// 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

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// 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.

#include "pw_stream/memory_stream.h"

#include <cstddef>

#include <cstring>

#include "pw_status/status_with_size.h"

namespace pw::stream {

Status MemoryWriter::DoWrite(ConstByteSpan data) {

  if (ConservativeWriteLimit() == 0) {

    return Status::OutOfRange();

  }

  if (ConservativeWriteLimit() < data.size_bytes()) {

    return Status::ResourceExhausted();

  }

  size_t bytes_to_write = data.size_bytes();

  if (bytes_to_write == 0) {

    // Calling memmove with a null pointer is undefined behavior, even when zero

    // bytes are moved. We must return early here to avoid performing such a

    // call when data is an empty span.

    return OkStatus();

  }

  std::memmove(dest_.data() + position_, data.data(), bytes_to_write);

  position_ += bytes_to_write;

  return OkStatus();

}

StatusWithSize MemoryReader::DoRead(ByteSpan dest) {

  if (source_.size_bytes() == position_) {

    return StatusWithSize::OutOfRange();

  }

  size_t bytes_to_read =

      std::min(dest.size_bytes(), source_.size_bytes() - position_);

  if (bytes_to_read == 0) {

    // Calling memcpy with a null pointer is undefined behavior, even when zero

    // bytes are copied. We must return early here to avoid performing such a

    // call when the dest span is empty.

    return StatusWithSize(0);

  }

  std::memcpy(dest.data(), source_.data() + position_, bytes_to_read);

  position_ += bytes_to_read;

  return StatusWithSize(bytes_to_read);

}

}  // namespace pw::stream