C - 使用动态数组复制结构

Question

有了这种类型的结构，如何将一个结构复制到另一个结构中。我首先声明了数组，然后声明了数组，然后初始化了这两个数组，并在每个数组中放入了不同的数据。

然后将first复制到second我尝试了second = first但它不起作用。

我该怎么做？

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


    //////////////////////////////////////

    typedef struct {

      int group[8];
      uint64_t points;

    } BestGroup;

    //////////////////////////////////////

    typedef struct {
      BestGroup *array;
      size_t used;
      size_t size;
    } Array;

    void initArray(Array *a, size_t initialSize) {
      a->array = (BestGroup *)malloc(initialSize * sizeof(BestGroup));
      a->used = 0;
      a->size = initialSize;
    }

    void insertArray(Array *a, int *group_add, uint64_t points_add) {

      // a->used is the number of used entries, because a->array[a->used++] updates a->used only *after* the array has been accessed.
      // Therefore a->used can go up to a->size 
      if (a->used == a->size) 
      {
        a->size *= 2;
        a->array = (BestGroup *)realloc(a->array, a->size * sizeof(BestGroup));
      }

      int i; 
      for (i = 0; i < 8; i++)
      {
        a->array[a->used].group[i] = group_add[i];
      }
      a->array[a->used].points = points_add;
      a->used++;
    }

    void freeArray(Array *a) {
      free(a->array);
      a->array = NULL;
      a->used = a->size = 0;
    }


    void CopyArray(Array *a, Array *b)
    {
        b = a;
    }

    int main()
    {
        Array first;
        Array second;

        int first_data[8] = {0, 1, 2, 3, 4, 5, 6, 7};
        int second_data[8] = {7, 6, 5, 4, 3, 2, 1, 0};

        initArray(&first, 2);
        initArray(&second, 2);

        insertArray(&first, first_data, 5);
        insertArray(&first, first_data, 5);
        insertArray(&first, first_data, 5);

        insertArray(&second, second_data, 2);

        ///////////////////////////////////////////

        printf("Total Points: %" PRIu64 "\n", first.array->points);
        printf("Number: %lu\n\n", first.used);
        printf("\n");

        int i;
        int j;

        for (i = 0; i < first.used; i++)
        {

          printf("[");

          for (j = 0; j < 8; j++)
          {
            if (j) printf(", ");
            printf("%d", first.array[i].group[j]);
          }

          printf("]\n");
        }

        ////////////////////////////////////////////

        printf("\n");
        printf("Total Points: %" PRIu64 "\n", second.array->points);
        printf("Number: %lu\n\n", second.used);
        printf("\n");

        for (i = 0; i < second.used; i++)
        {

          printf("[");

          for (j = 0; j < 8; j++)
          {
            if (j) printf(", ");
            printf("%d", second.array[i].group[j]);
          }

          printf("]\n");
        }

        /////////////////////////////////

        CopyArray(&first, &second);


        printf("\n");
        printf("\n");
        printf("\n");
        printf("\n");

        ///////////////////////////////////////////

        printf("Total Points: %" PRIu64 "\n", first.array->points);
        printf("Number: %lu\n\n", first.used);
        printf("\n");

        for (i = 0; i < first.used; i++)
        {

          printf("[");

          for (j = 0; j < 8; j++)
          {
            if (j) printf(", ");
            printf("%d", first.array[i].group[j]);
          }

          printf("]\n");
        }

        ////////////////////////////////////////////

        printf("\n");
        printf("Total Points: %" PRIu64 "\n", second.array->points);
        printf("Number: %lu\n\n", second.used);
        printf("\n");

        for (i = 0; i < second.used; i++)
        {

          printf("[");

          for (j = 0; j < 8; j++)
          {
            if (j) printf(", ");
            printf("%d", second.array[i].group[j]);
          }

          printf("]\n");
        }

        return 0;
    }

输出为:

Total Points: 5
Number: 3


[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]

