packets.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

/**
 * Packets contain read / write functionality for the different packet types
 * supported by the debugging protocol, so that a transport can focus on
 * delivery and queue management without worrying too much about the specific
 * packet types.
 *
 * They are intended to be "one use only", so a new packet should be
 * instantiated for each incoming or outgoing packet.
 *
 * A complete Packet type should expose at least the following:
 *   * read(stream, scriptableStream)
 *     Called when the input stream has data to read
 *   * write(stream)
 *     Called when the output stream is ready to write
 *   * get done()
 *     Returns true once the packet is done being read / written
 *   * destroy()
 *     Called to clean up at the end of use
 */

const DevToolsUtils = require("resource://devtools/shared/DevToolsUtils.js");
const { dumpn, dumpv } = DevToolsUtils;
const flags = require("resource://devtools/shared/flags.js");
const StreamUtils = require("resource://devtools/shared/transport/stream-utils.js");

DevToolsUtils.defineLazyGetter(this, "unicodeConverter", () => {
  // eslint-disable-next-line no-shadow
  const unicodeConverter = Cc[
    "@mozilla.org/intl/scriptableunicodeconverter"
  ].createInstance(Ci.nsIScriptableUnicodeConverter);
  unicodeConverter.charset = "UTF-8";
  return unicodeConverter;
});

// The transport's previous check ensured the header length did not exceed 20
// characters.  Here, we opt for the somewhat smaller, but still large limit of
// 1 TiB.
const PACKET_LENGTH_MAX = Math.pow(2, 40);

/**
 * A generic Packet processing object (extended by two subtypes below).
 */
function Packet(transport) {
  this._transport = transport;
  this._length = 0;
}

/**
 * Attempt to initialize a new Packet based on the incoming packet header we've
 * received so far.  We try each of the types in succession, trying JSON packets
 * first since they are much more common.
 * @param header string
 *        The packet header string to attempt parsing.
 * @param transport DebuggerTransport
 *        The transport instance that will own the packet.
 * @return Packet
 *         The parsed packet of the matching type, or null if no types matched.
 */
Packet.fromHeader = function (header, transport) {
  return (
    JSONPacket.fromHeader(header, transport) ||
    BulkPacket.fromHeader(header, transport)
  );
};

Packet.prototype = {
  get length() {
    return this._length;
  },

  set length(length) {
    if (length > PACKET_LENGTH_MAX) {
      throw Error(
        "Packet length " +
          length +
          " exceeds the max length of " +
          PACKET_LENGTH_MAX
      );
    }
    this._length = length;
  },

  destroy() {
    this._transport = null;
  },
};

exports.Packet = Packet;

/**
 * With a JSON packet (the typical packet type sent via the transport), data is
 * transferred as a JSON packet serialized into a string, with the string length
 * prepended to the packet, followed by a colon ([length]:[packet]). The
 * contents of the JSON packet are specified in the Remote Debugging Protocol
 * specification.
 * @param transport DebuggerTransport
 *        The transport instance that will own the packet.
 */
function JSONPacket(transport) {
  Packet.call(this, transport);
  this._data = "";
  this._done = false;
}

/**
 * Attempt to initialize a new JSONPacket based on the incoming packet header
 * we've received so far.
 * @param header string
 *        The packet header string to attempt parsing.
 * @param transport DebuggerTransport
 *        The transport instance that will own the packet.
 * @return JSONPacket
 *         The parsed packet, or null if it's not a match.
 */
JSONPacket.fromHeader = function (header, transport) {
  const match = this.HEADER_PATTERN.exec(header);

  if (!match) {
    return null;
  }

  dumpv("Header matches JSON packet");
  const packet = new JSONPacket(transport);
  packet.length = +match[1];
  return packet;
};

JSONPacket.HEADER_PATTERN = /^(\d+):$/;

JSONPacket.prototype = Object.create(Packet.prototype);

Object.defineProperty(JSONPacket.prototype, "object", {
  /**
   * Gets the object (not the serialized string) being read or written.
   */
  get() {
    return this._object;
  },

  /**
   * Sets the object to be sent when write() is called.
   */
  set(object) {
    this._object = object;
    const data = JSON.stringify(object);
    this._data = unicodeConverter.ConvertFromUnicode(data);
    this.length = this._data.length;
  },
});

JSONPacket.prototype.read = function (stream, scriptableStream) {
  dumpv("Reading JSON packet");

  // Read in more packet data.
  this._readData(stream, scriptableStream);

  if (!this.done) {
    // Don't have a complete packet yet.
    return;
  }

  let json = this._data;
  try {
    json = unicodeConverter.ConvertToUnicode(json);
    this._object = JSON.parse(json);
  } catch (e) {
    const msg =
      "Error parsing incoming packet: " +
      json +
      " (" +
      e +
      " - " +
      e.stack +
      ")";
    console.error(msg);
    dumpn(msg);
    return;
  }

  this._transport._onJSONObjectReady(this._object);
};

JSONPacket.prototype._readData = function (stream, scriptableStream) {
  if (flags.wantVerbose) {
    dumpv(
      "Reading JSON data: _l: " +
        this.length +
        " dL: " +
        this._data.length +
        " sA: " +
        stream.available()
    );
  }
  const bytesToRead = Math.min(
    this.length - this._data.length,
    stream.available()
  );
  this._data += scriptableStream.readBytes(bytesToRead);
  this._done = this._data.length === this.length;
};

JSONPacket.prototype.write = function (stream) {
  dumpv("Writing JSON packet");

  if (this._outgoing === undefined) {
    // Format the serialized packet to a buffer
    this._outgoing = this.length + ":" + this._data;
  }

  const written = stream.write(this._outgoing, this._outgoing.length);
  this._outgoing = this._outgoing.slice(written);
  this._done = !this._outgoing.length;
};

Object.defineProperty(JSONPacket.prototype, "done", {
  get() {
    return this._done;
  },
});

JSONPacket.prototype.toString = function () {
  return JSON.stringify(this._object, null, 2);
};

exports.JSONPacket = JSONPacket;

/**
 * With a bulk packet, data is transferred by temporarily handing over the
 * transport's input or output stream to the application layer for writing data
 * directly.  This can be much faster for large data sets, and avoids various
 * stages of copies and data duplication inherent in the JSON packet type.  The
 * bulk packet looks like:
 *
 * bulk [actor] [type] [length]:[data]
 *
 * The interpretation of the data portion depends on the kind of actor and the
 * packet's type.  See the Remote Debugging Protocol Stream Transport spec for
 * more details.
 * @param transport DebuggerTransport
 *        The transport instance that will own the packet.
 */
function BulkPacket(transport) {
  Packet.call(this, transport);
  this._done = false;
  let _resolve;
  this._readyForWriting = new Promise(resolve => {
    _resolve = resolve;
  });
  this._readyForWriting.resolve = _resolve;
}

/**
 * Attempt to initialize a new BulkPacket based on the incoming packet header
 * we've received so far.
 * @param header string
 *        The packet header string to attempt parsing.
 * @param transport DebuggerTransport
 *        The transport instance that will own the packet.
 * @return BulkPacket
 *         The parsed packet, or null if it's not a match.
 */
BulkPacket.fromHeader = function (header, transport) {
  const match = this.HEADER_PATTERN.exec(header);

  if (!match) {
    return null;
  }

  dumpv("Header matches bulk packet");
  const packet = new BulkPacket(transport);
  packet.header = {
    actor: match[1],
    type: match[2],
    length: +match[3],
  };
  return packet;
};

BulkPacket.HEADER_PATTERN = /^bulk ([^: ]+) ([^: ]+) (\d+):$/;

BulkPacket.prototype = Object.create(Packet.prototype);

