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https://github.com/mrtazz/restclient-cpp

C++ client for making HTTP/REST requests
https://github.com/mrtazz/restclient-cpp

c-plus-plus http http-client libcurl packagecloud rest rest-client restclient

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C++ client for making HTTP/REST requests

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# REST client for C++

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## About

This is a simple REST client for C++. It wraps [libcurl][] for HTTP requests.



## Usage

restclient-cpp provides two ways of interacting with REST endpoints. There is

a simple one, which doesn't need you to configure an object to interact with

an API. However the simple way doesn't provide a lot of configuration options

either. So if you need more than just a simple HTTP call, you will probably

want to check out the advanced usage.



### Simple Usage

The simple API is just some static methods modeled after the most common HTTP

verbs:



```cpp

#include "restclient-cpp/restclient.h"



RestClient::Response r = RestClient::get("http://url.com")

RestClient::Response r = RestClient::post("http://url.com/post", "application/json", "{\"foo\": \"bla\"}")

RestClient::Response r = RestClient::put("http://url.com/put", "application/json", "{\"foo\": \"bla\"}")

RestClient::Response r = RestClient::patch("http://url.com/patch", "application/json", "{\"foo\": \"bla\"}")

RestClient::Response r = RestClient::del("http://url.com/delete")

RestClient::Response r = RestClient::head("http://url.com")

RestClient::Response r = RestClient::options("http://url.com")

```



The response is of type [RestClient::Response][restclient_response] and has

three attributes:



```cpp

RestClient::Response.code // HTTP response code

RestClient::Response.body // HTTP response body

RestClient::Response.headers // HTTP response headers

```



### Advanced Usage

However if you want more sophisticated features like connection reuse,

timeouts or authentication, there is also a different, more configurable way.



```cpp

#include "restclient-cpp/connection.h"

#include "restclient-cpp/restclient.h"



// initialize RestClient

RestClient::init();



// get a connection object

RestClient::Connection* conn = new RestClient::Connection("http://url.com");



// configure basic auth

conn->SetBasicAuth("WarMachine68", "WARMACHINEROX");



// set connection timeout to 5s

conn->SetTimeout(5);



// set custom user agent

// (this will result in the UA "foo/cool restclient-cpp/VERSION")

conn->SetUserAgent("foo/cool");



// enable following of redirects (default is off)

conn->FollowRedirects(true);

// and limit the number of redirects (default is -1, unlimited)

conn->FollowRedirects(true, 3);



// set headers

RestClient::HeaderFields headers;

headers["Accept"] = "application/json";

conn->SetHeaders(headers)



// append additional headers

conn->AppendHeader("X-MY-HEADER", "foo")



// if using a non-standard Certificate Authority (CA) trust file

conn->SetCAInfoFilePath("/etc/custom-ca.crt")



RestClient::Response r = conn->get("/get")

RestClient::Response r = conn->head("/get")

RestClient::Response r = conn->del("/delete")

RestClient::Response r = conn->options("/options")



// set different content header for POST, PUT and PATCH

conn->AppendHeader("Content-Type", "application/json")

RestClient::Response r = conn->post("/post", "{\"foo\": \"bla\"}")

RestClient::Response r = conn->put("/put", "application/json", "{\"foo\": \"bla\"}")

RestClient::Response r = conn->patch("/patch", "text/plain", "foobar")



// deinit RestClient. After calling this you have to call RestClient::init()

// again before you can use it

RestClient::disable();

```



The responses are again of type [RestClient::Response][restclient_response]

and have three attributes:



```cpp

RestClient::Response.code // HTTP response code

RestClient::Response.body // HTTP response body

RestClient::Response.headers // HTTP response headers

