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   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

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   This program is distributed in the hope that it will be useful,
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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   You should have received a copy of the GNU General Public License
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/// @file buffer_view.h
///
/// Class that groups a pointer+size as one object, without managing
/// the memory for it.

#ifndef MYSQL_BINLOG_EVENT_COMPRESSION_BUFFER_BUFFER_VIEW_H
#define MYSQL_BINLOG_EVENT_COMPRESSION_BUFFER_BUFFER_VIEW_H

#include <cassert>  // assert
#include <string>   // std::string
#ifndef NDEBUG
#include <sstream>  // std::ostringstream
#endif

/// @addtogroup GroupLibsMysqlBinlogEvent
/// @{

namespace mysql::binlog::event::compression::buffer {

/// Non-owning view of a memory buffer with a fixed size.
///
/// This is a minimal class holding just a pointer and a size.  It
/// does not have a read/write position (@see Rw_buffer_sequence).  It
/// does not have methods to grow the buffer (@see
/// Growable_buffer_sequence).
template <class Char_tp = unsigned char>
class Buffer_view {
 public:
  using Char_t = Char_tp;
  /// The 'size' type.  Keep this equal to
  /// buffer::Grow_calculator::Size_t
  using Size_t = std::size_t;
  using Iterator_t = Char_t *;
  using Const_iterator_t = const Char_t *;

  /// Create a new Buffer_view with the specified size and data.
  Buffer_view(Char_t *data, Size_t size) : m_data(data), m_size(size) {
    if (data == nullptr) assert(size == 0);
  }

  /// Create a new "null Buffer_view": pointer is nullptr and size is
  /// 0.
  Buffer_view() = default;

  /// Shallow copy constructor.
  ///
  /// @note The data pointer is copied but not the contents.
  Buffer_view(const Buffer_view &) = default;

  /// Default move constructor.
  Buffer_view(Buffer_view &&) noexcept = default;

  /// Shallow copy assignment operator.
  ///
  /// @note The data pointer is copied but not the contents.
  Buffer_view &operator=(const Buffer_view &) = default;

  /// Default move assignment operator.
  Buffer_view &operator=(Buffer_view &&) noexcept = default;

  /// Default delete operator.
  virtual ~Buffer_view() = default;

  /// Return const pointer to the data.
  const Char_t *data() const { return m_data; }

  /// Return non-const pointer to the data.
  Char_t *data() { return m_data; }

  /// Return pointer to the first character of the data.
  Iterator_t begin() { return m_data; }

  /// Return pointer to one-past-the-last character of the data.
  Iterator_t end() { return m_data + m_size; }

  /// Return pointer to the first character of the data.
  Const_iterator_t begin() const { return m_data; }

  /// Return pointer to one-past-the-last character of the data.
  Const_iterator_t end() const { return m_data + m_size; }

  /// Return const pointer to the first character of the data.
  Const_iterator_t cbegin() const { return m_data; }

  /// Return const pointer to one-past-the-last character of the data.
  Const_iterator_t cend() const { return m_data + m_size; }

  /// Return the number of bytes.
  Size_t size() const { return m_size; }

  /// Return a copy of this object as a `std::string`.
  template <class Str_char_t = char,
            class Str_traits_t = std::char_traits<Str_char_t>,
            class Str_allocator_t = std::allocator<Str_char_t>>
  std::basic_string<Str_char_t, Str_traits_t, Str_allocator_t> str(
      const Str_allocator_t &allocator = Str_allocator_t()) const {
    return std::basic_string<Str_char_t, Str_traits_t, Str_allocator_t>(
        reinterpret_cast<const Str_char_t *>(m_data), m_size, allocator);
  }

  /// In debug mode, return a string with debug info.
  ///
  /// @param show_contents If true, includes the buffer contents.
  /// Otherwise, just pointers and sizes.
  std::string debug_string([[maybe_unused]] bool show_contents = false) const {
#ifdef NDEBUG
    return "";
#else
    std::ostringstream ss;
    // clang-format off
    ss << "Buffer_view(ptr=" << (const void *)this
       << ", data=" << (const void *)data()
       << ", size=" << size();
    // clang-format on
    if (show_contents && begin() != nullptr)
      ss << ", contents=\""
         << std::string(reinterpret_cast<const char *>(begin()), size())
         << "\"";
    ss << ")";
    return ss.str();
#endif
  }

 private:
  /// Pointer to the data.
  Char_t *m_data{nullptr};

  /// The number of bytes.
  Size_t m_size{0};
};

}  // namespace mysql::binlog::event::compression::buffer

/// @}

#endif  // MYSQL_BINLOG_EVENT_COMPRESSION_BUFFER_BUFFER_VIEW_H