allwpilib/src/WireEncoder.h

/*----------------------------------------------------------------------------*/
/* Copyright (c) FIRST 2015. All Rights Reserved.                             */
/* Open Source Software - may be modified and shared by FRC teams. The code   */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project.                                                               */
/*----------------------------------------------------------------------------*/

#ifndef NT_WIREENCODER_H_
#define NT_WIREENCODER_H_

#include <cassert>
#include <cstddef>

#include "ntcore.h"

namespace ntimpl {

class WireEncoder {
 public:
  explicit WireEncoder(unsigned int proto_rev);
  ~WireEncoder();

  void set_proto_rev(unsigned int proto_rev) { m_proto_rev = proto_rev; }

  void Reset() {
    m_cur = m_start;
    m_error = nullptr;
  }

  const char* error() const { return m_error; }

  const char* data() const { return m_start; }

  std::size_t size() const { return m_cur - m_start; }

  void Reserve(std::size_t len) {
    // assert(m_end > m_cur);
    if (static_cast<size_t>(m_end - m_cur) < len) ReserveSlow(len);
  }

  void Write8(unsigned int val) {
    Reserve(1);
    *m_cur++ = (char)(val & 0xff);
  }

  void Write16(unsigned int val) {
    Reserve(2);
    *m_cur++ = (char)((val >> 8) & 0xff);
    *m_cur++ = (char)(val & 0xff);
  }

  void Write32(unsigned long val) {
    Reserve(4);
    *m_cur++ = (char)((val >> 24) & 0xff);
    *m_cur++ = (char)((val >> 16) & 0xff);
    *m_cur++ = (char)((val >> 8) & 0xff);
    *m_cur++ = (char)(val & 0xff);
  }

  void WriteDouble(double val);

  void WriteUleb128(unsigned long val);
  void WriteType(NT_Type type);
  void WriteValue(const NT_Value& value);
  void WriteString(const NT_String& str);

  std::size_t GetValueSize(const NT_Value& value);
  std::size_t GetStringSize(const NT_String& str);

  WireEncoder(const WireEncoder&) = delete;
  WireEncoder& operator=(const WireEncoder&) = delete;

 protected:
  unsigned int m_proto_rev;
  const char* m_error;

 private:
  void ReserveSlow(std::size_t len);

  char* m_start;
  char* m_cur;
  char* m_end;
};

}  // namespace ntimpl

#endif  // NT_WIREENCODER_H_