add lwsl_notice

[profile/ivi/libwebsockets.git] / lib / libwebsockets.h

/*
 * libwebsockets - small server side websockets and web server implementation
 *
 * Copyright (C) 2010 Andy Green <andy@warmcat.com>
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation:
 *  version 2.1 of the License.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 *  MA  02110-1301  USA
 */

#ifndef __LIBWEBSOCKET_H__
#define __LIBWEBSOCKET_H__

#ifdef __cplusplus
extern "C" {
#include <cstddef>
#endif

#ifdef WIN32

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stddef.h>
#include "../win32port/win32helpers/websock-w32.h"

#include "../win32port/win32helpers/gettimeofday.h"

#define strcasecmp stricmp
#define getdtablesize() 30000

typedef int ssize_t;

#ifdef LWS_DLL
#ifdef LWS_INTERNAL
#define LWS_EXTERN extern __declspec(dllexport)
#else
#define LWS_EXTERN extern __declspec(dllimport)
#endif
#endif

#else
#include <poll.h>
#include <unistd.h>
#endif

#include <assert.h>

#ifndef LWS_EXTERN
#define LWS_EXTERN extern
#endif

#define CONTEXT_PORT_NO_LISTEN 0
#define MAX_MUX_RECURSION 2

enum lws_log_levels {
        LLL_ERR = 1 << 0,
        LLL_WARN = 1 << 1,
        LLL_NOTICE = 1 << 2,
        LLL_INFO = 1 << 3,
        LLL_DEBUG = 1 << 4,
        LLL_PARSER = 1 << 5,
        LLL_HEADER = 1 << 6,
        LLL_EXT = 1 << 7,
        LLL_CLIENT = 1 << 8,

        LLL_COUNT = 9 /* set to count of valid flags */
};

enum libwebsocket_context_options {
        LWS_SERVER_OPTION_DEFEAT_CLIENT_MASK = 1,
        LWS_SERVER_OPTION_REQUIRE_VALID_OPENSSL_CLIENT_CERT = 2,
        LWS_SERVER_OPTION_SKIP_SERVER_CANONICAL_NAME = 4,
};

enum libwebsocket_callback_reasons {
        LWS_CALLBACK_ESTABLISHED,
        LWS_CALLBACK_CLIENT_CONNECTION_ERROR,
        LWS_CALLBACK_CLIENT_ESTABLISHED,
        LWS_CALLBACK_CLOSED,
        LWS_CALLBACK_RECEIVE,
        LWS_CALLBACK_CLIENT_RECEIVE,
        LWS_CALLBACK_CLIENT_RECEIVE_PONG,
        LWS_CALLBACK_CLIENT_WRITEABLE,
        LWS_CALLBACK_SERVER_WRITEABLE,
        LWS_CALLBACK_HTTP,
        LWS_CALLBACK_HTTP_FILE_COMPLETION,
        LWS_CALLBACK_BROADCAST,
        LWS_CALLBACK_FILTER_NETWORK_CONNECTION,
        LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION,
        LWS_CALLBACK_OPENSSL_LOAD_EXTRA_CLIENT_VERIFY_CERTS,
        LWS_CALLBACK_OPENSSL_LOAD_EXTRA_SERVER_VERIFY_CERTS,
        LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION,
        LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER,
        LWS_CALLBACK_CONFIRM_EXTENSION_OKAY,
        LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED,
        /* external poll() management support */
        LWS_CALLBACK_ADD_POLL_FD,
        LWS_CALLBACK_DEL_POLL_FD,
        LWS_CALLBACK_SET_MODE_POLL_FD,
        LWS_CALLBACK_CLEAR_MODE_POLL_FD,
};

