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libhttpserver is a C++ library for building high performance RESTful web servers.libhttpserver is built uponlibmicrohttpd to provide a simple API for developers to create HTTP services in C++.

Features:

• HTTP 1.1 compatible request parser
• RESTful oriented interface
• Flexible handler API
• Cross-platform compatible
• Implementation is HTTP 1.1 compliant
• Multiple threading models
• Support for IPv6
• Support for SHOUTcast
• Support for incremental processing of POST data (optional)
• Support for basic and digest authentication (optional)
• Support for TLS (requires libgnutls, optional)

• Introduction
• Requirements
• Building
• Getting Started
• Structures and classes type definition
• Create and work with a webserver
• The resource object
• Registering resources
• Parsing requests
• Building responses to requests
• IP Blacklisting and Whitelisting
• Authentication
• HTTP Utils
• Other Examples

• Code of Conduct (on a separate page)
• Contributing (on a separate page)

• Copying statement
• GNU-LGPL: The GNU Lesser General Public License says how you can copy and share almost all of libhttpserver.
• GNU-FDL: The GNU Free Documentation License says how you can copy and share the documentation of libhttpserver.

libhttpserver is meant to constitute an easy system to build HTTP servers with REST fashion.libhttpserver is based onlibmicrohttpd and, like this, it is a daemon library (parts of this documentation are, in fact, matching those of the wrapped library).The mission of this library is to support all possible HTTP features directly and with a simple semantic allowing then the user to concentrate only on his application and not on HTTP request handling details.

The library is supposed to work transparently for the client Implementing the business logic and using the library itself to realize an interface.If the user wants it must be able to change every behavior of the library itself through the registration of callbacks.

libhttpserver is able to decode certain body formats and automatically format them in object oriented fashion. This is true for query arguments and forPOST andPUT requests bodies ifapplication/x-www-form-urlencoded ormultipart/form-data header are passed.

All functions are guaranteed to be completely reentrant and thread-safe (unless differently specified).Additionally, clients can specify resource limits on the overall number of connections, number of connections per IP address and memory used per connection to avoid resource exhaustion.

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libhttpserver can be used without any dependencies aside from libmicrohttpd.

The minimum versions required are:

• g++ >= 5.5.0 or clang-3.6
• C++17 or newer
• libmicrohttpd >= 0.9.64
• [Optionally]: for TLS (HTTPS) support, you'll needlibgnutls.
• [Optionally]: to compile the code-reference, you'll needdoxygen.

Additionally, for MinGW on windows you will need:

• libwinpthread (For MinGW-w64, if you use thread model posix then you have this)

For versions before 0.18.0, on MinGW, you will need:

• libgnurx >= 2.5.1

Furthermore, the testcases uselibcurl but you don't need it to compile the library.

Please refer to the readme file for your particular distribution if there is one for important notes.

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libhttpserver uses the standard system where the usual build process involves running

./bootstrap
mkdir build
cd build
../configure
make
make install # (optionally to install on the system)

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A complete list of parameters can be obtained running 'configure --help'.Here are listed the libhttpserver specific options (the canonical configure options are also supported).

• --enable-same-directory-build: enable to compile in the same directory. This is heavily discouraged. (def=no)
• --enable-debug: enable debug data generation. (def=no)
• --disable-doxygen-doc: don't generate any doxygen documentation. Doxygen is automatically invoked if present on the system. Automatically disabled otherwise.
• --enable-fastopen: enable use of TCP_FASTOPEN (def=yes)
• --enable-static: enable use static linking (def=yes)

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The most basic example of creating a server and handling a requests for the path/hello:

    #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:        std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("Hello, World!"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);        hello_world_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you could run the following command from a terminal:

curl -XGET -v http://localhost:8080/hello

You can also check this example ongithub.

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• webserver: Represents the daemon listening on a socket for HTTP traffic.
  • create_webserver: Builder class to support the creation of a webserver.
• http_resource: Represents the resource associated with a specific http endpoint.
• http_request: Represents the request received by the resource that process it.
• http_response: Represents the response sent by the server once the resource finished its work.
  • string_response: A simple string response.
  • file_response: A response getting content from a file.
  • basic_auth_fail_response: A failure in basic authentication.
  • digest_auth_fail_response: A failure in digest authentication.
  • deferred_response: A response getting content from a callback.

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As you can see from the example above, creating a webserver with standard configuration is quite simple:

    webserver ws = create_webserver(8080);

Thecreate_webserver class is a supportingbuilder class that eases the building of a webserver through chained syntax.

In this section we will explore other basic options that you can use when configuring your server. More advanced options (custom callbacks, https support, etc...) will be discussed separately.

