[nit.git] / lib / libevent.nit

# This file is part of NIT (http://www.nitlanguage.org).
#
# Copyright 2013 Jean-Philippe Caissy <jpcaissy@piji.ca>
# Copyright 2014 Alexis Laferrière <alexis.laf@xymus.net>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Low-level wrapper around the libevent library to manage events on file descriptors
#
# For mor information, refer to the libevent documentation at
# http://monkey.org/~provos/libevent/doxygen-2.0.1/
module libevent is pkgconfig("libevent")

in "C header" `{
        #include <event2/listener.h>
        #include <event2/bufferevent.h>
        #include <event2/buffer.h>
`}

in "C" `{
        #include <sys/stat.h>
        #include <sys/types.h>
        #include <fcntl.h>
        #include <errno.h>
        #include <string.h>

        #include <sys/socket.h>
        #include <arpa/inet.h>
        #include <netinet/in.h>
        #include <netinet/ip.h>

// Protect callbacks for compatibility with light FFI
#ifdef Connection_decr_ref
        // Callback forwarded to 'Connection.write_callback'
        static void c_write_cb(struct bufferevent *bev, Connection ctx) {
                Connection_write_callback(ctx);
        }

        // Callback forwarded to 'Connection.read_callback_native'
        static void c_read_cb(struct bufferevent *bev, Connection ctx)
        {
                Connection_read_callback_native(ctx, bev);
        }

        // Callback forwarded to 'Connection.event_callback'
        static void c_event_cb(struct bufferevent *bev, short events, Connection ctx)
        {
                int release = Connection_event_callback(ctx, events);
                if (release) Connection_decr_ref(ctx);
        }

        // Callback forwarded to 'ConnectionFactory.accept_connection'
        static void accept_connection_cb(struct evconnlistener *listener, evutil_socket_t fd,
                struct sockaddr *addrin, int socklen, ConnectionFactory ctx)
        {
                ConnectionFactory_accept_connection(ctx, listener, fd, addrin, socklen);
        }
#endif

#ifdef EventCallback_incr_ref
        // Callback forwarded to 'EventCallback.callback'
        static void signal_cb(evutil_socket_t fd, short events, void *data)
        {
                EventCallback handler = data;
                EventCallback_callback(handler, events);
        }
#endif
`}

# Structure to hold information and state for a Libevent dispatch loop.
#
# The event_base lies at the center of Libevent; every application will
# have one.  It keeps track of all pending and active events, and
# notifies your application of the active ones.
extern class NativeEventBase `{ struct event_base * `}

        # Create a new event_base to use with the rest of Libevent
        new `{ return event_base_new(); `}

        # Has `self` been correctly initialized?
        fun is_valid: Bool do return not address_is_null

        # Event dispatching loop
        #
        # This loop will run the event base until either there are no more added
        # events, or until something calls `loopexit`.
        fun dispatch `{ event_base_dispatch(self); `}

        # Exit the event loop
        #
        # TODO support timer
        fun loopexit `{ event_base_loopexit(self, NULL); `}

        redef fun free `{ event_base_free(self); `}
end

# Event, libevent's basic unit of operation
extern class NativeEvent `{ struct event * `}

        # Add to the set of pending events
        #
        # TODO support timeout
        fun add `{ event_add(self, NULL); `}

        # Remove from the set of monitored events
        fun del `{ event_del(self); `}

        redef fun free `{ event_free(self); `}
end

# Signal event
extern class NativeEvSignal
        super NativeEvent

        new (base: NativeEventBase, signal: Int, handler: EventCallback)
        import EventCallback.callback `{
                EventCallback_incr_ref(handler);
                return evsignal_new(base, signal, signal_cb, handler);
        `}
end

