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环形队列

news 2026/6/16 14:05:47

代码片段

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <assert.h>#define MAX_MSG_SIZE 256
#define QUEUE_EMPTY -1
#define QUEUE_FULL -2// 消息结构体
typedef struct {long mtype;           // 消息类型，Linux 消息队列中用于区分消息char mtext[MAX_MSG_SIZE]; // 消息内容
} Message;// 基于环形队列的消息队列结构体
typedef struct {Message *messages;    // 存储消息的环形缓冲区int front;            // 队头指针int rear;             // 队尾指针int capacity;         // 队列容量int size;             // 当前消息数量
} MessageQueue;// 创建消息队列
MessageQueue* msg_queue_create(int capacity) {if (capacity <= 0) {fprintf(stderr, "Error: Capacity must be positive\n");return NULL;}MessageQueue *mq = (MessageQueue*)malloc(sizeof(MessageQueue));if (!mq) {perror("Memory allocation failed for message queue");return NULL;}mq->messages = (Message*)malloc(sizeof(Message) * capacity);if (!mq->messages) {perror("Memory allocation failed for messages");free(mq);return NULL;}mq->front = 0;mq->rear = 0;mq->capacity = capacity;mq->size = 0;printf("Message queue created with capacity %d\n", capacity);return mq;
}// 检查消息队列是否为空
bool msg_queue_is_empty(MessageQueue *mq) {return mq->size == 0;
}// 检查消息队列是否已满
bool msg_queue_is_full(MessageQueue *mq) {return mq->size == mq->capacity;
}// 发送消息（入队）
int msg_send(MessageQueue *mq, long msg_type, const char *msg_text) {if (msg_queue_is_full(mq)) {printf("Message queue is full. Cannot send message.\n");return QUEUE_FULL;}if (strlen(msg_text) >= MAX_MSG_SIZE) {fprintf(stderr, "Error: Message text too long (max %d characters)\n", MAX_MSG_SIZE - 1);return -3;}// 构造消息Message msg;msg.mtype = msg_type;strncpy(msg.mtext, msg_text, MAX_MSG_SIZE - 1);msg.mtext[MAX_MSG_SIZE - 1] = '\0';// 存入环形缓冲区mq->messages[mq->rear] = msg;mq->rear = (mq->rear + 1) % mq->capacity;mq->size++;printf("Message sent: [type=%ld] %s\n", msg.mtype, msg.mtext);return 0;
}// 接收消息（出队），按先进先出顺序，忽略消息类型（简化版）
int msg_receive(MessageQueue *mq, long *msg_type, char *msg_text, int max_len) {if (msg_queue_is_empty(mq)) {printf("Message queue is empty. Cannot receive message.\n");return QUEUE_EMPTY;}// 从队头取出消息Message msg = mq->messages[mq->front];mq->front = (mq->front + 1) % mq->capacity;mq->size--;if (msg_type) {*msg_type = msg.mtype;}if (msg_text) {strncpy(msg_text, msg.mtext, max_len - 1);msg_text[max_len - 1] = '\0';}printf("Message received: [type=%ld] %s\n", msg.mtype, msg.mtext);return 0;
}// 获取消息队列当前消息数量
int msg_queue_size(MessageQueue *mq) {return mq->size;
}// 销毁消息队列
void msg_queue_destroy(MessageQueue *mq) {if (mq) {free(mq->messages);free(mq);printf("Message queue destroyed\n");}
}// 打印消息队列状态
void msg_queue_print_status(MessageQueue *mq) {printf("Message Queue Status: ");if (msg_queue_is_empty(mq)) {printf("Empty\n");} else if (msg_queue_is_full(mq)) {printf("Full\n");} else {printf("Partially filled\n");}printf("  Capacity: %d, Current size: %d\n", mq->capacity, mq->size);printf("  Front index: %d, Rear index: %d\n", mq->front, mq->rear);if (!msg_queue_is_empty(mq)) {printf("  Messages in queue (from front to rear):\n");int index = mq->front;for (int i = 0; i < mq->size; i++) {printf("    [%d] type=%ld, text='%s'\n",i, mq->messages[index].mtype, mq->messages[index].mtext);index = (index + 1) % mq->capacity;}}
}// 测试函数
int main() {printf("=== Message Queue Based on Circular Queue ===\n\n");// 1. 创建消息队列，容量为5MessageQueue *mq = msg_queue_create(5);if (!mq) {fprintf(stderr, "Failed to create message queue\n");return 1;}msg_queue_print_status(mq);printf("\n");// 2. 发送几条消息printf("--- Sending messages ---\n");msg_send(mq, 1, "Hello, this is the first message");msg_send(mq, 2, "Second message with higher priority");msg_send(mq, 1, "Another message of type 1");msg_send(mq, 3, "Test message number three");msg_send(mq, 2, "Final message before queue is full");msg_queue_print_status(mq);printf("\n");// 3. 尝试发送消息到已满队列printf("--- Attempt to send to full queue ---\n");int result = msg_send(mq, 4, "This should fail");if (result == QUEUE_FULL) {printf("Expected: queue is full, send failed.\n");}msg_queue_print_status(mq);printf("\n");// 4. 接收几条消息printf("--- Receiving messages ---\n");long received_type;char received_text[MAX_MSG_SIZE];for (int i = 0; i < 3; i++) {if (msg_receive(mq, &received_type, received_text, MAX_MSG_SIZE) == 0) {printf("  Received: type=%ld, text='%s'\n", received_type, received_text);}}msg_queue_print_status(mq);printf("\n");// 5. 再发送几条消息，测试环形特性printf("--- Sending more messages (testing circular behavior) ---\n");msg_send(mq, 4, "New message after some dequeues");msg_send(mq, 5, "Another new message");msg_queue_print_status(mq);printf("\n");// 6. 接收剩余的所有消息printf("--- Receiving all remaining messages ---\n");while (!msg_queue_is_empty(mq)) {msg_receive(mq, &received_type, received_text, MAX_MSG_SIZE);}msg_queue_print_status(mq);printf("\n");// 7. 尝试从空队列接收printf("--- Attempt to receive from empty queue ---\n");result = msg_receive(mq, NULL, NULL, 0);if (result == QUEUE_EMPTY) {printf("Expected: queue is empty, receive failed.\n");}// 8. 清理msg_queue_destroy(mq);return 0;
}