使用libcurl进行基于http get/post模式的C语言交互应用开发
简介
大多数在linux下的开发者，都会用到curl这个命令行工具。对于进行restful api的测试等，非常方便。其实，这个工具还提供了一个C的开发库，可以很方便的在C语言开发环境下完成基于http的请求和响应交互，高效的开发基于http/smtp等的网络应用程序
c
/* 2023-08-14 更新宏定义
1. 使用可变参数，支持多项输出;
2. 去除Z中默认加上的双引号;
*/
#define X_LOG_DEBUG(Z, X...) \
printf("[%s %s] [%s.%d] [%s] [DEBUG] " Z "\n", __DATE__, __TIME__, __FILE__, __LINE__, __FUNCTION__, ##X)环境准备
下载并安装curl的开发包
bash
yum install libcurl-devel.x86_64在线资源
开发过程中主要参考CURL官方介绍及API参考文档 | link
示例代码
多余的话就不多说了，直接上示例代码，通过代码中的注释来说明开发过程。
c
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "../include/xhttp.h"
/*
- 这个是一个回调函数，主要用于curl在执行过程中，当有被请求的数据到达时，被调用来向-curl_easy_setopt设置的chunk中写入数据。
这个回调函数在curl_easy_perform执行完成前会被调用多次。当执行完成后，从chunk中取出这次交互返回的数据。
*/
static size_t cb_write_data(void *data, size_t size, size_t nmemb, void *clientp)
{
size_t realsize = size * nmemb;
http_response *mem = (http_response *)clientp;
char *ptr = realloc(mem->response, mem->size + realsize + 1);
if(ptr == NULL)
return 0; /* out of response_st! */
mem->response = ptr;
memcpy(&(mem->response[mem->size]), data, realsize);
mem->size += realsize;
mem->response[mem->size] = 0;
return realsize;
}
/*
这个是向外发布的一个函数，调用的方式示例如下：
char* payload = "{\"code\":\"\",\"codeUuid\":\"\",\"loginName\":\"user@domain\",\"loginPwd\":\"xxxxxxxx\"}";
http_response *resp = http_post("https://local.domain/admin-api/session/login", NULL, payload);
使用完返回数据后，记得释放resp->reesponse，避免内存漏。
*/
http_response* http_post(char* url, char* token, char* payload)
{
http_response chunk = {0};
/* 设置curl上下文，对curl实例进行初始化 */
curl_global_init(CURL_GLOBAL_ALL);
CURL *curl = curl_easy_init();
CURLcode res;
if(curl)
{
X_LOG_DEBUG("%s", "libcurl curl_easy_setopt start ...");
/* 设置curl各个参数： 请求地址 */
curl_easy_setopt(curl, CURLOPT_URL, url);
/* 设置curl各个参数： 请求方式为post */
curl_easy_setopt(curl, CURLOPT_POST, 1L);
/* 设置curl各个参数： http中的请求头部分的内容 */
X_LOG_DEBUG("%s", "libcurl curl_easy_setopt CURLOPT_HTTPHEADER start ...");
struct curl_slist *list = {0};
list = curl_slist_append(NULL, "Content-Type: application/json;charset=utf8");
list = curl_slist_append(list, "routeurl: /project/project-list");
/* 设置curl各个参数： 可选部分，如果请求中要求token，可以设置上 */
if (token != NULL)
{
char* x_access_token_str = (char*)malloc( MAX_UTMP_TOKEN_SIZE );
sprintf(x_access_token_str, "x-access-token: %s", token);
X_LOG_DEBUG("%s", x_access_token_str);
list = curl_slist_append(list, x_access_token_str);
}
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);
X_LOG_DEBUG("%s", "libcurl curl_easy_setopt CURLOPT_USERAGENT start ...");
/* some servers do not like requests that are made without a user-agent
field, so we provide one */
curl_easy_setopt(curl, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:82.0) Gecko/20100101 Firefox/82.0");
/* 设置curl各个参数： http的请求体部分，主要是请求中携带的数据 */
/* POST data */
X_LOG_DEBUG("%s", "libcurl curl_easy_setopt CURLOPT_POSTFIELDSIZE/CURLOPT_POSTFIELDS start ...");
X_LOG_DEBUG("request body data is:%s", payload);
X_LOG_DEBUG("request body len is:%d", strlen(payload));
/* size of the POST data */
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, strlen(payload));
/* pass in a pointer to the data - libcurl will not copy */
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, payload);
/* 设置curl各个参数： 重要部分，设置了返回值的回调函数和返回值的内存放置区域 */
/* RECEIVE DATA */
X_LOG_DEBUG("%s", "libcurl curl_easy_setopt CURLOPT_WRITEFUNCTION/CURLOPT_WRITEDATA start ...");
/* send all data to this function */
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, cb_write_data);