enum libwebsocket_extension_callback_reasons {
        LWS_EXT_CALLBACK_SERVER_CONTEXT_CONSTRUCT,
        LWS_EXT_CALLBACK_CLIENT_CONTEXT_CONSTRUCT,
        LWS_EXT_CALLBACK_SERVER_CONTEXT_DESTRUCT,
        LWS_EXT_CALLBACK_CLIENT_CONTEXT_DESTRUCT,
        LWS_EXT_CALLBACK_CONSTRUCT,
        LWS_EXT_CALLBACK_CLIENT_CONSTRUCT,
        LWS_EXT_CALLBACK_CHECK_OK_TO_REALLY_CLOSE,
        LWS_EXT_CALLBACK_CHECK_OK_TO_PROPOSE_EXTENSION,
        LWS_EXT_CALLBACK_DESTROY,
        LWS_EXT_CALLBACK_DESTROY_ANY_WSI_CLOSING,
        LWS_EXT_CALLBACK_ANY_WSI_ESTABLISHED,
        LWS_EXT_CALLBACK_PACKET_RX_PREPARSE,
        LWS_EXT_CALLBACK_PACKET_TX_PRESEND,
        LWS_EXT_CALLBACK_PACKET_TX_DO_SEND,
        LWS_EXT_CALLBACK_HANDSHAKE_REPLY_TX,
        LWS_EXT_CALLBACK_FLUSH_PENDING_TX,
        LWS_EXT_CALLBACK_EXTENDED_PAYLOAD_RX,
        LWS_EXT_CALLBACK_CAN_PROXY_CLIENT_CONNECTION,
        LWS_EXT_CALLBACK_1HZ,
        LWS_EXT_CALLBACK_REQUEST_ON_WRITEABLE,
        LWS_EXT_CALLBACK_IS_WRITEABLE,
        LWS_EXT_CALLBACK_PAYLOAD_TX,
        LWS_EXT_CALLBACK_PAYLOAD_RX,
};

enum libwebsocket_write_protocol {
        LWS_WRITE_TEXT,
        LWS_WRITE_BINARY,
        LWS_WRITE_CONTINUATION,
        LWS_WRITE_HTTP,

        /* special 04+ opcodes */

        LWS_WRITE_CLOSE,
        LWS_WRITE_PING,
        LWS_WRITE_PONG,

        /* flags */

        LWS_WRITE_NO_FIN = 0x40,
        /*
         * client packet payload goes out on wire unmunged
         * only useful for security tests since normal servers cannot
         * decode the content if used
         */
        LWS_WRITE_CLIENT_IGNORE_XOR_MASK = 0x80
};

/*
 * you need these to look at headers that have been parsed if using the
 * LWS_CALLBACK_FILTER_CONNECTION callback.  If a header from the enum
 * list below is absent, .token = NULL and token_len = 0.  Otherwise .token
 * points to .token_len chars containing that header content.
 */

struct lws_tokens {
        char *token;
        int token_len;
};

enum lws_token_indexes {
        WSI_TOKEN_GET_URI,
        WSI_TOKEN_HOST,
        WSI_TOKEN_CONNECTION,
        WSI_TOKEN_KEY1,
        WSI_TOKEN_KEY2,
        WSI_TOKEN_PROTOCOL,
        WSI_TOKEN_UPGRADE,
        WSI_TOKEN_ORIGIN,
        WSI_TOKEN_DRAFT,
        WSI_TOKEN_CHALLENGE,

        /* new for 04 */
        WSI_TOKEN_KEY,
        WSI_TOKEN_VERSION,
        WSI_TOKEN_SWORIGIN,

        /* new for 05 */
        WSI_TOKEN_EXTENSIONS,

        /* client receives these */
        WSI_TOKEN_ACCEPT,
        WSI_TOKEN_NONCE,
        WSI_TOKEN_HTTP,
        WSI_TOKEN_MUXURL,

        /* always last real token index*/
        WSI_TOKEN_COUNT,
        /* parser state additions */
        WSI_TOKEN_NAME_PART,
        WSI_TOKEN_SKIPPING,
        WSI_TOKEN_SKIPPING_SAW_CR,
        WSI_PARSING_COMPLETE,
        WSI_INIT_TOKEN_MUXURL,
};

/*
 * From RFC 6455
   1000

      1000 indicates a normal closure, meaning that the purpose for
      which the connection was established has been fulfilled.

   1001

      1001 indicates that an endpoint is "going away", such as a server
      going down or a browser having navigated away from a page.

   1002

      1002 indicates that an endpoint is terminating the connection due
      to a protocol error.

   1003

      1003 indicates that an endpoint is terminating the connection
      because it has received a type of data it cannot accept (e.g., an
      endpoint that understands only text data MAY send this if it
      receives a binary message).

   1004

      Reserved.  The specific meaning might be defined in the future.

   1005

      1005 is a reserved value and MUST NOT be set as a status code in a
      Close control frame by an endpoint.  It is designated for use in
      applications expecting a status code to indicate that no status
      code was actually present.

   1006

      1006 is a reserved value and MUST NOT be set as a status code in a
      Close control frame by an endpoint.  It is designated for use in
      applications expecting a status code to indicate that the
      connection was closed abnormally, e.g., without sending or
      receiving a Close control frame.

   1007

      1007 indicates that an endpoint is terminating the connection
      because it has received data within a message that was not
      consistent with the type of the message (e.g., non-UTF-8 [RFC3629]
      data within a text message).

   1008

      1008 indicates that an endpoint is terminating the connection
      because it has received a message that violates its policy.  This
      is a generic status code that can be returned when there is no
      other more suitable status code (e.g., 1003 or 1009) or if there
      is a need to hide specific details about the policy.

   1009

      1009 indicates that an endpoint is terminating the connection
      because it has received a message that is too big for it to
      process.

   1010

      1010 indicates that an endpoint (client) is terminating the
      connection because it has expected the server to negotiate one or
      more extension, but the server didn't return them in the response
      message of the WebSocket handshake.  The list of extensions that
      are needed SHOULD appear in the /reason/ part of the Close frame.
      Note that this status code is not used by the server, because it
      can fail the WebSocket handshake instead.

   1011

      1011 indicates that a server is terminating the connection because
      it encountered an unexpected condition that prevented it from
      fulfilling the request.

   1015

      1015 is a reserved value and MUST NOT be set as a status code in a
      Close control frame by an endpoint.  It is designated for use in
      applications expecting a status code to indicate that the
      connection was closed due to a failure to perform a TLS handshake
      (e.g., the server certificate can't be verified).
*/

enum lws_close_status {
        LWS_CLOSE_STATUS_NOSTATUS = 0,
        LWS_CLOSE_STATUS_NORMAL = 1000,
        LWS_CLOSE_STATUS_GOINGAWAY = 1001,
        LWS_CLOSE_STATUS_PROTOCOL_ERR = 1002,
        LWS_CLOSE_STATUS_UNACCEPTABLE_OPCODE = 1003,
        LWS_CLOSE_STATUS_RESERVED = 1004,
        LWS_CLOSE_STATUS_NO_STATUS = 1005,
        LWS_CLOSE_STATUS_ABNORMAL_CLOSE = 1006,
        LWS_CLOSE_STATUS_INVALID_PAYLOAD = 1007,
        LWS_CLOSE_STATUS_POLICY_VIOLATION = 1008,
        LWS_CLOSE_STATUS_MESSAGE_TOO_LARGE = 1009,
        LWS_CLOSE_STATUS_EXTENSION_REQUIRED = 1010,
    LWS_CLOSE_STATUS_UNEXPECTED_CONDITION = 1011,
    LWS_CLOSE_STATUS_TLS_FAILURE = 1015,
};

struct libwebsocket;
struct libwebsocket_context;
struct libwebsocket_extension;

