firebuf/buffer.h

#pragma once

#include <glog/logging.h>
#include <memory>
#include <string_view>

namespace firebuf {

class ConstBuffer {
 public:
  ConstBuffer(const char *buf, size_t len);

  [[nodiscard]] size_t ReadMaxLen() const;
  [[nodiscard]] virtual const char *Read(size_t len);
  template <class T>
  [[nodiscard]] const T *ReadObj();

  bool Discard(size_t len);  // like Read() but don't use the result
  void ResetRead();          // next read from last commit
  void Commit();             // commit read position

  virtual void Reset();  // full reset

 protected:
  const char *const_buf_;
  size_t len_;
  size_t start_ = 0;
  size_t commit_ = 0;
};

class Buffer : public ConstBuffer {
 public:
  Buffer(char *buf, size_t size, size_t len);
  Buffer(size_t size);

  [[nodiscard]] char *WritePtr();
  [[nodiscard]] size_t WriteMaxLen() const;
  bool Write(const std::string_view &str);
  void Wrote(ssize_t len);

  void Consume();  // discard up to last commit

  void Reset() override;  // full reset

 protected:
  std::unique_ptr<char[]> own_buf_;
  char *buf_;
  const size_t size_;
};

template <class T>
const T *ConstBuffer::ReadObj() {
  if (ReadMaxLen() < sizeof(T)) {
    return nullptr;
  }
  return reinterpret_cast<const T *>(Read(sizeof(T)));
}

}  // namespace firebuf