数据类型转换 [英] Data type conversion

问题描述

Hi.guys！

我想将unsigned long转换为unsigned char []，或将unsigned char []转换为unsigned long。但我不会。

please帮我！谢谢



示例：

unsigned long a = 8; // memery中的数据是08 00 00 00< - 如何转换？



字节a [5]; //如何将其转换为Ulong变量

a [0] = 0x08;

a [1] = 0x00;

a [2] = 0x00;

a [3] = 0x00;

a [4] = 0x00;

Hi.guys!
I want to convert unsigned long to unsigned char[], or unsigned char[] into unsigned long.But I will not.
please help me! Thanks

Example:
unsigned long a = 8; // The data in memery is 08 00 00 00 <- how to convert ?

byte a[5]; // how to convert it into a Ulong variable
a[0] = 0x08;
a[1] = 0x00;
a[2] = 0x00;
a[3] = 0x00;
a[4] = 0x00;

推荐答案

unsigned char *tc;
unsigned long tl = 8;

tc = (unsigned char *)(&tl);

unsigned char al[sizeof(unsigned long)];

// Copy bytes to array
memcpy(&al, tc, sizeof(unsigned long));

// Back to ulong
unsigned long *tlptr = (unsigned long *) al;


for(int i = 0; i < sizeof(unsigned long); i++)
    std::cout << std::hex << (int) tc[i] << std::endl;

std::cout << std::hex << *tlptr << std::endl;

或者，您可以使用 union ：

Alternatively, you could use a union:

#include <iostream>
using namespace std;

union ULB
{
  unsigned long ul;
  unsigned char b[4];
};

int main()
{
  ULB ulb;

  ulb.ul = 8;
  for (const auto & b : ulb.b)
    cout << hex << (int)b << " ";
  cout << endl;

  ulb.b[0] = 0x32;
  cout << hex << ulb.ul << endl;
}

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