/**
 * callback_function() - User server actions
 * @context:    Websockets context
 * @wsi:        Opaque websocket instance pointer
 * @reason:     The reason for the call
 * @user:       Pointer to per-session user data allocated by library
 * @in:         Pointer used for some callback reasons
 * @len:        Length set for some callback reasons
 *
 *      This callback is the way the user controls what is served.  All the
 *      protocol detail is hidden and handled by the library.
 *
 *      For each connection / session there is user data allocated that is
 *      pointed to by "user".  You set the size of this user data area when
 *      the library is initialized with libwebsocket_create_server.
 *
 *      You get an opportunity to initialize user data when called back with
 *      LWS_CALLBACK_ESTABLISHED reason.
 *
 *      LWS_CALLBACK_ESTABLISHED:  after the server completes a handshake with
 *                              an incoming client
 *
 *  LWS_CALLBACK_CLIENT_CONNECTION_ERROR: the request client connection has
 *        been unable to complete a handshake with the remote server
 *
 *  LWS_CALLBACK_CLIENT_ESTABLISHED: after your client connection completed
 *                              a handshake with the remote server
 *
 *      LWS_CALLBACK_CLOSED: when the websocket session ends
 *
 *      LWS_CALLBACK_BROADCAST: signal to send to client (you would use
 *                              libwebsocket_write() taking care about the
 *                              special buffer requirements
 *
 *      LWS_CALLBACK_RECEIVE: data has appeared for this server endpoint from a
 *                              remote client, it can be found at *in and is
 *                              len bytes long
 *
 *      LWS_CALLBACK_CLIENT_RECEIVE_PONG: if you elected to see PONG packets,
 *                              they appear with this callback reason.  PONG
 *                              packets only exist in 04+ protocol
 *
 *      LWS_CALLBACK_CLIENT_RECEIVE: data has appeared from the server for the
 *                              client connection, it can be found at *in and
 *                              is len bytes long
 *
 *      LWS_CALLBACK_HTTP: an http request has come from a client that is not
 *                              asking to upgrade the connection to a websocket
 *                              one.  This is a chance to serve http content,
 *                              for example, to send a script to the client
 *                              which will then open the websockets connection.
 *                              @in points to the URI path requested and
 *                              libwebsockets_serve_http_file() makes it very
 *                              simple to send back a file to the client.
 *                              Normally after sending the file you are done
 *                              with the http connection, since the rest of the
 *                              activity will come by websockets from the script
 *                              that was delivered by http, so you will want to
 *                              return 1; to close and free up the connection.
 *                              That's important because it uses a slot in the
 *                              total number of client connections allowed set
 *                              by MAX_CLIENTS.
 *
 *      LWS_CALLBACK_HTTP_FILE_COMPLETION: a file requested to be send down
 *                              http link has completed.
 *
 *      LWS_CALLBACK_CLIENT_WRITEABLE:
 *      LWS_CALLBACK_SERVER_WRITEABLE:   If you call
 *              libwebsocket_callback_on_writable() on a connection, you will
 *              get one of these callbacks coming when the connection socket
 *              is able to accept another write packet without blocking.
 *              If it already was able to take another packet without blocking,
 *              you'll get this callback at the next call to the service loop
 *              function.  Notice that CLIENTs get LWS_CALLBACK_CLIENT_WRITEABLE
 *              and servers get LWS_CALLBACK_SERVER_WRITEABLE.
 *
 *      LWS_CALLBACK_FILTER_NETWORK_CONNECTION: called when a client connects to
 *              the server at network level; the connection is accepted but then
 *              passed to this callback to decide whether to hang up immediately
 *              or not, based on the client IP.  @user contains the connection
 *              socket's descriptor.  Return non-zero to terminate
 *              the connection before sending or receiving anything.
 *              Because this happens immediately after the network connection
 *              from the client, there's no websocket protocol selected yet so
 *              this callback is issued only to protocol 0.
 *
 *      LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION: called when the handshake has
 *              been received and parsed from the client, but the response is
 *              not sent yet.  Return non-zero to disallow the connection.
 *              @user is a pointer to an array of struct lws_tokens, you can
 *              use the header enums lws_token_indexes from libwebsockets.h
 *              to check for and read the supported header presence and
 *              content before deciding to allow the handshake to proceed or
 *              to kill the connection.
 *
 *      LWS_CALLBACK_OPENSSL_LOAD_EXTRA_CLIENT_VERIFY_CERTS: if configured for
 *              including OpenSSL support, this callback allows your user code
 *              to perform extra SSL_CTX_load_verify_locations() or similar
 *              calls to direct OpenSSL where to find certificates the client
 *              can use to confirm the remote server identity.  @user is the
 *              OpenSSL SSL_CTX*
 *
 *      LWS_CALLBACK_OPENSSL_LOAD_EXTRA_SERVER_VERIFY_CERTS: if configured for
 *              including OpenSSL support, this callback allows your user code
 *              to load extra certifcates into the server which allow it to
 *              verify the validity of certificates returned by clients.  @user
 *              is the server's OpenSSL SSL_CTX*
 *
 *      LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION: if the
 *              libwebsockets context was created with the option
 *              LWS_SERVER_OPTION_REQUIRE_VALID_OPENSSL_CLIENT_CERT, then this
 *              callback is generated during OpenSSL verification of the cert
 *              sent from the client.  It is sent to protocol[0] callback as
 *              no protocol has been negotiated on the connection yet.
 *              Notice that the libwebsockets context and wsi are both NULL
 *              during this callback.  See
 *               http://www.openssl.org/docs/ssl/SSL_CTX_set_verify.html
 *              to understand more detail about the OpenSSL callback that
 *              generates this libwebsockets callback and the meanings of the
 *              arguments passed.  In this callback, @user is the x509_ctx,
 *              @in is the ssl pointer and @len is preverify_ok
 *              Notice that this callback maintains libwebsocket return
 *              conventions, return 0 to mean the cert is OK or 1 to fail it.
 *              This also means that if you don't handle this callback then
 *              the default callback action of returning 0 allows the client
 *              certificates.
 *
 *      LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER: this callback happens
 *              when a client handshake is being compiled.  @user is NULL,
 *              @in is a char **, it's pointing to a char * which holds the
 *              next location in the header buffer where you can add
 *              headers, and @len is the remaining space in the header buffer,
 *              which is typically some hundreds of bytes.  So, to add a canned
 *              cookie, your handler code might look similar to:
 *
 *              char **p = (char **)in;
 *
 *              if (len < 100)
 *                      return 1;
 *
 *              *p += sprintf(*p, "Cookie: a=b\x0d\x0a");
 *
 *              return 0;
 *
 *              Notice if you add anything, you just have to take care about
 *              the CRLF on the line you added.  Obviously this callback is
 *              optional, if you don't handle it everything is fine.
 *
 *              Notice the callback is coming to protocols[0] all the time,
 *              because there is no specific protocol handshook yet.
 *
 *      LWS_CALLBACK_CONFIRM_EXTENSION_OKAY: When the server handshake code
 *              sees that it does support a requested extension, before
 *              accepting the extension by additing to the list sent back to
 *              the client it gives this callback just to check that it's okay
 *              to use that extension.  It calls back to the requested protocol
 *              and with @in being the extension name, @len is 0 and @user is
 *              valid.  Note though at this time the ESTABLISHED callback hasn't
 *              happened yet so if you initialize @user content there, @user
 *              content during this callback might not be useful for anything.
 *              Notice this callback comes to protocols[0].
 *
 *      LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED:        When a client
 *              connection is being prepared to start a handshake to a server,
 *              each supported extension is checked with protocols[0] callback
 *              with this reason, giving the user code a chance to suppress the
 *              claim to support that extension by returning non-zero.  If
 *              unhandled, by default 0 will be returned and the extension
 *              support included in the header to the server.  Notice this
 *              callback comes to protocols[0].
 *
 *      The next four reasons are optional and only need taking care of if you
 *      will be integrating libwebsockets sockets into an external polling
 *      array.
 * 
 *      LWS_CALLBACK_ADD_POLL_FD: libwebsocket deals with its poll() loop
 *              internally, but in the case you are integrating with another
 *              server you will need to have libwebsocket sockets share a
 *              polling array with the other server.  This and the other
 *              POLL_FD related callbacks let you put your specialized
 *              poll array interface code in the callback for protocol 0, the
 *              first protocol you support, usually the HTTP protocol in the
 *              serving case.  This callback happens when a socket needs to be
 *              added to the polling loop: @user contains the fd, and
 *              @len is the events bitmap (like, POLLIN).  If you are using the
 *              internal polling loop (the "service" callback), you can just
 *              ignore these callbacks.
 *
 *      LWS_CALLBACK_DEL_POLL_FD: This callback happens when a socket descriptor
 *              needs to be removed from an external polling array.  @user is
 *              the socket desricptor.  If you are using the internal polling
 *              loop, you can just ignore it.
 *
 *      LWS_CALLBACK_SET_MODE_POLL_FD: This callback happens when libwebsockets
 *              wants to modify the events for the socket descriptor in @user.
 *              The handler should OR @len on to the events member of the pollfd
 *              struct for this socket descriptor.  If you are using the
 *              internal polling loop, you can just ignore it.
 *
 *      LWS_CALLBACK_CLEAR_MODE_POLL_FD: This callback occurs when libwebsockets
 *              wants to modify the events for the socket descriptor in @user.
 *              The handler should AND ~@len on to the events member of the
 *              pollfd struct for this socket descriptor.  If you are using the
 *              internal polling loop, you can just ignore it.
 */
LWS_EXTERN int callback(struct libwebsocket_context * context,
                        struct libwebsocket *wsi,
                         enum libwebsocket_callback_reasons reason, void *user,
                                                          void *in, size_t len);

typedef int (callback_function)(struct libwebsocket_context * context,
                        struct libwebsocket *wsi,
                         enum libwebsocket_callback_reasons reason, void *user,
                                                          void *in, size_t len);


/**
 * extension_callback_function() - Hooks to allow extensions to operate
 * @context:    Websockets context
 * @ext:        This extension
 * @wsi:        Opaque websocket instance pointer
 * @reason:     The reason for the call
 * @user:       Pointer to per-session user data allocated by library
 * @in:         Pointer used for some callback reasons
 * @len:        Length set for some callback reasons
 *
 *      Each extension that is active on a particular connection receives
 *      callbacks during the connection lifetime to allow the extension to
 *      operate on websocket data and manage itself.
 *
 *      Libwebsockets takes care of allocating and freeing "user" memory for
 *      each active extension on each connection.  That is what is pointed to
 *      by the @user parameter.
 *
 *      LWS_EXT_CALLBACK_CONSTRUCT:  called when the server has decided to
 *              select this extension from the list provided by the client,
 *              just before the server will send back the handshake accepting
 *              the connection with this extension active.  This gives the
 *              extension a chance to initialize its connection context found
 *              in @user.
 *
 *      LWS_EXT_CALLBACK_CLIENT_CONSTRUCT: same as LWS_EXT_CALLBACK_CONSTRUCT
 *              but called when client is instantiating this extension.  Some
 *              extensions will work the same on client and server side and then
 *              you can just merge handlers for both CONSTRUCTS.
 *
 *      LWS_EXT_CALLBACK_DESTROY:  called when the connection the extension was
 *              being used on is about to be closed and deallocated.  It's the
 *              last chance for the extension to deallocate anything it has
 *              allocated in the user data (pointed to by @user) before the
 *              user data is deleted.  This same callback is used whether you
 *              are in client or server instantiation context.
 *
 *      LWS_EXT_CALLBACK_PACKET_RX_PREPARSE: when this extension was active on
 *              a connection, and a packet of data arrived at the connection,
 *              it is passed to this callback to give the extension a chance to
 *              change the data, eg, decompress it.  @user is pointing to the
 *              extension's private connection context data, @in is pointing
 *              to an lws_tokens struct, it consists of a char * pointer called
 *              token, and an int called token_len.  At entry, these are
 *              set to point to the received buffer and set to the content
 *              length.  If the extension will grow the content, it should use
 *              a new buffer allocated in its private user context data and
 *              set the pointed-to lws_tokens members to point to its buffer.
 *
 *      LWS_EXT_CALLBACK_PACKET_TX_PRESEND: this works the same way as
 *              LWS_EXT_CALLBACK_PACKET_RX_PREPARSE above, except it gives the
 *              extension a chance to change websocket data just before it will
 *              be sent out.  Using the same lws_token pointer scheme in @in,
 *              the extension can change the buffer and the length to be
 *              transmitted how it likes.  Again if it wants to grow the
 *              buffer safely, it should copy the data into its own buffer and
 *              set the lws_tokens token pointer to it.
 */
LWS_EXTERN int extension_callback(struct libwebsocket_context * context,
                        struct libwebsocket_extension *ext,
                        struct libwebsocket *wsi,
                         enum libwebsocket_extension_callback_reasons reason, void *user,
                                                          void *in, size_t len);

typedef int (extension_callback_function)(struct libwebsocket_context * context,
                        struct libwebsocket_extension *ext,
                        struct libwebsocket *wsi,
                         enum libwebsocket_extension_callback_reasons reason, void *user,
                                                          void *in, size_t len);