# Receiver of event callbacks
interface EventCallback

        # Callback on an event
        fun callback(events: Int) do end
end

# Spawned to manage a specific connection
#
# TODO, use polls
class Connection
        super Writer

        # Closing this connection has been requested, but may not yet be `closed`
        var close_requested = false

        # This connection is closed
        var closed = false

        # The native libevent linked to `self`
        var native_buffer_event: NativeBufferEvent

        # Close this connection if possible, otherwise mark it to be closed later
        redef fun close
        do
                if closed then return

                var i = native_buffer_event.input_buffer
                var o = native_buffer_event.output_buffer
                if i.length > 0 or o.length > 0 then
                        close_requested = true
                else
                        force_close
                end
        end

        # Force closing this connection and freeing `native_buffer_event`
        fun force_close
        do
                if closed then return

                native_buffer_event.free
                closed = true
        end

        # Callback method on a write event
        fun write_callback
        do
                if close_requested then close
        end

        private fun read_callback_native(bev: NativeBufferEvent)
        do
                var evbuffer = bev.input_buffer
                var len = evbuffer.length
                var buf = new NativeString(len)
                evbuffer.remove(buf, len)
                var str = buf.to_s_with_length(len)
                read_callback str
        end

        # Callback method when data is available to read
        fun read_callback(content: String)
        do
                if close_requested then close
        end

        # Callback method on events: EOF, user-defined timeout and unrecoverable errors
        #
        # Returns `true` if the native handles to `self` can be released.
        fun event_callback(events: Int): Bool
        do
                if events & bev_event_error != 0 or events & bev_event_eof != 0 then
                        if events & bev_event_error != 0 then
                                var sock_err = evutil_socket_error
                                # Ignore some normal errors and print the others for debugging
                                if sock_err == 110 then
                                        # Connection timed out (ETIMEDOUT)
                                else if sock_err == 104 then
                                        # Connection reset by peer (ECONNRESET)
                                else
                                        print_error "libevent error event: {evutil_socket_error_to_string(sock_err)} ({sock_err})"
                                end
                        end
                        force_close
                        return true
                end

                return false
        end

        # Write a string to the connection
        redef fun write(str)
        do
                if close_requested then return
                native_buffer_event.write(str.to_cstring, str.byte_length)
        end

        redef fun write_byte(byte)
        do
                if close_requested then return
                native_buffer_event.write_byte(byte)
        end

        redef fun write_bytes(bytes)
        do
                if close_requested then return
                native_buffer_event.write(bytes.items, bytes.length)
        end

        # Write a file to the connection
        #
        # If `not path.file_exists`, the method returns.
        fun write_file(path: String)
        do
                if close_requested then return

                var file = new FileReader.open(path)
                if file.last_error != null then
                        var error = new IOError("Failed to open file at '{path}'")
                        error.cause = file.last_error
                        self.last_error = error
                        file.close
                        return
                end

                var stat = file.file_stat
                if stat == null then
                        last_error = new IOError("Failed to stat file at '{path}'")
                        file.close
                        return
                end

                var err = native_buffer_event.output_buffer.add_file(file.fd, 0, stat.size)
                if err then
                        last_error = new IOError("Failed to add file at '{path}'")
                        file.close
                end
        end
end

# ---
# Error code for event callbacks

# error encountered while reading
fun bev_event_reading: Int `{ return BEV_EVENT_READING; `}

# error encountered while writing
fun bev_event_writing: Int `{ return BEV_EVENT_WRITING; `}

# eof file reached
fun bev_event_eof: Int `{ return BEV_EVENT_EOF; `}

# unrecoverable error encountered
fun bev_event_error: Int `{ return BEV_EVENT_ERROR; `}

# user-specified timeout reached
fun bev_event_timeout: Int `{ return BEV_EVENT_TIMEOUT; `}

# connect operation finished.
fun bev_event_connected: Int `{ return BEV_EVENT_CONNECTED; `}

# Global error code for the last socket operation on the calling thread
#
# Not idempotent on all platforms.
fun evutil_socket_error: Int `{
        return EVUTIL_SOCKET_ERROR();
`}

