C
Scenarios
To use C to call an API through App authentication, obtain the C SDK, and then call the API by referring to the API calling example.
Prerequisites
- You have obtained API calling information. For details, see Preparations.
- Install the OpenSSL library.
apt-get install libssl-dev
- Install the curl library.
apt-get install libcurl4-openssl-dev
Obtaining the SDK
Old version: Log in to the ROMA Connect console, choose API Connect > API Calling > SDKs, and download the SDK.
New version: Log in to the ROMA Connect console, choose API Connect > Credentials > SDKs, and download the SDK.
The following shows the directory structure after the decompression.
Name |
Description |
---|---|
signer_common.c |
SDK code |
signer_common.h |
|
signer.c |
|
signer.h |
|
Makefile |
Makefile file |
main.c |
Sample code |
API Calling Example
- Add the following references to main.c:
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <curl/curl.h> #include "signer.h"
- Generate a variable of the sig_params_t type and enter the key and secret of the authorized credential. For details, see Obtaining API Calling Information.
sig_params_t params; sig_params_init(¶ms); // Directly writing AK/SK in code is risky. For security, encrypt your AK/SK and store them in the configuration file or environment variables. // In this example, the AK/SK are stored in environment variables for identity authentication. Before running this example, set environment variables HUAWEICLOUD_SDK_AK and HUAWEICLOUD_SDK_SK. sig_str_t app_key = sig_str(getenv("HUAWEICLOUD_SDK_AK")); sig_str_t app_secret = sig_str(getenv("HUAWEICLOUD_SDK_SK")); params.key = app_key; params.secret = app_secret;
- Specify the method, domain name, request URI, query strings, and request body. For details about how to obtain the information, see Obtaining API Calling Information
sig_str_t host = sig_str("c967a237-cd6c-470e-906f-a8655461897e.apigw.exampleRegion.com"); sig_str_t method = sig_str("GET"); sig_str_t uri = sig_str("/app1"); sig_str_t query_str = sig_str("a=1&b=2"); sig_str_t payload = sig_str(""); params.host = host; params.method = method; params.uri = uri; params.query_str = query_str; params.payload = payload;
- Add the x-stage header to the request to specify the environment. Add other headers to sign as required.
sig_headers_add(¶ms.headers, "x-stage", "RELEASE");
- Execute the following function to add the generated headers as request variables.
sig_sign(¶ms);
- 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 = malloc(1); resp_header.size = 0; struct MemoryStruct resp_body; resp_body.memory = malloc(1); resp_body.size = 0; curl_global_init(CURL_GLOBAL_ALL); curl = curl_easy_init(); curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, params.method.data); char url[1024]; sig_snprintf(url, 1024, "http://%V%V?%V", ¶ms.host, ¶ms.uri, ¶ms.query_str); curl_easy_setopt(curl, CURLOPT_URL, url); struct curl_slist *chunk = NULL; for (int i = 0; i < params.headers.len; i++) { char header[1024]; sig_snprintf(header, 1024, "%V: %V", ¶ms.headers.data[i].name, ¶ms.headers.data[i].value); printf("%s\n", header); chunk = curl_slist_append(chunk, header); } printf("-------------\n"); curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk); curl_easy_setopt(curl, CURLOPT_POSTFIELDS, params.payload.data); 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(); //free signature params sig_params_free(¶ms); return 0; }
- Run the make command to obtain a main file, execute the file, and then view the execution result.
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