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API Gateway
API Gateway
- What's New
- Function Overview
- Product Bulletin
- Service Overview
- Getting Started
-
User Guide
- Overview
- Gateway Management
- API Group Management
- API Management
- Request Throttling
- Access Control
- Environment Management
- Signature Key Management
- VPC Channel Management
- Custom Authorizers
- Plug-ins
- Monitoring
- App Management
- Log Analysis
- SDKs
- Calling Published APIs
- Permissions Management
- Key Operations Recorded by CTS
-
Developer Guide
- Overview
- Authentication Mode Selection
- Calling APIs Through App Authentication
- Calling APIs Through IAM Authentication
- Creating a Function for Frontend Custom Authentication
- Creating a Function for Backend Custom Authentication
- Creating Signatures for Backend Requests
-
Importing and Exporting APIs
- Restrictions and Compatibility
- Extended Definition
- API Import Precautions
- Examples of Importing APIs
- API Export Precautions
-
API Reference
- Before You Start
- Calling APIs
-
Dedicated Gateway APIs (V2)
- API Group Management
- Environment Management
- Environment Variable Management
- Request Throttling Policy Management
-
API Management
- Registering an API
- Modifying an API
- Deleting an API
- Publishing an API or Taking an API Offline
- Querying API Details
- Querying APIs
- Debugging an API
- Publishing APIs or Taking APIs Offline
- Querying Historical Versions of an API
- Switching the Version of an API
- Querying the Runtime Definition of an API
- Querying API Version Details
- Taking an API Version Offline
- Signature Key Management
- Binding/Unbinding Signature Keys
- Binding/Unbinding Request Throttling Policies
- Excluded Request Throttling Configuration
- App Authorization Management
- Resource Query
- App Management
- Domain Name Management
- Access Control Policy Management
- Binding/Unbinding Access Control Policies
- Custom Authorizer Management
- API Import and Export
- VPC Channel Management
- Monitoring Information Query
- Group Response Management
- Tag Management
- Gateway Feature Management
- Configuration Management
-
Gateway Management
- Creating a Dedicated Gateway
- Querying Dedicated Gateway Details
- Updating a Dedicated Gateway
- Querying the Creation Progress of a Dedicated Gateway
- Updating or Binding an EIP to a Dedicated Gateway
- Unbinding the EIP of a Dedicated Gateway
- Enabling Public Access for a Dedicated Gateway
- Updating the Outbound Access Bandwidth of a Dedicated Gateway
- Disabling Public Access for a Dedicated Gateway
- Querying AZs
- Querying Dedicated Gateways
- Deleting a Dedicated Gateway
- Permissions Policies and Supported Actions
- Appendix
- Change History
- SDK Reference
- Best Practices
-
FAQs
- Common FAQs
-
API Creation
- Why Can't I Create APIs?
- How Do I Define Response Codes for an API?
- How Do I Specify the Host Port for a VPC Channel (or Load Balance Channel)?
- How Do I Set the Backend Address If I Will Not Use a VPC Channel (or Load Balance Channel)?
- How Can I Configure the Backend Service Address?
- Can I Specify a Private Network Load Balancer Address for the Backend Service?
- Can I Specify the Backend Address as a Subnet IP Address?
- Does APIG Support Multiple Backend Endpoints?
- What Should I Do After Applying for an Independent Domain Name?
- Can I Bind Private Domain Names for API Access?
- Why Does an API Failed to Be Called Across Domains?
-
API Calling
- What Are the Possible Causes for an API Calling Failure?
- What Should I Do If an Error Code Is Returned During API Calling?
- Why Am I Seeing the Error Message "414 Request-URI Too Large" When I Call an API?
- What Should I Do If "The API does not exist or has not been published in the environment." Is Displayed?
- Why Am I Seeing the Message "No backend available"?
- What Are the Possible Causes If the Message "Backend unavailable" or "Backend timeout" Is Displayed?
- Why Am I Seeing the Message "Backend domain name resolution failed" When a Backend Service Is Called?
- Why Doesn't Modification of the backend_timeout Parameter Take Effect?
- How Do I Switch the Environment for API Calling?
- What Is the Maximum Size of an API Request Package?
- How Do I Perform App Authentication in iOS System?
- Why Can't I Create a Header Parameter Named x-auth-token for an API Called Through IAM Authentication?
- App FAQs
- Can Mobile Apps Call APIs?
- Can Applications Deployed in a VPC Call APIs?
- How Do I Implement WebSocket Data Transmission?
- Does APIG Support Persistent Connections?
- How Will the Requests for an API with Multiple Backend Policies Be Matched and Executed?
- Is There a Limit on the Size of the Response to an API Request?
- How Can I Access Backend Services over Public Networks Through APIG?
-
API Authentication
- Does APIG Support HTTPS Two-Way Authentication?
- How Do I Call an API That Does Not Require Authentication?
- Which TLS Versions Does APIG Support?
- Does APIG Support Custom Authentication?
- Will the Request Body Be Signed for Security Authentication?
- Common Errors Related to IAM Authentication Information
- API Control Policies
- API Publishing
- API Import and Export
- API Security
-
Other FAQs
- What Are the Relationships Between an API, Environment, and App?
- How Can I Use APIG?
- What SDK Languages Does APIG Support?
- Can I Upload Files Using the POST Method?
- What Are the Error Messages Returned by APIG Like?
- How Do I Use APIG to Open Up Services Deployed on Huawei Cloud?
- Can APIG Be Deployed in a Local Data Center?
- Videos
On this page
C
Updated on 2023-04-06 GMT+08:00
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.
Preparing the Environment
- Obtain the domain name, request URL, and request method of the API to be called, and the AppKey and AppSecret of the app for calling the API. For more information, see Preparation.
- Install the OpenSSL library.
apt-get install libssl-dev
- Install the curl library.
apt-get install libcurl4-openssl-dev
Obtaining the SDK
Log in to the APIG console, and download the SDK on the SDKs page by referring to section "SDKs" in the User Guide.
The following table shows the files decompressed from the package.
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 sig_params_t variable, and enter the AppKey and AppSecret.
sig_params_t params; sig_params_init(¶ms); sig_str_t app_key = sig_str("4f5f626b-073f-402f-a1e0-e52171c6100c"); sig_str_t app_secret = sig_str("******"); params.key = app_key; params.secret = app_secret;
- Specify the method, domain name, request URI, query strings, and request body.
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 an environment name. Add other headers to be signed as necessary.
sig_headers_add(¶ms.headers, "x-stage", "RELEASE");
- Execute the following function to add the generated headers to the request variable.
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 executable file, execute the file, and then view the execution result.
Parent topic: Calling APIs Through App Authentication
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