) Error!void {32        try self.validate();33        const second = @as(u32, self.size) << 16 | self.opcode;34        std.mem.writeInt(u32, destination[0..4], self.object_id, builtin.cpu.arch.endian());35        std.mem.writeInt(u32, destination[4..8], second, builtin.cpu.arch.endian());36    }3738    pub fn validate(self: Header) Error!void {39        if (self.object_id == 0) return error.InvalidObject;40        if (self.size < header_size or self.size % 4 != 0) return error.InvalidSize;41    }42};4344pub fn decode(bytes: []const u8) Error!Header {45    if (bytes.len < header_size) return error.IncompleteHeader;46    const second = std.mem.readInt(u32, bytes[4..8], builtin.cpu.arch.endian());47    const header: Header = .{48        .object_id = std.mem.readInt(u32, bytes[0..4], builtin.cpu.arch.endian()),49        .opcode = @truncate(second),50        .size = @intCast(second >> 16),51    };52    try header.validate();53    return header;54}5556test "Wayland header round trips in host byte order" {57    const expected: Header = .{ .object_id = 0x1234, .opcode = 7, .size = 20 };58    var encoded: [header_size]u8 = undefined;59    try expected.encode(&encoded);60    try std.testing.expectEqual(expected, try decode(&encoded));61}6263test "Wayland header rejects invalid object and size fields" {64    try std.testing.expectError(error.InvalidObject, Header.init(0, 0, 0));65    try std.testing.expectError(error.InvalidSize, Header.init(1, 0, 2));66    try std.testing.expectError(error.MessageTooLarge, Header.init(1, 0, maximum_message_size));6768    var encoded: [header_size]u8 = @splat(0);69    std.mem.writeInt(u32, encoded[0..4], 1, builtin.cpu.arch.endian());70    std.mem.writeInt(u32, encoded[4..8], @as(u32, 6) << 16, builtin.cpu.arch.endian());71    try std.testing.expectError(error.InvalidSize, decode(&encoded));72}