/**
 * struct libwebsocket_protocols -      List of protocols and handlers server
 *                                      supports.
 * @name:       Protocol name that must match the one given in the client
 *              Javascript new WebSocket(url, 'protocol') name
 * @callback:   The service callback used for this protocol.  It allows the
 *              service action for an entire protocol to be encapsulated in
 *              the protocol-specific callback
 * @per_session_data_size:      Each new connection using this protocol gets
 *              this much memory allocated on connection establishment and
 *              freed on connection takedown.  A pointer to this per-connection
 *              allocation is passed into the callback in the 'user' parameter
 * @owning_server:      the server init call fills in this opaque pointer when
 *              registering this protocol with the server.
 * @broadcast_socket_port: the server init call fills this in with the
 *              localhost port number used to forward broadcasts for this
 *              protocol
 * @broadcast_socket_user_fd:  the server init call fills this in ... the main()
 *              process context can write to this socket to perform broadcasts
 *              (use the libwebsockets_broadcast() api to do this instead,
 *              it works from any process context)
 * @protocol_index: which protocol we are starting from zero
 *
 *      This structure represents one protocol supported by the server.  An
 *      array of these structures is passed to libwebsocket_create_server()
 *      allows as many protocols as you like to be handled by one server.
 */

struct libwebsocket_protocols {
        const char *name;
        callback_function *callback;
        size_t per_session_data_size;

        /*
         * below are filled in on server init and can be left uninitialized,
         * no need for user to use them directly either
         */

        struct libwebsocket_context *owning_server;
        int broadcast_socket_port;
        int broadcast_socket_user_fd;
        int protocol_index;
};

/**
 * struct libwebsocket_extension -      An extension we know how to cope with
 *
 * @name:                       Formal extension name, eg, "deflate-stream"
 * @callback:                   Service callback
 * @per_session_data_size:      Libwebsockets will auto-malloc this much
 *                              memory for the use of the extension, a pointer
 *                              to it comes in the @user callback parameter
 * @per_context_private_data:   Optional storage for this externsion that
 *                              is per-context, so it can track stuff across
 *                              all sessions, etc, if it wants
 */

struct libwebsocket_extension {
        const char *name;
        extension_callback_function *callback;
        size_t per_session_data_size;
        void * per_context_private_data;
};

LWS_EXTERN
void lws_set_log_level(int level, void (*log_emit_function)(int level, const char *line));

LWS_EXTERN struct libwebsocket_context *
libwebsocket_create_context(int port, const char * interf,
                  struct libwebsocket_protocols *protocols,
                  struct libwebsocket_extension *extensions,
                  const char *ssl_cert_filepath,
                  const char *ssl_private_key_filepath,
                  const char *ssl_ca_filepath,
                  int gid, int uid,
                  unsigned int options, void *user);

LWS_EXTERN void
libwebsocket_context_destroy(struct libwebsocket_context *context);

LWS_EXTERN int
libwebsockets_fork_service_loop(struct libwebsocket_context *context);

LWS_EXTERN int
libwebsocket_service(struct libwebsocket_context *context, int timeout_ms);

LWS_EXTERN int
libwebsocket_service_fd(struct libwebsocket_context *context,
                                                         struct pollfd *pollfd);

LWS_EXTERN void *
libwebsocket_context_user(struct libwebsocket_context *context);

/*
 * IMPORTANT NOTICE!
 *
 * When sending with websocket protocol (LWS_WRITE_TEXT or LWS_WRITE_BINARY)
 * the send buffer has to have LWS_SEND_BUFFER_PRE_PADDING bytes valid BEFORE
 * buf, and LWS_SEND_BUFFER_POST_PADDING bytes valid AFTER (buf + len).
 *
 * This allows us to add protocol info before and after the data, and send as
 * one packet on the network without payload copying, for maximum efficiency.
 *
 * So for example you need this kind of code to use libwebsocket_write with a
 * 128-byte payload
 *
 *   char buf[LWS_SEND_BUFFER_PRE_PADDING + 128 + LWS_SEND_BUFFER_POST_PADDING];
 *
 *   // fill your part of the buffer... for example here it's all zeros
 *   memset(&buf[LWS_SEND_BUFFER_PRE_PADDING], 0, 128);
 *
 *   libwebsocket_write(wsi, &buf[LWS_SEND_BUFFER_PRE_PADDING], 128);
 *
 * When sending LWS_WRITE_HTTP, there is no protocol addition and you can just
 * use the whole buffer without taking care of the above.
 */

