Add support for AIO using filedescriptors.

[meshlink] / src / meshlink++.h

#ifndef MESHLINKPP_H
#define MESHLINKPP_H

/*
    meshlink++.h -- MeshLink C++ API
    Copyright (C) 2014, 2017 Guus Sliepen <guus@meshlink.io>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include <meshlink.h>
#include <new> // for 'placement new'

namespace meshlink {
class mesh;
class node;
class channel;
class submesh;

/// Severity of log messages generated by MeshLink.
typedef meshlink_log_level_t log_level_t;

/// Code of most recent error encountered.
typedef meshlink_errno_t errno_t;

/// A callback for receiving data from the mesh.
/** @param mesh      A handle which represents an instance of MeshLink.
 *  @param source    A pointer to a meshlink::node describing the source of the data.
 *  @param data      A pointer to a buffer containing the data sent by the source.
 *  @param len       The length of the received data.
 */
typedef void (*receive_cb_t)(mesh *mesh, node *source, const void *data, size_t len);

/// A callback reporting the meta-connection attempt made by the host node to an another node.
/** @param mesh      A handle which represents an instance of MeshLink.
 *  @param node      A pointer to a meshlink_node_t describing the node to whom meta-connection is being tried.
 *                   This pointer is valid until meshlink_close() is called.
 */
typedef void (*connection_try_cb_t)(mesh *mesh, node *node);

/// A callback reporting node status changes.
/** @param mesh       A handle which represents an instance of MeshLink.
 *  @param node       A pointer to a meshlink::node describing the node whose status changed.
 *  @param reachable  True if the node is reachable, false otherwise.
 */
typedef void (*node_status_cb_t)(mesh *mesh, node *node, bool reachable);

/// A callback reporting duplicate node detection.
/** @param mesh       A handle which represents an instance of MeshLink.
 *  @param node       A pointer to a meshlink_node_t describing the node which is duplicate.
 *                    This pointer is valid until meshlink_close() is called.
 */
typedef void (*duplicate_cb_t)(mesh *mesh, node *node);

/// A callback for receiving log messages generated by MeshLink.
/** @param mesh      A handle which represents an instance of MeshLink.
 *  @param level     An enum describing the severity level of the message.
 *  @param text      A pointer to a string containing the textual log message.
 */
typedef void (*log_cb_t)(mesh *mesh, log_level_t level, const char *text);

/// A callback for accepting incoming channels.
/** @param mesh         A handle which represents an instance of MeshLink.
 *  @param channel      A handle for the incoming channel.
 *  @param port         The port number the peer wishes to connect to.
 *  @param data         A pointer to a buffer containing data already received. (Not yet used.)
 *  @param len          The length of the data. (Not yet used.)
 *
 *  @return             This function should return true if the application accepts the incoming channel, false otherwise.
 *                      If returning false, the channel is invalid and may not be used anymore.
 */
typedef bool (*channel_accept_cb_t)(mesh *mesh, channel *channel, uint16_t port, const void *data, size_t len);

/// A callback for receiving data from a channel.
/** @param mesh         A handle which represents an instance of MeshLink.
 *  @param channel      A handle for the channel.
 *  @param data         A pointer to a buffer containing data sent by the source.
 *  @param len          The length of the data.
 */
typedef void (*channel_receive_cb_t)(mesh *mesh, channel *channel, const void *data, size_t len);

/// A callback that is called when data can be send on a channel.
/** @param mesh         A handle which represents an instance of MeshLink.
 *  @param channel      A handle for the channel.
 *  @param len          The maximum length of data that is guaranteed to be accepted by a call to channel_send().
 */
typedef void (*channel_poll_cb_t)(mesh *mesh, channel *channel, size_t len);

/// A callback for cleaning up buffers submitted for asynchronous I/O.
/** This callbacks signals that MeshLink has finished using this buffer.
 *  The ownership of the buffer is now back into the application's hands.
 *
 *  @param mesh      A handle which represents an instance of MeshLink.
 *  @param channel   A handle for the channel which used this buffer.
 *  @param data      A pointer to a buffer containing the enqueued data.
 *  @param len       The length of the buffer.
 *  @param priv      A private pointer which was set by the application when submitting the buffer.
 */
typedef void (*aio_cb_t)(mesh *mesh, channel *channel, const void *data, size_t len, void *priv);

/// A callback for asynchronous I/O to and from filedescriptors.
/** This callbacks signals that MeshLink has finished using this filedescriptor.
 *
 *  @param mesh      A handle which represents an instance of MeshLink.
 *  @param channel   A handle for the channel which used this filedescriptor.
 *  @param fd        The filedescriptor that was used.
 *  @param len       The length of the data that was successfully sent or received.
 *  @param priv      A private pointer which was set by the application when submitting the buffer.
 */
typedef void (*aio_fd_cb_t)(mesh *mesh, channel *channel, int fd, size_t len, void *priv);