• .port(int port): The port at which the server will listen. This can also be passed to the consturctor ofcreate_webserver. E.g.create_webserver(8080).
• .max_connections(int max_conns): Maximum number of concurrent connections to accept. The default isFD_SETSIZE - 4 (the maximum number of file descriptors supported byselect minus four forstdin,stdout,stderr and the server socket). In other words, the default is as large as possible. Note that if you set a low connection limit, you can easily get into trouble with browsers doing request pipelining.For example, if your connection limit is “1”, a browser may open a first connection to access your “index.html” file, keep it open but use a second connection to retrieve CSS files, images and the like. In fact, modern browsers are typically by default configured for up to 15 parallel connections to a single server. If this happens, the library will refuse to even accept the second connection until the first connection is closed — which does not happen until timeout. As a result, the browser will fail to render the page and seem to hang. If you expect your server to operate close to the connection limit, you should first consider using a lower timeout value and also possibly add a “Connection: close” header to your response to ensure that request pipelining is not used and connections are closed immediately after the request has completed.
• .content_size_limit(size_t size_limit): Sets the maximum size of the content that a client can send over in a single block. The default is-1 = unlimited.
• .connection_timeout(int timeout): Determines after how many seconds of inactivity a connection should be timed out automatically. The default timeout is180 seconds.
• .memory_limit(int memory_limit): Maximum memory size per connection (followed by asize_t). The default is 32 kB (32*1024 bytes). Values above 128k are unlikely to result in much benefit, as half of the memory will be typically used for IO, and TCP buffers are unlikely to support window sizes above 64k on most systems.
• .per_IP_connection_limit(int connection_limit): Limit on the number of (concurrent) connections made to the server from the same IP address. Can be used to prevent one IP from taking over all of the allowed connections. If the same IP tries to establish more than the specified number of connections, they will be immediately rejected. The default is0, which means no limit on the number of connections from the same IP address.
• .bind_socket(int socket_fd): Listen socket to use. Pass a listen socket for the daemon to use (systemd-style). If this option is used, the daemon will not open its own listen socket(s). The argument passed must be of type "int" and refer to an existing socket that has been bound to a port and is listening.
• .max_thread_stack_size(int stack_size): Maximum stack size for threads created by the library. Not specifying this option or using a value of zero means using the system default (which is likely to differ based on your platform). Default is0 (system default).
• .use_ipv6() and .no_ipv6(): Enable or disable the IPv6 protocol support (by default, libhttpserver will just support IPv4). If you specify this and the local platform does not support it, starting up the server will throw an exception.off by default.
• .use_dual_stack() and .no_dual_stack(): Enable or disable the support for both IPv6 and IPv4 protocols at the same time (by default, libhttpserver will just support IPv4). If you specify this and the local platform does not support it, starting up the server will throw an exception. Note that this will mean that IPv4 addresses are returned in the IPv6-mapped format (the ’structsockaddrin6’ format will be used for IPv4 and IPv6).off by default.
• .pedantic() and .no_pedantic(): Enables pedantic checks about the protocol (as opposed to as tolerant as possible). Specifically, at the moment, this flag causes the library to reject HTTP 1.1 connections without aHost header. This is required by the standard, but of course in violation of the “be as liberal as possible in what you accept” norm. It is recommended to turn thisoff if you are testing clients against the library, andon in production.off by default.
• .debug() and .no_debug(): Enables debug messages from the library.off by default.
• .regex_checking() and .no_regex_checking(): Enables pattern matching for endpoints. Read morehere.on by default.
• .post_process() and .no_post_process(): Enables/Disables the library to automatically parse the body of the http request as arguments if in querystring format. Read morehere.on by default.
• .put_processed_data_to_content() and .no_put_processed_data_to_content(): Enables/Disables the library to copy parsed body data to the content or to only store it in the arguments map.on by default.
• .file_upload_target(file_upload_target_T file_upload_target): Controls, how the library stores uploaded files. Default value isFILE_UPLOAD_MEMORY_ONLY.
  • FILE_UPLOAD_MEMORY_ONLY: The content of the file is only stored in memory. Depending onput_processed_data_to_content only as part of the arguments map or additionally in the content.
  • FILE_UPLOAD_DISK_ONLY: The content of the file is stored only in the file system. The path is created fromfile_upload_dir and either a random name (ifgenerate_random_filename_on_upload is true) or the actually uploaded file name.
  • FILE_UPLOAD_MEMORY_AND_DISK: The content of the file is stored in memory and on the file system.
• .file_upload_dir(const std::string& file_upload_dir): Specifies the directory to store all uploaded files. Default value is/tmp.
• .generate_random_filename_on_upload() and .no_generate_random_filename_on_upload(): Enables/Disables the library to generate a unique and unused filename to store the uploaded file to. Otherwise the actually uploaded file name is used.off by default.
• .deferred() and.no_deferred(): Enables/Disables the ability for the server to suspend and resume connections. Simply put, it enables/disables the ability to usedeferred_response. Read morehere.on by default.
• .single_resource() and .no_single_resource: Sets or unsets the server in single resource mode. This limits all endpoints to be served from a single resource. The resultant is that the webserver will process the request matching to the endpoint skipping any complex semantic. Because of this, the option is incompatible withregex_checking and requires the resource to be registered against an empty endpoint or the root endpoint ("/"). The resource will also have to be registered as family. (For more information on resource registration, read morehere).off by default.

• .start_method(const http::http_utils::start_method_T& start_method): libhttpserver can operate with two different threading models that can be selected through this method. Default value isINTERNAL_SELECT.
  • http::http_utils::INTERNAL_SELECT: In this mode, libhttpserver uses only a single thread to handle listening on the port and processing of requests. This mode is preferable if spawning a thread for each connection would be costly. If the HTTP server is able to quickly produce responses without much computational overhead for each connection, this mode can be a great choice. Note that libhttpserver will still start a single thread for itself -- this way, the main program can continue with its operations after calling the start method. Naturally, if the HTTP server needs to interact with shared state in the main application, synchronization will be required. If such synchronization in code providing a response results in blocking, all HTTP server operations on all connections will stall. This mode is a bad choice if response data cannot always be provided instantly. The reason is that the code generating responses should not block (since that would block all other connections) and on the other hand, if response data is not available immediately, libhttpserver will start to busy wait on it. If you need to scale along the number of concurrent connection and scale on multiple thread you can specify a value formax_threads (see below) thus enabling a thread pool - this is different fromTHREAD_PER_CONNECTION below where a new thread is spawned for each connection.
  • http::http_utils::THREAD_PER_CONNECTION: In this mode, libhttpserver starts one thread to listen on the port for new connections and then spawns a new thread to handle each connection. This mode is great if the HTTP server has hardly any state that is shared between connections (no synchronization issues!) and may need to perform blocking operations (such as extensive IO or running of code) to handle an individual connection.
• .max_threads(int max_threads): A thread pool can be combined with theINTERNAL_SELECT mode to benefit implementations that require scalability. As said before, by default this mode only uses a single thread. When combined with the thread pool option, it is possible to handle multiple connections with multiple threads. Any value greater than one for this option will activate the use of the thread pool. In contrast to theTHREAD_PER_CONNECTION mode (where each thread handles one and only one connection), threads in the pool can handle a large number of concurrent connections. UsingINTERNAL_SELECT in combination with a thread pool is typically the most scalable (but also hardest to debug) mode of operation for libhttpserver. Default value is1. This option is incompatible withTHREAD_PER_CONNECTION.

libhttpserver allows to override internal error retrieving functions to provide custom messages to the HTTP client. There are only 3 cases in which implementing logic (an http_resource) cannot be invoked: (1) a not found resource, where the library is not being able to match the URL requested by the client to any implementing http_resource object; (2) a not allowed method, when the HTTP client is requesting a method explicitly marked as not allowed (more infohere) by the implementation; (3) an exception being thrown.In all these 3 cases libhttpserver would provide a standard HTTP response to the client with the correct error code; respectively a404, a405 and a500. The library allows its user to specify custom callbacks that will be called to replace the default behavior.

