1 files changed, 254 insertions, 0 deletions
diff --git a/devtools/shared/transport/stream-utils.js b/devtools/shared/transport/stream-utils.js
new file mode 100644
index 0000000000..a3efd1d2aa
--- /dev/null
+++ b/devtools/shared/transport/stream-utils.js
@@ -0,0 +1,254 @@
+/* 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";
+
+const DevToolsUtils = require("resource://devtools/shared/DevToolsUtils.js");
+const { dumpv } = DevToolsUtils;
+const EventEmitter = require("resource://devtools/shared/event-emitter.js");
+
+DevToolsUtils.defineLazyGetter(this, "IOUtil", () => {
+  return Cc["@mozilla.org/io-util;1"].getService(Ci.nsIIOUtil);
+});
+
+DevToolsUtils.defineLazyGetter(this, "ScriptableInputStream", () => {
+  return Components.Constructor(
+    "@mozilla.org/scriptableinputstream;1",
+    "nsIScriptableInputStream",
+    "init"
+  );
+});
+
+const BUFFER_SIZE = 0x8000;
+
+/**
+ * This helper function (and its companion object) are used by bulk senders and
+ * receivers to read and write data in and out of other streams.  Functions that
+ * make use of this tool are passed to callers when it is time to read or write
+ * bulk data.  It is highly recommended to use these copier functions instead of
+ * the stream directly because the copier enforces the agreed upon length.
+ * Since bulk mode reuses an existing stream, the sender and receiver must write
+ * and read exactly the agreed upon amount of data, or else the entire transport
+ * will be left in a invalid state.  Additionally, other methods of stream
+ * copying (such as NetUtil.asyncCopy) close the streams involved, which would
+ * terminate the debugging transport, and so it is avoided here.
+ *
+ * Overall, this *works*, but clearly the optimal solution would be able to just
+ * use the streams directly.  If it were possible to fully implement
+ * nsIInputStream / nsIOutputStream in JS, wrapper streams could be created to
+ * enforce the length and avoid closing, and consumers could use familiar stream
+ * utilities like NetUtil.asyncCopy.
+ *
+ * The function takes two async streams and copies a precise number of bytes
+ * from one to the other.  Copying begins immediately, but may complete at some
+ * future time depending on data size.  Use the returned promise to know when
+ * it's complete.
+ *
+ * @param input nsIAsyncInputStream
+ *        The stream to copy from.
+ * @param output nsIAsyncOutputStream
+ *        The stream to copy to.
+ * @param length Integer
+ *        The amount of data that needs to be copied.
+ * @return Promise
+ *         The promise is resolved when copying completes or rejected if any
+ *         (unexpected) errors occur.
+ */
+function copyStream(input, output, length) {
+  const copier = new StreamCopier(input, output, length);
+  return copier.copy();
+}
+
+function StreamCopier(input, output, length) {
+  EventEmitter.decorate(this);
+  this._id = StreamCopier._nextId++;
+  this.input = input;
+  // Save off the base output stream, since we know it's async as we've required
+  this.baseAsyncOutput = output;
+  if (IOUtil.outputStreamIsBuffered(output)) {
+    this.output = output;
+  } else {
+    this.output = Cc[
+      "@mozilla.org/network/buffered-output-stream;1"
+    ].createInstance(Ci.nsIBufferedOutputStream);
+    this.output.init(output, BUFFER_SIZE);
+  }
+  this._length = length;
+  this._amountLeft = length;
+  let _resolve;
+  let _reject;
+  this._deferred = new Promise((resolve, reject) => {
+    _resolve = resolve;
+    _reject = reject;
+  });
+  this._deferred.resolve = _resolve;
+  this._deferred.reject = _reject;
+
+  this._copy = this._copy.bind(this);
+  this._flush = this._flush.bind(this);
+  this._destroy = this._destroy.bind(this);
+
+  // Copy promise's then method up to this object.
+  // Allows the copier to offer a promise interface for the simple succeed or
+  // fail scenarios, but also emit events (due to the EventEmitter) for other
+  // states, like progress.
+  this.then = this._deferred.then.bind(this._deferred);
+  this.then(this._destroy, this._destroy);
+
+  // Stream ready callback starts as |_copy|, but may switch to |_flush| at end
+  // if flushing would block the output stream.
