added make browserlist(autoprefixer) work fixed

1 files changed, 909 insertions, 754 deletions

diff --git a/node_modules/source-map/lib/source-map-consumer.js b/node_modules/source-map/lib/source-map-consumer.js
index 6abcc280..9aaf92f5 100644
--- a/node_modules/source-map/lib/source-map-consumer.js
+++ b/node_modules/source-map/lib/source-map-consumer.js
@@ -5,248 +5,144 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-var util = require('./util');
-var binarySearch = require('./binary-search');
-var ArraySet = require('./array-set').ArraySet;
-var base64VLQ = require('./base64-vlq');
-var quickSort = require('./quick-sort').quickSort;
-
-function SourceMapConsumer(aSourceMap) {
-  var sourceMap = aSourceMap;
-  if (typeof aSourceMap === 'string') {
-    sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
-  }
+const util = require("./util");
+const binarySearch = require("./binary-search");
+const ArraySet = require("./array-set").ArraySet;
+const base64VLQ = require("./base64-vlq"); // eslint-disable-line no-unused-vars
+const readWasm = require("../lib/read-wasm");
+const wasm = require("./wasm");
+
+const INTERNAL = Symbol("smcInternal");
+
+class SourceMapConsumer {
+  constructor(aSourceMap, aSourceMapURL) {
+    // If the constructor was called by super(), just return Promise<this>.
+    // Yes, this is a hack to retain the pre-existing API of the base-class
+    // constructor also being an async factory function.
+    if (aSourceMap == INTERNAL) {
+      return Promise.resolve(this);
+    }
 
-  return sourceMap.sections != null
-    ? new IndexedSourceMapConsumer(sourceMap)
-    : new BasicSourceMapConsumer(sourceMap);
-}
+    return _factory(aSourceMap, aSourceMapURL);
+  }
 
-SourceMapConsumer.fromSourceMap = function(aSourceMap) {
-  return BasicSourceMapConsumer.fromSourceMap(aSourceMap);
-}
+  static initialize(opts) {
+    readWasm.initialize(opts["lib/mappings.wasm"]);
+  }
 
-/**
- * The version of the source mapping spec that we are consuming.
- */
-SourceMapConsumer.prototype._version = 3;
+  static fromSourceMap(aSourceMap, aSourceMapURL) {
+    return _factoryBSM(aSourceMap, aSourceMapURL);
+  }
 
-// `__generatedMappings` and `__originalMappings` are arrays that hold the
-// parsed mapping coordinates from the source map's "mappings" attribute. They
-// are lazily instantiated, accessed via the `_generatedMappings` and
-// `_originalMappings` getters respectively, and we only parse the mappings
-// and create these arrays once queried for a source location. We jump through
-// these hoops because there can be many thousands of mappings, and parsing
-// them is expensive, so we only want to do it if we must.
-//
-// Each object in the arrays is of the form:
-//
-//     {
-//       generatedLine: The line number in the generated code,
-//       generatedColumn: The column number in the generated code,
-//       source: The path to the original source file that generated this
-//               chunk of code,
-//       originalLine: The line number in the original source that
-//                     corresponds to this chunk of generated code,
-//       originalColumn: The column number in the original source that
-//                       corresponds to this chunk of generated code,
-//       name: The name of the original symbol which generated this chunk of
-//             code.
-//     }
-//
-// All properties except for `generatedLine` and `generatedColumn` can be
-// `null`.
-//
-// `_generatedMappings` is ordered by the generated positions.
-//
-// `_originalMappings` is ordered by the original positions.
-
-SourceMapConsumer.prototype.__generatedMappings = null;
-Object.defineProperty(SourceMapConsumer.prototype, '_generatedMappings', {
-  get: function () {
-    if (!this.__generatedMappings) {
-      this._parseMappings(this._mappings, this.sourceRoot);
+  /**
+   * Construct a new `SourceMapConsumer` from `rawSourceMap` and `sourceMapUrl`
+   * (see the `SourceMapConsumer` constructor for details. Then, invoke the `async
+   * function f(SourceMapConsumer) -> T` with the newly constructed consumer, wait
+   * for `f` to complete, call `destroy` on the consumer, and return `f`'s return
+   * value.
+   *
+   * You must not use the consumer after `f` completes!
+   *
+   * By using `with`, you do not have to remember to manually call `destroy` on
+   * the consumer, since it will be called automatically once `f` completes.
+   *
+   * ```js
+   * const xSquared = await SourceMapConsumer.with(
+   *   myRawSourceMap,
+   *   null,
+   *   async function (consumer) {
+   *     // Use `consumer` inside here and don't worry about remembering
+   *     // to call `destroy`.
+   *
+   *     const x = await whatever(consumer);
+   *     return x * x;
+   *   }
+   * );
+   *
+   * // You may not use that `consumer` anymore out here; it has
+   * // been destroyed. But you can use `xSquared`.
+   * console.log(xSquared);
+   * ```
+   */
+  static async with(rawSourceMap, sourceMapUrl, f) {
+    const consumer = await new SourceMapConsumer(rawSourceMap, sourceMapUrl);
+    try {
+      return await f(consumer);
+    } finally {
+      consumer.destroy();
     }
+  }
 
