请用C语言编程：持续接收数据至缓存，每组数据长度为20，每10ms从缓存中提取最先存入的一组数据到buffer并将缓存中该组数据清除，数据缓存先进先出

以下是一种可能的实现，使用了一个循环队列作为数据缓存：

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

#define BUFFER_SIZE 10
#define DATA_LENGTH 20
#define EXTRACT_INTERVAL 10 // in milliseconds

typedef struct {
    char data[DATA_LENGTH];
} Data;

typedef struct {
    Data buffer[BUFFER_SIZE];
    int front; // index of the first element
    int rear; // index of the next available position
    int count; // number of elements in the buffer
} CircularBuffer;

void initBuffer(CircularBuffer *buffer) {
    buffer->front = 0;
    buffer->rear = 0;
    buffer->count = 0;
}

int isBufferEmpty(CircularBuffer *buffer) {
    return buffer->count == 0;
}

int isBufferFull(CircularBuffer *buffer) {
    return buffer->count == BUFFER_SIZE;
}

void enqueue(CircularBuffer *buffer, Data data) {
    if (isBufferFull(buffer)) {
        printf("Error: buffer is full\n");
        exit(EXIT_FAILURE);
    }
    buffer->buffer[buffer->rear] = data;
    buffer->rear = (buffer->rear + 1) % BUFFER_SIZE;
    buffer->count++;
}

Data dequeue(CircularBuffer *buffer) {
    if (isBufferEmpty(buffer)) {
        printf("Error: buffer is empty\n");
        exit(EXIT_FAILURE);
    }
    Data data = buffer->buffer[buffer->front];
    buffer->front = (buffer->front + 1) % BUFFER_SIZE;
    buffer->count--;
    return data;
}

int main() {
    CircularBuffer buffer;
    initBuffer(&buffer);

    // simulation of data receiving
    srand(time(NULL));
    for (int i = 0; i < 100; i++) {
        Data data;
        for (int j = 0; j < DATA_LENGTH; j++) {
            data.data[j] = rand() % 26 + 'A'; // generate a random uppercase letter
        }
        enqueue(&buffer, data);
        printf("Data received: %s\n", data.data);
        usleep(EXTRACT_INTERVAL * 1000); // sleep for the extraction interval
        if (i % (EXTRACT_INTERVAL / 10) == 0) { // time to extract data
            if (!isBufferEmpty(&buffer)) {
                Data extractedData = dequeue(&buffer);
                printf("Data extracted: %s\n", extractedData.data);
            }
        }
    }

    return 0;
}

说明：

- `CircularBuffer` 结构体定义了循环队列的基本属性：缓存数组、队首和队尾的下标以及元素个数；
- `initBuffer` 函数用于初始化缓存；
- `isBufferEmpty` 和 `isBufferFull` 函数分别判断缓存是否为空和已满；
- `enqueue` 和 `dequeue` 函数分别用于入队和出队操作，循环队列的关键在于对下标的处理；
- 在 `main` 函数中模拟了数据的接收过程，每隔一定时间就提取缓存中最先存入的一组数据并将其清除。使用了 `usleep` 函数来实现等待一段时间，单位是微秒，需要乘以 1000 转换为毫秒。