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var assert = require('assert');
var Serializer = require('./framer').Serializer;
var Deserializer = require('./framer').Deserializer;
var Compressor = require('./compressor').Compressor;
var Decompressor = require('./compressor').Decompressor;
var Connection = require('./connection').Connection;
var Duplex = require('stream').Duplex;
var Transform = require('stream').Transform;
exports.Endpoint = Endpoint;
// The Endpoint class
// ==================
// Public API
// ----------
// - **new Endpoint(log, role, settings, filters)**: create a new Endpoint.
//
// - `log`: bunyan logger of the parent
// - `role`: 'CLIENT' or 'SERVER'
// - `settings`: initial HTTP/2 settings
// - `filters`: a map of functions that filter the traffic between components (for debugging or
// intentional failure injection).
//
// Filter functions get three arguments:
// 1. `frame`: the current frame
// 2. `forward(frame)`: function that can be used to forward a frame to the next component
// 3. `done()`: callback to signal the end of the filter process
//
// Valid filter names and their position in the stack:
// - `beforeSerialization`: after compression, before serialization
// - `beforeCompression`: after multiplexing, before compression
// - `afterDeserialization`: after deserialization, before decompression
// - `afterDecompression`: after decompression, before multiplexing
//
// * **Event: 'stream' (Stream)**: 'stream' event forwarded from the underlying Connection
//
// * **Event: 'error' (type)**: signals an error
//
// * **createStream(): Stream**: initiate a new stream (forwarded to the underlying Connection)
//
// * **close([error])**: close the connection with an error code
// Constructor
// -----------
// The process of initialization:
function Endpoint(log, role, settings, filters) {
Duplex.call(this);
// * Initializing logging infrastructure
this._log = log.child({ component: 'endpoint', e: this });
// * First part of the handshake process: sending and receiving the client connection header
// prelude.
assert((role === 'CLIENT') || role === 'SERVER');
if (role === 'CLIENT') {
this._writePrelude();
} else {
this._readPrelude();
}
// * Initialization of component. This includes the second part of the handshake process:
// sending the first SETTINGS frame. This is done by the connection class right after
// initialization.
this._initializeDataFlow(role, settings, filters || {});
// * Initialization of management code.
this._initializeManagement();
// * Initializing error handling.
this._initializeErrorHandling();
}
Endpoint.prototype = Object.create(Duplex.prototype, { constructor: { value: Endpoint } });
// Handshake
// ---------
var CLIENT_PRELUDE = Buffer.from('PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n');
// Writing the client header is simple and synchronous.
Endpoint.prototype._writePrelude = function _writePrelude() {
this._log.debug('Sending the client connection header prelude.');
this.push(CLIENT_PRELUDE);
};
// The asynchronous process of reading the client header:
Endpoint.prototype._readPrelude = function _readPrelude() {
// * progress in the header is tracker using a `cursor`
var cursor = 0;
// * `_write` is temporarily replaced by the comparator function
this._write = function _temporalWrite(chunk, encoding, done) {
// * which compares the stored header with the current `chunk` byte by byte and emits the
// 'error' event if there's a byte that doesn't match
var offset = cursor;
while(cursor < CLIENT_PRELUDE.length && (cursor - offset) < chunk.length) {
if (CLIENT_PRELUDE[cursor] !== chunk[cursor - offset]) {
this._log.fatal({ cursor: cursor, offset: offset, chunk: chunk },
'Client connection header prelude does not match.');
this._error('handshake', 'PROTOCOL_ERROR');
return;
}
cursor += 1;
}
// * if the whole header is over, and there were no error then restore the original `_write`
// and call it with the remaining part of the current chunk
if (cursor === CLIENT_PRELUDE.length) {
this._log.debug('Successfully received the client connection header prelude.');
delete this._write;
chunk = chunk.slice(cursor - offset);
this._write(chunk, encoding, done);
}
};
};
// Data flow
// ---------
// +---------------------------------------------+
