109 lines
2.8 KiB
C++
109 lines
2.8 KiB
C++
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// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_hdlc/encoder.h"
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#include <algorithm>
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#include <array>
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#include <cstddef>
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#include <cstring>
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#include "pw_bytes/endian.h"
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#include "pw_hdlc/encoded_size.h"
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#include "pw_hdlc/internal/encoder.h"
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#include "pw_span/span.h"
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#include "pw_varint/varint.h"
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using std::byte;
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namespace pw::hdlc {
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namespace internal {
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Status EscapeAndWrite(const byte b, stream::Writer& writer) {
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if (b == kFlag) {
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return writer.Write(kEscapedFlag);
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}
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if (b == kEscape) {
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return writer.Write(kEscapedEscape);
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}
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return writer.Write(b);
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}
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Status Encoder::WriteData(ConstByteSpan data) {
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auto begin = data.begin();
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while (true) {
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auto end = std::find_if(begin, data.end(), NeedsEscaping);
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if (Status status = writer_.Write(span(begin, end)); !status.ok()) {
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return status;
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}
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if (end == data.end()) {
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fcs_.Update(data);
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return OkStatus();
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}
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if (Status status = EscapeAndWrite(*end, writer_); !status.ok()) {
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return status;
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}
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begin = end + 1;
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}
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}
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Status Encoder::FinishFrame() {
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if (Status status =
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WriteData(bytes::CopyInOrder(endian::little, fcs_.value()));
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!status.ok()) {
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return status;
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}
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return writer_.Write(kFlag);
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}
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Status Encoder::StartFrame(uint64_t address, std::byte control) {
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fcs_.clear();
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if (Status status = writer_.Write(kFlag); !status.ok()) {
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return status;
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}
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std::array<std::byte, 16> metadata_buffer;
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size_t metadata_size =
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varint::Encode(address, metadata_buffer, kAddressFormat);
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if (metadata_size == 0) {
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return Status::InvalidArgument();
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}
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metadata_buffer[metadata_size++] = control;
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return WriteData(span(metadata_buffer).first(metadata_size));
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}
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} // namespace internal
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Status WriteUIFrame(uint64_t address,
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ConstByteSpan payload,
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stream::Writer& writer) {
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if (MaxEncodedFrameSize(address, payload) > writer.ConservativeWriteLimit()) {
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return Status::ResourceExhausted();
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}
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internal::Encoder encoder(writer);
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if (Status status = encoder.StartUnnumberedFrame(address); !status.ok()) {
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return status;
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}
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if (Status status = encoder.WriteData(payload); !status.ok()) {
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return status;
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}
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return encoder.FinishFrame();
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}
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} // namespace pw::hdlc
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