serialization.h

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//==============================================================================
// Copyright (c) 2012, Johannes Meyer, TU Darmstadt
// All rights reserved.

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in the
//       documentation and/or other materials provided with the distribution.
//     * Neither the name of the Flight Systems and Automatic Control group,
//       TU Darmstadt, nor the names of its contributors may be used to
//       endorse or promote products derived from this software without
//       specific prior written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
// DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//==============================================================================

#ifndef UBLOX_SERIALIZATION_H
#define UBLOX_SERIALIZATION_H

#include <ros/console.h>
#include <stdint.h>
#include <boost/call_traits.hpp>
#include <vector>
#include <algorithm>

#include "checksum.h"



namespace ublox {

static const uint8_t DEFAULT_SYNC_A = 0xB5; 
static const uint8_t DEFAULT_SYNC_B = 0x62; 
static const uint8_t kHeaderLength = 6; 
static const uint8_t kChecksumLength = 2; 

template <typename T>
struct Serializer {
  static void read(const uint8_t *data, uint32_t count, 
                   typename boost::call_traits<T>::reference message);
  static uint32_t serializedLength(
      typename boost::call_traits<T>::param_type message);
  
  static void write(uint8_t *data, uint32_t size, 
                    typename boost::call_traits<T>::param_type message);
};

template <typename T>
class Message {
 public:
  static bool canDecode(uint8_t class_id, uint8_t message_id) {
    return std::find(keys_.begin(), keys_.end(), 
                     std::make_pair(class_id, message_id)) != keys_.end();
  }
  
  static void addKey(uint8_t class_id, uint8_t message_id) {
    keys_.push_back(std::make_pair(class_id, message_id));
  }

  struct StaticKeyInitializer
  {
    StaticKeyInitializer(uint8_t class_id, uint8_t message_id) { 
      Message<T>::addKey(class_id, message_id); 
    }
  };

 private:
  static std::vector<std::pair<uint8_t,uint8_t> > keys_;
};

struct Options {
  Options() : sync_a(DEFAULT_SYNC_A), sync_b(DEFAULT_SYNC_B), 
              header_length(kHeaderLength), checksum_length(kChecksumLength) {}
  uint8_t sync_a; 
  uint8_t sync_b; 
  uint8_t header_length; 
  uint8_t checksum_length; 
  
  int wrapper_length() {
    return header_length + checksum_length; 
  }
};

class Reader {
 public:
  Reader(const uint8_t *data, uint32_t count, 
         const Options &options = Options()) : 
      data_(data), count_(count), found_(false), options_(options) {}

  typedef const uint8_t *iterator;

  iterator search()
  {
    if (found_) next();

    // Search for a message header
    for( ; count_ > 0; --count_, ++data_) {
      if (data_[0] == options_.sync_a && 
          (count_ == 1 || data_[1] == options_.sync_b)) 
        break;
    }

    return data_;
  }

  bool found()
  {
    if (found_) return true;
    // Verify message is long enough to have sync chars, id, length & checksum
    if (count_ < options_.wrapper_length()) return false;
    // Verify the header bits
    if (data_[0] != options_.sync_a || data_[1] != options_.sync_b) 
      return false;
    // Verify that the buffer length is long enough based on the received
    // message length
    if (count_ < length() + options_.wrapper_length()) return false;

    found_ = true;
    return true;
  }

  iterator next() {
    if (found()) {
      uint32_t size = length() + options_.wrapper_length();
      data_ += size; count_ -= size;
    }
    found_ = false;
    return data_;
  }

  iterator pos() {
    return data_;
  }

  iterator end() {
    return data_ + count_;
  }

  uint8_t classId() { return data_[2]; }
  uint8_t messageId() { return data_[3]; }

  uint32_t length() { return (data_[5] << 8) + data_[4]; }
  const uint8_t *data() { return data_ + options_.header_length; }
  
  uint16_t checksum() { 
    return *reinterpret_cast<const uint16_t *>(data_ + options_.header_length +
                                               length()); 
  }

  template <typename T>
  bool read(typename boost::call_traits<T>::reference message, 
            bool search = false) {
    if (search) this->search();
    if (!found()) return false; 
    if (!Message<T>::canDecode(classId(), messageId())) return false;

    uint16_t chk;
    if (calculateChecksum(data_ + 2, length() + 4, chk) != this->checksum()) {
      // checksum error
      ROS_DEBUG("U-Blox read checksum error: 0x%02x / 0x%02x", classId(), 
                messageId());
      return false;
    }

