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mongoose/docs/API.md
Sergey Lyubka a8a017a048 docs updated
2014-03-10 09:23:06 +00:00

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Mongoose API Reference

struct mg_server *mg_create_server(void *server_param);

Creates web server instance. Returns opaque instance pointer, or NULL if there is not enough memory. server_param: Could be any pointer, or NULL. This pointer will be passed to the callback functions as struct mg_connection::server_param field. A common use case is to pass this pointer of the C++ wrapper class as user_param, to let the callback get the pointer to the C++ object.

Note that this function doesn't make the server instance to serve. Serving is done by mg_poll_server() function. Mongoose has single-threaded, event-driven, asynchronous, non-blocking core. When server instance is created, it contains an information about the configuration and the state of each connection. Server instance is capable on listening on only one port. After creation, struct mg_server has a list of active connections and configuration parameters.

Side-effect: on UNIX, mg_create_server() ignores SIGPIPE signals. If custom processing is required SIGPIPE, signal handler must be set up after calling mg_create_server().

Important: Mongoose does not install SIGCHLD handler. If CGI is used, SIGCHLD handler must be set up to reap CGI zombie processes.

void mg_destroy_server(struct mg_server **server);

Deallocates web server instance, closes all pending connections, and makes server pointer a NULL pointer.

const char mg_set_option(struct mg_server *server, const char *name,
                         const char *value);

Sets a particular server option. Note that at least one option, listening_port, must be specified. To serve static files, document_root must be specified too. If document_root option is left unset, Mongoose will not access filesystem at all. mg_set_option() returns NULL if option was set successfully, otherwise it returns human-readable error string. It is allowed to call mg_set_option() by the same thread that does mg_poll_server() (Mongoose thread) and change server configuration while it is serving, in between mg_poll_server() calls.

void mg_poll_server(struct mg_server *server, int milliseconds);

Performs one iteration of IO loop by iterating over all active connections, performing select() syscall on all sockets with a timeout of milliseconds. When select() returns, Mongoose does an IO for each socket that has data to be sent or received. Application code must call mg_poll_server() in a loop. It is an error to have more then one thread calling mg_poll_server(), mg_set_option() or any other function that take struct mg_server * parameter. Mongoose does not mutex-protect struct mg_server *, therefore only single thread (Mongoose thread) should make Mongoose calls.

mg_poll_server() calls user-specified event handler when certain events occur. Sequence of events for the accepted connection is this:

  • MG_AUTH - Mongoose asks whether this connection is authorized. If event handler returns MG_FALSE, then Mongoose does not serve the request but sends authorization request to the client. If MG_TRUE is returned, then Mongoose continues on with the request.

  • MG_REQUEST - Mongoose asks event handler to serve the request. If event handler serves the request by sending a reply, it should return MG_TRUE. Otherwise, it should return MG_FALSE which tells Mongoose that request is not served and Mongoose should serve it. For example, event handler might choose to serve only RESTful API requests with URIs that start with certain prefix, and let Mongoose serve all static files. If event handler decides to serve the request, but doesn't have all the data at the moment, it should return MG_MORE. That tells Mongoose to send MG_POLL events on each iteration of mg_poll_server()

    mg_connection::connection_param pointer is a placeholder to keep user-specific data. For example, handler could decide to open a DB connection and store DB connection handle in connection_param.

  • MG_POLL is sent only to those connections which returned MG_MORE. Event handler should try to complete the reply. If reply is completed, then event handler should return MG_TRUE. Otherwise, it should return MG_FALSE, and polling will continue until handler returns MG_TRUE.

  • MG_HTTP_ERROR sent when Mongoose is about to send HTTP error back to the client. Event handler can choose to send a reply itself, in which case event handler must return MG_TRUE. Otherwise, event handler must return MG_FALSE

  • MG_CLOSE is sent when the connection is closed. This event is used to cleanup per-connection state stored in connection_param if it was allocated.

Sequence of events for the client connection is this:

  • MG_CONNECT sent when Mongoose has connected to the remote host. This event is sent to the connection initiated by mg_connect() call. Connection status is held in mg_connection::status_code: if zero, then connection was successful, otherwise connection was not established. User should send a request upon successful connection.
  • MG_REPLY is sent when response has been received from the remote host.
  • MG_CLOSE same as for the accepted connection.

When mongoose buffers in HTTP request and successfully parses it, it sends MG_REQUEST event for GET requests immediately. For POST requests, Mongoose delays the call until the whole POST request is buffered in memory. POST data is available to the callback as struct mg_connection::content, and POST data length is in struct mg_connection::content_len.