// | |
// | +-------------------------------------+ |
// | | +---------+ +---------+ +---------+ | |
// | | | stream1 | | stream2 | | ... | | |
// | | +---------+ +---------+ +---------+ | |
// | | connection | |
// | +-------------------------------------+ |
// | | ^ |
// | pipe | | pipe |
// | v | |
// | +------------------+------------------+ |
// | | compressor | decompressor | |
// | +------------------+------------------+ |
// | | ^ |
// | pipe | | pipe |
// | v | |
// | +------------------+------------------+ |
// | | serializer | deserializer | |
// | +------------------+------------------+ |
// | | ^ |
// | _read() | | _write() |
// | v | |
// | +------------+ +-----------+ |
// | |output queue| |input queue| |
// +------+------------+-----+-----------+-------+
// | ^
// read() | | write()
// v |
function createTransformStream(filter) {
var transform = new Transform({ objectMode: true });
var push = transform.push.bind(transform);
transform._transform = function(frame, encoding, done) {
filter(frame, push, done);
};
return transform;
}
function pipeAndFilter(stream1, stream2, filter) {
if (filter) {
stream1.pipe(createTransformStream(filter)).pipe(stream2);
} else {
stream1.pipe(stream2);
}
}
Endpoint.prototype._initializeDataFlow = function _initializeDataFlow(role, settings, filters) {
var firstStreamId, compressorRole, decompressorRole;
if (role === 'CLIENT') {
firstStreamId = 1;
compressorRole = 'REQUEST';
decompressorRole = 'RESPONSE';
} else {
firstStreamId = 2;
compressorRole = 'RESPONSE';
decompressorRole = 'REQUEST';
}
this._serializer = new Serializer(this._log);
this._deserializer = new Deserializer(this._log);
this._compressor = new Compressor(this._log, compressorRole);
this._decompressor = new Decompressor(this._log, decompressorRole);
this._connection = new Connection(this._log, firstStreamId, settings);
pipeAndFilter(this._connection, this._compressor, filters.beforeCompression);
pipeAndFilter(this._compressor, this._serializer, filters.beforeSerialization);
pipeAndFilter(this._deserializer, this._decompressor, filters.afterDeserialization);
pipeAndFilter(this._decompressor, this._connection, filters.afterDecompression);
this._connection.on('ACKNOWLEDGED_SETTINGS_HEADER_TABLE_SIZE',
this._decompressor.setTableSizeLimit.bind(this._decompressor));
this._connection.on('RECEIVING_SETTINGS_HEADER_TABLE_SIZE',
this._compressor.setTableSizeLimit.bind(this._compressor));
};
var noread = {};
Endpoint.prototype._read = function _read() {
this._readableState.sync = true;
var moreNeeded = noread, chunk;
while (moreNeeded && (chunk = this._serializer.read())) {
moreNeeded = this.push(chunk);
}
if (moreNeeded === noread) {
this._serializer.once('readable', this._read.bind(this));
}
this._readableState.sync = false;
};
Endpoint.prototype._write = function _write(chunk, encoding, done) {
this._deserializer.write(chunk, encoding, done);
};
// Management
// --------------
Endpoint.prototype._initializeManagement = function _initializeManagement() {
this._connection.on('stream', this.emit.bind(this, 'stream'));
};
Endpoint.prototype.createStream = function createStream() {
return this._connection.createStream();
};
// Error handling
// --------------
Endpoint.prototype._initializeErrorHandling = function _initializeErrorHandling() {
this._serializer.on('error', this._error.bind(this, 'serializer'));
this._deserializer.on('error', this._error.bind(this, 'deserializer'));
this._compressor.on('error', this._error.bind(this, 'compressor'));
this._decompressor.on('error', this._error.bind(this, 'decompressor'));
this._connection.on('error', this._error.bind(this, 'connection'));
this._connection.on('peerError', this.emit.bind(this, 'peerError'));
};
Endpoint.prototype._error = function _error(component, error) {
this._log.fatal({ source: component, message: error }, 'Fatal error, closing connection');
this.close(error);
setImmediate(this.emit.bind(this, 'error', error));
};
Endpoint.prototype.close = function close(error) {
this._connection.close(error);
};
// Bunyan serializers
// ------------------
exports.serializers = {};
var nextId = 0;
exports.serializers.e = function(endpoint) {
if (!('id' in endpoint)) {
endpoint.id = nextId;
nextId += 1;
}
return endpoint.id;
};