Total Points: 2
Number: 1


[7, 6, 5, 4, 3, 2, 1, 0]




Total Points: 5
Number: 3


[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]

Total Points: 2
Number: 1


[7, 6, 5, 4, 3, 2, 1, 0]

何时应以最后一个列表结尾:

Total Points: 5
Number: 3


[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]

Total Points: 5
Number: 3


[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]

编辑

按照建议，我使用了 memcpy()，因此我将 CopyArray() 函数更改为:

    void CopyArray(Array *a, Array *b)
    {
        // b = a;
        memcpy(b, a, a->size * sizeof(BestGroup));
    }

看起来结果会很好，直到到达程序末尾并输出

*** 检测到堆栈崩溃 ***

Answer 1

此代码产生您想要的答案。 CopyArray()函数现在释​​放 b 中已有的数据，然后初始化b ，最后复制 a 中的数据至b 。代码中有些地方使用了8但可能应该使用不同的变量来表示大小——我已经在这段代码中对它们进行了注释。 dump_array() function 是我在调试复杂结构时经常编写和使用的函数示例。它需要一个标签字符串(它允许您识别正在打印的调用)加上要打印的对象。我也经常采用文件流参数，如有疑问，请添加 fflush()用于输出流。

/* SO 4639-4467 */
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct
{
    int group[8];
    uint64_t points;
} BestGroup;

typedef struct
{
    BestGroup *array;
    size_t used;
    size_t size;
} Array;

static void initArray(Array *a, size_t initialSize)
{
    a->array = (BestGroup *)malloc(initialSize * sizeof(BestGroup));
    a->used = 0;
    a->size = initialSize;
}

static void insertArray(Array *a, const int *group_add, uint64_t points_add)
{
    if (a->used == a->size)
    {
        a->size *= 2;
        a->array = (BestGroup *)realloc(a->array, a->size * sizeof(BestGroup));
    }

    for (int i = 0; i < 8; i++)     // Why 8 and not points_add?
    {
        a->array[a->used].group[i] = group_add[i];
    }
    a->array[a->used].points = points_add;
    a->used++;
}

static void freeArray(Array *a)
{
    free(a->array);
    a->array = NULL;
    a->used = a->size = 0;
}

static void CopyArray(const Array *a, Array *b)
{
    freeArray(b);
    initArray(b, a->used);
    memmove(b->array, a->array, a->used * sizeof(a->array[0]));
    b->used = a->used;
}

static void dump_array(const char *tag, const Array *arr)
{
    printf("Array: %s\n", tag);
    printf("Total Points: %" PRIu64 "\n", arr->array->points);
    printf("Number: %lu\n", arr->used);

    for (size_t i = 0; i < arr->used; i++)
    {
        printf("[");
        for (size_t j = 0; j < 8; j++)  // Why 8 and not arr->array[i].points?
        {
            if (j)
                printf(", ");
            printf("%d", arr->array[i].group[j]);
        }
        printf("]\n");
    }
    putchar('\n');
}

int main(void)
{
    Array first;
    Array second;

    int first_data[8] = {0, 1, 2, 3, 4, 5, 6, 7};
    int second_data[8] = {7, 6, 5, 4, 3, 2, 1, 0};

    initArray(&first, 2);
    initArray(&second, 2);

    insertArray(&first, first_data, 5);
    insertArray(&first, first_data, 5);
    insertArray(&first, first_data, 5);
    insertArray(&second, second_data, 2);

    dump_array("first", &first);
    dump_array("second", &second);

    CopyArray(&first, &second);

    printf("\n");
    dump_array("first", &first);
    dump_array("second", &second);

    return 0;
}

运行的输出是:

Array: first
Total Points: 5
Number: 3
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]

Array: second
Total Points: 2
Number: 1
[7, 6, 5, 4, 3, 2, 1, 0]


Array: first
Total Points: 5
Number: 3
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]

Array: second
Total Points: 5
Number: 3
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7]