+  this._streamReadyCallback = this._copy;
+}
+StreamCopier._nextId = 0;
+
+StreamCopier.prototype = {
+  copy() {
+    // Dispatch to the next tick so that it's possible to attach a progress
+    // event listener, even for extremely fast copies (like when testing).
+    Services.tm.dispatchToMainThread(() => {
+      try {
+        this._copy();
+      } catch (e) {
+        this._deferred.reject(e);
+      }
+    });
+    return this;
+  },
+
+  _copy() {
+    const bytesAvailable = this.input.available();
+    const amountToCopy = Math.min(bytesAvailable, this._amountLeft);
+    this._debug("Trying to copy: " + amountToCopy);
+
+    let bytesCopied;
+    try {
+      bytesCopied = this.output.writeFrom(this.input, amountToCopy);
+    } catch (e) {
+      if (e.result == Cr.NS_BASE_STREAM_WOULD_BLOCK) {
+        this._debug("Base stream would block, will retry");
+        this._debug("Waiting for output stream");
+        this.baseAsyncOutput.asyncWait(this, 0, 0, Services.tm.currentThread);
+        return;
+      }
+      throw e;
+    }
+
+    this._amountLeft -= bytesCopied;
+    this._debug("Copied: " + bytesCopied + ", Left: " + this._amountLeft);
+    this._emitProgress();
+
+    if (this._amountLeft === 0) {
+      this._debug("Copy done!");
+      this._flush();
+      return;
+    }
+
+    this._debug("Waiting for input stream");
+    this.input.asyncWait(this, 0, 0, Services.tm.currentThread);
+  },
+
+  _emitProgress() {
+    this.emit("progress", {
+      bytesSent: this._length - this._amountLeft,
+      totalBytes: this._length,
+    });
+  },
+
+  _flush() {
+    try {
+      this.output.flush();
+    } catch (e) {
+      if (
+        e.result == Cr.NS_BASE_STREAM_WOULD_BLOCK ||
+        e.result == Cr.NS_ERROR_FAILURE
+      ) {
+        this._debug("Flush would block, will retry");
+        this._streamReadyCallback = this._flush;
+        this._debug("Waiting for output stream");
+        this.baseAsyncOutput.asyncWait(this, 0, 0, Services.tm.currentThread);
+        return;
+      }
+      throw e;
+    }
+    this._deferred.resolve();
+  },
+
+  _destroy() {
+    this._destroy = null;
+    this._copy = null;
+    this._flush = null;
+    this.input = null;
+    this.output = null;
+  },
+
+  // nsIInputStreamCallback
+  onInputStreamReady() {
+    this._streamReadyCallback();
+  },
+
+  // nsIOutputStreamCallback
+  onOutputStreamReady() {
+    this._streamReadyCallback();
+  },
+
+  _debug(msg) {
+    // Prefix logs with the copier ID, which makes logs much easier to
+    // understand when several copiers are running simultaneously
+    dumpv("Copier: " + this._id + " " + msg);
+  },
+};
+
+/**
+ * Read from a stream, one byte at a time, up to the next |delimiter|
+ * character, but stopping if we've read |count| without finding it.  Reading
+ * also terminates early if there are less than |count| bytes available on the
+ * stream.  In that case, we only read as many bytes as the stream currently has
+ * to offer.
+ * TODO: This implementation could be removed if bug 984651 is fixed, which
+ *       provides a native version of the same idea.
+ * @param stream nsIInputStream
+ *        The input stream to read from.
+ * @param delimiter string
+ *        The character we're trying to find.
+ * @param count integer
+ *        The max number of characters to read while searching.
+ * @return string
+ *         The data collected.  If the delimiter was found, this string will
+ *         end with it.
+ */
+function delimitedRead(stream, delimiter, count) {
+  dumpv(
+    "Starting delimited read for " + delimiter + " up to " + count + " bytes"
+  );
+
+  let scriptableStream;
+  if (stream instanceof Ci.nsIScriptableInputStream) {
+    scriptableStream = stream;
+  } else {
+    scriptableStream = new ScriptableInputStream(stream);
+  }
+
+  let data = "";
+
+  // Don't exceed what's available on the stream
+  count = Math.min(count, stream.available());
+
+  if (count <= 0) {
+    return data;
+  }
+
+  let char;
+  while (char !== delimiter && count > 0) {
+    char = scriptableStream.readBytes(1);
+    count--;
+    data += char;
+  }
+
+  return data;
+}
+
+module.exports = {
+  copyStream,
+  delimitedRead,
+};