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feat(redis): 添加 Redis 协议相关的客户端和服务器示例代码- 新增多个 Redis 协议实现的客户端和服务器代码示例
- 演示了如何使用 socket 进行网络通信- 实现了基本的请求响应模型和数据传输 - 优化了错误处理和资源管理
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‎C++/C++常见知识点.adoc

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@@ -94,6 +94,7 @@ struct _Vector_impl
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==== 虚函数实现
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C++多态分为静态多态(编译时多态)和动态多态(运行时多态)两大类，静态多态通过重载，模板来实现；动态多态是通过虚函数实现。
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虚函数通过虚函数表vtbl(virtual table)和虚函数表指针vptr(virtual table pointer)来实现动态多态。当调用一个虚函数时，被执行的代码和调用函数的对象的动态类型相一致，当一个类声明了虚函数或者继承了虚函数，这个类就会有自己的vtbl，vtbl实际上就是一个函数指针数组，有的编译器用的是链表，不过方法都差不多。vtbl中每一个元素都对应一个函数指针，函数指针指向该类的一个虚函数，实际上每一个对象都会包含一个vptr，vptr指向该类的vtbl;
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|===

‎src/redis/03/03_client.cpp

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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include <arpa/inet.h>
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#include <sys/socket.h>
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#include <netinet/ip.h>
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static void die(const char *msg) {
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int err = errno;
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fprintf(stderr, "[%d] %s\n", err, msg);
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abort();
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}
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int main() {
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int fd = socket(AF_INET, SOCK_STREAM, 0);
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if (fd < 0) {
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die("socket()");
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}
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struct sockaddr_in addr = {};
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addr.sin_family = AF_INET;
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addr.sin_port = ntohs(1234);
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addr.sin_addr.s_addr = ntohl(INADDR_LOOPBACK); // 127.0.0.1
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int rv = connect(fd, (const struct sockaddr *)&addr, sizeof(addr));
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if (rv) {
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die("connect");
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}
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char msg[] = "hello";
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write(fd, msg, strlen(msg));
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char rbuf[64] = {};
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ssize_t n = read(fd, rbuf, sizeof(rbuf) - 1);
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if (n < 0) {
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die("read");
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}
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printf("server says: %s\n", rbuf);
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close(fd);
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return 0;
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}

‎src/redis/03/03_server.cpp

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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include <arpa/inet.h>
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#include <sys/socket.h>
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#include <netinet/ip.h>
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static void msg(const char *msg) {
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fprintf(stderr, "%s\n", msg);
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}
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static void die(const char *msg) {
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int err = errno;
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fprintf(stderr, "[%d] %s\n", err, msg);
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abort();
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}
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static void do_something(int connfd) {
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char rbuf[64] = {};
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ssize_t n = read(connfd, rbuf, sizeof(rbuf) - 1);
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if (n < 0) {
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msg("read() error");
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return;
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}
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fprintf(stderr, "client says: %s\n", rbuf);
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char wbuf[] = "world";
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write(connfd, wbuf, strlen(wbuf));
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}
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int main() {
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int fd = socket(AF_INET, SOCK_STREAM, 0);
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if (fd < 0) {
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die("socket()");
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}
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// this is needed for most server applications
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int val = 1;
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setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
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// bind
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struct sockaddr_in addr = {};
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addr.sin_family = AF_INET;
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addr.sin_port = ntohs(1234);
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addr.sin_addr.s_addr = ntohl(0); // wildcard address 0.0.0.0
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int rv = bind(fd, (const struct sockaddr *)&addr, sizeof(addr));
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if (rv) {
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die("bind()");
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}
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// listen
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rv = listen(fd, SOMAXCONN);
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if (rv) {
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die("listen()");
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}
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while (true) {
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// accept
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struct sockaddr_in client_addr = {};
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socklen_t addrlen = sizeof(client_addr);
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int connfd = accept(fd, (struct sockaddr *)&client_addr, &addrlen);
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if (connfd < 0) {
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continue; // error
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}
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do_something(connfd);
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close(connfd);
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}
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return 0;
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}

