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+/* 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";
+
+var {Class} = require("sdk/core/heritage");
+
+/**
+ * A helper class that stores stack frame objects. Each frame is
+ * assigned an index, and if a frame is added more than once, the same
+ * index is used. Users of the class can get an array of all frames
+ * that have been added.
+ */
+var StackFrameCache = Class({
+ /**
+ * Initialize this object.
+ */
+ initialize: function () {
+ this._framesToIndices = null;
+ this._framesToForms = null;
+ this._lastEventSize = 0;
+ },
+
+ /**
+ * Prepare to accept frames.
+ */
+ initFrames: function () {
+ if (this._framesToIndices) {
+ // The maps are already initialized.
+ return;
+ }
+
+ this._framesToIndices = new Map();
+ this._framesToForms = new Map();
+ this._lastEventSize = 0;
+ },
+
+ /**
+ * Forget all stored frames and reset to the initialized state.
+ */
+ clearFrames: function () {
+ this._framesToIndices.clear();
+ this._framesToIndices = null;
+ this._framesToForms.clear();
+ this._framesToForms = null;
+ this._lastEventSize = 0;
+ },
+
+ /**
+ * Add a frame to this stack frame cache, and return the index of
+ * the frame.
+ */
+ addFrame: function (frame) {
+ this._assignFrameIndices(frame);
+ this._createFrameForms(frame);
+ return this._framesToIndices.get(frame);
+ },
+
+ /**
+ * A helper method for the memory actor. This populates the packet
+ * object with "frames" property. Each of these
+ * properties will be an array indexed by frame ID. "frames" will
+ * contain frame objects (see makeEvent).
+ *
+ * @param packet
+ * The packet to update.
+ *
+ * @returns packet
+ */
+ updateFramePacket: function (packet) {
+ // Now that we are guaranteed to have a form for every frame, we know the
+ // size the "frames" property's array must be. We use that information to
+ // create dense arrays even though we populate them out of order.
+ const size = this._framesToForms.size;
+ packet.frames = Array(size).fill(null);
+
+ // Populate the "frames" properties.
+ for (let [stack, index] of this._framesToIndices) {
+ packet.frames[index] = this._framesToForms.get(stack);
+ }
+
+ return packet;
+ },
+
+ /**
+ * If any new stack frames have been added to this cache since the
+ * last call to makeEvent (clearing the cache also resets the "last
+ * call"), then return a new array describing the new frames. If no
+ * new frames are available, return null.
+ *
+ * The frame cache assumes that the user of the cache keeps track of
+ * all previously-returned arrays and, in theory, concatenates them
+ * all to form a single array holding all frames added to the cache
+ * since the last reset. This concatenated array can be indexed by
+ * the frame ID. The array returned by this function, though, is
+ * dense and starts at 0.
+ *
+ * Each element in the array is an object of the form:
+ * {
+ * line: <line number for this frame>,
+ * column: <column number for this frame>,
+ * source: <filename string for this frame>,
+ * functionDisplayName: <this frame's inferred function name function or null>,
+ * parent: <frame ID -- an index into the concatenated array mentioned above>
+ * asyncCause: the async cause, or null
+ * asyncParent: <frame ID -- an index into the concatenated array mentioned above>
+ * }
+ *
+ * The intent of this approach is to make it simpler to efficiently
+ * send frame information over the debugging protocol, by only
+ * sending new frames.
+ *
+ * @returns array or null
+ */
+ makeEvent: function () {
+ const size = this._framesToForms.size;
+ if (!size || size <= this._lastEventSize) {
+ return null;
+ }
+
+ let packet = Array(size - this._lastEventSize).fill(null);
+ for (let [stack, index] of this._framesToIndices) {
+ if (index >= this._lastEventSize) {
+ packet[index - this._lastEventSize] = this._framesToForms.get(stack);
+ }
+ }
+
+ this._lastEventSize = size;
+
+ return packet;
+ },
+
+ /**
+ * Assigns an index to the given frame and its parents, if an index is not
+ * already assigned.
+ *
+ * @param SavedFrame frame
+ * A frame to assign an index to.
+ */
+ _assignFrameIndices: function (frame) {
+ if (this._framesToIndices.has(frame)) {
+ return;
+ }
+
+ if (frame) {
+ this._assignFrameIndices(frame.parent);
+ this._assignFrameIndices(frame.asyncParent);
+ }
+
+ const index = this._framesToIndices.size;
+ this._framesToIndices.set(frame, index);
+ },
+
+ /**
+ * Create the form for the given frame, if one doesn't already exist.
+ *
+ * @param SavedFrame frame
+ * A frame to create a form for.
+ */
+ _createFrameForms: function (frame) {
+ if (this._framesToForms.has(frame)) {
+ return;
+ }
+
+ let form = null;
+ if (frame) {
+ form = {
+ line: frame.line,
+ column: frame.column,
+ source: frame.source,
+ functionDisplayName: frame.functionDisplayName,
+ parent: this._framesToIndices.get(frame.parent),
+ asyncParent: this._framesToIndices.get(frame.asyncParent),
+ asyncCause: frame.asyncCause
+ };
+ this._createFrameForms(frame.parent);
+ this._createFrameForms(frame.asyncParent);
+ }
+
+ this._framesToForms.set(frame, form);
+ },
+});
+
+exports.StackFrameCache = StackFrameCache;