/*
 * .============.
 * // M A K E / \
 * // C++ DEV / \
 * // E A S Y / \/ \
 * ++ ----------. \/\ .
 * \\ \ \ /\ /
 * \\ \ \ /
 * \\ \ \ /
 * -============'
 *
 * Copyright (c) 2018 Hevake and contributors, all rights reserved.
 *
 * This file is part of cpp-tbox (https://github.com/cpp-main/cpp-tbox)
 * Use of this source code is governed by MIT license that can be found
 * in the LICENSE file in the root of the source tree. All contributing
 * project authors may be found in the CONTRIBUTORS.md file in the root
 * of the source tree.
 */
#ifndef TBOX_UTIL_BUFFER_H_20171028
#define TBOX_UTIL_BUFFER_H_20171028

#include <stdint.h>

namespace tbox {
namespace util {

/**
 * 缓冲区类
 *
 * buffer_ptr_ buffer_size_
 * | |
 * v V
 * +----+----------------+----------------+
 * | | readable bytes | writable bytes |
 * +----+----------------+----------------+
 * ^ ^
 * | |
 * read_index_ write_index_
 *
 * 使用示例:
 * Buffer b;
 * b.append("abc", 4); //! 往缓冲中写入4字节的数据
 * char buff[10];
 * b.fetch(buff, 4); //! 从缓冲中取出4字节的数据
 *
 * b.ensureWritableSize(10); //! 预留10个字节
 * memset(b.writableBegin(), 0xcc, 10); //! 将该10个字节全置为0xcc
 * b.hasWritten(10); //! 标该已写入10个字节
 *
 * \warnning 多线程使用需在外部加锁
 */
class Buffer {
 public:
 static const size_t kInitialSize = 256;

 explicit Buffer(size_t reverse_size = kInitialSize);
 virtual ~Buffer();

 Buffer(const Buffer &other);
 Buffer(Buffer &&other);

 Buffer& operator = (const Buffer &other);
 Buffer& operator = (Buffer &&other);

 void swap(Buffer &other);
 void reset();

 public:
 /**
 * 写缓冲操作
 */

 //! 获取可写空间大小
 inline size_t writableSize() const { return buffer_size_ - write_index_; }

 //! 保障有指定容量的可写空间
 bool ensureWritableSize(size_t write_size);

 //! 获取写首地址
 inline uint8_t* writableBegin() const {
 return (buffer_ptr_ != nullptr) ? (buffer_ptr_ + write_index_) : nullptr;
 }

 //! 标记已写入数据大小
 void hasWritten(size_t write_size);

 //! 往缓冲区追加指定的数据块,返回实现写入的大小
 size_t append(const void *p_data, size_t data_size);

 /**
 * 读缓冲操作
 */

 //! 获取可读区域大小
 inline size_t readableSize() const { return write_index_ - read_index_; }

 //! 获取可读区首地址
 inline uint8_t* readableBegin() const {
 return (buffer_ptr_ != nullptr) ? (buffer_ptr_ + read_index_) : nullptr;
 }

 //! 标记已读数据大小
 void hasRead(size_t read_size);

 //! 标记已读取全部数据
 void hasReadAll();

 //! 从缓冲区读取指定的数据块,返回实际读到的数据大小
 size_t fetch(void *p_buff, size_t buff_size);

 /**
 * 其它
 */
 //! 缩减缓冲多余容量
 void shrink();

 protected:
 void cloneFrom(const Buffer &other);

 private:
 uint8_t *buffer_ptr_ = nullptr; //! 缓冲区地址
 size_t buffer_size_ = 0; //! 缓冲区大小

 size_t read_index_ = 0; //! 读位置偏移
 size_t write_index_ = 0; //! 写位置偏移
};

}
}

#endif //TBOX_UTIL_BUFFER_H_20171028