# Convert an error code from `evutil_socket_error` to a string
fun evutil_socket_error_to_string(error_code: Int): NativeString `{
        return evutil_socket_error_to_string(error_code);
`}

# ---
# Options that can be specified when creating a `NativeBufferEvent`

# Close the underlying file descriptor/bufferevent/whatever when this bufferevent is freed.
fun bev_opt_close_on_free: Int `{ return BEV_OPT_CLOSE_ON_FREE; `}

# If threading is enabled, protect the operations on this bufferevent with a lock.
fun bev_opt_threadsafe: Int `{ return BEV_OPT_THREADSAFE; `}

# Run callbacks deferred in the event loop.
fun bev_opt_defer_callbacks: Int `{ return BEV_OPT_DEFER_CALLBACKS; `}

# If set, callbacks are executed without locks being held on the bufferevent.
fun bev_opt_unlock_callbacks: Int `{ return BEV_OPT_UNLOCK_CALLBACKS; `}

# ---
# Options for `NativeBufferEvent::enable`

# Read operation
fun ev_read: Int `{ return EV_READ; `}

# Write operation
fun ev_write: Int `{ return EV_WRITE; `}

# ---

# A buffer event structure, strongly associated to a connection, an input buffer and an output_buffer
extern class NativeBufferEvent `{ struct bufferevent * `}

        # Socket-based `NativeBufferEvent` that reads and writes data onto a network
        new socket(base: NativeEventBase, fd, options: Int) `{
                return bufferevent_socket_new(base, fd, options);
        `}

        # Enable a bufferevent.
        fun enable(operation: Int) `{
                bufferevent_enable(self, operation);
        `}

        # Set callbacks to `read_callback_native`, `write_callback` and `event_callback` of `conn`
        fun setcb(conn: Connection) import Connection.read_callback_native,
        Connection.write_callback, Connection.event_callback, NativeString `{
                Connection_incr_ref(conn);
                bufferevent_setcb(self,
                        (bufferevent_data_cb)c_read_cb,
                        (bufferevent_data_cb)c_write_cb,
                        (bufferevent_event_cb)c_event_cb, conn);
        `}

        # Write `length` bytes of `line`
        fun write(line: NativeString, length: Int): Int `{
                return bufferevent_write(self, line, length);
        `}

        # Write the byte `value`
        fun write_byte(value: Byte): Int `{
                unsigned char byt = (unsigned char)value;
                return bufferevent_write(self, &byt, 1);
        `}

        redef fun free `{ bufferevent_free(self); `}

        # The output buffer associated to `self`
        fun output_buffer: OutputNativeEvBuffer `{ return bufferevent_get_output(self); `}

        # The input buffer associated to `self`
        fun input_buffer: InputNativeEvBuffer `{ return bufferevent_get_input(self); `}

        # Read data from this buffer
        fun read_buffer(buf: NativeEvBuffer): Int `{ return bufferevent_read_buffer(self, buf); `}

        # Write data to this buffer
        fun write_buffer(buf: NativeEvBuffer): Int `{ return bufferevent_write_buffer(self, buf); `}
end

# A single buffer
extern class NativeEvBuffer `{ struct evbuffer * `}
        # Length of data in this buffer
        fun length: Int `{ return evbuffer_get_length(self); `}

        # Read data from an evbuffer and drain the bytes read
        fun remove(buffer: NativeString, len: Int) `{
                evbuffer_remove(self, buffer, len);
        `}
end

# An input buffer
extern class InputNativeEvBuffer
        super NativeEvBuffer

        # Empty/clear `length` data from buffer
        fun drain(length: Int) `{ evbuffer_drain(self, length); `}
end

# An output buffer
extern class OutputNativeEvBuffer
        super NativeEvBuffer

        # Add file to buffer
        fun add_file(fd, offset, length: Int): Bool `{
                return evbuffer_add_file(self, fd, offset, length);
        `}
end