Note that websocket connections are treated the same way. Mongoose buffers websocket frame in memory, and calls event handler when frame is fully buffered. Frame data is available struct mg_connection::content, and data length is in struct mg_connection::content_len, i.e. very similar to the POST request. struct mg_connection::is_websocket flag indicates whether the request is websocket or not. Also, for websocket requests, there is struct mg_connection::wsbits field which contains first byte of the websocket frame which URI handler can examine. Note that to reply to the websocket client, mg_websocket_write() should be used. To reply to the plain HTTP client, mg_write_data() should be used.

const char **mg_get_valid_option_names(void);

Returns a NULL-terminated array of option names and their default values. There are two entries per option in an array: an option name followed by a default value. A default value could be NULL. A NULL name indicates an end of the array.

const char *mg_get_option(const struct mg_server *server, const char *name);

Returns the value of particular configuration parameter. If given parameter name is not valid, NULL is returned. For valid names, return value is guaranteed to be non-NULL. If parameter is not set, zero-length string is returned.

void mg_iterate_over_connections(struct mg_server *, mg_handler_t func);

This is an interface primarily designed to push arbitrary data to websocket connections at any time. This function could be called from the Mongoose thread only. When it returns, Mongoose thread calls func() for each active connection. It is allowed to call mg_send_data() or mg_websocket_write() within a callback, cause func is executed in the context of the Mongoose thread.

void mg_wakeup_server(struct mg_server *);

Makes mg_poll_server() that could be sleeping in the select() syscall to break the call and return. This function can be called from any thread. It is designed to let other threads wake up Mongoose thread from the sleep and let it do a fresh new IO iteration over all connection. Usually it is done when other threads decides there is new data ready to be sent by Mongoose.

void mg_send_status(struct mg_connection *, int status_code);
void mg_send_header(struct mg_connection *, const char *name,
                    const char *value);
void mg_send_data(struct mg_connection *, const void *data, int data_len);
void mg_printf_data(struct mg_connection *, const char *format, ...);

These functions are used to construct a response to the client. HTTP response consists of three parts: a status line, zero or more HTTP headers, a response body. Mongoose provides functions for all three parts:

  • mg_send_status() is used to create status line. This function can be called zero or once. If mg_send_status() is not called, then Mongoose will send status 200 (success) implicitly.
  • mg_send_header() adds HTTP header to the response. This function could be called zero or more times.
  • mg_send_data() and mg_printf_data() are used to send data to the client. Note that Mongoose adds Transfer-Encoding: chunked header implicitly, and sends data in chunks. Therefore, it is not necessary to set Content-Length header. Note that mg_send_data() and mg_printf_data() do not send data immediately. Instead, they spool data in memory, and Mongoose sends that data later after URI handler returns. If data to be sent is huge, an URI handler might send data in pieces by saving state in struct mg_connection::connection_param variable and returning 0. Then Mongoose will call a handler repeatedly after each socket write.
int mg_websocket_write(struct mg_connection* conn, int opcode,
                       const char *data, size_t data_len);

Similar to mg_write(), but wraps the data into a websocket frame with a given websocket opcode.

const char *mg_get_header(const struct mg_connection *, const char *name);

Get the value of particular HTTP header. This is a helper function. It traverses http_headers array, and if the header is present in the array, returns its value. If it is not present, NULL is returned.

int mg_get_var(const struct mg_connection *conn, const char *var_name,
               char *buf, size_t buf_len);

Gets HTTP form variable. Both POST buffer and query string are inspected. Form variable is url-decoded and written to the buffer. On success, this function returns the length of decoded variable. On error, -1 is returned if variable not found, and -2 is returned if destination buffer is too small to hold the variable. Destination buffer is guaranteed to be '\0' - terminated if it is not NULL or zero length.

int mg_parse_header(const char *hdr, const char *var_name, char *buf,
                    size_t buf_size);

This function parses HTTP header and fetches given variable's value in a buffer. A header should be like x=123, y=345, z="other value". This function is designed to parse Cookie headers, Authorization headers, and similar. Returns the length of the fetched value, or 0 if variable not found.

int mg_modify_passwords_file(const char *passwords_file_name,
                             const char *domain,
                             const char *user,
                             const char *password);

Add, edit or delete the entry in the passwords file.
This function allows an application to manipulate .htpasswd files on the fly by adding, deleting and changing user records. This is one of the several ways of implementing authentication on the server side. For another, cookie-based way please refer to the examples/chat.c in the source tree.
If password is not NULL, entry is added (or modified if already exists). If password is NULL, entry is deleted.
Return: 1 on success, 0 on error.

int mg_parse_multipart(const char *buf, int buf_len,
                       char *var_name, int var_name_len,
                       char *file_name, int file_name_len,
                       const char **data, int *data_len);

Parses a buffer that contains multipart form data. Stores chunk name in a var_name buffer. If chunk is an uploaded file, then file_name will have a file name. data and data_len will point to the chunk data. Returns number of bytes to skip to the next chunk.

 struct mg_connection *mg_connect(struct mg_server *server,
                                  const char *host, int port, int use_ssl);

Create connection to the remote host. Returns NULL on error, non-null if the connection has been scheduled for connection. Upon a connection, Mongoose will send MG_CONNECT event to the event handler.