‎src/redis/04/04_client.cpp

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#include <assert.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include <arpa/inet.h>
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#include <sys/socket.h>
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#include <netinet/ip.h>
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static void msg(const char *msg) {
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fprintf(stderr, "%s\n", msg);
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}
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static void die(const char *msg) {
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int err = errno;
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fprintf(stderr, "[%d] %s\n", err, msg);
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abort();
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}
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static int32_t read_full(int fd, char *buf, size_t n) {
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while (n > 0) {
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ssize_t rv = read(fd, buf, n);
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if (rv <= 0) {
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return -1; // error, or unexpected EOF
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}
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assert((size_t)rv <= n);
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n -= (size_t)rv;
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buf += rv;
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}
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return 0;
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}
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static int32_t write_all(int fd, const char *buf, size_t n) {
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while (n > 0) {
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ssize_t rv = write(fd, buf, n);
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if (rv <= 0) {
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return -1; // error
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}
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assert((size_t)rv <= n);
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n -= (size_t)rv;
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buf += rv;
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}
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return 0;
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}
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const size_t k_max_msg = 4096;
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static int32_t query(int fd, const char *text) {
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uint32_t len = (uint32_t)strlen(text);
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if (len > k_max_msg) {
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return -1;
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}
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char wbuf[4 + k_max_msg];
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memcpy(wbuf, &len, 4); // assume little endian
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memcpy(&wbuf[4], text, len);
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if (int32_t err = write_all(fd, wbuf, 4 + len)) {
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return err;
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}
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// 4 bytes header
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char rbuf[4 + k_max_msg + 1];
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errno = 0;
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int32_t err = read_full(fd, rbuf, 4);
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if (err) {
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msg(errno == 0 ? "EOF" : "read() error");
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return err;
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}
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memcpy(&len, rbuf, 4); // assume little endian
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if (len > k_max_msg) {
75+
msg("too long");
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return -1;
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}
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// reply body
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err = read_full(fd, &rbuf[4], len);
81+
if (err) {
82+
msg("read() error");
83+
return err;
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}
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// do something
87+
printf("server says: %.*s\n", len, &rbuf[4]);
88+
return 0;
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}
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int main() {
92+
int fd = socket(AF_INET, SOCK_STREAM, 0);
93+
if (fd < 0) {
94+
die("socket()");
95+
}
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struct sockaddr_in addr = {};
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addr.sin_family = AF_INET;
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addr.sin_port = ntohs(1234);
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addr.sin_addr.s_addr = ntohl(INADDR_LOOPBACK); // 127.0.0.1
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int rv = connect(fd, (const struct sockaddr *)&addr, sizeof(addr));
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if (rv) {
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die("connect");
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}
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// multiple requests
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int32_t err = query(fd, "hello1");
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if (err) {
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goto L_DONE;
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}
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err = query(fd, "hello2");
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if (err) {
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goto L_DONE;
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}
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err = query(fd, "hello3");
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if (err) {
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goto L_DONE;
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}
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L_DONE:
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close(fd);
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return 0;
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}

‎src/redis/04/04_server.cpp

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#include <assert.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include <arpa/inet.h>
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#include <sys/socket.h>
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#include <netinet/ip.h>
11+
12+
13+
static void msg(const char *msg) {
14+
fprintf(stderr, "%s\n", msg);
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}
16+
17+
static void die(const char *msg) {
18+
int err = errno;
19+
fprintf(stderr, "[%d] %s\n", err, msg);
20+
abort();
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}
22+
23+
const size_t k_max_msg = 4096;
24+
25+
static int32_t read_full(int fd, char *buf, size_t n) {
26+
while (n > 0) {
27+
ssize_t rv = read(fd, buf, n);
28+
if (rv <= 0) {
29+
return -1; // error, or unexpected EOF
30+
}
31+
assert((size_t)rv <= n);
32+
n -= (size_t)rv;
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buf += rv;
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}
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return 0;
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}
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38+
static int32_t write_all(int fd, const char *buf, size_t n) {
39+
while (n > 0) {
40+
ssize_t rv = write(fd, buf, n);
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if (rv <= 0) {
42+
return -1; // error
43+
}
44+
assert((size_t)rv <= n);
45+
n -= (size_t)rv;
46+
buf += rv;
47+
}
48+
return 0;
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}
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51+
static int32_t one_request(int connfd) {
52+
// 4 bytes header
53+
char rbuf[4 + k_max_msg];
54+
errno = 0;
55+
int32_t err = read_full(connfd, rbuf, 4);
56+
if (err) {
57+
msg(errno == 0 ? "EOF" : "read() error");
58+
return err;
59+
}
60+
61+
uint32_t len = 0;
62+
memcpy(&len, rbuf, 4); // assume little endian
63+
if (len > k_max_msg) {
64+
msg("too long");
65+
return -1;
66+
}
67+
68+
// request body
69+
err = read_full(connfd, &rbuf[4], len);
70+
if (err) {
71+
msg("read() error");
72+
return err;
73+
}
74+
75+
// do something
76+
fprintf(stderr, "client says: %.*s\n", len, &rbuf[4]);
77+
78+
// reply using the same protocol
79+
const char reply[] = "world";
80+
char wbuf[4 + sizeof(reply)];
81+
len = (uint32_t)strlen(reply);
82+
memcpy(wbuf, &len, 4);
83+
memcpy(&wbuf[4], reply, len);
84+
return write_all(connfd, wbuf, 4 + len);
85+
}
86+
87+
int main() {
88+
int fd = socket(AF_INET, SOCK_STREAM, 0);
89+
if (fd < 0) {
90+
die("socket()");
91+
}
92+
93+
// this is needed for most server applications
94+
int val = 1;
95+
setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
96+
97+
// bind
98+
struct sockaddr_in addr = {};
99+
addr.sin_family = AF_INET;
100+
addr.sin_port = ntohs(1234);
101+
addr.sin_addr.s_addr = ntohl(0); // wildcard address 0.0.0.0
102+
int rv = bind(fd, (const sockaddr *)&addr, sizeof(addr));
103+
if (rv) {
104+
die("bind()");
105+
}
106+
107+
// listen
108+
rv = listen(fd, SOMAXCONN);
109+
if (rv) {
110+
die("listen()");
111+
}
112+
113+
while (true) {
114+
// accept
115+
struct sockaddr_in client_addr = {};
116+
socklen_t addrlen = sizeof(client_addr);
117+
int connfd = accept(fd, (struct sockaddr *)&client_addr, &addrlen);
118+
if (connfd < 0) {
119+
continue; // error
120+
}
121+
122+
while (true) {
123+
// here the server only serves one client connection at once
124+
int32_t err = one_request(connfd);
125+
if (err) {
126+
break;
127+
}
128+
}
129+
close(connfd);
130+
}
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return 0;
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}

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