```



The connection object also provides a simple way to get some diagnostics and

metrics information via `conn->GetInfo()`. The result is a

`RestClient::Connection::Info` struct and looks like this:



```cpp

typedef struct {

  std::string base_url;

  RestClients::HeaderFields headers;

  int timeout;

  struct {

    std::string username;

    std::string password;

  } basicAuth;



  std::string certPath;

  std::string certType;

  std::string keyPath;

  std::string keyPassword;

  std::string customUserAgent;

  std::string uriProxy;

  struct {

    // total time of the last request in seconds Total time of previous

    // transfer. See CURLINFO_TOTAL_TIME

    int totalTime;

    // time spent in DNS lookup in seconds Time from start until name

    // resolving completed. See CURLINFO_NAMELOOKUP_TIME

    int nameLookupTime;

    // time it took until Time from start until remote host or proxy

    // completed. See CURLINFO_CONNECT_TIME

    int connectTime;

    // Time from start until SSL/SSH handshake completed. See

    // CURLINFO_APPCONNECT_TIME

    int appConnectTime;

    // Time from start until just before the transfer begins. See

    // CURLINFO_PRETRANSFER_TIME

    int preTransferTime;

    // Time from start until just when the first byte is received. See

    // CURLINFO_STARTTRANSFER_TIME

    int startTransferTime;

    // Time taken for all redirect steps before the final transfer. See

    // CURLINFO_REDIRECT_TIME

    int redirectTime;

    // number of redirects followed. See CURLINFO_REDIRECT_COUNT

    int redirectCount;

  } lastRequest;

} Info;

```



#### Persistent connections/Keep-Alive

The connection object stores the curl easy handle in an instance variable and

uses that for the lifetime of the object. This means curl will [automatically

reuse connections][curl_keepalive] made with that handle.



### Progress callback



Two wrapper functions are provided to setup the progress callback for uploads/downloads. 



Calling `conn->SetFileProgressCallback(callback)` with a callback parameter matching the prototype `int progress_callback(void *clientp, double dltotal, double dlnow, double ultotal, double ulnow)` will setup the progress callback.



Calling `conn->SetFileProgressCallbackData(data)` is optional. This will set the data pointer which is the first parameter fed back to the progress callback - `clientp`. If this isn't set then `clientp` will default to the connection object `conn`.



```cpp

// set CURLOPT_NOPROGRESS

// set CURLOPT_PROGRESSFUNCTION

conn->SetFileProgressCallback(progressFunc);

// set CURLOPT_PROGRESSDATA

conn->SetFileProgressCallbackData(data);

```



### Write callback



A write callback function can be provided for processing data as it's received from a GET call (for instance the [Kubernetes Watch API](https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes)).



Calling `conn->SetWriteFunction(callback)` with a function parameter matching the prototype `size_t write_function(void *data, size_t size, size_t nmemb, void *userdata)int progress_callback(void *clientp, double dltotal, double dlnow, double ultotal, double ulnow)` will setup the write function.



Here is an example of a write callback function, processing result data line by line.



```cpp

auto writeCallback = [](void *data, size_t size, size_t nmemb, void *userdata) -> size_t

{

  size_t bytes = size * nmemb;

  try

  {

      // Add to the buffer

      auto res = reinterpret_cast(userdata);

      res->body.append(static_cast(data), bytes);

      // If the last character is not a new line, wait for the rest.

      if ('\n' != *(res->body.end() - 1))

      {

          return bytes;

      }

      // Process data one line at a time.

      std::stringstream stream(res->body);

      std::string line;

      while (std::getline(stream, line))

      {

        // Do something with the line here...

      }

      // Done processing the line

      res->body.clear();

  }

  catch(std::exception e)

  {

      // Log caught exception here

      return 0;

  }

  return bytes;

};

```



## Error handling

When restclient-cpp encounters an error, generally the error (or "status") code is returned in the `Response` (see

[Response struct in restclient.h](https://github.com/mrtazz/restclient-cpp/blob/master/include/restclient-cpp/restclient.h)). This error code can be either

an [HTTP error code](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status), or if a lower-level cURL error was encountered, it may be

a [CURLCode](https://curl.haxx.se/libcurl/c/libcurl-errors.html). Currently, libcurl only defines 92 error codes, which means

there is no overlap between cURL error codes and HTTP response codes (which start at 1xx). However, if in the future, libcurl defines more than 99

error codes, meaning that cURL errors overlap with the HTTP 1xx class of responses, restclient-cpp will return a -1 if the CURLCode is 100 or higher.

In this case, callers can use `GetInfo().lastRequest.curlCode` to inspect the actual cURL error.



## Thread Safety

restclient-cpp leans heavily on libcurl as it aims to provide a thin wrapper

around it. This means it adheres to the basic level of thread safety [provided

by libcurl][curl_threadsafety]. The `RestClient::init()` and

`RestClient::disable()` methods basically correspond to `curl_global_init` and

`curl_global_cleanup` and thus need to be called right at the beginning of

your program and before shutdown respectively. These set up the environment

and are **not thread-safe**. After that you can create connection objects in

your threads. Do not share connection objects across threads as this would

mean accessing curl handles from multiple threads at the same time which is

not allowed.