-    return this.__generatedMappings;
+  /**
+   * Parse the mappings in a string in to a data structure which we can easily
+   * query (the ordered arrays in the `this.__generatedMappings` and
+   * `this.__originalMappings` properties).
+   */
+  _parseMappings(aStr, aSourceRoot) {
+    throw new Error("Subclasses must implement _parseMappings");
   }
-});
 
-SourceMapConsumer.prototype.__originalMappings = null;
-Object.defineProperty(SourceMapConsumer.prototype, '_originalMappings', {
-  get: function () {
-    if (!this.__originalMappings) {
-      this._parseMappings(this._mappings, this.sourceRoot);
-    }
+  /**
+   * Iterate over each mapping between an original source/line/column and a
+   * generated line/column in this source map.
+   *
+   * @param Function aCallback
+   *        The function that is called with each mapping.
+   * @param Object aContext
+   *        Optional. If specified, this object will be the value of `this` every
+   *        time that `aCallback` is called.
+   * @param aOrder
+   *        Either `SourceMapConsumer.GENERATED_ORDER` or
+   *        `SourceMapConsumer.ORIGINAL_ORDER`. Specifies whether you want to
+   *        iterate over the mappings sorted by the generated file's line/column
+   *        order or the original's source/line/column order, respectively. Defaults to
+   *        `SourceMapConsumer.GENERATED_ORDER`.
+   */
+  eachMapping(aCallback, aContext, aOrder) {
+    throw new Error("Subclasses must implement eachMapping");
+  }
 
-    return this.__originalMappings;
+  /**
+   * Returns all generated line and column information for the original source,
+   * line, and column provided. If no column is provided, returns all mappings
+   * corresponding to a either the line we are searching for or the next
+   * closest line that has any mappings. Otherwise, returns all mappings
+   * corresponding to the given line and either the column we are searching for
+   * or the next closest column that has any offsets.
+   *
+   * The only argument is an object with the following properties:
+   *
+   *   - source: The filename of the original source.
+   *   - line: The line number in the original source.  The line number is 1-based.
+   *   - column: Optional. the column number in the original source.
+   *    The column number is 0-based.
+   *
+   * and an array of objects is returned, each with the following properties:
+   *
+   *   - line: The line number in the generated source, or null.  The
+   *    line number is 1-based.
+   *   - column: The column number in the generated source, or null.
+   *    The column number is 0-based.
+   */
+  allGeneratedPositionsFor(aArgs) {
+    throw new Error("Subclasses must implement allGeneratedPositionsFor");
   }
-});
 
-SourceMapConsumer.prototype._charIsMappingSeparator =
-  function SourceMapConsumer_charIsMappingSeparator(aStr, index) {
-    var c = aStr.charAt(index);
-    return c === ";" || c === ",";
-  };
+  destroy() {
+    throw new Error("Subclasses must implement destroy");
+  }
+}
 