/*
 * this is the frame nonce plus two header plus 8 length
 *   there's an additional two for mux extension per mux nesting level
 * 2 byte prepend on close will already fit because control frames cannot use
 * the big length style
 */

#define LWS_SEND_BUFFER_PRE_PADDING (4 + 10 + (2 * MAX_MUX_RECURSION))
#define LWS_SEND_BUFFER_POST_PADDING 4

LWS_EXTERN int
libwebsocket_write(struct libwebsocket *wsi, unsigned char *buf, size_t len,
                                     enum libwebsocket_write_protocol protocol);

LWS_EXTERN int
libwebsockets_serve_http_file(struct libwebsocket_context *context,
                        struct libwebsocket *wsi, const char *file,
                                                     const char *content_type);
LWS_EXTERN int
libwebsockets_serve_http_file_fragment(struct libwebsocket_context *context,
                        struct libwebsocket *wsi);

/* notice - you need the pre- and post- padding allocation for buf below */

LWS_EXTERN int
libwebsockets_broadcast(const struct libwebsocket_protocols *protocol,
                                                unsigned char *buf, size_t len);

LWS_EXTERN const struct libwebsocket_protocols *
libwebsockets_get_protocol(struct libwebsocket *wsi);

LWS_EXTERN int
libwebsocket_callback_on_writable(struct libwebsocket_context *context,
                                                      struct libwebsocket *wsi);

LWS_EXTERN int
libwebsocket_callback_on_writable_all_protocol(
                                 const struct libwebsocket_protocols *protocol);

LWS_EXTERN int
libwebsocket_get_socket_fd(struct libwebsocket *wsi);

LWS_EXTERN int
libwebsocket_is_final_fragment(struct libwebsocket *wsi);

LWS_EXTERN unsigned char
libwebsocket_get_reserved_bits(struct libwebsocket *wsi);

LWS_EXTERN void *
libwebsocket_ensure_user_space(struct libwebsocket *wsi);

LWS_EXTERN int
libwebsocket_rx_flow_control(struct libwebsocket *wsi, int enable);

LWS_EXTERN size_t
libwebsockets_remaining_packet_payload(struct libwebsocket *wsi);

LWS_EXTERN struct libwebsocket *
libwebsocket_client_connect(struct libwebsocket_context *clients,
                              const char *address,
                              int port,
                              int ssl_connection,
                              const char *path,
                              const char *host,
                              const char *origin,
                              const char *protocol,
                              int ietf_version_or_minus_one);

LWS_EXTERN struct libwebsocket *
libwebsocket_client_connect_extended(struct libwebsocket_context *clients,
                              const char *address,
                              int port,
                              int ssl_connection,
                              const char *path,
                              const char *host,
                              const char *origin,
                              const char *protocol,
                              int ietf_version_or_minus_one,
                              void *userdata);

LWS_EXTERN const char *
libwebsocket_canonical_hostname(struct libwebsocket_context *context);


LWS_EXTERN void
libwebsockets_get_peer_addresses(int fd, char *name, int name_len,
                                        char *rip, int rip_len);

LWS_EXTERN void
libwebsockets_hangup_on_client(struct libwebsocket_context *context, int fd);

LWS_EXTERN void
libwebsocket_close_and_free_session(struct libwebsocket_context *context,
                               struct libwebsocket *wsi, enum lws_close_status);

LWS_EXTERN int
libwebsockets_get_random(struct libwebsocket_context *context,
                                                            void *buf, int len);

LWS_EXTERN int
lws_daemonize(const char *_lock_path);

LWS_EXTERN int
lws_send_pipe_choked(struct libwebsocket *wsi);

LWS_EXTERN int
lws_frame_is_binary(struct libwebsocket *wsi);

LWS_EXTERN unsigned char *
libwebsockets_SHA1(const unsigned char *d, size_t n, unsigned char *md);

LWS_EXTERN int
lws_b64_encode_string(const char *in, int in_len, char *out, int out_size);

LWS_EXTERN int
lws_b64_decode_string(const char *in, char *out, int out_size);

LWS_EXTERN struct libwebsocket_extension libwebsocket_internal_extensions[];

#ifdef __cplusplus
}
#endif

#endif