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做OTA升级功能时，能直接拿到的往往只是升级包的链接，需要我们自己去下载，这时候就需要用到http下载器，下文介绍一个C语言实现的http下载器。功能 1、支持chunked方式传输的下载2、被重定向时能下载重定向页面3、要实现的接口为int http_download(char *url, char *save_path) 思路1、解析输入的URL，分离出主机，端口号，文件路径的信息2、解析主机的DNS3、填充http请求的头部，给服务器发包4、解析收到的http头，提取状态码，Content-length, Transfer-Encoding等字段信息（1）如果是普通的头则进行接下来的正常收包流程（2）如果状态码为302，则从头里提取出重定向地址，用新的地址重新开始下载动作（3）如果传送方式是chunked的，则进行分段读取数据并拼接（4）如果是404或其他状态码则打印错误信息 缺陷其他1、如何移植到没有文件系统的系统中？修改sava_data接口里面的保存就好了2、如何提高下载速度？ - 增大读写buffer缓冲区
- 改为多线程，使用Range字段分段读取，最后再拼在一起
代码
/************************************************************Copyright (C), 2016, Leon, All Rights Reserved.FileName: download.ccoding: UTF-8Description: 实现简单的http下载功能Author: LeonVersion: 1.0Date: 2016-12-2 10:49:32Function:History:<author> <time> <version> <description> Leon************************************************************/#include <stdio.h>#include <stdlib.h>#include <string.h>#include <arpa/inet.h>#include <sys/types.h>#include <sys/socket.h>#include <fcntl.h>#include <unistd.h>#include <netdb.h>#include <errno.h>#define HOST_NAME_LEN 256#define URI_MAX_LEN 2048#define RECV_BUF 8192#define RCV_SND_TIMEOUT (10*1000) //收发数据超时时间(ms)typedef struct { int sock; //与服务器通信的socket FILE *in; //sock描述符转为文件指针，方便读写 char host_name[HOST_NAME_LEN]; //主机名 int port; //主机端口号 char uri[URI_MAX_LEN]; //资源路径 char buffer[RECV_BUF]; //读写缓冲 int status_code; //http状态码 int chunked_flag; //chunked传输的标志位 int len; //Content-length里的长度 char location[URI_MAX_LEN]; //重定向地址 char *save_path; //保存内容的路径指针 FILE *save_file; //保存内容的文件指针 int recv_data_len; //收到数据的总长度 time_t start_recv_time; //开始接受数据的时间 time_t end_recv_time; //结束接受数据的时间} http_t;/* 打印宏 */#define MSG_DEBUG 0x01#define MSG_INFO 0x02#define MSG_ERROR 0x04static int print_level = /*MSG_DEBUG |*/ MSG_INFO | MSG_ERROR;#define lprintf(level, format, argv...) do{ \ if(level & print_level) \ printf("[%s][%s(%d)]:"format, #level, __FUNCTION__, __LINE__, ##argv); \}while(0)#define MIN(x, y) ((x) > (y) ? (y) : (x))#define HTTP_OK 200#define HTTP_REDIRECT 302#define HTTP_NOT_FOUND 404/* 不区分大小写的strstr */char *strncasestr(char *str, char *sub){ if(!str || !sub) return NULL; int len = strlen(sub); if (len == 0) { return NULL; } while (*str) { if (strncasecmp(str, sub, len) == 0) { return str; } ++str; } return NULL;}/* 解析URL, 成功返回0，失败返回-1 *//* http://127.0.0.1:8080/testfile */int parser_URL(char *url, http_t *info){ char *tmp = url, *start = NULL, *end = NULL; int len = 0; /* 跳过http:// */ if(strncasestr(tmp, "http://")) { tmp += strlen("http://"); } start = tmp; if(!