 /**
- * Parse the mappings in a string in to a data structure which we can easily
- * query (the ordered arrays in the `this.__generatedMappings` and
- * `this.__originalMappings` properties).
+ * The version of the source mapping spec that we are consuming.
  */
-SourceMapConsumer.prototype._parseMappings =
-  function SourceMapConsumer_parseMappings(aStr, aSourceRoot) {
-    throw new Error("Subclasses must implement _parseMappings");
-  };
-
+SourceMapConsumer.prototype._version = 3;
 SourceMapConsumer.GENERATED_ORDER = 1;
 SourceMapConsumer.ORIGINAL_ORDER = 2;
 
 SourceMapConsumer.GREATEST_LOWER_BOUND = 1;
 SourceMapConsumer.LEAST_UPPER_BOUND = 2;
 
-/**
- * Iterate over each mapping between an original source/line/column and a
- * generated line/column in this source map.
- *
- * @param Function aCallback
- *        The function that is called with each mapping.
- * @param Object aContext
- *        Optional. If specified, this object will be the value of `this` every
- *        time that `aCallback` is called.
- * @param aOrder
- *        Either `SourceMapConsumer.GENERATED_ORDER` or
- *        `SourceMapConsumer.ORIGINAL_ORDER`. Specifies whether you want to
- *        iterate over the mappings sorted by the generated file's line/column
- *        order or the original's source/line/column order, respectively. Defaults to
- *        `SourceMapConsumer.GENERATED_ORDER`.
- */
-SourceMapConsumer.prototype.eachMapping =
-  function SourceMapConsumer_eachMapping(aCallback, aContext, aOrder) {
-    var context = aContext || null;
-    var order = aOrder || SourceMapConsumer.GENERATED_ORDER;
-
-    var mappings;
-    switch (order) {
-    case SourceMapConsumer.GENERATED_ORDER:
-      mappings = this._generatedMappings;
-      break;
-    case SourceMapConsumer.ORIGINAL_ORDER:
-      mappings = this._originalMappings;
-      break;
-    default:
-      throw new Error("Unknown order of iteration.");
-    }
-
-    var sourceRoot = this.sourceRoot;
-    mappings.map(function (mapping) {
-      var source = mapping.source === null ? null : this._sources.at(mapping.source);
-      if (source != null && sourceRoot != null) {
-        source = util.join(sourceRoot, source);
-      }
-      return {
-        source: source,
-        generatedLine: mapping.generatedLine,
-        generatedColumn: mapping.generatedColumn,
-        originalLine: mapping.originalLine,
-        originalColumn: mapping.originalColumn,
-        name: mapping.name === null ? null : this._names.at(mapping.name)
-      };
-    }, this).forEach(aCallback, context);
-  };
-
-/**
- * Returns all generated line and column information for the original source,
- * line, and column provided. If no column is provided, returns all mappings
- * corresponding to a either the line we are searching for or the next
- * closest line that has any mappings. Otherwise, returns all mappings
- * corresponding to the given line and either the column we are searching for
- * or the next closest column that has any offsets.
- *
- * The only argument is an object with the following properties:
- *
- *   - source: The filename of the original source.
- *   - line: The line number in the original source.
- *   - column: Optional. the column number in the original source.
- *
- * and an array of objects is returned, each with the following properties:
- *
- *   - line: The line number in the generated source, or null.
- *   - column: The column number in the generated source, or null.
- */
-SourceMapConsumer.prototype.allGeneratedPositionsFor =
-  function SourceMapConsumer_allGeneratedPositionsFor(aArgs) {
-    var line = util.getArg(aArgs, 'line');
-
-    // When there is no exact match, BasicSourceMapConsumer.prototype._findMapping
-    // returns the index of the closest mapping less than the needle. By
-    // setting needle.originalColumn to 0, we thus find the last mapping for
-    // the given line, provided such a mapping exists.
-    var needle = {
-      source: util.getArg(aArgs, 'source'),
-      originalLine: line,
-      originalColumn: util.getArg(aArgs, 'column', 0)
-    };
-
-    if (this.sourceRoot != null) {
-      needle.source = util.relative(this.sourceRoot, needle.source);
-    }
-    if (!this._sources.has(needle.source)) {
-      return [];
-    }
-    needle.source = this._sources.indexOf(needle.source);
-
-    var mappings = [];
-
-    var index = this._findMapping(needle,
-                                  this._originalMappings,
-                                  "originalLine",
-                                  "originalColumn",
-                                  util.compareByOriginalPositions,
-                                  binarySearch.LEAST_UPPER_BOUND);
-    if (index >= 0) {
-      var mapping = this._originalMappings[index];
-
-      if (aArgs.column === undefined) {
-        var originalLine = mapping.originalLine;
-
-        // Iterate until either we run out of mappings, or we run into
-        // a mapping for a different line than the one we found. Since
-        // mappings are sorted, this is guaranteed to find all mappings for
-        // the line we found.
-        while (mapping && mapping.originalLine === originalLine) {
-          mappings.push({
-            line: util.getArg(mapping, 'generatedLine', null),
-            column: util.getArg(mapping, 'generatedColumn', null),
-            lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
-          });
-
-          mapping = this._originalMappings[++index];
-        }
-      } else {
-        var originalColumn = mapping.originalColumn;
-
-        // Iterate until either we run out of mappings, or we run into
-        // a mapping for a different line than the one we were searching for.
-        // Since mappings are sorted, this is guaranteed to find all mappings for
-        // the line we are searching for.
-        while (mapping &&
-               mapping.originalLine === line &&
-               mapping.originalColumn == originalColumn) {
-          mappings.push({
-            line: util.getArg(mapping, 'generatedLine', null),
-            column: util.getArg(mapping, 'generatedColumn', null),
-            lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
-          });
-
-          mapping = this._originalMappings[++index];
-        }
-      }
-    }
-
-    return mappings;
-  };
-
 exports.SourceMapConsumer = SourceMapConsumer;
 
