unsigned char 数组与 long 类型互转

C/C++ 中，如果需要将 int 或者 unsigned int 以及 long 和 unsigned long 类型数据互转，则可以参考一下代码

 

#include<cstdio>

typedef unsigned int uint32_t;
typedef unsigned long int uint64_t;
typedef unsigned char uint8_t;

bool transferLong2ByteArray(uint8_t* byte, uint8_t length, uint64_t version){
    uint64_t temp = version;
    for(uint8_t i = 0; i < length; ++i){
        uint8_t res = (uint8_t)(temp & 0xff);
        byte[i] = res;
        temp = temp >> 8;
    }
    return true;
}

uint64_t transferByteArrayToLong(uint8_t* byte, uint8_t length)
{
    uint64_t version = 0;
#if 1
    for(int i = 0; i < length; ++i){
        uint64_t temp = byte[i];
        version |= (temp << i * 8);
    }
#else
    long s = 0;
    long s0 = (byte[0] & 0xff);
    long s1 = (byte[1] & 0xff) << 8;
    long s2 = (byte[2] & 0xff) << 16;
    long s3 = (byte[3] & 0xff << 24);

    version = s0 | s1 | s2 | s3;
#endif
    return version;
}

int main()
{
    uint32_t version = 0x000710;
    uint64_t longVersion = (uint64_t)version;

    uint8_t byte[4] = {0};
    transferLong2ByteArray(byte, 4, longVersion);

    uint64_t finalVersion = transferByteArrayToLong(byte, 4);
    printf("vrsion %ld\n", finalVersion);

    return 0;
}