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// Copyright 2020 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 "pw_checksum/crc32.h"
#include "pw_hdlc/internal/protocol.h"
#include "pw_stream/stream.h"
namespace pw::hdlc::internal {
// Encodes and writes HDLC frames.
class Encoder {
constexpr Encoder(stream::Writer& output) : writer_(output) {}
// Writes the header for an I-frame. After successfully calling
// StartInformationFrame, WriteData may be called any number of times.
Status StartInformationFrame(uint64_t address) {
return StartFrame(address, kUnusedControl);
// Writes the header for an U-frame. After successfully calling
// StartUnnumberedFrame, WriteData may be called any number of times.
Status StartUnnumberedFrame(uint64_t address) {
return StartFrame(address, UFrameControl::UnnumberedInformation().data());
// Writes data for an ongoing frame. Must only be called after a successful
// StartInformationFrame call, and prior to a FinishFrame() call.
Status WriteData(ConstByteSpan data);
// Finishes a frame. Writes the frame check sequence and a terminating flag.
Status FinishFrame();
// Runs a pass through a payload, returning the worst-case encoded size for a
// frame containing it. Does not calculate CRC to improve efficiency.
static size_t MaxEncodedSize(uint64_t address, ConstByteSpan payload);
// Indicates this an information packet with sequence numbers set to 0.
static constexpr std::byte kUnusedControl = std::byte{0};
Status StartFrame(uint64_t address, std::byte control);
stream::Writer& writer_;
checksum::Crc32 fcs_;
} // namespace pw::hdlc::internal