Question

我有以下问题：我正在填充一个2D数组，其行数是我正在读取的文件数。因此，每一行的列数对应于从文件读取的数据字节。

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的字节数组和每个文件的大小。这就是我所拥有的：

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;
}

该代码在主函数的'j'循环中出现段错误。有人可以给点灯吗？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复制为指针，因此在执行fillArrays函数之后，main函数中的fileArray是不受影响-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，您需要添加以下修改：

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;
}

Answer 2

您的array和dataSize在fillArrays函数的本地，并且在fillArrays内为它们分配内存不会影响main内的数组。

// Allocates the memory to local variables
dataSize = (size_t *)malloc(nrows * sizeof(size_t));
array = (unsigned char**)malloc(nrows * sizeof(unsigned char *));

因此，您需要使用指向char*和fileArray的指针指向size_t*的{{1}}的指针。

您的原型将如下所示。

fileSize

然后调用以下函数。

void fillArrays(unsigned char ***array, size_t **dataSize, int *nFiles)

示例代码：

fillArrays(&fileArray,&fileSize, &noFiles);

替代方法：

我建议您不要将指向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; }的指针作为参数，而只需从char*返回填充的数组，如下所示。

fillArrays

，然后按如下所示调用函数。

char** fillArrays(size_t **dataSize, int *nFiles)
{
    printf("Calling fillArrays\n");
    int i, j, nrows;
    char **array = NULL;
    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';

    }
  return array;
}

二维二维数组动态分配并将其作为参数传递的问题

2 个答案: