c - 如何将指针传递给抽象数据类型的多维数组

Question

我已经阅读了一些有关将指针传递给多维数组的 Material ，但我无法让它为我自己工作。

我有:

/* This code basically, in order, does this--or tries to:
    - Create 2D array of cell structs
    - Create info_pass detailing certain attributes of the 2D array
         + in particular, I am trying to include a pointer to the 2D array so that I
           can pass the info_pass struct between functions and update the contents of 
           the 2D array in each function.
    - The updating is done in struct info_pass* update(...){}
    - ... however, in my full program, there are several other functions it is passed 
      to, so being able to pass a pointer that allows manipulation of the 2D array is
      what I'm really after.
*/

struct info_pass {
    /* stuff */
    struct cell* master;
};
struct cell {
    /* values */
    /* lots of pointers to other cells */
};
struct info_pass* genesis() {                 /* creating an the multiD array */
    /* stuff */
    struct cell* (*cells)[width];
    cells = malloc(sizeof(struct cell) * width * length);

    struct info_pass* keycard = NULL;
    keycard = malloc(sizeof(struct info_pass));
    /* assign values to key card */
    keycard->master = cells;     /* problem here?! */  <==== (A)

    /* update cells */

    return keycard;                           /* therefore problem here too */
}
struct info_pass* update(struct info_pass* key) {
    struct info_pass* keyRef = NULL;
    keyRef = malloc(sizeof(struct info_pass));
    keyRef = key;                             /* and of course here */

    struct cell* home1 = NULL;
    home1 = malloc(sizeof(struct cell));

    /*here I want to update the multidimensional array*/ <===== (B)
    /*... and then send it back ...*/
    return keyRef;
 }

错误@(A) =警告:来自不兼容指针类型的赋值。

Error @ (B) = 错误:下标值既不是数组也不是指针。

只是希望能朝正确的方向插入。

编辑

根据 ThePosey 的建议，我将展示更多涉及“错误:下标值既不是指针也不是数组”的代码。我将在下面添加它，而不是将其放入上面的代码示例中，以便保留原始问题的状态以供将来使用。

struct info_pass* update(struct info_pass* key) {      

    /* passing data, including a pointer to a 2D array from info_pass     */
    /* struct then I want to access the 2D array and change it's contents */
    /* contents and then send it back in another info_pass struct         */

    struct info_pass* keyRef = NULL;      
    keyRef = malloc(sizeof(struct info_pass));
    keyRef = key;                     /* to pass the info back afterwards */

    int len = keyRef->length;
    int wid = keyRef->width;

    struct cell* home1 = NULL;
    home1 = malloc(sizeof(struct cell));
    home1 = key->masterRef[len][wid];       /* to access and change the data */

    int fate = 0;
    int a = 0;
    int b = 0;

    for (a = 0; a < len; a++) {
            for (b = 0; b <  wid; b++) {
                    if (keyRef->masterRef[a][b].go_up.state == 1) { 
     /* just trying different styles of calls */
                            fate++;
                    } if (home1[a][b].go_down.state == 1) {
                            fate++;
                    } if (home1[a][b]->go_left->state == 1) {
                            fate++;
                    } if (home1[a][b]->go_right->state == 1) {
                            fate++;
     /* there more calls to the array, and all generate the same error: */
     /* subscripted value is neither array nor pointer */

Answer 1

这并不是一个真正的答案，而是一个需要一些格式的注释。 :-) 很容易理解 C 中的“数组”只是指针算术。例如:

char* ptr = "abcd";

    printf("Letter = %c\n", ptr[1]);
    printf("Letter = %c\n", 1[ptr]); // Same damn thing!
    printf("Letter = %c\n", *(1 + ptr)); // and again!

因此，当您执行看似“数组索引”的操作时，C 只是添加内容并通过它们进行间接访问。语法“x[y]”的意思是“将 x 添加到 y 并将结果用作指针”。 (当然，需要注意的是，C 在将整数添加到指针之前将它们乘以所指向的对象的大小)

IOW，[] 运算符的真正含义是“添加和间接”。

古老的 ANSI C 是否有多维数组？事实并非如此，不像像 FORTRAN 这样经常使用它们的语言那样。但是，只要您掌握了简单的数组和指针算术，您就可以自己进行操作。因此，如果我想要一个一维数组，我需要的只是一个指向 malloc() 提供的内存的指针。但如果我想要一个二维数组，那么我需要一个指针数组，每个指针都指向 malloc() 返回的一些内存。因为这样:

int** Matrix = MallocMatrix(3, 5);

Matrix[2][3] = 0;

表示“将 2*sizeof(int*) 添加到矩阵并间接。然后将 3*sizeof(int) 添加到该矩阵并间接。”