C++ Signing Guide

Preparing the Environment

This section uses Linux Ubuntu as an example. Before calling APIs, install the required SSL tools.

Install the OpenSSL library.
```
apt-get install libssl-dev
```
Install the curl library.
```
apt-get install libcurl4-openssl-dev
```

Obtaining the SDK

Decompress the downloaded package to the current folder. The following table shows the directory structure.

Name	Description
hasher.cpp	SDK code
hasher.h
header.h
RequestParams.cpp
RequestParams.h
signer.cpp
signer.h
constants.h
Makefile	Makefile file
main.cpp	Sample code

Request Signing and API Calling

After the calling information is modified, the sample code can be directly called. For details about the calling information, see Preparations.

Add the following references to main.cpp:

      
           #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include "signer.h"

Generate a new signer and enter the AK and SK.

In this example, the AK and SK stored in the environment variables are used. Specify the environment variables CLOUD_SDK_AK and CLOUD_SDK_SK in the local environment first. The following uses Linux as an example to describe how to set the obtained AK/SK as environment variables.
1. Open the terminal and run the following command to open the environment variable configuration file:
  vi ~/.bashrc
2. Set environment variables, save the file, and exit the editor.
```
export CLOUD_SDK_AK="Obtained AK"
export CLOUD_SDK_SK="Obtained SK"
```
3. Run the following command to apply the modification:
  source ~/.bashrc

Generate a new signer and enter the configured environment variables.

        
             //Set the AK/SK to sign and authenticate the request.
Signer signer(getenv("CLOUD_SDK_AK"), getenv("CLOUD_SDK_SK"));

Generate a new RequestParams request, and specify the method, domain name, request URI, query strings, and request body.

      
           //Specify a request method, such as GET, PUT, POST, DELETE, HEAD, and PATCH.
//Set a request URL.
//Set parameters for the request URL.
//Add a body if you have specified the PUT or POST method. Special characters, such as the double quotation mark ("), contained in the body must be escaped.
RequestParams* request = new RequestParams("GET", "service.region.example.com", "/v1/{project_id}/vpcs",
        "limit=2", "");

Add other headers required for request signing or other purposes. For example, add the X-Project-Id header in multi-project scenarios or the X-Domain-Id header for a global service.

      
           //Add header parameters, for example, X-Domain-Id for invoking a global service and X-Project-Id for invoking a project-level service.
request->addHeader("X-Project-Id", "xxx");

Execute the following function to add the generated headers as request variables.
1

signer.createSignature(request);

Use the curl library to access the API and view the access result.

      
       
         
         
           static size_t
WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
    size_t realsize = size * nmemb;
    struct MemoryStruct *mem = (struct MemoryStruct *)userp;

    mem->memory = (char*)realloc(mem->memory, mem->size + realsize + 1);
    if (mem->memory == NULL) {
        /* out of memory! */
        printf("not enough memory (realloc returned NULL)\n");
        return 0;
    }

    memcpy(&(mem->memory[mem->size]), contents, realsize);
    mem->size += realsize;
    mem->memory[mem->size] = 0;

    return realsize;
}

//send http request using curl library
int perform_request(RequestParams* request)
{
    CURL *curl;
    CURLcode res;
    struct MemoryStruct resp_header;
    resp_header.memory = (char*)malloc(1);
    resp_header.size = 0;
    struct MemoryStruct resp_body;
    resp_body.memory = (char*)malloc(1);
    resp_body.size = 0;

    curl_global_init(CURL_GLOBAL_ALL);
    curl = curl_easy_init();

    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, request->getMethod().c_str());
    std::string url = "http://" + request->getHost() + request->getUri() + "?" + request->getQueryParams();
    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
    struct curl_slist *chunk = NULL;
    std::set<Header>::iterator it;
    for (auto header : *request->getHeaders()) {
        std::string headerEntry = header.getKey() + ": " + header.getValue();
        printf("%s\n", headerEntry.c_str());
        chunk = curl_slist_append(chunk, headerEntry.c_str());
    }
    printf("-------------\n");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
    curl_easy_setopt(curl, CURLOPT_COPYPOSTFIELDS, request->getPayload().c_str());
    curl_easy_setopt(curl, CURLOPT_NOBODY, 0L);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl, CURLOPT_HEADERDATA, (void *)&resp_header);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&resp_body);
    //curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
    res = curl_easy_perform(curl);
    if (res != CURLE_OK) {
        fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
    }
    else {
        long status;
        curl_easy_getinfo(curl, CURLINFO_HTTP_CODE, &status);
        printf("status %d\n", status);
        printf(resp_header.memory);
        printf(resp_body.memory);
    }
    free(resp_header.memory);
    free(resp_body.memory);
    curl_easy_cleanup(curl);

    curl_global_cleanup();

    return 0;
}

          

        

      
     