# A listener acting on an interface and port, spawns `Connection` on new connections
extern class ConnectionListener `{ struct evconnlistener * `}

        private new bind_to(base: NativeEventBase, address: NativeString, port: Int, factory: ConnectionFactory)
        import ConnectionFactory.accept_connection, error_callback `{

                struct sockaddr_in sin;
                struct evconnlistener *listener;
                ConnectionFactory_incr_ref(factory);

                struct hostent *hostent = gethostbyname(address);

                if (!hostent) {
                        return NULL;
                }

                memset(&sin, 0, sizeof(sin));
                sin.sin_family = hostent->h_addrtype;
                sin.sin_port = htons(port);
                memcpy( &(sin.sin_addr.s_addr), (const void*)hostent->h_addr, hostent->h_length );

                listener = evconnlistener_new_bind(base,
                        (evconnlistener_cb)accept_connection_cb, factory,
                        LEV_OPT_CLOSE_ON_FREE | LEV_OPT_REUSEABLE, -1,
                        (struct sockaddr*)&sin, sizeof(sin));

                if (listener != NULL) {
                        evconnlistener_set_error_cb(listener, (evconnlistener_errorcb)ConnectionListener_error_callback);
                }

                return listener;
        `}

        # Get the `NativeEventBase` associated to `self`
        fun base: NativeEventBase `{ return evconnlistener_get_base(self); `}

        # Callback method on listening error
        fun error_callback do
                var cstr = evutil_socket_error_to_string(evutil_socket_error)
                print_error "libevent error: '{cstr}'"
        end
end

# Factory to listen on sockets and create new `Connection`
class ConnectionFactory
        # The `NativeEventBase` for the dispatch loop of this factory
        var event_base: NativeEventBase

        # Accept a connection on `listener`
        #
        # By default, it creates a new NativeBufferEvent and calls `spawn_connection`.
        fun accept_connection(listener: ConnectionListener, fd: Int, addrin: Pointer, socklen: Int)
        do
                var base = listener.base
                var bev = new NativeBufferEvent.socket(base, fd, bev_opt_close_on_free)

                # Human representation of remote client address
                var addr_len = 46 # Longest possible IPv6 address + null byte
                var addr_buf = new NativeString(addr_len)
                addr_buf = addrin_to_address(addrin, addr_buf, addr_len)
                var addr = if addr_buf.address_is_null then
                                "Unknown address"
                        else addr_buf.to_s

                var conn = spawn_connection(bev, addr)
                bev.enable ev_read|ev_write
                bev.setcb conn
        end

        # Create a new `Connection` object for `buffer_event`
        fun spawn_connection(buffer_event: NativeBufferEvent, address: String): Connection
        do
                return new Connection(buffer_event)
        end

        # Listen on `address`:`port` for new connection, which will callback `spawn_connection`
        fun bind_to(address: String, port: Int): nullable ConnectionListener
        do
                var listener = new ConnectionListener.bind_to(event_base, address.to_cstring, port, self)
                if listener.address_is_null then
                        sys.stderr.write "libevent warning: Opening {address}:{port} failed\n"
                end
                return listener
        end

        # Put string representation of source `address` into `buf`
        private fun addrin_to_address(address: Pointer, buf: NativeString, buf_len: Int): NativeString `{
                struct sockaddr *addrin = (struct sockaddr*)address;

                if (addrin->sa_family == AF_INET) {
                        struct in_addr *src = &((struct sockaddr_in*)addrin)->sin_addr;
                        return (char *)inet_ntop(addrin->sa_family, src, buf, buf_len);
                }
                else if (addrin->sa_family == AF_INET6) {
                        struct in6_addr *src = &((struct sockaddr_in6*)addrin)->sin6_addr;
                        return (char *)inet_ntop(addrin->sa_family, src, buf, buf_len);
                }
                return NULL;
        `}
end

# Enable some relatively expensive debugging checks that would normally be turned off
fun enable_debug_mode `{ event_enable_debug_mode(); `}