大家好，我是冲哥。
本次给大家分享一个C语言实现http的下载器。比如做OTA升级功能时，我们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。
这里分享一个：
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DNS
3、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：
- 太多错误处理，让代码看起来不太舒服
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：
代码语言：javascript复制/************************************************************
Copyright (C), 2016, Leon, All Rights Reserved.
FileName: download.c
coding: UTF-8
Description: 实现简单的http下载功能
Author: Leon
Version: 1.0
Date: 2016-12-2 10:49:32
Function:
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 0x04
static 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 invaildn");
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] = ' ';
if((tmp = strchr(start, ':')) && tmp < end)
{
info->port = atoi(tmp 1);
if(info->port <= 0 || info->port >= 65535)
{
lprintf(MSG_ERROR, "url port invaildn");
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] = ' ';
}
/* 复制uri */
start = end;
strncpy(info->uri, start, URI_MAX_LEN - 1);
lprintf(MSG_INFO, "parse url oknhost:%s, port:%d, uri:%sn",
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 failedn", host_name);
return -1;
}
pp = host->h_addr_list;
if (*pp!=NULL)
{
addr.s_addr = *((unsigned int *)*pp);
lprintf(MSG_INFO, "%s address is %sn", 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_TIMEOUT00*1000;
lprintf(MSG_DEBUG, "%ds %dusn", (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: %mn");
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: %mn");
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 failedn");
goto failed;
}
if(-1 == set_socket_option(sockfd))
{
goto failed;
}
if ((addr = dns(info->host_name)) == -1)
{
lprintf(MSG_ERROR, "Get Dns Failedn");
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: %mn");
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/1.1rn"
"Accept: */*rn"
"User-Agent: Mozilla/5.0 (compatible; MSIE 5.01; Windows NT 5.0)rn"
"Host: %srn"
"Connection: Closernrn", info->uri, info->host_name);
lprintf(MSG_DEBUG, "request:n%sn", 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 headn");
return -1;
}
info->status_code = atoi(p 1);
lprintf(MSG_DEBUG, "http status code: %dn", 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, "rn"))
{
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: %dn", 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: %sn", info->location);
}
}
lprintf(MSG_ERROR, "bad http headn");
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: %mn", 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: %mn");
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: %dn", 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: %dmsn", RCV_SND_TIMEOUT);
total_len -= rtn_len;
lprintf(MSG_DEBUG, "read len: %dn", rtn_len);
break;
}
else /* 其他错误 */
{
lprintf(MSG_ERROR, "fread error: %mn");
break;
}
}
else /* 读到文件尾 */
{
lprintf(MSG_ERROR, "socket closed by peern");
total_len -= rtn_len;
lprintf(MSG_DEBUG, "read len: %dn", rtn_len);
break;
}
}
// lprintf(MSG_DEBUG, " %sn", info->buffer);
total_len -= rtn_len;
lprintf(MSG_DEBUG, "read len: %dn", 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 nown",
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: %ldn", part_len);
if(-1 == read_data(info, part_len))
return -1;
//读走后面的rn两个字符
if(2 != fread(info->buffer, sizeof(char), 2, info->in))
{
lprintf(MSG_ERROR, "fread \r\n error : %mn");
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 failedn");
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 errorn");
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 nown");
info->start_recv_time = time(0);
if(-1 == recv_response(info))
goto failed;
info->end_recv_time = time(0);
lprintf(MSG_INFO, "recv %d bytesn", info->recv_data_len);
lprintf(MSG_INFO, "Average download speed: %.2fKB/sn",
calc_download_speed(info)/1000);
break;
case HTTP_REDIRECT:
// 重启本函数
lprintf(MSG_INFO, "redirect: %sn", 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 foundn");
goto failed;
break;
default:
lprintf(MSG_INFO, "Not supported http code %dn", 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;
}
版权声明：本文为CSDN博主「普朗克常量」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/u013401853/article/details/53434167
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