/// A class describing a MeshLink node.
class node: public meshlink_node_t {
};

/// A class describing a MeshLink Sub-Mesh.
class submesh: public meshlink_submesh_t {
};

/// A class describing a MeshLink channel.
class channel: public meshlink_channel_t {
public:
        static const uint32_t RELIABLE = MESHLINK_CHANNEL_RELIABLE;
        static const uint32_t ORDERED = MESHLINK_CHANNEL_ORDERED;
        static const uint32_t FRAMED = MESHLINK_CHANNEL_FRAMED;
        static const uint32_t DROP_LATE = MESHLINK_CHANNEL_DROP_LATE;
        static const uint32_t NO_PARTIAL = MESHLINK_CHANNEL_NO_PARTIAL;
        static const uint32_t TCP = MESHLINK_CHANNEL_TCP;
        static const uint32_t UDP = MESHLINK_CHANNEL_UDP;
};

/// A class describing a MeshLink mesh.
class mesh {
public:
        mesh() : handle(0) {}

        virtual ~mesh() {
                this->close();
        }

        bool isOpen() const {
                return (handle != 0);
        }

// TODO: please enable C++11 in autoconf to enable "move constructors":
//              mesh(mesh&& other)
//              : handle(other.handle)
//              {
//                      if(handle)
//                              handle->priv = this;
//                      other.handle = 0;
//              }

        /// Initialize MeshLink's configuration directory.
        /** This function causes MeshLink to initialize its configuration directory,
         *  if it hasn't already been initialized.
         *  It only has to be run the first time the application starts,
         *  but it is not a problem if it is run more than once, as long as
         *  the arguments given are the same.
         *
         *  This function does not start any network I/O yet. The application should
         *  first set callbacks, and then call meshlink_start().
         *
         *  @param confbase The directory in which MeshLink will store its configuration files.
         *  @param name     The name which this instance of the application will use in the mesh.
         *  @param appname  The application name which will be used in the mesh.
         *  @param devclass The device class which will be used in the mesh.
         *
         *  @return         This function will return a pointer to a meshlink::mesh if MeshLink has successfully set up its configuration files, NULL otherwise.
         */
        bool open(const char *confbase, const char *name, const char *appname, dev_class_t devclass) {
                handle = meshlink_open(confbase, name, appname, devclass);

                if(handle) {
                        handle->priv = this;
                }

                return isOpen();
        }

        mesh(const char *confbase, const char *name, const char *appname, dev_class_t devclass) {
                open(confbase, name, appname, devclass);
        }

        /// Close the MeshLink handle.
        /** This function calls meshlink_stop() if necessary,
         *  and frees all memory allocated by MeshLink.
         *  Afterwards, the handle and any pointers to a struct meshlink_node are invalid.
         */
        void close() {
                if(handle) {
                        handle->priv = 0;
                        meshlink_close(handle);
                }

                handle = 0;
        }

        /** instead of registerin callbacks you derive your own class and overwrite the following abstract member functions.
         *  These functions are run in MeshLink's own thread.
         *  It is therefore important that these functions use apprioriate methods (queues, pipes, locking, etc.)
         *  to hand the data over to the application's thread.
         *  These functions should also not block itself and return as quickly as possible.
         * The default member functions are no-ops, so you are not required to overwrite all these member functions
         */

        /// This function is called whenever another node sends data to the local node.
        virtual void receive(node *source, const void *data, size_t length) {
                /* do nothing */
                (void)source;
                (void)data;
                (void) length;
        }

        /// This functions is called whenever another node's status changed.
        virtual void node_status(node *peer, bool reachable) {
                /* do nothing */
                (void)peer;
                (void)reachable;
        }

        /// This functions is called whenever a duplicate node is detected.
        virtual void node_duplicate(node *peer) {
                /* do nothing */
                (void)peer;
        }

        /// This functions is called whenever MeshLink has some information to log.
        virtual void log(log_level_t level, const char *message) {
                /* do nothing */
                (void)level;
                (void)message;
        }

        /// This functions is called whenever MeshLink a meta-connection attempt is made.
        virtual void connection_try(node *peer) {
                /* do nothing */
                (void)peer;
        }

        /// This functions is called whenever another node attempts to open a channel to the local node.
        /**
         *  If the channel is accepted, the poll_callback will be set to channel_poll and can be
         *  changed using set_channel_poll_cb(). Likewise, the receive callback is set to
         *  channel_receive().
         *
         *  The function is run in MeshLink's own thread.
         *  It is therefore important that the callback uses apprioriate methods (queues, pipes, locking, etc.)
         *  to pass data to or from the application's thread.
         *  The callback should also not block itself and return as quickly as possible.
         *
         *  @param channel      A handle for the incoming channel.
         *  @param port         The port number the peer wishes to connect to.
         *  @param data         A pointer to a buffer containing data already received. (Not yet used.)
         *  @param len          The length of the data. (Not yet used.)
         *
         *  @return             This function should return true if the application accepts the incoming channel, false otherwise.
         *                      If returning false, the channel is invalid and may not be used anymore.
         */
        virtual bool channel_accept(channel *channel, uint16_t port, const void *data, size_t len) {
                /* by default reject all channels */
                (void)channel;
                (void)port;
                (void)data;
                (void)len;
                return false;
        }