/* we pass our 'chunk' struct to the callback function */
curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
X_LOG_DEBUG("%s", "libcurl curl_easy_setopt successfully complete ...");
/* 执行curl请求，并获取返回值：CURLE_OK，表示执行成功 */
X_LOG_DEBUG("%s", "libcurl curl_easy_perform start ...");
res = curl_easy_perform(curl);
X_LOG_DEBUG("%s", "libcurl curl_easy_perform successfully complete ...");
if(res != CURLE_OK) {
fprintf(stderr, "curl_easy_perform() is failed: %s", curl_easy_strerror(res));
curl_slist_free_all(list); /* free the list again */
curl_easy_cleanup(curl);
} else {
/* 处理curl返回的数据 */
X_LOG_DEBUG("chunk size %d", chunk.size);
http_response response = {0};
response.response = (char*)malloc(1048576*5);
memset(response.response, 0, chunk.size+1);
memcpy(response.response, chunk.response, chunk.size+1);
response.size = chunk.size;
/* remember to free the buffer */
free(chunk.response);
curl_slist_free_all(list); /* free the list again */
curl_global_cleanup();
return &response;
}
}
}引用的头文件如下：
c
#ifndef __X_HTTP_H__
#define __X_HTTP_H__
#include <stdlib.h>
#include <curl/curl.h>
/* 更新宏定义 1. 使用可变参数，支持多项输出; 2. 去除Z中默认加上的双引号; */
#define X_LOG_DEBUG(Z, X...) \
printf("[%s %s] [%s.%d] [%s] [DEBUG] " Z "\n", __DATE__, __TIME__, __FILE__, __LINE__, __FUNCTION__, ##X)
#define MAX_UTMP_TOKEN_SIZE 8192
typedef struct http_response_s {
char *response;
size_t size;
} http_response;
typedef struct http_request_s {
char *request;
size_t size;
} http_request;
http_response* http_post(char* url, char* token, char* payload);
#endif测试调用
c
int main(int argc, char** argv) {
char* payload = "{\"code\":\"\",\"codeUuid\":\"\",\"loginName\":\"user@domain\",\"loginPwd\":\"xxxxxxxx\"}";
http_response *resp = http_post("https://local.domain/admin-api/session/login", NULL, payload);
printf("http_response [%d] is: %s\n", resp->size, resp->response);
char *tokenVal = strstr(resp->response, "xaccessToken");
int end = strlen(tokenVal);
*(tokenVal + end-2) = 0;
char** token_arr;
__strtok_r(tokenVal, ":", token_arr);
char* replacementKey = strtrim(token_arr[0], '\"');
exit(0)
}运行结果
bash
[Aug 11 2023 10:20:02] [src/xhttp.c.37] [http_post] [DEBUG] "libcurl curl_easy_setopt start ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.42] [http_post] [DEBUG] "libcurl curl_easy_setopt CURLOPT_HTTPHEADER start ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.55] [http_post] [DEBUG] "libcurl curl_easy_setopt CURLOPT_USERAGENT start ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.61] [http_post] [DEBUG] "libcurl curl_easy_setopt CURLOPT_POSTFIELDSIZE/CURLOPT_POSTFIELDS start ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.62] [http_post] [DEBUG] "request body data is:{"code":"","codeUuid":"","loginName":"user@domain","loginPwd":"xxxxxxxx"}"
[Aug 11 2023 10:20:02] [src/xhttp.c.63] [http_post] [DEBUG] "request body len is:75"
[Aug 11 2023 10:20:02] [src/xhttp.c.70] [http_post] [DEBUG] "libcurl curl_easy_setopt CURLOPT_WRITEFUNCTION/CURLOPT_WRITEDATA start ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.76] [http_post] [DEBUG] "libcurl curl_easy_setopt successfully complete ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.79] [http_post] [DEBUG] "libcurl curl_easy_perform start ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.81] [http_post] [DEBUG] "libcurl curl_easy_perform successfully complete ..."
[Aug 11 2023 10:20:02] [src/xhttp.c.90] [http_post] [DEBUG] "chunk size 6693"