message.h

// Copyright 2025 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.
#pragma once
 
#include <cstddef>
#include <cstdint>
 
#include "pw_assert/assert.h"
#include "pw_bytes/span.h"
#include "pw_i2c/address.h"
 
namespace pw::i2c {
 
class Message {
 public:
  static constexpr Message WriteMessage(Address address, ConstByteSpan data) {
    return Message(address,
                   ByteSpan(const_cast<std::byte*>(data.data()), data.size()),
                   Direction::kWrite,
                   /*no_start=*/false);
  }
 
  static constexpr Message WriteMessageContinuation(ConstByteSpan data) {
    return Message(Address::SevenBit<1>(),
                   ByteSpan(const_cast<std::byte*>(data.data()), data.size()),
                   Direction::kWrite,
                   /*no_start=*/true);
  }
 
  static constexpr Message ReadMessage(Address address, ByteSpan data) {
    return Message(address, data, Direction::kRead, /*no_start=*/false);
  }
 
  bool IsRead() const { return direction_ == Direction::kRead; }
 
  bool IsTenBit() const { return address_.IsTenBit(); }
 
  bool IsWriteContinuation() const { return no_start_; }
 
  Address GetAddress() const { return address_; }
 
  ByteSpan GetMutableData() const {
    PW_ASSERT(IsRead());
    return data_;
  }
 
  ConstByteSpan GetData() const { return data_; }
 
 private:
  enum class Direction : uint8_t {
    kWrite,
    kRead,
  };
 
  constexpr Message(const Address& address,
                    ByteSpan data,
                    Direction direction,
                    bool no_start)
      : address_(address),
        data_(data),
        direction_(direction),
        no_start_(no_start) {}
 
  // I2c address of target device.
  Address address_;
 
  // Data buffer to send from or receive into.
  ByteSpan data_;
 
  // Message represents an i2c read.
  Direction direction_;
 
  // Message should be transmitted without an i2c start condition and without
  // an address.
  bool no_start_;
};
 
}  // namespace pw::i2c