• .not_found_resource(const shared_ptr<http_response>(*render_ptr)(const http_request&) resource): Specifies a function to handle a request when no matching registered endpoint exist for the URL requested by the client.
• .method_not_allowed_resource(const shared_ptr<http_response>(*render_ptr)(const http_request&) resource): Specifies a function to handle a request that is asking for a method marked as not allowed on the matching http_resource.
• .internal_error_resource(const shared_ptr<http_response>(*render_ptr)(const http_request&) resource): Specifies a function to handle a request that is causing an uncaught exception during its execution.REMEMBER: is this callback is causing an exception itself, the standard default response from libhttpserver will be reported to the HTTP client.

      #include<httpserver.hpp>usingnamespacehttpserver;      std::shared_ptr<http_response>not_found_custom(const http_request& req) {return std::shared_ptr<string_response>(newstring_response("Not found custom",404,"text/plain"));      }      std::shared_ptr<http_response>not_allowed_custom(const http_request& req) {return std::shared_ptr<string_response>(newstring_response("Not allowed custom",405,"text/plain"));      }classhello_world_resource :publichttp_resource {public:          std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("Hello, World!"));          }      };intmain(int argc,char** argv) {          webserver ws =create_webserver(8080)              .not_found_resource(not_found_custom)              .method_not_allowed_resource(not_allowed_custom);          hello_world_resource hwr;          hwr.disallow_all();          hwr.set_allowing("GET",true);          ws.register_resource("/hello", &hwr);          ws.start(true);return0;      }

To test the above example, you can run the following command from a terminal:

curl -XGET -v http://localhost:8080/hello

If you try to run either of the two following commands, you'll see your custom errors:

• curl -XGET -v http://localhost:8080/morning: will return your customnot found error.
• curl -XPOST -v http://localhost:8080/hello: will return your customnot allowed error.

You can also check this example ongithub.

• .log_access(void(*log_access_ptr)(const std::string&) functor): Specifies a function used to log accesses (requests) to the server.
• .log_error(void(*log_error_ptr)(const std::string&) functor): Specifies a function used to log errors generating from the server.

    #include<httpserver.hpp>    #include<iostream>usingnamespacehttpserver;voidcustom_access_log(const std::string& url) {        std::cout <<"ACCESSING:" << url << std::endl;    }classhello_world_resource :publichttp_resource {public:        std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("Hello, World!"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080)            .log_access(custom_access_log);        hello_world_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v http://localhost:8080/hello

You'll notice how, on the terminal runing your server, the logs will now be printed in output for each request received.

You can also check this example ongithub.

• .use_ssl() and .no_ssl(): Determines whether to run in HTTPS-mode or not. If you set this as on and libhttpserver was compiled without SSL support, the library will throw an exception at start of the server.off by default.
• .cred_type(const http::http_utils::cred_type_T& cred_type): Daemon credentials type. Either certificate or anonymous. Acceptable values are:
  • NONE: No credentials.
  • CERTIFICATE: Certificate credential.
  • ANON: Anonymous credential.
  • SRP: SRP credential.
  • PSK: PSK credential.
  • IA: IA credential.
• .https_mem_key(const std::string& filename): String representing the path to a file containing the private key to be used by the HTTPS daemon. This must be used in conjunction withhttps_mem_cert.
• .https_mem_cert(const std::string& filename): String representing the path to a file containing the certificate to be used by the HTTPS daemon. This must be used in conjunction withhttps_mem_key.
• .https_mem_trust(const std::string& filename): String representing the path to a file containing the CA certificate to be used by the HTTPS daemon to authenticate and trust clients certificates. The presence of this option activates the request of certificate to the client. The request to the client is marked optional, and it is the responsibility of the server to check the presence of the certificate if needed. Note that most browsers will only present a client certificate only if they have one matching the specified CA, not sending any certificate otherwise.
• .https_priorities(const std::string& priority_string): SSL/TLS protocol version and ciphers. Must be followed by a string specifying the SSL/TLS protocol versions and ciphers that are acceptable for the application. The string is passed unchanged to gnutls_priority_init. If this option is not specified,"NORMAL" is used.

    #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:        std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("Hello, World!"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080)            .use_ssl()            .https_mem_key("key.pem")            .https_mem_cert("cert.pem");        hello_world_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v -k 'https://localhost:8080/hello'

You can also check this example ongithub.

libhttpserver supports IP blacklisting and whitelisting as an internal feature. This section explains the startup options related with IP blacklisting/whitelisting. See thespecific section to read more about the topic.

• .ban_system() and .no_ban_system: Can be used to enable/disable the ban system.on by default.
• .default_policy(const http::http_utils::policy_T& default_policy): Specifies what should be the default behavior when receiving a request. Possible values areACCEPT andREJECT. Default isACCEPT.

• .basic_auth() and .no_basic_auth: Can be used to enable/disable parsing of the basic authorization header sent by the client.on by default.
• .digest_auth() and .no_digest_auth: Can be used to enable/disable parsing of the digested authentication data sent by the client.on by default.
• .nonce_nc_size(int nonce_size): Size of an array of nonce and nonce counter map. This option represents the size (number of elements) of a map of a nonce and a nonce-counter. If this option is not specified, a default value of 4 will be used (which might be too small for servers handling many requests).You should calculate the value of NC_SIZE based on the number of connections per second multiplied by your expected session duration plus a factor of about two for hash table collisions. For example, if you expect 100 digest-authenticated connections per second and the average user to stay on your site for 5 minutes, then you likely need a value of about 60000. On the other hand, if you can only expect only 10 digest-authenticated connections per second, tolerate browsers getting a fresh nonce for each request and expect a HTTP request latency of 250 ms, then a value of about 5 should be fine.
• .digest_auth_random(const std::string& nonce_seed): Digest Authentication nonce’s seed. For security, you SHOULD provide a fresh random nonce when actually using Digest Authentication with libhttpserver in production.

    webserver ws = create_webserver(8080)        .no_ssl()        .no_ipv6()        .no_debug()        .no_pedantic()        .no_basic_auth()        .no_digest_auth()        .no_comet()        .no_regex_checking()        .no_ban_system()        .no_post_process();

    webserver ws = create_webserver(8080)        .use_ssl()        .https_mem_key("key.pem")        .https_mem_cert("cert.pem");

Once a webserver is created, you can manage its execution through the following methods on thewebserver class:

• void webserver::start(bool blocking): Allows to start a server. If theblocking flag is passed astrue, it will block the execution of the current thread until a call to stop on the same webserver object is performed.
• void webserver::stop(): Allows to stop a server. It immediately stops it.
• bool webserver::is_running(): Checks if a server is running
• void webserver::sweet_kill(): Allows to stop a server. It doesn't guarantee an immediate halt to allow for thread termination and connection closure.