        /// This function is called by Meshlink for receiving data from a channel.
        /**
         *  The function is run in MeshLink's own thread.
         *  It is therefore important that the callback uses apprioriate methods (queues, pipes, locking, etc.)
         *  to pass data to or from the application's thread.
         *  The callback should also not block itself and return as quickly as possible.
         *
         *  @param channel      A handle for the channel.
         *  @param data         A pointer to a buffer containing data sent by the source.
         *  @param len          The length of the data.
         */
        virtual void channel_receive(channel *channel, const void *data, size_t len) {
                /* do nothing */
                (void)channel;
                (void)data;
                (void)len;
        }

        /// This function is called by Meshlink when data can be send on a channel.
        /**
         *  The function is run in MeshLink's own thread.
         *  It is therefore important that the callback uses apprioriate methods (queues, pipes, locking, etc.)
         *  to pass data to or from the application's thread.
         *
         *  The callback should also not block itself and return as quickly as possible.
         *  @param channel      A handle for the channel.
         *  @param len          The maximum length of data that is guaranteed to be accepted by a call to channel_send().
         */
        virtual void channel_poll(channel *channel, size_t len) {
                /* do nothing */
                (void)channel;
                (void)len;
        }

        /// Start MeshLink.
        /** This function causes MeshLink to open network sockets, make outgoing connections, and
         *  create a new thread, which will handle all network I/O.
         *
         *  @return         This function will return true if MeshLink has successfully started its thread, false otherwise.
         */
        bool start() {
                meshlink_set_receive_cb(handle, &receive_trampoline);
                meshlink_set_node_status_cb(handle, &node_status_trampoline);
                meshlink_set_node_duplicate_cb(handle, &node_duplicate_trampoline);
                meshlink_set_log_cb(handle, MESHLINK_DEBUG, &log_trampoline);
                meshlink_set_channel_accept_cb(handle, &channel_accept_trampoline);
                meshlink_set_connection_try_cb(handle, &connection_try_trampoline);
                return meshlink_start(handle);
        }

        /// Stop MeshLink.
        /** This function causes MeshLink to disconnect from all other nodes,
         *  close all sockets, and shut down its own thread.
         */
        void stop() {
                meshlink_stop(handle);
        }

        /// Send data to another node.
        /** This functions sends one packet of data to another node in the mesh.
         *  The packet is sent using UDP semantics, which means that
         *  the packet is sent as one unit and is received as one unit,
         *  and that there is no guarantee that the packet will arrive at the destination.
         *  The application should take care of getting an acknowledgement and retransmission if necessary.
         *
         *  @param destination  A pointer to a meshlink::node describing the destination for the data.
         *  @param data         A pointer to a buffer containing the data to be sent to the source.
         *  @param len          The length of the data.
         *  @return             This function will return true if MeshLink has queued the message for transmission, and false otherwise.
         *                      A return value of true does not guarantee that the message will actually arrive at the destination.
         */
        bool send(node *destination, const void *data, unsigned int len) {
                return meshlink_send(handle, destination, data, len);
        }

        /// Get a handle for a specific node.
        /** This function returns a handle for the node with the given name.
         *
         *  @param name         The name of the node for which a handle is requested.
         *
         *  @return             A pointer to a meshlink::node which represents the requested node,
         *                      or NULL if the requested node does not exist.
         */
        node *get_node(const char *name) {
                return (node *)meshlink_get_node(handle, name);
        }

        /// Get a handle for a specific submesh.
        /** This function returns a handle for the submesh with the given name.
         *
         *  @param name         The name of the submesh for which a handle is requested.
         *
         *  @return             A pointer to a meshlink::submesh which represents the requested submesh,
         *                      or NULL if the requested submesh does not exist.
         */
        submesh *get_submesh(const char *name) {
                return (submesh *)meshlink_get_submesh(handle, name);
        }

        /// Get a handle for our own node.
        /** This function returns a handle for the local node.
         *
         *  @return             A pointer to a meshlink::node which represents the local node.
         */
        node *get_self() {
                return (node *)meshlink_get_self(handle);
        }

