Function peekStruct [src]

Asserts the buffer was initialized with a capacity at least @sizeOf(T). This function is inline to avoid referencing std.mem.byteSwapAllFields when endian is comptime-known and matches the host endianness. See also: takeStruct peekStructPointer

Prototype

pub inline fn peekStruct(r: *Reader, comptime T: type, endian: std.builtin.Endian) Error!T

Parameters

r: *ReaderT: typeendian: std.builtin.Endian

Possible Errors

EndOfStream

ReadFailed

See the Reader implementation for detailed diagnostics.

Example

 test peekStruct {
    var r: Reader = .fixed(&.{ 0x12, 0x00, 0x34, 0x56 });
    const S = extern struct { a: u8, b: u16 };
    try testing.expectEqual(@as(S, .{ .a = 0x12, .b = 0x3456 }), try r.peekStruct(S, .big));
    try testing.expectEqual(@as(S, .{ .a = 0x12, .b = 0x5634 }), try r.peekStruct(S, .little));
}

Source

  pub inline fn peekStruct(r: *Reader, comptime T: type, endian: std.builtin.Endian) Error!T {
    switch (@typeInfo(T)) {
        .@"struct" => |info| switch (info.layout) {
            .auto => @compileError("ill-defined memory layout"),
            .@"extern" => {
                var res = (try r.peekStructPointer(T)).*;
                if (native_endian != endian) std.mem.byteSwapAllFields(T, &res);
                return res;
            },
            .@"packed" => {
                return @bitCast(try peekInt(r, info.backing_integer.?, endian));
            },
        },
        else => @compileError("not a struct"),
    }
}  