(tmp = strchr(start, '/'))) { lprintf(MSG_ERROR, "url invaild\n"); return -1; } end = tmp; /*解析端口号和主机*/ info->port = 80; //先附默认值80 len = MIN(end - start, HOST_NAME_LEN - 1); strncpy(info->host_name, start, len); info->host_name[len] = '\0'; if((tmp = strchr(start, ':')) && tmp < end) { info->port = atoi(tmp + 1); if(info->port <= 0 || info->port >= 65535) { lprintf(MSG_ERROR, "url port invaild\n"); return -1; } /* 覆盖之前的赋值 */ len = MIN(tmp - start, HOST_NAME_LEN - 1); strncpy(info->host_name, start, len); info->host_name[len] = '\0'; } /* 复制uri */ start = end; strncpy(info->uri, start, URI_MAX_LEN - 1); lprintf(MSG_INFO, "parse url ok\nhost:%s, port:%d, uri:%s\n", info->host_name, info->port, info->uri); return 0;}/* dns解析,返回解析到的第一个地址，失败返回-1，成功则返回相应地址 */unsigned long dns(char* host_name){ struct hostent* host; struct in_addr addr; char **pp; host = gethostbyname(host_name); if (host == NULL) { lprintf(MSG_ERROR, "gethostbyname %s failed\n", host_name); return -1; } pp = host->h_addr_list; if (*pp!=NULL) { addr.s_addr = *((unsigned int *)*pp); lprintf(MSG_INFO, "%s address is %s\n", host_name, inet_ntoa(addr)); pp++; return addr.s_addr; } return -1;}/* 设置发送接收超时 */int set_socket_option(int sock){ struct timeval timeout; timeout.tv_sec = RCV_SND_TIMEOUT/1000; timeout.tv_usec = RCV_SND_TIMEOUT%1000*1000; lprintf(MSG_DEBUG, "%ds %dus\n", (int)timeout.tv_sec, (int)timeout.tv_usec); //设置socket为非阻塞 // fcntl(sock ,F_SETFL, O_NONBLOCK); //以非阻塞的方式，connect需要重新处理 // 设置发送超时 if(-1 == setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout, sizeof(struct timeval))) { lprintf(MSG_ERROR, "setsockopt error: %m\n"); return -1; } // 设置接送超时 if(-1 == setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(struct timeval))) { lprintf(MSG_ERROR, "setsockopt error: %m\n"); return -1; } return 0;}/* 连接到服务器 */int connect_server(http_t *info){ int sockfd; struct sockaddr_in server; unsigned long addr = 0; unsigned short port = info->port; sockfd = socket(AF_INET, SOCK_STREAM, 0); if (-1 == sockfd) { lprintf(MSG_ERROR, "socket create failed\n"); goto failed; } if(-1 == set_socket_option(sockfd)) { goto failed; } if ((addr = dns(info->host_name)) == -1) { lprintf(MSG_ERROR, "Get Dns Failed\n"); goto failed; } memset(&server, 0, sizeof(server)); server.sin_family = AF_INET; server.sin_port = htons(port); server.sin_addr.s_addr = addr; if (-1 == connect(sockfd, (struct sockaddr *)&server, sizeof(struct sockaddr))) { lprintf(MSG_ERROR, "connect failed: %m\n"); goto failed; } info->sock = sockfd; return 0;failed: if(sockfd != -1) close(sockfd); return -1;}/* 发送http请求 */int send_request(http_t *info){ int len; memset(info->buffer, 0x0, RECV_BUF); snprintf(info->buffer, RECV_BUF - 1, "GET %s HTTP/1.1\r\n" "Accept: */*\r\n" "User-Agent: Mozilla/5.0 (compatible; MSIE 5.01; Windows NT 5.0)\r\n" "Host: %s\r\n" "Connection: Close\r\n\r\n", info->uri, info->host_name); lprintf(MSG_DEBUG, "request:\n%s\n", info->buffer); return send(info->sock, info->buffer, strlen(info->buffer), 0);}/* 解析http头 */int parse_http_header(http_t *info){ char *p = NULL; // 解析第一行 fgets(info->buffer, RECV_BUF, info->in); p = strchr(info->buffer, ' '); //简单检查http头第一行是否合法 if(!p || !strcasestr(info->buffer, "HTTP")) { lprintf(MSG_ERROR, "bad http head\n"); return -1; } info->status_code = atoi(p + 1); lprintf(MSG_DEBUG, "http status code: %d\n", info->status_code); // 循环读取解析http头 while(fgets(info->buffer, RECV_BUF, info->in)) { // 判断头部是否读完 if(!strcmp(info->buffer, "\r\n")) { return 0; /* 头解析正常 */ } lprintf(MSG_DEBUG, "%s", info->buffer); // 解析长度 Content-length: 554 if(p = strncasestr(info->buffer, "Content-length")) { p = strchr(p, ':'); p += 2; // 跳过冒号和后面的空格 info->len = atoi(p); lprintf(MSG_INFO, "Content-length: %d\n", info->len); } else if(p = strncasestr(info->buffer, "Transfer-Encoding")) { if(strncasestr(info->buffer, "chunked")) { info->chunked_flag = 1; } else { /* 不支持其他编码的传送方式 */ lprintf(MSG_ERROR, "Not support %s", info->buffer); return -1; } lprintf(MSG_INFO, "%s", info->buffer); } else if(p = strncasestr(info->buffer, "Location")) { p = strchr(p, ':'); p += 2; // 跳过冒号和后面的空格 strncpy(info->location, p, URI_MAX_LEN - 1); lprintf(MSG_INFO, "Location: %s\n", info->location); } } lprintf(MSG_ERROR, "bad http head\n"); return -1; /* 头解析出错 */}/* 保存服务器响应的内容 */int save_data(http_t *info, const char *buf, int len){ int total_len = len; int write_len = 0; // 文件没有打开则先打开 if(!info->save_file) { info->save_file = fopen(info->save_path, "w"); if(!info->save_file) { lprintf(MSG_ERROR, "fopen %s error: %m\n", info->save_path); return -1; } } while(total_len) { write_len = fwrite(buf, sizeof(char), len, info->save_file); if(write_len < len && errno != EINTR) { lprintf(MSG_ERROR, "fwrite error: %m\n"); return -1; } total_len -= write_len; }}/* 读数据 */int read_data(http_t *info, int len){ int total_len = len; int read_len = 0; int rtn_len = 0; while(total_len) { read_len = MIN(total_len, RECV_BUF); // lprintf(MSG_DEBUG, "need read len: %d\n", read_len); rtn_len = fread(info->buffer, sizeof(char), read_len, info->in); if(rtn_len < read_len) { if(ferror(info->in)) { if(errno == EINTR) /* 信号中断了读操作 */ { ; /* 不做处理继续往下走 */ } else if(errno == EAGAIN || errno == EWOULDBLOCK) /* 超时 */ { lprintf(MSG_ERROR, "socket recvice timeout: %dms\n", RCV_SND_TIMEOUT); total_len -= rtn_len; lprintf(MSG_DEBUG, "read len: %d\n", rtn_len); break; } else /* 其他错误 */ { lprintf(MSG_ERROR, "fread error: %m\n"); break; } } else /* 读到文件尾 */ { lprintf(MSG_ERROR, "socket closed by peer\n"); total_len -= rtn_len; lprintf(MSG_DEBUG, "read len: %d\n", rtn_len); break; } } // lprintf(MSG_DEBUG, " %s\n", info->buffer); total_len -= rtn_len; lprintf(MSG_DEBUG, "read len: %d\n", rtn_len); if(-1 == save_data(info, info->buffer, rtn_len)) { return -1; } info->recv_data_len += rtn_len; } if(total_len != 0) { lprintf(MSG_ERROR, "we need to read %d bytes, but read %d bytes now\n", len, len - total_len); return -1; }}/* 接收服务器发回的chunked数据 */int recv_chunked_response(http_t *info){ long part_len; //有chunked，content length就没有了 do{ // 获取这一个部分的长度 fgets(info->buffer, RECV_BUF, info->in); part_len = strtol(info->buffer, NULL, 16); lprintf(MSG_DEBUG, "part len: %ld\n", part_len); if(-1 == read_data(info, part_len)) return -1; //读走后面的\r\n两个字符 if(2 != fread(info->buffer, sizeof(char), 2, info->in)) { lprintf(MSG_ERROR, "fread \\r\\n error : %m\n"); return -1; } }while(part_len); return 0;}/* 计算平均下载速度，单位byte/s */float calc_download_speed(http_t *info){ int diff_time = 0; float speed = 0.0; diff_time = info->end_recv_time - info->start_recv_time; /* 最小间隔1s，避免计算浮点数结果为inf */ if(0 == diff_time) diff_time = 1; speed = (float)info->recv_data_len / diff_time; return speed;}/* 接收服务器的响应数据 */int recv_response(http_t *info){ int len = 0, total_len = info->len; if(info->chunked_flag) return recv_chunked_response(info); if(-1 == read_data(info, total_len)) return -1; return 0;}/* 清理操作 */void clean_up(http_t *info){ if(info->in) fclose(info->in); if(-1 != info->sock) close(info->sock); if(info->save_file) fclose(info->save_file); if(info) free(info);}/* 下载主函数 */int http_download(char *url, char *save_path){ http_t *info = NULL; char tmp[URI_MAX_LEN] = {0}; if(!url || !save_path) return -1; //初始化结构体 info = malloc(sizeof(http_t)); if(!info) { lprintf(MSG_ERROR, "malloc failed\n"); return -1; } memset(info, 0x0, sizeof(http_t)); info->sock = -1; info->save_path = save_path; // 解析url if(-1 == parser_URL(url, info)) goto failed; // 连接到server if(-1 == connect_server(info)) goto failed; // 发送http请求报文 if(-1 == send_request(info)) goto failed; // 接收响应的头信息 info->in = fdopen(info->sock, "r"); if(!info->in) { lprintf(MSG_ERROR, "fdopen error\n"); goto failed; } // 解析头部 if(-1 == parse_http_header(info)) goto failed; switch(info->status_code) { case HTTP_OK: // 接收数据 lprintf(MSG_DEBUG, "recv data now\n"); info->start_recv_time = time(0); if(-1 == recv_response(info)) goto failed; info->end_recv_time = time(0); lprintf(MSG_INFO, "recv %d bytes\n", info->recv_data_len); lprintf(MSG_INFO, "Average download speed: %.2fKB/s\n", calc_download_speed(info)/1000); break; case HTTP_REDIRECT: // 重启本函数 lprintf(MSG_INFO, "redirect: %s\n", info->location); strncpy(tmp, info->location, URI_MAX_LEN - 1); clean_up(info); return http_download(tmp, save_path); case HTTP_NOT_FOUND: // 退出 lprintf(MSG_ERROR, "Page not found\n"); goto failed; break; default: lprintf(MSG_INFO, "Not supported http code %d\n", info->status_code); goto failed; } clean_up(info); return 0;failed: clean_up(info); return -1;}/****************************************************************************测试用例:(1)chunked接收测试./a.out "http://www.httpwatch.com/httpgallery/chunked/chunkedimage.aspx" test.aspx(2)重定向测试./a.out "192.168.10.1/main.html" test.txt(3)错误输入测试./a.out "32131233" test.txt(4)根目录输入测试./a.out "www.baidu.com/" test.txt(5)端口号访问测试./a.out "192.168.0.200:8000/FS_AC6V1.0BR_V15.03.4.12_multi_TD01.bin" test.txt****************************************************************************/int main(int argc, char *argv[]){ if(argc < 3) return -1; http_download(argv[1], argv[2]); return 0;}
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