BulkPacket.prototype.read = function (stream) {
  dumpv("Reading bulk packet, handing off input stream");

  // Temporarily pause monitoring of the input stream
  this._transport.pauseIncoming();

  new Promise(resolve => {
    this._transport._onBulkReadReady({
      actor: this.actor,
      type: this.type,
      length: this.length,
      copyTo: output => {
        dumpv("CT length: " + this.length);
        const copying = StreamUtils.copyStream(stream, output, this.length);
        resolve(copying);
        return copying;
      },
      stream,
      done: resolve,
    });
    // Await the result of reading from the stream
  }).then(() => {
    dumpv("onReadDone called, ending bulk mode");
    this._done = true;
    this._transport.resumeIncoming();
  }, this._transport.close);

  // Ensure this is only done once
  this.read = () => {
    throw new Error("Tried to read() a BulkPacket's stream multiple times.");
  };
};

BulkPacket.prototype.write = function (stream) {
  dumpv("Writing bulk packet");

  if (this._outgoingHeader === undefined) {
    dumpv("Serializing bulk packet header");
    // Format the serialized packet header to a buffer
    this._outgoingHeader =
      "bulk " + this.actor + " " + this.type + " " + this.length + ":";
  }

  // Write the header, or whatever's left of it to write.
  if (this._outgoingHeader.length) {
    dumpv("Writing bulk packet header");
    const written = stream.write(
      this._outgoingHeader,
      this._outgoingHeader.length
    );
    this._outgoingHeader = this._outgoingHeader.slice(written);
    return;
  }

  dumpv("Handing off output stream");

  // Temporarily pause the monitoring of the output stream
  this._transport.pauseOutgoing();

  new Promise(resolve => {
    this._readyForWriting.resolve({
      copyFrom: input => {
        dumpv("CF length: " + this.length);
        const copying = StreamUtils.copyStream(input, stream, this.length);
        resolve(copying);
        return copying;
      },
      stream,
      done: resolve,
    });
    // Await the result of writing to the stream
  }).then(() => {
    dumpv("onWriteDone called, ending bulk mode");
    this._done = true;
    this._transport.resumeOutgoing();
  }, this._transport.close);

  // Ensure this is only done once
  this.write = () => {
    throw new Error("Tried to write() a BulkPacket's stream multiple times.");
  };
};

Object.defineProperty(BulkPacket.prototype, "streamReadyForWriting", {
  get() {
    return this._readyForWriting;
  },
});

Object.defineProperty(BulkPacket.prototype, "header", {
  get() {
    return {
      actor: this.actor,
      type: this.type,
      length: this.length,
    };
  },

  set(header) {
    this.actor = header.actor;
    this.type = header.type;
    this.length = header.length;
  },
});

Object.defineProperty(BulkPacket.prototype, "done", {
  get() {
    return this._done;
  },
});

BulkPacket.prototype.toString = function () {
  return "Bulk: " + JSON.stringify(this.header, null, 2);
};

exports.BulkPacket = BulkPacket;

/**
 * RawPacket is used to test the transport's error handling of malformed
 * packets, by writing data directly onto the stream.
 * @param transport DebuggerTransport
 *        The transport instance that will own the packet.
 * @param data string
 *        The raw string to send out onto the stream.
 */
function RawPacket(transport, data) {
  Packet.call(this, transport);
  this._data = data;
  this.length = data.length;
  this._done = false;
}

RawPacket.prototype = Object.create(Packet.prototype);

RawPacket.prototype.read = function () {
  // This hasn't yet been needed for testing.
  throw Error("Not implmented.");
};

RawPacket.prototype.write = function (stream) {
  const written = stream.write(this._data, this._data.length);
  this._data = this._data.slice(written);
  this._done = !this._data.length;
};

Object.defineProperty(RawPacket.prototype, "done", {
  get() {
    return this._done;
  },
});

exports.RawPacket = RawPacket;