IO+select.c

#define MAX_LINE 1024
#define FD_INIT_SIZE 128

char rot13_char(char c) {
    if ((c >= 'a' && c <= 'm') || (c >= 'A' && c <= 'M'))
        return c + 13;
    else if ((c >= 'n' && c <= 'z') || (c >= 'N' && c <= 'Z'))
        return c - 13;
    else
        return c;
}

//数据缓冲区
struct Buffer {
    int connect_fd;  //连接字
    char buffer[MAX_LINE];  //实际缓冲
    size_t writeIndex;      //缓冲写入位置
    size_t readIndex;       //缓冲读取位置
    int readable;           //是否可以读
};

struct Buffer *alloc_Buffer() {
    struct Buffer *buffer = malloc(sizeof(struct Buffer));
    if (!buffer)
        return NULL;
    buffer->connect_fd = 0;
    buffer->writeIndex = buffer->readIndex = buffer->readable = 0;
    return buffer;
}

void free_Buffer(struct Buffer *buffer) {
    free(buffer);
}

int onSocketRead(int fd, struct Buffer *buffer) {
    char buf[1024];
    int i;
    ssize_t result;
    while (1) {
        result = recv(fd, buf, sizeof(buf), 0);
        if (result <= 0)
            break;

        for (i = 0; i < result; ++i) {
            if (buffer->writeIndex < sizeof(buffer->buffer))
                buffer->buffer[buffer->writeIndex++] = rot13_char(buf[i]);
            if (buf[i] == '\n') {
                buffer->readable = 1;  //缓冲区可以读
            }
        }
    }

    if (result == 0) {
        return 1;
    } else if (result < 0) {
        if (errno == EAGAIN)
            return 0;
        return -1;
    }

    return 0;
}

int onSocketWrite(int fd, struct Buffer *buffer) {
    while (buffer->readIndex < buffer->writeIndex) {
        ssize_t result = send(fd, buffer->buffer + buffer->readIndex, buffer->writeIndex - buffer->readIndex, 0);
        if (result < 0) {
            if (errno == EAGAIN)
                return 0;
            return -1;
        }

        buffer->readIndex += result;
    }

    if (buffer->readIndex == buffer->writeIndex)
        buffer->readIndex = buffer->writeIndex = 0;

    buffer->readable = 0;

    return 0;
}

int main(int argc, char **argv) {
    int listen_fd;
    int i, maxfd;

    struct Buffer *buffer[FD_INIT_SIZE];
    for (i = 0; i < FD_INIT_SIZE; ++i) {
        buffer[i] = alloc_Buffer();
    }

    listen_fd = tcp_nonblocking_server_listen(SERV_PORT);

    fd_set readset, writeset, exset;
    FD_ZERO(&readset);
    FD_ZERO(&writeset);
    FD_ZERO(&exset);

    while (1) {
        maxfd = listen_fd;

        FD_ZERO(&readset);
        FD_ZERO(&writeset);
        FD_ZERO(&exset);

        // listener加入readset
        FD_SET(listen_fd, &readset);

        for (i = 0; i < FD_INIT_SIZE; ++i) {
            if (buffer[i]->connect_fd > 0) {
                if (buffer[i]->connect_fd > maxfd)
                    maxfd = buffer[i]->connect_fd;
                FD_SET(buffer[i]->connect_fd, &readset);
                if (buffer[i]->readable) {
                    FD_SET(buffer[i]->connect_fd, &writeset);
                }
            }
        }
        // 调用 select 进行 I/O 事件分发处理
        if (select(maxfd + 1, &readset, &writeset, &exset, NULL) < 0) {
            error(1, errno, "select error");
        }

        if (FD_ISSET(listen_fd, &readset)) {
            printf("listening socket readable\n");
            sleep(5);
            struct sockaddr_storage ss;
            socklen_t slen = sizeof(ss);
           int fd = accept(listen_fd, (struct sockaddr *) &ss, &slen);
            if (fd < 0) {
                error(1, errno, "accept failed");
            } else if (fd > FD_INIT_SIZE) {
                error(1, 0, "too many connections");
                close(fd);
            } else {
                make_nonblocking(fd);
                if (buffer[fd]->connect_fd == 0) {
                    buffer[fd]->connect_fd = fd;
                } else {
                    error(1, 0, "too many connections");
                }
            }
        }

        for (i = 0; i < maxfd + 1; ++i) {
            int r = 0;
            if (i == listen_fd)
                continue;

            if (FD_ISSET(i, &readset)) {
                r = onSocketRead(i, buffer[i]);
            }
            if (r == 0 && FD_ISSET(i, &writeset)) {
                r = onSocketWrite(i, buffer[i]);
            }
            if (r) {
                buffer[i]->connect_fd = 0;
                close(i);
            }
        }
    }
}