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Thehttp_resource class represents a logical collection of HTTP methods that will be associated to a URL when registered on the webserver. The class isdesigned for extension and it is where most of your code should ideally live. When the webserver matches a request against a resource (see:resource registration), the method correspondent to the one in the request (GET, POST, etc..) (see below) is called on the resource.

Given this, thehttp_resource class contains the following extensible methods (also calledhandlers orrender methods):

• std::shared_ptr<http_response> http_resource::render_GET(const http_request& req): Invoked on an HTTP GET request.
• std::shared_ptr<http_response> http_resource::render_POST(const http_request& req): Invoked on an HTTP POST request.
• std::shared_ptr<http_response> http_resource::render_PUT(const http_request& req): Invoked on an HTTP PUT request.
• std::shared_ptr<http_response> http_resource::render_HEAD(const http_request& req): Invoked on an HTTP HEAD request.
• std::shared_ptr<http_response> http_resource::render_DELETE(const http_request& req): Invoked on an HTTP DELETE request.
• std::shared_ptr<http_response> http_resource::render_TRACE(const http_request& req): Invoked on an HTTP TRACE request.
• std::shared_ptr<http_response> http_resource::render_OPTIONS(const http_request& req): Invoked on an HTTP OPTIONS request.
• std::shared_ptr<http_response> http_resource::render_CONNECT(const http_request& req): Invoked on an HTTP CONNECT request.
• std::shared_ptr<http_response> http_resource::render(const http_request& req): Invoked as a backup method if the matching method is not implemented. It can be used whenever you want all the invocations on a URL to activate the same behavior regardless of the HTTP method requested. The default implementation of therender method returns an empty response with a404.

    #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:        std::shared_ptr<http_response>render_GET(const http_request&) {return std::shared_ptr<http_response>(newstring_response("GET: Hello, World!"));        }        std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("OTHER: Hello, World!"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);        hello_world_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following commands from a terminal:

• curl -XGET -v http://localhost:8080/hello: will returnGET: Hello, World!.
• curl -XPOST -v http://localhost:8080/hello: will returnOTHER: Hello, World!. You can try requesting other methods besidePOST to verify how the same message will be returned.

You can also check this example ongithub.

By default, all methods an a resource are allowed, meaning that an HTTP request with that method will be invoked. It is possible to mark methods asnot allowed on a resource. When a method not allowed is requested on a resource, the defaultmethod_not_allowed method is invoked - the default can be overriden as explain in the sectionCustom defaulted error messages.The basehttp_resource class has a set of methods that can be used to allow and disallow HTTP methods.

• void http_resource::set_allowing(const std::string& method,bool allowed): Used to allow or disallow a method. Themethod parameter is a string representing an HTTP method (GET, POST, PUT, etc...).
• void http_resource::allow_all(): Marks all HTTP methods as allowed.
• void http_resource::disallow_all(): Marks all HTTP methods as not allowed.

      #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:          std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("Hello, World!"));          }      };intmain(int argc,char** argv) {          webserver ws =create_webserver(8080);          hello_world_resource hwr;          hwr.disallow_all();          hwr.set_allowing("GET",true);          ws.register_resource("/hello", &hwr);          ws.start(true);return0;      }

To test the above example, you can run the following command from a terminal:

curl -XGET -v http://localhost:8080/hello

If you try to run the following command, you'll see amethod_not_allowed error:

• curl -XPOST -v http://localhost:8080/hello.

You can also check this example ongithub.

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Once you have created your resource and extended its methods, you'll have to register the resource on the webserver. Registering a resource will associate it with an endpoint and allows the webserver to route it.Thewebserver class offers a method to register a resource:

• bool register_resource(const std::string& endpoint,http_resource* resource,bool family =false): Registers theresource to anendpoint. The endpoint is a string representing the path on your webserver from where you want your resource to be served from (e.g."/path/to/resource"). The optionalfamily parameter allows to register a resource as a "family" resource that will match any path nested into the one specified. For example, if family is set totrue and endpoint is set to"/path", the webserver will route to the resource not only the requests against"/path" but also everything in its nested path"/path/on/the/previous/one".

There are essentially four ways to specify an endpoint string:

• A simple path (e.g."/path/to/resource"). In this case, the webserver will try to match exactly the value of the endpoint.
• A regular exception. In this case, the webserver will try to match the URL of the request with the regex passed. For example, if passing"/path/as/decimal/[0-9]+, requests on URLs like"/path/as/decimal/5" or"/path/as/decimal/42" will be matched; instead, URLs like"/path/as/decimal/three" will not.
• A parametrized path. (e.g."/path/to/resource/with/{arg1}/{arg2}/in/url"). In this case, the webserver will match the argument with any value passed. In addition to this, the arguments will be passed to the resource as part of the arguments (readable from thehttp_request::get_arg method - seehere). For example, if passing"/path/to/resource/with/{arg1}/{arg2}/in/url" will match any request on URL with any value in place of{arg1} and{arg2}.
• A parametrized path with custom parameters. This is the same of a normal parametrized path, but allows to specify a regular expression for the argument (e.g."/path/to/resource/with/{arg1|[0-9]+}/{arg2|[a-z]+}/in/url". In this case, the webserver will match the arguments with any value passed that satisfies the regex. In addition to this, as above, the arguments will be passed to the resource as part of the arguments (readable from thehttp_request::get_arg method - seehere). For example, if passing"/path/to/resource/with/{arg1|[0-9]+}/{arg2|[a-z]+}/in/url" will match requests on URLs like"/path/to/resource/with/10/AA/in/url" but not like""/path/to/resource/with/BB/10/in/url""
• Any of the above marked asfamily. Will match any request on URLs having path that is prefixed by the path passed. For example, if family is set totrue and endpoint is set to"/path", the webserver will route to the resource not only the requests against"/path" but also everything in its nested path"/path/on/the/previous/one".

