c - 二维动态分配数组并将其作为参数传递的问题

Question

我有以下问题:我正在填充一个二维数组，其行数是我正在读取的文件数。因此，每行中的列数对应于从文件中读取的数据字节数。

考虑到这张图片，我有以下程序:我必须返回从每个文件读取的数据字节数组和每个文件的大小。这是我的:

void fillArrays(unsigned char **array, size_t dataSize[], int *nFiles)
{
    printf("Calling fillArrays\n"); 
    int i, j, nrows;
    nrows = 3;
    *nFiles = nrows; // assuming no. of files to be read = 3

    dataSize = (size_t *)malloc(nrows * sizeof(size_t));
    array = (unsigned char**)malloc(nrows * sizeof(unsigned char *));

    dataSize[0] = 4; // assuming file 1 contains 4 bytes
    dataSize[1] = 3; // assuming file 2 contains 3 bytes
    dataSize[2] = 1;// assuming file 3 contains 1 bytes

    //populating file data into a 2D array. Here for test purpose assuming each file has data = 0x03!!
    for(i = 0; i < nrows; i++)
    {
        array[i] = (unsigned char *) malloc(dataSize[i] * sizeof(unsigned char));
        for(j = 0; j < dataSize[i]; j++){   
            printf("round %d %d\n", i,j);
            array[i][j] = 0x03;
            printf("array [%d][%d]  = %02X\n ", i, j , array[i][j]); 
        }
        //array[i][dataSize[i]]= '\0';

    }

}


int main(int argc, char *argv[])
{
    unsigned char **fileArray;
    int noFiles = 0;
    size_t *fileSize;

    fillArrays(fileArray,fileSize, &noFiles);
    printf("Returned no. of files = %d\n", noFiles);
    printf("fileSize[0] = %lu\n", fileSize[0]);
    printf("fileSize[1] = %lu\n", fileSize[1]);
    printf("fileSize[2] = %lu\n", fileSize[2]);
    int j = 0;
    for (int i = 0; i <  noFiles; i++){
        printf("i = %d\n", i);
        for (int j = 0; j <  fileSize[i]; j++){
            printf("Obtained data from file %d :  (fileArray [%d][%d])  = %02X\n ", i, i, j , fileArray[i][j]); 
            //j++;
        }
    }


    return 0;
}

代码在主函数的“j”循环中出现段错误。有人可以点灯吗？如何做得更好？

谢谢。

Answer 1

您正在按值传递 fileArray，因此在 fillArrays 中，您正在将该指针的副本修改为指针，因此在执行 fillArrays 函数后， main 函数中的 fileArray 不受影响 - 它仍未初始化，您需要通过 reference 传递此变量(传递指向 fileArray 的指针):

fillArrays(&fileArray,fileSize, &noFiles);

然后在 fillArrays 中您需要添加这些修改:

void fillArrays(unsigned char ***array, size_t dataSize[], int *nFiles)
{
    //...
    *array = (unsigned char**)malloc(nrows * sizeof(unsigned char *));
    //...
        (*array)[i] = (unsigned char *) malloc(dataSize[i] * sizeof(unsigned char));
    ///...
            (*array)[i][j] = 0x03;
}