帮我设计c语言一个环形缓冲,要求读写的基本单位不是字节而是可变长度数据包
时间: 2024-02-10 19:10:56 浏览: 30
好的,这里是一个支持可变长度数据包的环形缓冲设计:
```c
#define BUF_SIZE 10 // 缓冲区大小
typedef struct {
char* data;
int len;
} Packet;
typedef struct {
Packet buffer[BUF_SIZE];
int head; // 缓冲区头部下标
int tail; // 缓冲区尾部下标
} RingBuffer;
void init(RingBuffer* buf) {
buf->head = 0;
buf->tail = 0;
}
int is_empty(RingBuffer* buf) {
return (buf->head == buf->tail);
}
int is_full(RingBuffer* buf) {
int next_tail = (buf->tail + 1) % BUF_SIZE;
if (next_tail == buf->head) {
return 1; // 缓冲区已满
}
if (next_tail < buf->head) {
return (buf->head - next_tail == 1); // 缓冲区已满
}
return 0;
}
int write(RingBuffer* buf, Packet* packet) {
if (is_full(buf)) {
return -1; // 缓冲区已满
}
int next_tail = (buf->tail + 1) % BUF_SIZE;
if (next_tail < buf->tail) {
// 采用分段写入的方式
int len1 = BUF_SIZE - buf->tail;
int len2 = next_tail;
if (len1 >= packet->len) {
// 数据包可以全部放在第一段
buf->buffer[buf->tail].data = packet->data;
buf->buffer[buf->tail].len = packet->len;
buf->tail = next_tail;
return 0;
}
if (len1 + len2 >= packet->len) {
// 数据包可以分别放在第一段和第二段
memcpy(&(buf->buffer[buf->tail]), packet->data, len1);
memcpy(&(buf->buffer[0]), packet->data + len1, packet->len - len1);
buf->buffer[0].len = packet->len - len1;
buf->tail = 0;
return 0;
}
// 数据包无法放入缓冲区
return -1;
}
// 数据包可以全部放在一段
buf->buffer[buf->tail].data = packet->data;
buf->buffer[buf->tail].len = packet->len;
buf->tail = next_tail;
return 0;
}
int read(RingBuffer* buf, Packet* packet) {
if (is_empty(buf)) {
return -1; // 缓冲区为空
}
int next_head = (buf->head + 1) % BUF_SIZE;
if (next_head < buf->head) {
// 采用分段读取的方式
int len1 = BUF_SIZE - buf->head;
int len2 = next_head;
if (len1 >= buf->buffer[buf->head].len) {
// 数据包全部在第一段
packet->data = buf->buffer[buf->head].data;
packet->len = buf->buffer[buf->head].len;
buf->head = next_head;
return 0;
}
if (len1 + len2 >= buf->buffer[buf->head].len) {
// 数据包分别在第一段和第二段
memcpy(packet->data, &(buf->buffer[buf->head]), len1);
memcpy(packet->data + len1, &(buf->buffer[0]), buf->buffer[buf->head].len - len1);
packet->len = buf->buffer[buf->head].len;
buf->head = 0;
return 0;
}
// 数据包无法完整读取
return -1;
}
// 数据包在一段
packet->data = buf->buffer[buf->head].data;
packet->len = buf->buffer[buf->head].len;
buf->head = next_head;
return 0;
}
```
使用示例:
```c
RingBuffer buf;
Packet pkt1 = {"hello", 5};
Packet pkt2 = {"world", 5};
Packet pkt3 = {"this is a long packet", 22};
char buf1[10], buf2[10], buf3[30];
init(&buf);
// 写入数据包
write(&buf, &pkt1);
write(&buf, &pkt2);
write(&buf, &pkt3);
// 读取数据包
read(&buf, &pkt1);
printf("%.*s\n", pkt1.len, pkt1.data);
read(&buf, &pkt2);
printf("%.*s\n", pkt2.len, pkt2.data);
read(&buf, &pkt3);
printf("%.*s\n", pkt3.len, pkt3.data);
```
这个环形缓冲可以存储 `BUF_SIZE` 个可变长度数据包,如果缓冲区已满则无法写入,如果缓冲区为空则无法读取。写入数据包时,如果数据包可以全部放在一段,则直接写入;否则采用分段写入的方式。读取数据包时,如果数据包可以全部放在一段,则直接读取;否则采用分段读取的方式。