        /// Get a list of all nodes.
        /** This function returns a list with handles for all known nodes.
         *
         *  @param nodes        A pointer to an array of pointers to meshlink::node, which should be allocated by the application.
         *  @param nmemb        The maximum number of pointers that can be stored in the nodes array.
         *
         *  @return             The number of known nodes, or -1 in case of an error.
         *                      This can be larger than nmemb, in which case not all nodes were stored in the nodes array.
         */
        node **get_all_nodes(node **nodes, size_t *nmemb) {
                return (node **)meshlink_get_all_nodes(handle, (meshlink_node_t **)nodes, nmemb);
        }

        /// Sign data using the local node's MeshLink key.
        /** This function signs data using the local node's MeshLink key.
         *  The generated signature can be securely verified by other nodes.
         *
         *  @param data         A pointer to a buffer containing the data to be signed.
         *  @param len          The length of the data to be signed.
         *  @param signature    A pointer to a buffer where the signature will be stored.
         *  @param siglen       The size of the signature buffer. Will be changed after the call to match the size of the signature itself.
         *
         *  @return             This function returns true if the signature is valid, false otherwise.
         */
        bool sign(const void *data, size_t len, void *signature, size_t *siglen) {
                return meshlink_sign(handle, data, len, signature, siglen);
        }

        /// Verify the signature generated by another node of a piece of data.
        /** This function verifies the signature that another node generated for a piece of data.
         *
         *  @param source       A pointer to a meshlink_node_t describing the source of the signature.
         *  @param data         A pointer to a buffer containing the data to be verified.
         *  @param len          The length of the data to be verified.
         *  @param signature    A pointer to a string containing the signature.
         *  @param siglen       The size of the signature.
         *
         *  @return             This function returns true if the signature is valid, false otherwise.
         */
        bool verify(node *source, const void *data, size_t len, const void *signature, size_t siglen) {
                return meshlink_verify(handle, source, data, len, signature, siglen);
        }

        /// Set the canonical Address for a node.
        /** This function sets the canonical Address for a node.
         *  This address is stored permanently until it is changed by another call to this function,
         *  unlike other addresses associated with a node,
         *  such as those added with meshlink_hint_address() or addresses discovered at runtime.
         *
         *  If a canonical Address is set for the local node,
         *  it will be used for the hostname part of generated invitation URLs.
         *
         *  @param node         A pointer to a meshlink_node_t describing the node.
         *  @param address      A nul-terminated C string containing the address, which can be either in numeric format or a hostname.
         *  @param port         A nul-terminated C string containing the port, which can be either in numeric or symbolic format.
         *                      If it is NULL, the listening port's number will be used.
         *
         *  @return             This function returns true if the address was added, false otherwise.
         */
        bool set_canonical_address(node *node, const char *address, const char *port = NULL) {
                return meshlink_set_canonical_address(handle, node, address, port);
        }

        /// Set the canonical Address for the local node.
        /** This function sets the canonical Address for the local node.
         *  This address is stored permanently until it is changed by another call to this function,
         *  unlike other addresses associated with a node,
         *  such as those added with meshlink_hint_address() or addresses discovered at runtime.
         *
         *  @param address      A nul-terminated C string containing the address, which can be either in numeric format or a hostname.
         *  @param port         A nul-terminated C string containing the port, which can be either in numeric or symbolic format.
         *                      If it is NULL, the listening port's number will be used.
         *
         *  @return             This function returns true if the address was added, false otherwise.
         */
        bool set_canonical_address(const char *address, const char *port = NULL) {
                return meshlink_set_canonical_address(handle, get_self(), address, port);
        }

        /// Add an Address for the local node.
        /** This function adds an Address for the local node, which will be used for invitation URLs.
         *
         *  @param address      A string containing the address, which can be either in numeric format or a hostname.
         *
         *  @return             This function returns true if the address was added, false otherwise.
         */
        bool add_address(const char *address) {
                return meshlink_add_address(handle, address);
        }

        /** This function performs tries to discover the local node's external address
         *  by contacting the meshlink.io server. If a reverse lookup of the address works,
         *  the FQDN associated with the address will be returned.
         *
         *  Please note that this is function only returns a single address,
         *  even if the local node might have more than one external address.
         *  In that case, there is no control over which address will be selected.
         *  Also note that if you have a dynamic IP address, or are behind carrier-grade NAT,
         *  there is no guarantee that the external address will be valid for an extended period of time.
         *
         *  This function is blocking. It can take several seconds before it returns.
         *  There is no guarantee it will be able to resolve the external address.
         *  Failures might be because by temporary network outages.
         *
         *  @param family       The address family to check, for example AF_INET or AF_INET6. If AF_UNSPEC is given,
         *                      this might return the external address for any working address family.
         *
         *  @return             This function returns a pointer to a C string containing the discovered external address,
         *                      or NULL if there was an error looking up the address.
         *                      After get_external_address() returns, the application is free to overwrite or free this string.
         */
        bool get_external_address(int family = AF_UNSPEC) {
                return meshlink_get_external_address_for_family(handle, family);
        }