      #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:          std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("Hello, World!"));          }      };classhandling_multiple_resource :publichttp_resource {public:          std::shared_ptr<http_response>render(const http_request& req) {return std::shared_ptr<http_response>(newstring_response("Your URL:" + req.get_path()));          }      };classurl_args_resource :publichttp_resource {public:          std::shared_ptr<http_response>render(const http_request& req) {              std::stringarg1(req.get_arg("arg1"));              std::stringarg2(req.get_arg("arg2"));return std::shared_ptr<http_response>(newstring_response("ARGS:" + arg1 +" and" + arg2));          }      };intmain(int argc,char** argv) {          webserver ws =create_webserver(8080);          hello_world_resource hwr;          ws.register_resource("/hello", &hwr);          handling_multiple_resource hmr;          ws.register_resource("/family", &hmr,true);          ws.register_resource("/with_regex_[0-9]+", &hmr);          url_args_resource uar;          ws.register_resource("/url/with/{arg1}/and/{arg2}", &uar);          ws.register_resource("/url/with/parametric/args/{arg1|[0-9]+}/and/{arg2|[A-Z]+}", &uar);          ws.start(true);return0;      }

To test the above example, you can run the following commands from a terminal:

• curl -XGET -v http://localhost:8080/hello: will return theHello, World! message.
• curl -XGET -v http://localhost:8080/family: will return theYour URL: /family message.
• curl -XGET -v http://localhost:8080/family/with/suffix: will return theYour URL: /family/with/suffix message.
• curl -XGET -v http://localhost:8080/with_regex_10: will return theYour URL: /with_regex_10 message.
• curl -XGET -v http://localhost:8080/url/with/AA/and/BB: will return theARGS: AA and BB message. You can changeAA andBB with any value and observe how the URL is still matched and parameters are read.
• curl -XGET -v http://localhost:8080/url/with/parametric/args/10/and/AA: will return theARGS: 10 and AA message. You can change10 andAA with any value matching the regexes and observe how the URL is still matched and parameters are read.

Conversely, you can observe how these URL will not be matched (al the following will give you anot found message):

• curl -XGET -v http://localhost:8080/with_regex_A
• curl -XGET -v http://localhost:8080/url/with/parametric/args/AA/and/BB

You can also check this example ongithub.

Back to TOC

As seen in the documentation ofhttp_resource, every extensible method takes in input ahttp_request object. The webserver takes the responsibility to extract the data from the HTTP request on the network and does all the heavy lifting to build the instance ofhttp_request.

Thehttp_request class has a set of methods you will have access to when implementing your handlers:

• const std::string& get_path()const: Returns the path as requested from the HTTP client.
• const std::vector<std::string>& get_path_pieces()const: Returns the components of the path requested by the HTTP client (each piece of the path split by'/'.
• const std::string& get_path_piece(int index)const: Returns one piece of the path requested by the HTTP client. The piece is selected through theindex parameter (0-indexed).
• const std::string& get_method()const: Returns the method requested by the HTTP client.
• std::string_view get_header(std::string_view key)const: Returns the header with name equal tokey if present in the HTTP request. Returns anempty string otherwise.
• std::string_view get_cookie(std::string_view key)const: Returns the cookie with name equal tokey if present in the HTTP request. Returns anempty string otherwise.
• std::string_view get_footer(std::string_view key)const: Returns the footer with name equal tokey if present in the HTTP request (only for http 1.1 chunked encodings). Returns anempty string otherwise.
• http_arg_value get_arg(std::string_view key)const: Returns the argument with name equal tokey if present in the HTTP request. Arguments can be (1) querystring parameters, (2) path argument (in case of parametric endpoint, (3) parameters parsed from the HTTP request body if the body is inapplication/x-www-form-urlencoded ormultipart/form-data formats and the postprocessor is enabled in the webserver (enabled by default). Arguments are collected in a domain object that allows to collect multiple arguments with the same key while keeping the access transparent in the most common case of a single value provided per key.
• std::string_view get_arg_flat(std::string_view key)const Returns the argument in the same way asget_arg but as a string. If multiple values are provided with the same key, this method only returns the first value provided.
• const std::map<std::string_view, std::string_view, http::header_comparator> get_headers()const: Returns a map containing all the headers present in the HTTP request.
• const std::map<std::string_view, std::string_view, http::header_comparator> get_cookies()const: Returns a map containing all the cookies present in the HTTP request.
• const std::map<std::string_view, std::string_view, http::header_comparator> get_footers()const: Returns a map containing all the footers present in the HTTP request (only for http 1.1 chunked encodings).
• const std::map<http_arg_value, std::string, http::arg_comparator> get_args()const: Returns all the arguments present in the HTTP request. Arguments can be (1) querystring parameters, (2) path argument (in case of parametric endpoint, (3) parameters parsed from the HTTP request body if the body is inapplication/x-www-form-urlencoded ormultipart/form-data formats and the postprocessor is enabled in the webserver (enabled by default). For each key, arguments are collected in a domain object that allows to collect multiple arguments with the same key while keeping the access transparent in the most common case of a single value provided per key.
• const std::map<std::string, std::string, http::arg_comparator> get_args_flat()const: Returns all the arguments as theget_args method but as strings. If multiple values are provided with the same key, this method will only return the first value provided.
• const std::map<std::string, std::map<std::string, http::file_info>> get_files()const: Returns information about all the uploaded files (if the files are stored to disk). This information includes the key (as identifier of the outer map), the original file name (as identifier of the inner map) and a classfile_info, which includes the size of the file and the path to the file in the file system.
• const std::string& get_content()const: Returns the body of the HTTP request.
• bool content_too_large()const: Returnstrue if the body length of the HTTP request sent by the client is longer than the max allowed on the server.
• const std::string get_querystring()const: Returns thequerystring of the HTTP request.
• const std::string& get_version()const: Returns the HTTP version of the client request.
• const std::string get_requestor()const: Returns the IP from which the client is sending the request.
• unsigned short get_requestor_port()const: Returns the port from which the client is sending the request.
• const std::string get_user()const: Returns theuser as self-identified through basic authentication. The content of the user header will be parsed only if basic authentication is enabled on the server (enabled by default).
• const std::string get_pass()const: Returns thepassword as self-identified through basic authentication. The content of the password header will be parsed only if basic authentication is enabled on the server (enabled by default).
• const std::string get_digested_user()const: Returns thedigested user as self-identified through digest authentication. The content of the user header will be parsed only if digest authentication is enabled on the server (enabled by default).
• bool check_digest_auth(const std::string& realm,const std::string& password,int nonce_timeout,bool* reload_nonce)const: Allows to check the validity of the authentication token sent through digest authentication (if the provided values in the WWW-Authenticate header are valid and sound according to RFC2716). Takes in input therealm of validity of the authentication, thepassword as known to the server to compare against, thenonce_timeout to indicate how long the nonce is valid andreload_nonce a boolean that will be set by the method to indicate a nonce being reloaded. The method returnstrue if the authentication is valid,false otherwise.
• bool has_tls_session()const: Tests if there is am underlying TLS state of the current request.
• gnutls_session_t get_tls_session()const: Returns the underlying TLS state of the current request for inspection. (It is an error to call this if the state does not exist.)

