blob: f11b34fabf4acd57559126aca47ddb96b183f120 [file] [log] [blame]
// Copyright 2021 The Pigweed Authors
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once
#include <cstddef>
#include "pw_varint/varint.h"
namespace pw::hdlc {
inline constexpr std::byte kFlag = std::byte{0x7E};
inline constexpr std::byte kEscape = std::byte{0x7D};
inline constexpr std::byte kEscapeConstant = std::byte{0x20};
inline constexpr std::array<std::byte, 2> kEscapedFlag = {kEscape,
inline constexpr std::array<std::byte, 2> kEscapedEscape = {kEscape,
inline constexpr varint::Format kAddressFormat =
constexpr bool NeedsEscaping(std::byte b) {
return (b == kFlag || b == kEscape);
constexpr std::byte Escape(std::byte b) { return b ^ kEscapeConstant; }
// Class that manages the 1-byte control field of an HDLC U-frame.
class UFrameControl {
static constexpr UFrameControl UnnumberedInformation() {
return UFrameControl(kUnnumberedInformation);
constexpr std::byte data() const { return data_; }
// Types of HDLC U-frames and their bit patterns.
enum Type : uint8_t {
kUnnumberedInformation = 0x00,
constexpr UFrameControl(Type type)
: data_(kUFramePattern | std::byte{type}) {}
// U-frames are identified by having the bottom two control bits set.
static constexpr std::byte kUFramePattern = std::byte{0x03};
std::byte data_;
} // namespace pw::hdlc