        /** This function performs tries to discover the address of the local interface used for outgoing connection.
         *
         *  Please note that this is function only returns a single address,
         *  even if the local node might have more than one external address.
         *  In that case, there is no control over which address will be selected.
         *  Also note that if you have a dynamic IP address, or are behind carrier-grade NAT,
         *  there is no guarantee that the external address will be valid for an extended period of time.
         *
         *  This function will fail if it couldn't find a local address for the given address family.
         *  If hostname resolving is requested, this function may block for a few seconds.
         *
         *  @param family       The address family to check, for example AF_INET or AF_INET6. If AF_UNSPEC is given,
         *                      this might return the external address for any working address family.
         *
         *  @return             This function returns a pointer to a C string containing the discovered external address,
         *                      or NULL if there was an error looking up the address.
         *                      After get_external_address() returns, the application is free to overwrite or free this string.
         */
        bool get_local_address(int family = AF_UNSPEC) {
                return meshlink_get_local_address_for_family(handle, family);
        }

        /// Try to discover the external address for the local node, and add it to its list of addresses.
        /** This function is equivalent to:
         *
         *    mesh->add_address(mesh->get_external_address());
         *
         *  Read the description of get_external_address() for the limitations of this function.
         *
         *  @return             This function returns true if the address was added, false otherwise.
         */
        bool add_external_address() {
                return meshlink_add_external_address(handle);
        }

        /// Get the network port used by the local node.
        /** This function returns the network port that the local node is listening on.
         *
         *  @return              This function returns the port number, or -1 in case of an error.
         */
        int get_port() {
                return meshlink_get_port(handle);
        }

        /// Set the network port used by the local node.
        /** This function sets the network port that the local node is listening on.
         *  It may only be called when the mesh is not running.
         *  If unsure, call stop() before calling this function.
         *  Also note that if your node is already part of a mesh with other nodes,
         *  that the other nodes may no longer be able to initiate connections to the local node,
         *  since they will try to connect to the previously configured port.
         *
         *  @param port          The port number to listen on. This must be between 0 and 65535.
         *                       If the port is set to 0, then MeshLink will listen on a port
         *                       that is randomly assigned by the operating system every time open() is called.
         *
         *  @return              This function returns true if the port was successfully changed
         *                       to the desired port, false otherwise. If it returns false, there
         *                       is no guarantee that MeshLink is listening on the old port.
         */
        bool set_port(int port) {
                return meshlink_set_port(handle, port);
        }

        /// Set the timeout for invitations.
        /** This function sets the timeout for invitations.
         *  The timeout is retroactively applied to all outstanding invitations.
         *
         *  @param timeout      The timeout for invitations in seconds.
         */
        void set_invitation_timeout(int timeout) {
                meshlink_set_invitation_timeout(handle, timeout);
        }

        /// Invite another node into the mesh.
        /** This function generates an invitation that can be used by another node to join the same mesh as the local node.
         *  The generated invitation is a string containing a URL.
         *  This URL should be passed by the application to the invitee in a way that no eavesdroppers can see the URL.
         *  The URL can only be used once, after the user has joined the mesh the URL is no longer valid.
         *
         *  @param submesh      A handle to the submesh to put the invitee in.
         *  @param name         The name that the invitee will use in the mesh.
         *  @param flags        A bitwise-or'd combination of flags that controls how the URL is generated.
         *
         *  @return             This function returns a string that contains the invitation URL.
         *                      The application should call free() after it has finished using the URL.
         */
        char *invite(submesh *submesh, const char *name, uint32_t flags = 0) {
                return meshlink_invite_ex(handle, submesh, name, flags);
        }

        /// Use an invitation to join a mesh.
        /** This function allows the local node to join an existing mesh using an invitation URL generated by another node.
         *  An invitation can only be used if the local node has never connected to other nodes before.
         *  After a successfully accepted invitation, the name of the local node may have changed.
         *
         *  This function may only be called on a mesh that has not been started yet and which is not already part of an existing mesh.
         *
         *  This function is blocking. It can take several seconds before it returns.
         *  There is no guarantee it will perform a successful join.
         *  Failures might be caused by temporary network outages, or by the invitation having expired.
         *
         *  @param invitation   A string containing the invitation URL.
         *
         *  @return             This function returns true if the local node joined the mesh it was invited to, false otherwise.
         */
        bool join(const char *invitation) {
                return meshlink_join(handle, invitation);
        }

        /// Export the local node's key and addresses.
        /** This function generates a string that contains the local node's public key and one or more IP addresses.
         *  The application can pass it in some way to another node, which can then import it,
         *  granting the local node access to the other node's mesh.
         *
         *  @return             This function returns a string that contains the exported key and addresses.
         *                      The application should call free() after it has finished using this string.
         */
        char *export_key() {
                return meshlink_export(handle);
        }