 /**
@@ -254,13 +150,13 @@ exports.SourceMapConsumer = SourceMapConsumer;
  * query for information about the original file positions by giving it a file
  * position in the generated source.
  *
- * The only parameter is the raw source map (either as a JSON string, or
+ * The first parameter is the raw source map (either as a JSON string, or
  * already parsed to an object). According to the spec, source maps have the
  * following attributes:
  *
  *   - version: Which version of the source map spec this map is following.
  *   - sources: An array of URLs to the original source files.
- *   - names: An array of identifiers which can be referrenced by individual mappings.
+ *   - names: An array of identifiers which can be referenced by individual mappings.
  *   - sourceRoot: Optional. The URL root from which all sources are relative.
  *   - sourcesContent: Optional. An array of contents of the original source files.
  *   - mappings: A string of base64 VLQs which contain the actual mappings.
@@ -277,359 +173,348 @@ exports.SourceMapConsumer = SourceMapConsumer;
  *       mappings: "AA,AB;;ABCDE;"
  *     }
  *
+ * The second parameter, if given, is a string whose value is the URL
+ * at which the source map was found.  This URL is used to compute the
+ * sources array.
+ *
  * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit?pli=1#
  */
-function BasicSourceMapConsumer(aSourceMap) {
-  var sourceMap = aSourceMap;
-  if (typeof aSourceMap === 'string') {
-    sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
-  }
+class BasicSourceMapConsumer extends SourceMapConsumer {
+  constructor(aSourceMap, aSourceMapURL) {
+    return super(INTERNAL).then(that => {
+      let sourceMap = aSourceMap;
+      if (typeof aSourceMap === "string") {
+        sourceMap = util.parseSourceMapInput(aSourceMap);
+      }
 
-  var version = util.getArg(sourceMap, 'version');
-  var sources = util.getArg(sourceMap, 'sources');
-  // Sass 3.3 leaves out the 'names' array, so we deviate from the spec (which
-  // requires the array) to play nice here.
-  var names = util.getArg(sourceMap, 'names', []);
-  var sourceRoot = util.getArg(sourceMap, 'sourceRoot', null);
-  var sourcesContent = util.getArg(sourceMap, 'sourcesContent', null);
-  var mappings = util.getArg(sourceMap, 'mappings');
-  var file = util.getArg(sourceMap, 'file', null);
-
-  // Once again, Sass deviates from the spec and supplies the version as a
-  // string rather than a number, so we use loose equality checking here.
-  if (version != this._version) {
-    throw new Error('Unsupported version: ' + version);
-  }
+      const version = util.getArg(sourceMap, "version");
+      let sources = util.getArg(sourceMap, "sources");
+      // Sass 3.3 leaves out the 'names' array, so we deviate from the spec (which
+      // requires the array) to play nice here.
+      const names = util.getArg(sourceMap, "names", []);
+      let sourceRoot = util.getArg(sourceMap, "sourceRoot", null);
+      const sourcesContent = util.getArg(sourceMap, "sourcesContent", null);
+      const mappings = util.getArg(sourceMap, "mappings");
+      const file = util.getArg(sourceMap, "file", null);
+
+      // Once again, Sass deviates from the spec and supplies the version as a
+      // string rather than a number, so we use loose equality checking here.
+      if (version != that._version) {
+        throw new Error("Unsupported version: " + version);
+      }
 
