• 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：

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

6. 源码地址

更多详细代码，请查看本人写的C++ 通用工具库: common_util, 本项目已开源，代码简洁，且有详细的文档和Demo。

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