        /// Import another node's key and addresses.
        /** This function accepts a string containing the exported public key and addresses of another node.
         *  By importing this data, the local node grants the other node access to its mesh.
         *
         *  @param data         A string containing the other node's exported key and addresses.
         *
         *  @return             This function returns true if the data was valid and the other node has been granted access to the mesh, false otherwise.
         */
        bool import_key(const char *data) {
                return meshlink_import(handle, data);
        }

        /// Blacklist a node from the mesh.
        /** This function causes the local node to blacklist another node.
         *  The local node will drop any existing connections to that node,
         *  and will not send data to it nor accept any data received from it any more.
         *
         *  @param node         A pointer to a meshlink::node describing the node to be blacklisted.
         */
        void blacklist(node *node) {
                return meshlink_blacklist(handle, node);
        }

        /// Set the poll callback.
        /** This functions sets the callback that is called whenever data can be sent to another node.
         *  The callback is run in MeshLink's own thread.
         *  It is therefore important that the callback uses apprioriate methods (queues, pipes, locking, etc.)
         *  to pass data to or from the application's thread.
         *  The callback should also not block itself and return as quickly as possible.
         *
         *  @param channel   A handle for the channel.
         *  @param cb        A pointer to the function which will be called when data can be sent to another node.
         *                   If a NULL pointer is given, the callback will be disabled.
         */
        void set_channel_poll_cb(channel *channel, channel_poll_cb_t cb) {
                meshlink_set_channel_poll_cb(handle, channel, (meshlink_channel_poll_cb_t)cb);
        }

        /// Set the send buffer size of a channel.
        /** This function sets the desired size of the send buffer.
         *  The default size is 128 kB.
         *
         *  @param channel   A handle for the channel.
         *  @param size      The desired size for the send buffer.
         *                   If a NULL pointer is given, the callback will be disabled.
         */
        void set_channel_sndbuf(channel *channel, size_t size) {
                meshlink_set_channel_sndbuf(handle, channel, size);
        }

        /// Set the receive buffer size of a channel.
        /** This function sets the desired size of the receive buffer.
         *  The default size is 128 kB.
         *
         *  @param channel   A handle for the channel.
         *  @param size      The desired size for the send buffer.
         *                   If a NULL pointer is given, the callback will be disabled.
         */
        void set_channel_rcvbuf(channel *channel, size_t size) {
                meshlink_set_channel_rcvbuf(handle, channel, size);
        }

        /// Open a reliable stream channel to another node.
        /** This function is called whenever a remote node wants to open a channel to the local node.
         *  The application then has to decide whether to accept or reject this channel.
         *
         *  This function sets the channel poll callback to channel_poll_trampoline, which in turn
         *  calls channel_poll. To set a different, channel-specific poll callback, use set_channel_poll_cb.
         *
         *  @param node         The node to which this channel is being initiated.
         *  @param port         The port number the peer wishes to connect to.
         *  @param cb           A pointer to the function which will be called when the remote node sends data to the local node.
         *  @param data         A pointer to a buffer containing data to already queue for sending.
         *  @param len          The length of the data.
         *  @param flags        A bitwise-or'd combination of flags that set the semantics for this channel.
         *
         *  @return             A handle for the channel, or NULL in case of an error.
         */
        channel *channel_open(node *node, uint16_t port, channel_receive_cb_t cb, const void *data, size_t len, uint32_t flags = channel::TCP) {
                channel *ch = (channel *)meshlink_channel_open_ex(handle, node, port, (meshlink_channel_receive_cb_t)cb, data, len, flags);
                meshlink_set_channel_poll_cb(handle, ch, &channel_poll_trampoline);
                return ch;
        }

        /// Open a reliable stream channel to another node.
        /** This function is called whenever a remote node wants to open a channel to the local node.
         *  The application then has to decide whether to accept or reject this channel.
         *
         *  This function sets the channel receive callback to channel_receive_trampoline,
         *  which in turn calls channel_receive.
         *
         *  This function sets the channel poll callback to channel_poll_trampoline, which in turn
         *  calls channel_poll. To set a different, channel-specific poll callback, use set_channel_poll_cb.
         *
         *  @param node         The node to which this channel is being initiated.
         *  @param port         The port number the peer wishes to connect to.
         *  @param data         A pointer to a buffer containing data to already queue for sending.
         *  @param len          The length of the data.
         *  @param flags        A bitwise-or'd combination of flags that set the semantics for this channel.
         *
         *  @return             A handle for the channel, or NULL in case of an error.
         */
        channel *channel_open(node *node, uint16_t port, const void *data, size_t len, uint32_t flags = channel::TCP) {
                channel *ch = (channel *)meshlink_channel_open_ex(handle, node, port, &channel_receive_trampoline, data, len, flags);
                meshlink_set_channel_poll_cb(handle, ch, &channel_poll_trampoline);
                return ch;
        }