    Serializer<T>::read(data_ + options_.header_length, length(), message);
    return true;
  }

  template <typename T> 
  bool hasType() {
    if (!found()) return false;
    return Message<T>::canDecode(classId(), messageId());
  }

  bool isMessage(uint8_t class_id, uint8_t message_id) {
    if (!found()) return false;
    return (classId() == class_id && messageId() == message_id);
  }

 private:
  const uint8_t *data_; 
  uint32_t count_; 
  bool found_; 
  Options options_; 
};

class Writer {
 public:
  typedef uint8_t *iterator;

  Writer(uint8_t *data, uint32_t size, const Options &options = Options()) : 
      data_(data), size_(size), options_(options) {}

  template <typename T> bool write(const T& message, 
                                   uint8_t class_id = T::CLASS_ID, 
                                   uint8_t message_id = T::MESSAGE_ID) {
    // Check for buffer overflow
    uint32_t length = Serializer<T>::serializedLength(message);
    if (size_ < length + options_.wrapper_length()) {
      ROS_ERROR("u-blox write buffer overflow. Message %u / %u not written", 
                class_id, message_id);
      return false;
    }
    // Encode the message and add it to the buffer
    Serializer<T>::write(data_ + options_.header_length, 
                         size_ - options_.header_length, message);
    return write(0, length, class_id, message_id);
  }

  bool write(const uint8_t* message, uint32_t length, uint8_t class_id, 
             uint8_t message_id) {
    if (size_ < length + options_.wrapper_length()) {
      ROS_ERROR("u-blox write buffer overflow. Message %u / %u not written", 
                class_id, message_id);
      return false;
    }
    iterator start = data_;

    // write header
    *data_++ = options_.sync_a;
    *data_++ = options_.sync_b;
    *data_++ = class_id;
    *data_++ = message_id;
    *data_++ = length & 0xFF;
    *data_++ = (length >> 8) & 0xFF;
    size_ -= options_.header_length;

    // write message
    if (message) std::copy(message, message + length, data_);
    data_ += length;
    size_ -= length;

    // write checksum
    uint8_t ck_a, ck_b;
    calculateChecksum(start + 2, length + 4, ck_a, ck_b);
    *data_++ = ck_a;
    *data_++ = ck_b;
    size_ -= options_.checksum_length;

    return true;
  }

  iterator end() {
    return data_;
  }

 private:
  iterator data_; 

  uint32_t size_; 
  Options options_; 
};

} // namespace ublox

// Use to declare u-blox messages and message serializers
#define DECLARE_UBLOX_MESSAGE(class_id, message_id, package, message) \
  template class ublox::Serializer<package::message>; \
  template class ublox::Message<package::message>; \
  namespace package { namespace { \
    static const ublox::Message<message>::StaticKeyInitializer static_key_initializer_##message(class_id, message_id); \
  } } \

// Use for messages which have the same structure but different IDs, e.g. INF
// Call DECLARE_UBLOX_MESSAGE for the first message and DECLARE_UBLOX_MESSAGE_ID
// for following declarations
#define DECLARE_UBLOX_MESSAGE_ID(class_id, message_id, package, message, name) \
  namespace package { namespace { \
    static const ublox::Message<message>::StaticKeyInitializer static_key_initializer_##name(class_id, message_id); \
  } } \


// use implementation of class Serializer in "serialization_ros.h"
#include "serialization_ros.h"

#endif // UBLOX_SERIALIZATION_H