c - 根据用户输入声明特定宽度变量的最佳方式

Question

我有一个如下所示的代码。这里的代码是如果word_size = 64. 以类似的方式，我也需要 32 和 16。我找不到encrypt为所有尺寸重用相同功能的方法。此外，我还需要根据word_size声明变量，即。使用uint_16or or uint_32oruint_64取决于 word_size。在这种情况下，你能帮我写一个可重用的代码吗？

#include<stdio.h>
#include<stdint.h>

void encrypt(uint64_t* , uint64_t*, uint64_t*);

int main(){

    int block_size;

    // Get the user inputs
    printf("input the block size: \n");
    scanf("%d", &block_size);   // can be 32, 64 or 128

    int word_size = block_size/2;   // 16,32 or 64

    // Depending on the word_size, I should declare the variables with 
    // corresponding width
    uint64_t plain_text[2] = {0,0};  
    uint64_t cipher_text[2] = {0,0}; 
    uint64_t key_text[2] = {0,0};   

    uint64_t * pt, *ct, *k;
    encrypt(pt, ct,k);
    }

 /*
 * Ecnryption Method
 */
void encrypt(uint64_t* pt, uint64_t* ct, uint64_t* k){

    // Involves bit shifting algorithm which works only on exact sizes i.e eiter 16,32 or 64.
        }

如果需要，我可以提供更多信息。

Answer 1

在 C 中有一种方法可以做到这一点 - 使用structandunion

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>

enum type {
    U64,
    U32,
    U16,
    U8,
};
struct container {
    enum type type;
    union {
        uint64_t u64;
        uint32_t u32;
        uint16_t u16;
        uint8_t  u8;
    } value;
};

int test(struct container container) {
    switch(container.type) {
        case U64:
            printf("Value is  :%" PRIu64 "\n", container.value);
            break;
        case U32:
            printf("Value is  :%" PRIu32 "\n", container.value);
            break;
        case U16:
            printf("Value is  :%" PRIu16 "\n", container.value);
            break;
        case U8:
            printf("Value is  :%" PRIu8 "\n", container.value);
            break;
    }
    return 0;
}

int main(int argc, char **argv) {
    struct container c1, c2;

    c1.type = U64;
    c1.value.u64 = 10000000000ULL;

    c2.type = U8;
    c2.value.u8 = 100;

    test(c1);
    test(c2);
    return 0;
}

产生的输出是：

Value is  :10000000000
Value is  :100