        /// Partially close a reliable stream channel.
        /** This shuts down the read or write side of a channel, or both, without closing the handle.
         *  It can be used to inform the remote node that the local node has finished sending all data on the channel,
         *  but still allows waiting for incoming data from the remote node.
         *
         *  @param channel      A handle for the channel.
         *  @param direction    Must be one of SHUT_RD, SHUT_WR or SHUT_RDWR.
         */
        void channel_shutdown(channel *channel, int direction) {
                return meshlink_channel_shutdown(handle, channel, direction);
        }

        /// Close a reliable stream channel.
        /** This informs the remote node that the local node has finished sending all data on the channel.
         *  It also causes the local node to stop accepting incoming data from the remote node.
         *  Afterwards, the channel handle is invalid and must not be used any more.
         *
         *  @param channel      A handle for the channel.
         */
        void channel_close(meshlink_channel_t *channel) {
                return meshlink_channel_close(handle, channel);
        }

        /// Transmit data on a channel
        /** This queues data to send to the remote node.
         *
         *  @param channel      A handle for the channel.
         *  @param data         A pointer to a buffer containing data sent by the source.
         *  @param len          The length of the data.
         *
         *  @return             The amount of data that was queued, which can be less than len, or a negative value in case of an error.
         *                      If MESHLINK_CHANNEL_NO_PARTIAL is set, then the result will either be len,
         *                      0 if the buffer is currently too full, or -1 if len is too big even for an empty buffer.
         */
        ssize_t channel_send(channel *channel, void *data, size_t len) {
                return meshlink_channel_send(handle, channel, data, len);
        }

        /// Transmit data on a channel asynchronously
        /** This registers a buffer that will be used to send data to the remote node.
         *  Multiple buffers can be registered, in which case data will be sent in the order the buffers were registered.
         *  While there are still buffers with unsent data, the poll callback will not be called.
         *
         *  @param channel      A handle for the channel.
         *  @param data         A pointer to a buffer containing data sent by the source, or NULL if there is no data to send.
         *                      After meshlink_channel_aio_send() returns, the buffer may not be modified or freed by the application
         *                      until the callback routine is called.
         *  @param len          The length of the data, or 0 if there is no data to send.
         *  @param cb           A pointer to the function which will be called when MeshLink has finished using the buffer.
         *
         *  @return             True if the buffer was enqueued, false otherwise.
         */
        bool channel_aio_send(channel *channel, const void *data, size_t len, meshlink_aio_cb_t cb, void *priv) {
                return meshlink_channel_aio_send(handle, channel, data, len, cb, priv);
        }

        /// Transmit data on a channel asynchronously from a filedescriptor
        /** This will read up to the specified length number of bytes from the given filedescriptor, and send it over the channel.
         *  The callback may be returned early if there is an error reading from the filedescriptor.
         *  While there is still with unsent data, the poll callback will not be called.
         *
         *  @param channel      A handle for the channel.
         *  @param fd           A file descriptor from which data will be read.
         *  @param len          The length of the data, or 0 if there is no data to send.
         *  @param cb           A pointer to the function which will be called when MeshLink has finished using the filedescriptor.
         *
         *  @return             True if the buffer was enqueued, false otherwise.
         */
        bool channel_aio_fd_send(channel *channel, int fd, size_t len, meshlink_aio_fd_cb_t cb, void *priv) {
                return meshlink_channel_aio_fd_send(handle, channel, fd, len, cb, priv);
        }

        /// Receive data on a channel asynchronously
        /** This registers a buffer that will be filled with incoming channel data.
         *  Multiple buffers can be registered, in which case data will be received in the order the buffers were registered.
         *  While there are still buffers that have not been filled, the receive callback will not be called.
         *
         *  @param channel      A handle for the channel.
         *  @param data         A pointer to a buffer that will be filled with incoming data.
         *                      After meshlink_channel_aio_receive() returns, the buffer may not be modified or freed by the application
         *                      until the callback routine is called.
         *  @param len          The length of the data.
         *  @param cb           A pointer to the function which will be called when MeshLink has finished using the buffer.
         *
         *  @return             True if the buffer was enqueued, false otherwise.
         */
        bool channel_aio_receive(channel *channel, const void *data, size_t len, meshlink_aio_cb_t cb, void *priv) {
                return meshlink_channel_aio_receive(handle, channel, data, len, cb, priv);
        }

