我在没有任何文档的情况下从一些旧的repo中获得了一个队列文件，我试图将数据从中排队和取消排队
.h文件如下
#include"limits.h"
#include"stdio.h"
#include"pthread.h"
#include"unistd.h"
#include"stdlib.h"
#include"string.h"
#include"time.h"
pthread_mutex_t lock;
typedef struct{
int* message;
void*in_array;
}data_pack;
data_pack* createpack()
{
data_pack* pack = malloc(sizeof( data_pack));
return pack;
}
// Queue Structure
struct Queue {
int front, rear, size; // front, rare and the size of the Queue
unsigned long long capacity; // stores the capacity of the Queue
data_pack** array; //2D array to store the array of arrays
int* array_sizes; //1D array to store the number of elements of each array
data_pack** remArray; //2D array to store the remaining array of arrays(used for flush)
};
// Creates a Queue
struct Queue* createQueue()
{
struct Queue* queue = (struct Queue*)malloc(sizeof(struct Queue));
queue->front = queue->size = 0;
queue->capacity = queue->size + 1;
queue->rear = queue->capacity - 1;
queue->array = (data_pack **)malloc(queue->capacity * sizeof(data_pack));// changed to my struct
queue->array_sizes = (int *)malloc(queue->capacity * sizeof(int));
if (pthread_mutex_init(&lock, NULL) != 0) {
printf("n mutex init has failedn");
return 0;
}
return queue;
}
// Queue is empty when size is 0
int isEmpty(struct Queue* queue)
{
return (queue->size == 0);
}
// Function to add an array to the queue.
// It changes rear and size
void enqueue(struct Queue* queue, data_pack arr[], int n)
{
int i=0;
pthread_mutex_lock(&lock);// lock variables
queue->rear = (queue->rear + 1) % queue->capacity;
queue->array[queue->rear] = (data_pack *)malloc(n*sizeof(data_pack));
if(queue->array[queue->rear]==NULL) printf("Error in memoryn");
for(i=0;i<n;i++){
queue->array[queue->rear][i] = arr[i];// u need to input struct here
}
queue->array_sizes[queue->rear] = n;
queue->size = queue->size + 1;
queue->capacity = queue->capacity + 1;
queue->array = (data_pack**)realloc(queue->array,queue->capacity*sizeof(data_pack));
if(queue->array == NULL) printf("Not 2d array");
queue->array_sizes = (int*)realloc(queue->array_sizes,queue->capacity*sizeof(int));
if(queue->array_sizes == NULL) printf("not 1dn array sizes");
pthread_mutex_unlock(&lock);// unlock variables
}
// Function to remove an array from queue.
// It changes front and size
data_pack* dequeue(struct Queue* queue)
{
int i=0;
pthread_mutex_lock(&lock);// lock variables
int len = queue->array_sizes[queue->front];
data_pack* deqArray = (data_pack*)malloc(len*sizeof(data_pack));
if (isEmpty(queue))
return 0;
for( i=0;i<queue->array_sizes[queue->front];i++){
deqArray[i] = queue->array[queue->front][i];
}
queue->front = (queue->front + 1) % queue->capacity;
queue->size = queue->size - 1;
pthread_mutex_unlock(&lock);// unlock variables
free(queue->array[queue->front-1]);
return deqArray;
}
// Function to flush all the arrays and its elements from the queue.
data_pack** flush(struct Queue* queue)
{
int i=0;
int j=0;
queue->remArray = (data_pack **)malloc(queue->size * sizeof(data_pack));
int k=0;
for( i=queue->front;i<=queue->rear;i++){
int len = queue->array_sizes[i];
queue->remArray[k] = (data_pack *)malloc(len*sizeof(data_pack));
for( j=0;j<len;j++){
//queue->remArray[k][j] = queue->array[i][j];
}
free(queue->array[i]);
k++;
}
free(queue->array);
free(queue->array_sizes);
queue->front = queue->size = 0;
queue->capacity = queue->size + 1;
queue->rear = queue->capacity - 1;
queue->array_sizes = (int *)malloc(1 * sizeof(int));
queue->array = (data_pack **)malloc(1 * sizeof(data_pack));
return queue->remArray;
}
// Function to know number of arrays in queue
int no_elements(struct Queue* queue)
{
return queue->size;
}
在我的代码中，我试图使元素入队，获取队列和出队元素的大小
struct Queue * send_data_queue;
data_pack data_to_send[0];
data_pack * rec_data;
typedef struct SenderData {
unsigned short CommandCode;
int DataSize;
void * Data;
}
SenderData;
int cont[200];
SenderData data, dat;
int main(int argc, char * argv[]) {
send_data_queue = createQueue();
while (1) {
data.DataSize = sizeof(cont);
data.Data = & cont;
data.CommandCode = 20;
data_to_send[0].message = 20;
data_to_send[0].in_array = & data;
enqueue(send_data_queue, data_to_send, 1);
int nos = no_elements(send_data_queue);
printf("No of elements in q = %dn", nos); // this is printing correctly
rec_data = dequeue(send_data_queue);
dat = ((SenderData * )(rec_data -> in_array)[0]); // i get error here Invalid use of void Expression
}
return 0;
}
解释我的代码
-我正在尝试将一个数组入队，该数组是200个元素的数组
我正在用所需的信息更新我的结构数据，如大小、命令和实际数据
这个队列使用一个结构来传递数据，所以我将结构数据更新为这个结构
然后我调用排队功能
然后我检查队列大小，它的更新是否正确
我正在尝试退出数据队列
在这里，我将数据转换为结构，即Sender数据
但在这一点上，我得到了错误作为无效使用无效表达式
为什么会出现这样的错误？
在这一行：
dat = ((SenderData * )(rec_data -> in_array)[0]);
数组下标运算符的优先级高于类型转换运算符。因此，首先得到评估的是rec_data -> in_array[0]。这将取消引用不允许的void *。
您需要先使用括号应用强制转换：
dat = ((SenderData *)(rec_data->in_array))[0];
或者使用解引用运算符而不是数组索引：
dat = *(SenderData *)rec_data->in_array;