The connection level method SetNoSignal can be set to skip all signal handling. This is important in multi-threaded applications as DNS resolution timeouts use signals. The signal handlers quite readily get executed on other threads. Note that with this option DNS resolution timeouts do not work. If you have crashes in your multi-threaded executable that appear to be in DNS resolution, this is probably why.



In order to provide an easy to use API, the simple usage via the static

methods implicitly calls the curl global functions and is therefore also **not

thread-safe**.



## HTTPS User Certificate



Simple wrapper functions are provided to allow clients to authenticate using certificates.

Under the hood these wrappers set cURL options, e.g. `CURLOPT_SSLCERT`, using `curl_easy_setopt`.

Note: currently `libcurl` compiled with `gnutls` (e.g. `libcurl4-gnutls-dev` on

ubuntu) is buggy in that it returns a wrong error code when these options are set to invalid values.



```cpp

// set CURLOPT_SSLCERT

conn->SetCertPath(certPath);

// set CURLOPT_SSLCERTTYPE

conn->SetCertType(type);

// set CURLOPT_SSLKEY

conn->SetKeyPath(keyPath);

// set CURLOPT_KEYPASSWD

conn->SetKeyPassword(keyPassword);

```



## HTTP Proxy Tunneling Support



An HTTP Proxy can be set to use for the upcoming request.

To specify a port number, append :[port] to the end of the host name. If not specified, `libcurl` will default to using port 1080 for proxies. The proxy string may be prefixed with `http://` or `https://`. If no HTTP(S) scheme is specified, the address provided to `libcurl` will be prefixed with `http://` to specify an HTTP proxy. A proxy host string can embedded user + password.

The operation will be tunneled through the proxy as curl option `CURLOPT_HTTPPROXYTUNNEL` is enabled by default.

A numerical IPv6 address must be written within [brackets].



```cpp

// set CURLOPT_PROXY

conn->SetProxy("https://37.187.100.23:3128");

/* or you can set it without the protocol scheme and

http:// will be prefixed by default */

conn->SetProxy("37.187.100.23:3128");

/* the following request will be tunneled through the proxy */

RestClient::Response res = conn->get("/get");

```



## Unix Socket Support



- https://docs.docker.com/develop/sdk/examples/

- $ curl --unix-socket /var/run/docker.sock http:/v1.24/containers/json



Note that the URL used with a unix socket has only ONE leading forward slash.



```cpp

RestClient::Connection* conn = new RestClient::Connection("http:/v1.30");

conn->SetUnixSocketPath("/var/run/docker.sock");

RestClient::HeaderFields headers;

headers["Accept"] = "application/json; charset=UTF-8";

headers["Expect"] = "";

conn->SetHeaders(headers);

auto resp = conn->get("/images/json");

```



## Dependencies

- [libcurl][]



## Installation

There are some packages available for Linux on [packagecloud][packagecloud].

And for OSX you can get it from the mrtazz/oss homebrew tap:



```bash

brew tap mrtazz/oss

brew install restclient-cpp

```



Otherwise you can do the regular autotools dance:



```bash

./autogen.sh

./configure

make install

```



Alternatively, you can build and install restclient-cpp using [vcpkg](https://github.com/microsoft/vcpkg/) dependency manager:



```bash

git clone https://github.com/Microsoft/vcpkg.git

cd vcpkg

./bootstrap-vcpkg.sh

./vcpkg integrate install

./vcpkg install restclient-cpp

```



The restclient-cpp port in vcpkg is kept up to date by Microsoft team members and community contributors.

If the version is out of date, please [create an issue or pull request](https://github.com/Microsoft/vcpkg) on the vcpkg repository.



## Contribute

All contributions are highly appreciated. This includes filing issues,

updating documentation and writing code. Please take a look at the

[contributing guidelines][contributing] before so your contribution can be

merged as fast as possible.



[libcurl]: http://curl.haxx.se/libcurl/

[gtest]: http://code.google.com/p/googletest/

[packagecloud]: https://packagecloud.io/mrtazz/restclient-cpp

[contributing]: https://github.com/mrtazz/restclient-cpp/blob/master/.github/CONTRIBUTING.md

[curl_keepalive]: http://curl.haxx.se/docs/faq.html#What_about_Keep_Alive_or_persist

[curl_threadsafety]: http://curl.haxx.se/libcurl/c/threadsafe.html

[restclient_response]: http://code.mrtazz.com/restclient-cpp/ref/struct_rest_client_1_1_response.html