        /// Receive data on a channel asynchronously and send it to a filedescriptor
        /** This will read up to the specified length number of bytes from the channel, and send it to the filedescriptor.
         *  The callback may be returned early if there is an error writing to the filedescriptor.
         *  While there is still unread data, the receive callback will not be called.
         *
         *  @param channel      A handle for the channel.
         *  @param fd           A file descriptor to which data will be written.
         *  @param len          The length of the data.
         *  @param cb           A pointer to the function which will be called when MeshLink has finished using the filedescriptor.
         *
         *  @return             True if the buffer was enqueued, false otherwise.
         */
        bool channel_aio_fd_receive(channel *channel, int fd, size_t len, meshlink_aio_fd_cb_t cb, void *priv) {
                return meshlink_channel_aio_fd_receive(handle, channel, fd, len, cb, priv);
        }

        /// Get the amount of bytes in the send buffer.
        /** This returns the amount of bytes in the send buffer.
         *  These bytes have not been received by the peer yet.
         *
         *  @param channel      A handle for the channel.
         *
         *  @return             The amount of un-ACKed bytes in the send buffer.
         */
        size_t channel_get_sendq(channel *channel) {
                return meshlink_channel_get_sendq(handle, channel);
        }

        /// Get the amount of bytes in the receive buffer.
        /** This returns the amount of bytes in the receive buffer.
         *  These bytes have not been processed by the application yet.
         *
         *  @param channel      A handle for the channel.
         *
         *  @return             The amount of bytes in the receive buffer.
         */
        size_t channel_get_recvq(channel *channel) {
                return meshlink_channel_get_recvq(handle, channel);
        }

        /// Enable or disable zeroconf discovery of local peers
        /** This controls whether zeroconf discovery using the Catta library will be
         *  enabled to search for peers on the local network. By default, it is enabled.
         *
         *  @param enable  Set to true to enable discovery, false to disable.
         */
        void enable_discovery(bool enable = true) {
                meshlink_enable_discovery(handle, enable);
        }

private:
        // non-copyable:
        mesh(const mesh &) /* TODO: C++11: = delete */;
        void operator=(const mesh &) /* TODO: C++11: = delete */;

        /// static callback trampolines:
        static void receive_trampoline(meshlink_handle_t *handle, meshlink_node_t *source, const void *data, size_t length) {
                if(!(handle->priv)) {
                        return;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                that->receive(static_cast<node *>(source), data, length);
        }

        static void node_status_trampoline(meshlink_handle_t *handle, meshlink_node_t *peer, bool reachable) {
                if(!(handle->priv)) {
                        return;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                that->node_status(static_cast<node *>(peer), reachable);
        }

        static void node_duplicate_trampoline(meshlink_handle_t *handle, meshlink_node_t *peer) {
                if(!(handle->priv)) {
                        return;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                that->node_duplicate(static_cast<node *>(peer));
        }

        static void log_trampoline(meshlink_handle_t *handle, log_level_t level, const char *message) {
                if(!(handle->priv)) {
                        return;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                that->log(level, message);
        }

        static void connection_try_trampoline(meshlink_handle_t *handle, meshlink_node_t *peer) {
                if(!(handle->priv)) {
                        return;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                that->connection_try(static_cast<node *>(peer));
        }

        static bool channel_accept_trampoline(meshlink_handle_t *handle, meshlink_channel *channel, uint16_t port, const void *data, size_t len) {
                if(!(handle->priv)) {
                        return false;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                bool accepted = that->channel_accept(static_cast<meshlink::channel *>(channel), port, data, len);

                if(accepted) {
                        meshlink_set_channel_receive_cb(handle, channel, &channel_receive_trampoline);
                        meshlink_set_channel_poll_cb(handle, channel, &channel_poll_trampoline);
                }

                return accepted;
        }

        static void channel_receive_trampoline(meshlink_handle_t *handle, meshlink_channel *channel, const void *data, size_t len) {
                if(!(handle->priv)) {
                        return;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                that->channel_receive(static_cast<meshlink::channel *>(channel), data, len);
        }

        static void channel_poll_trampoline(meshlink_handle_t *handle, meshlink_channel *channel, size_t len) {
                if(!(handle->priv)) {
                        return;
                }

                meshlink::mesh *that = static_cast<mesh *>(handle->priv);
                that->channel_poll(static_cast<meshlink::channel *>(channel), len);
        }

        meshlink_handle_t *handle;
};

static inline const char *strerror(errno_t err = meshlink_errno) {
        return meshlink_strerror(err);
}

/// Destroy a MeshLink instance.
/** This function remove all configuration files of a MeshLink instance. It should only be called when the application
 *  does not have an open handle to this instance. Afterwards, a call to meshlink_open() will create a completely
 *  new instance.
 *
 *  @param confbase The directory in which MeshLink stores its configuration files.
 *                  After the function returns, the application is free to overwrite or free @a confbase @a.
 *
 *  @return         This function will return true if the MeshLink instance was successfully destroyed, false otherwise.
 */
static inline bool destroy(const char *confbase) {
        return meshlink_destroy(confbase);
}
}

#endif