Details on thehttp::file_info structure.

• size_t get_file_size()const: Returns the size of the file uploaded through the HTTP request.
• const std::string get_file_system_file_name()const: Returns the name of the file uploaded through the HTTP request as stored on the filesystem.
• const std::string get_content_type()const: Returns the content type of the file uploaded through the HTTP request.
• const std::string get_transfer_encoding()const: Returns the transfer encoding of the file uploaded through the HTTP request.

Details on thehttp_arg_value structure.

• std::string_view get_flat_value()const: Returns only the first value provided for the key.
• std::vector<std::string_view> get_all_values()const: Returns all the values provided for the key.
• operator std::string()const: Converts the http_arg_value to a string with the same logic asget_flat_value.
• operator std::string_view()const: Converts the http_arg_value to a string_view with the same logic asget_flat_value.
• operator std::vector<std::string>()const: Converts the http_arg_value to a std::vectorstd::string with the same logic asget_value.

    #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:        std::shared_ptr<http_response>render(const http_request& req) {return std::shared_ptr<http_response>(newstring_response("Hello:" +std::string(req.get_arg("name"))));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);        hello_world_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v "http://localhost:8080/hello?name=John"

You will receive the messageHello: John in reply. Given that the body post processing is enabled, you can also runcurl -d "name=John" -X POST http://localhost:8080/hello to obtain the same result.

You can also check this example ongithub.

Back to TOC

As seen in the documentation ofhttp_resource, every extensible method returns in output ahttp_response object. The webserver takes the responsibility to convert thehttp_response object you create into a response on the network.

There are 5 types of response that you can create - we will describe them here through their constructors:

• string_response(const std::string& content,int response_code =200,const std::string& content_type ="text/plain"): The most basic type of response. It uses thecontent string passed in construction as body of the HTTP response. The other two optional parameters are theresponse_code and thecontent_type. You can find constant definition for the various response codes within thehttp_utils library file.
• file_response(const std::string& filename,int response_code =200,const std::string& content_type ="text/plain"): Uses thefilename passed in construction as pointer to a file on disk. The body of the HTTP response will be set using the content of the file. The file must be a regular file and exist on disk. Otherwise libhttpserver will return an error 500 (Internal Server Error). The other two optional parameters are theresponse_code and thecontent_type. You can find constant definition for the various response codes within thehttp_utils library file.
• basic_auth_fail_response(const std::string& content,const std::string& realm ="",int response_code =200,const std::string& content_type ="text/plain"): A response in return to a failure during basic authentication. It allows to specify acontent string as a message to send back to the client. Therealm parameter should contain your realm of authentication (if any). The other two optional parameters are theresponse_code and thecontent_type. You can find constant definition for the various response codes within thehttp_utils library file.
• digest_auth_fail_response(const std::string& content,const std::string& realm ="",const std::string& opaque ="",bool reload_nonce =false,int response_code =200,const std::string& content_type ="text/plain"): A response in return to a failure during digest authentication. It allows to specify acontent string as a message to send back to the client. Therealm parameter should contain your realm of authentication (if any). Theopaque represents a value that gets passed to the client and expected to be passed again to the server as-is. This value can be a hexadecimal or base64 string. Thereload_nonce parameter tells the server to reload the nonce (you should use the value returned by thecheck_digest_auth method on thehttp_request. The other two optional parameters are theresponse_code and thecontent_type. You can find constant definition for the various response codes within thehttp_utils library file.
• deferred_response(ssize_t(*cycle_callback_ptr)(shared_ptr<T>, char*, size_t) cycle_callback,const std::string& content ="",int response_code =200,const std::string& content_type ="text/plain"): A response that obtains additional content from a callback executed in a deferred way. It leaves the client in pending state (returning a100 CONTINUE message) and suspends the connection. Besides the callback, optionally, you can provide acontent parameter that sets the initial message sent immediately to the client. The other two optional parameters are theresponse_code and thecontent_type. You can find constant definition for the various response codes within thehttp_utils library file. To usedeferred_response you need to have thedeferred option active on your webserver (enabled by default).
  • Thecycle_callback_ptr has this shape:ssize_t cycle_callback(shared_ptr<T> closure_data, char* buf,size_t max_size).You are supposed to implement a function in this shape and provide it to thedeferred_repsonse method. The webserver will provide achar* to the function. It is responsibility of the function to allocate it and fill its content. The method is supposed to respect themax_size parameter passed in input. The function must return assize_t value representing the actual size you filled thebuf with. Any value different from-1 will keep the resume the connection, deliver the content and suspend it again (with a100 CONTINUE). If the method returns-1, the webserver will complete the communication with the client and close the connection. You can also pass ashared_ptr pointing to a data object of your choice (this will be templetized with a class of your choice). The server will guarantee that this object is passed at each invocation of the method allowing the client code to use it as a memory buffer during computation.

Thehttp_response class offers an additional set of methods to "decorate" your responses. This set of methods is:

• void with_header(const std::string& key,const std::string& value): Sets an HTTP header with name set tokey and value set tovalue.
• void with_footer(const std::string& key,const std::string& value): Sets an HTTP footer with name set tokey and value set tovalue.
• void with_cookie(const std::string& key,const std::string& value): Sets an HTTP cookie with name set tokey and value set tovalue (only for http 1.1 chunked encodings).
• void shoutCAST(): Mark the response as ashoutCAST one.

    #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:        std::shared_ptr<http_response>render(const http_request&) {            std::shared_ptr<http_response> response = std::shared_ptr<http_response>(newstring_response("Hello, World!"));            response->with_header("MyHeader","MyValue");return response;        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);        hello_world_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you could run the following command from a terminal:

curl -XGET -v "http://localhost:8080/hello"

You will receive the message custom header in reply.

You can also check this example ongithub.

Back to TOC

libhttpserver provides natively a system to blacklist and whitelist IP addresses. To enable/disable the system, it is possible to use theban_system andno_ban_system methods on thecreate_webserver class. In the same way, you can specify what you want to be your "default behavior" (allow by default or disallow by default) by using thedefault_policy method (seehere).

