C++系统相关操作7 - 判断系统大小端大小端的数据转换

1. 关键词
2. sysutil.h
3. sysutil.cpp
4. 测试代码
5. 运行结果
6. 源码地址

1. 关键词

关键词：

C++ 大端小端数据转换跨平台

大小端的定义：

大端（Big Endian）和小端（Little Endian）是指在计算机内存中存储多字节数据类型的字节顺序。以下是它们的区别：

大小端	定义	区别	示例(0x1234)
大端	数据的最高有效字节（Most Significant Byte, MSB）存储在内存的最低地址，而最低有效字节（Least Significant Byte, LSB）存储在内存的最高地址。	最高有效字节存储在最低地址又称：网络字节序	内存地址：高 -> 低存储内容： 0x34 0x12
小端	数据的最低有效字节（Least Significant Byte, LSB）存储在内存的最低地址，而最高有效字节（Most Significant Byte, MSB）存储在内存的最高地址。	最低有效字节存储在最低地址又称：主机字节序	内存地址：高 -> 低存储内容： 0x12 0x34

实现原理：

通过高低地址位的数据判断大端或小端。

应用场景：

网络传输协议中，大端和小端的字节序不同，需要转换为网络字节序。
不同平台的数据交换，需要转换为统一的字节序。

2. sysutil.h

#pragma once#include <cstdint>
#include <string>namespace cutl
{/*** @brief Endianness type.**/enum class endian{/** little endian */little,/** big endian */big,};/*** @brief Get the program endianness.** @return endian the program endianness.*/endian endian_type();/*** @brief Byteswap a 16-bit value.** @param value the value to byteswap.* @return uint16_t the byteswapped value.*/uint16_t byteswap(uint16_t value);/*** @brief Byteswap a 32-bit value.** @param value the value to byteswap.* @return uint32_t the byteswapped value.*/uint32_t byteswap(uint32_t value);/*** @brief Byteswap a 64-bit value.** @param value the value to byteswap.* @return uint64_t the byteswapped value.*/uint64_t byteswap(uint64_t value);/*** @brief Byteswap an array of bytes.** @param data the array of bytes to byteswap.* @param size the size of the array.*/void byteswap(uint8_t *data, uint32_t size);
} // namespace cutl

3. sysutil.cpp


#include <map>
#include <iostream>
#include <strutil.h>
#include <cstdlib>
#include "sysutil.h"
#include "inner/logger.h"
#include "inner/system_util.h"
#include "inner/filesystem.h"namespace cutl
{endian endian_type(){int a = 1;int *p = &a;uint8_t *pBtye = (uint8_t *)p;if (*pBtye == 1){return endian::little;}else{return endian::big;}}uint16_t byteswap(uint16_t value){auto data = (uint8_t *)(&value);byteswap(data, 2);return value;}uint32_t byteswap(uint32_t value){auto data = (uint8_t *)(&value);byteswap(data, 4);return value;}uint64_t byteswap(uint64_t value){auto data = (uint8_t *)(&value);byteswap(data, 8);return value;}void byteswap(uint8_t *data, uint32_t size){uint32_t n = size / 2;for (uint32_t i = 0; i < n; i++){uint8_t temp = data[i];data[i] = data[size - i - 1];data[size - i - 1] = temp;}}
} // namespace cutl

4. 测试代码

#include "common.hpp"
#include "sysutil.h"void TestEndian()
{PrintSubTitle("TestEndian");if (cutl::endian_type() == cutl::endian::little){std::cout << "OS endianness: little endian" << std::endl;}else{std::cout << "OS endianness: big endian" << std::endl;}uint16_t a = 0x1234;std::cout << "byteswap for a: " << cutl::to_hex(cutl::byteswap(a)) << std::endl;uint32_t b = 0x12345678;std::cout << "byteswap for b: " << cutl::to_hex(cutl::byteswap(b)) << std::endl;uint64_t c = 0x123456789ABCDEF0;std::cout << "byteswap for c: " << cutl::to_hex(cutl::byteswap(c)) << std::endl;uint8_t bytes[] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10};cutl::byteswap(bytes, 16);std::cout << "byteswap for bytes: " << cutl::to_hex(bytes, 16) << std::endl;
}

5. 运行结果

---------------------------------------------TestEndian---------------------------------------------
OS endianness: little endian
byteswap for a: 3412
byteswap for b: 78563412
byteswap for c: F0DEBC9A78563412
byteswap for bytes: 10 0F 0E 0D 0C 0B 0A 09 08 07 06 05 04 03 02 01