495个C语言问题经典之"达夫设备"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/**
 * @brief 达夫设备（拷贝 - 把语言玩成这样，很cool，虽然争议多）
 * @From: dstm Duff
 */
char * dafuStrnCopy(char * dst, const char * from, int count)
{
    char * p = dst;
    register n = (count + 7) / 8; /* count > 0 assumed */
    switch (count % 8)              /* 以8的倍数为基准，不是8的倍数则先把“零头“拷贝，剩下的就循环拷贝！很cool吧.. */
    {
        case 0: do { *dst++ = *from++;
                    case 7: *dst++ = *from++;
                    case 6: *dst++ = *from++;
                    case 5: *dst++ = *from++;
                    case 4: *dst++ = *from++;
                    case 3: *dst++ = *from++;
                    case 2: *dst++ = *from++;
                    case 1: *dst++ = *from++;
                } while (--n > 0);
    }
    return p;
}

/**
 * @brief 真实从未见过如此用法，挺酷的；虽然看上去代码很多！关键思维方式确实与众不同！
 */
int main(int argc, const char *argv[])
{
    char * dst = NULL;
    char * from = "kissm";

    dst = (char *)malloc(32 * sizeof(char));
    if (!dst)
        return -1;

    dafuStrnCopy(dst, from, strlen(from));
    printf("%s\n", dst);

    free(dst);

    return 0;
}