The system supports both IPV4 and IPV6 and manages them transparently. The only requirement is for ipv6 to be enabled on your server - you'll have to enable this by using theuse_ipv6 method oncreate_webserver.

You can explicitly ban or allow an IP address using the following methods on thewebserver class:

• void ban_ip(const std::string& ip): Adds one IP (or a range of IPs) to the list of the banned ones. Takes in input astring that contains the IP (or range of IPs) to ban. To use when thedefault_policy isACCEPT.
• void allow_ip(const std::string& ip): Adds one IP (or a range of IPs) to the list of the allowed ones. Takes in input astring that contains the IP (or range of IPs) to allow. To use when thedefault_policy isREJECT.
• void unban_ip(const std::string& ip): Removes one IP (or a range of IPs) from the list of the banned ones. Takes in input astring that contains the IP (or range of IPs) to remove from the list. To use when thedefault_policy isACCEPT.
• void disallow_ip(const std::string& ip): Removes one IP (or a range of IPs) from the list of the allowed ones. Takes in input astring that contains the IP (or range of IPs) to remove from the list. To use when thedefault_policy isREJECT.

The IP string format can represent both IPV4 and IPV6. Addresses will be normalized by the webserver to operate in the same sapce. Any valid IPV4 or IPV6 textual representation works.It is also possible to specify ranges of IPs. To do so, omit the octect you want to express as a range and specify a'*' in its place.Examples of valid IPs include:

• "192.168.5.5": standard IPV4
• "192.168.*.*": range of IPV4 addresses. In the example, everything between192.168.0.0 and192.168.255.255.
• "2001:db8:8714:3a90::12": standard IPV6 - clustered empty ranges are fully supported.
• "2001:db8:8714:3a90:*:*": range of IPV6 addresses.
• "::ffff:192.0.2.128": IPV4 IPs nested into IPV6.
• "::192.0.2.128": IPV4 IPs nested into IPV6 (without'ffff' prefix)
• "::ffff:192.0.*.*": ranges of IPV4 IPs nested into IPV6.

    #include<httpserver.hpp>usingnamespacehttpserver;classhello_world_resource :publichttp_resource {public:        std::shared_ptr<http_response>render(const http_request&) {return std::shared_ptr<http_response>(newstring_response("Hello, World!"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080)            .default_policy(http::http_utils::REJECT);        ws.allow_ip("127.0.0.1");        hello_world_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you could run the following command from a terminal:

curl -XGET -v "http://localhost:8080/hello"

You can also check this example ongithub.

Back to TOC

libhttpserver support three types of client authentication.

Basic authentication uses a simple authentication method based on BASE64 algorithm. Username and password are exchanged in clear between the client and the server, so this method must only be used for non-sensitive content or when the session is protected with https. When using basic authentication libhttpserver will have access to the clear password, possibly allowing to create a chained authentication toward an external authentication server. You can enable/disable support for Basic authentication through thebasic_auth andno_basic_auth methods of thecreate_webserver class.

Digest authentication uses a one-way authentication method based on MD5 hash algorithm. Only the hash will transit over the network, hence protecting the user password. The nonce will prevent replay attacks. This method is appropriate for general use, especially when https is not used to encrypt the session. You can enable/disable support for Digest authentication through thedigest_auth andno_digest_auth methods of thecreate_webserver class.

Client certificate authentication uses a X.509 certificate from the client. This is the strongest authentication mechanism but it requires the use of HTTPS. Client certificate authentication can be used simultaneously with Basic or Digest Authentication in order to provide a two levels authentication (like for instance separate machine and user authentication). You can enable/disable support for Certificate authentication through theuse_ssl andno_ssl methods of thecreate_webserver class.

    #include<httpserver.hpp>usingnamespacehttpserver;classuser_pass_resource :publichttpserver::http_resource {public:        std::shared_ptr<http_response>render_GET(const http_request& req) {if (req.get_user() !="myuser" || req.get_pass() !="mypass") {return std::shared_ptr<basic_auth_fail_response>(newbasic_auth_fail_response("FAIL","test@example.com"));            }return std::shared_ptr<string_response>(newstring_response(req.get_user() +"" + req.get_pass(),200,"text/plain"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);        user_pass_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v -u myuser:mypass "http://localhost:8080/hello"

You will receive back the user and password you passed in input. Try to pass the wrong credentials to see the failure.

You can also check this example ongithub.

    #include<httpserver.hpp>    #defineMY_OPAQUE"11733b200778ce33060f31c9af70a870ba96ddd4"usingnamespacehttpserver;classdigest_resource :publichttpserver::http_resource {public:        std::shared_ptr<http_response>render_GET(const http_request& req) {if (req.get_digested_user() =="") {return std::shared_ptr<digest_auth_fail_response>(newdigest_auth_fail_response("FAIL","test@example.com", MY_OPAQUE,true));            }else {bool reload_nonce =false;if(!req.check_digest_auth("test@example.com","mypass",300, reload_nonce)) {return std::shared_ptr<digest_auth_fail_response>(newdigest_auth_fail_response("FAIL","test@example.com", MY_OPAQUE, reload_nonce));                }            }return std::shared_ptr<string_response>(newstring_response("SUCCESS",200,"text/plain"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);        digest_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v --digest --user myuser:mypass localhost:8080/hello

You will receive aSUCCESS in response (observe the response message from the server in detail and you'll see the full interaction). Try to pass the wrong credentials or send a request withoutdigest active to see the failure.

You can also check this example ongithub.

Back to TOC

libhttpserver provides a set of constants to help you develop your HTTP server. It would be redundant to list them here; so, please, consult the list directlyhere.

Back to TOC

    #include<httpserver.hpp>usingnamespacehttpserver;classfile_response_resource :publichttp_resource {public:        std::shared_ptr<http_response>render_GET(const http_request& req) {return std::shared_ptr<file_response>(newfile_response("test_content",200,"text/plain"));        }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);        file_response_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v localhost:8080/hello

You can also check this example ongithub.

    #include<httpserver.hpp>usingnamespacehttpserver;staticint counter =0;ssize_ttest_callback (std::shared_ptr<void> closure_data,char* buf,size_t max) {if (counter ==2) {return -1;        }else {memset(buf,0, max);strcat(buf," test");            counter++;returnstd::string(buf).size();        }    }classdeferred_resource :publichttp_resource {public:            std::shared_ptr<http_response>render_GET(const http_request& req) {return std::shared_ptr<deferred_response<void> >(new deferred_response<void>(test_callback,nullptr,"cycle callback response"));            }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);            deferred_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v localhost:8080/hello

You can also check this example ongithub.

    #include<atomic>    #include<httpserver.hpp>usingnamespacehttpserver;        std::atomic<int> counter;ssize_ttest_callback (std::shared_ptr<std::atomic<int> > closure_data,char* buf,size_t max) {int reqid;if (closure_data ==nullptr) {            reqid = -1;        }else {            reqid = *closure_data;        }// only first 5 connections can be establishedif (reqid >=5) {return -1;        }else {// respond corresponding request IDs to the clients            std::string str ="";            str +=std::to_string(reqid) +"";memset(buf,0, max);std::copy(str.begin(), str.end(), buf);// keep sending reqidsleep(1);return (ssize_t)max;        }    }classdeferred_resource :publichttp_resource {public:            std::shared_ptr<http_response>render_GET(const http_request& req) {                std::shared_ptr<std::atomic<int> >closure_data(new std::atomic<int>(counter++));return std::shared_ptr<deferred_response<std::atomic<int> > >(new deferred_response<std::atomic<int> >(test_callback, closure_data,"cycle callback response"));            }    };intmain(int argc,char** argv) {        webserver ws =create_webserver(8080);            deferred_resource hwr;        ws.register_resource("/hello", &hwr);        ws.start(true);return0;    }

To test the above example, you can run the following command from a terminal:

curl -XGET -v localhost:8080/hello

You can also check this example ongithub.

Back to TOC

This manual is for libhttpserver, C++ library for creating an embedded Rest HTTP server (and more).

Permission is granted to copy, distribute and/or modify this documentunder the terms of the GNU Free Documentation License, Version 1.3or any later version published by the Free Software Foundation;with no Invariant Sections, no Front-Cover Texts, and no Back-CoverTexts. A copy of the license is included in the section entitled GNUFree Documentation License.

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Version 2.1, February 1999

Copyright © 1991, 1999 Free Software Foundation, Inc.51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USAEveryone is permitted to copy and distribute verbatim copiesof this license document, but changing it is not allowed.

This is the first released version of the Lesser GPL. It also countsas the successor of the GNU Library Public License, version 2, hencethe version number 2.1.

The licenses for most software are designed to take away yourfreedom to share and change it. By contrast, the GNU General PublicLicenses are intended to guarantee your freedom to share and changefree software--to make sure the software is free for all its users.

This license, the Lesser General Public License, applies to somespecially designated software packages--typically libraries--of theFree Software Foundation and other authors who decide to use it. Youcan use it too, but we suggest you first think carefully about whetherthis license or the ordinary General Public License is the betterstrategy to use in any particular case, based on the explanations below.

When we speak of free software, we are referring to freedom of use,not price. Our General Public Licenses are designed to make sure thatyou have the freedom to distribute copies of free software (and chargefor this service if you wish); that you receive source code or can getit if you want it; that you can change the software and use pieces ofit in new free programs; and that you are informed that you can dothese things.

To protect your rights, we need to make restrictions that forbiddistributors to deny you these rights or to ask you to surrender theserights. These restrictions translate to certain responsibilities foryou if you distribute copies of the library or if you modify it.

For example, if you distribute copies of the library, whether gratisor for a fee, you must give the recipients all the rights that we gaveyou. You must make sure that they, too, receive or can get the sourcecode. If you link other code with the library, you must providecomplete object files to the recipients, so that they can relink themwith the library after making changes to the library and recompilingit. And you must show them these terms so they know their rights.

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This library has been originally developed under the zencoders flags and this community has always supported me all along this work so I am happy to put the logo on this readme.

          When you see this tree, know that you've came across ZenCoders                               with open('ZenCoders.                                                     `num` in numbers   synchronized                                             datetime d      glob.     sys.argv[2] .                                      def myclass   `..` @@oscla   org.   .  class {                               displ  hooks(   public static void   ma    functor:                           $myclass->method(  impport sys, os.pipe `   @param name`                      fcl   if(system(cmd) myc. /de   `  $card( array("a"   srand                   format  lists:  ++:   conc   ++ "my  an   WHERE  for(   == myi                `sys:  myvalue(myvalue) sys.t   Console.W  try{    rais     using              connec  SELECT * FROM table mycnf acco desc and or selector::clas  at          openldap string  sys.   print "zenc der " { 'a':  `ls -l` >  appe &firs        import Tkinter    paste( $obh  &a or it myval  bro roll:  :: [] require a      case `` super. +y  <svg x="100">  expr    say " %rooms 1  --account fb- yy     proc    meth Animate => send(D, open)    putd    EndIf 10  whi   myc`   cont   and    main (--) import loop $$ or  end onload  UNION WITH tab   timer 150 *2   end. begin True GtkLabel *label    doto partition te   let auto  i<- (i + d ); .mushup ``/.  ^/zenc/    myclass->her flv   op             <> element >> 71  or QFileDi   :   and  ..    with myc  toA  channel::bo    myc isEmpty a  not  bodt;class T  public pol    str    mycalc d   pt &&a     *i fc  add               ^ac::ZenCoders::core::namespac  boost::function st  f = std:   ;;     int    assertcout << endl   public genera   #include "b ost   ::ac myna const cast<char*> mysac  size_t   return ran  int (*getNextValue)(void) ff   double sa_family_t familpu        a   do puts("      ac   int main(int argc, char*   "%5d    struct namcs               float       for     typedef    enum  puts            getchar() if(                        else      #define     fp    FILE* f         char* s  i++                                 strcat(           %s                  int  31]                                 total+=                               do    }do                                while(1)                             sle    getc                              strcpy( a                            for      prin                            scanf(%d, &                          get         int                       void myfunc(int pa                     retu             BEQ                   BNEQZ R1 10 ANDI R1 R2                  SYS                XOR                SYSCALL 5 SLTIU MFLO 15 SW               JAL                   BNE            BLTZAL R1 1 LUI 001 NOOP MULTU           SLLV                      MOV R1     ADD R1 R2  JUMP  10 1001 BEQ R1 R2 1      ANDI                           1101  1010001100  111 001 01  1010 101100 1001  100                               110110 100   0  01 101 01100 100 100 1000100011                                    11101001001  00   11  100   11  10100010                                            000101001001 10  1001   101000101                                                    010010010010110101001010

For further information:visit our websitehttps://zencoders.github.io

Author: Sebastiano Merlino

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