-  sources = sources
-    .map(String)
-    // Some source maps produce relative source paths like "./foo.js" instead of
-    // "foo.js".  Normalize these first so that future comparisons will succeed.
-    // See bugzil.la/1090768.
-    .map(util.normalize)
-    // Always ensure that absolute sources are internally stored relative to
-    // the source root, if the source root is absolute. Not doing this would
-    // be particularly problematic when the source root is a prefix of the
-    // source (valid, but why??). See github issue #199 and bugzil.la/1188982.
-    .map(function (source) {
-      return sourceRoot && util.isAbsolute(sourceRoot) && util.isAbsolute(source)
-        ? util.relative(sourceRoot, source)
-        : source;
-    });
+      if (sourceRoot) {
+        sourceRoot = util.normalize(sourceRoot);
+      }
 
-  // Pass `true` below to allow duplicate names and sources. While source maps
-  // are intended to be compressed and deduplicated, the TypeScript compiler
-  // sometimes generates source maps with duplicates in them. See Github issue
-  // #72 and bugzil.la/889492.
-  this._names = ArraySet.fromArray(names.map(String), true);
-  this._sources = ArraySet.fromArray(sources, true);
-
-  this.sourceRoot = sourceRoot;
-  this.sourcesContent = sourcesContent;
-  this._mappings = mappings;
-  this.file = file;
-}
+      sources = sources
+        .map(String)
+        // Some source maps produce relative source paths like "./foo.js" instead of
+        // "foo.js".  Normalize these first so that future comparisons will succeed.
+        // See bugzil.la/1090768.
+        .map(util.normalize)
+        // Always ensure that absolute sources are internally stored relative to
+        // the source root, if the source root is absolute. Not doing this would
+        // be particularly problematic when the source root is a prefix of the
+        // source (valid, but why??). See github issue #199 and bugzil.la/1188982.
+        .map(function(source) {
+          return sourceRoot && util.isAbsolute(sourceRoot) && util.isAbsolute(source)
+            ? util.relative(sourceRoot, source)
+            : source;
+        });
+
+      // Pass `true` below to allow duplicate names and sources. While source maps
+      // are intended to be compressed and deduplicated, the TypeScript compiler
+      // sometimes generates source maps with duplicates in them. See Github issue
+      // #72 and bugzil.la/889492.
+      that._names = ArraySet.fromArray(names.map(String), true);
+      that._sources = ArraySet.fromArray(sources, true);
+
+      that._absoluteSources = that._sources.toArray().map(function(s) {
+        return util.computeSourceURL(sourceRoot, s, aSourceMapURL);
+      });
 
-BasicSourceMapConsumer.prototype = Object.create(SourceMapConsumer.prototype);
-BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;
+      that.sourceRoot = sourceRoot;
+      that.sourcesContent = sourcesContent;
+      that._mappings = mappings;
+      that._sourceMapURL = aSourceMapURL;
+      that.file = file;
 
-/**
- * Create a BasicSourceMapConsumer from a SourceMapGenerator.
- *
- * @param SourceMapGenerator aSourceMap
- *        The source map that will be consumed.
- * @returns BasicSourceMapConsumer
- */
-BasicSourceMapConsumer.fromSourceMap =
-  function SourceMapConsumer_fromSourceMap(aSourceMap) {
-    var smc = Object.create(BasicSourceMapConsumer.prototype);
-
-    var names = smc._names = ArraySet.fromArray(aSourceMap._names.toArray(), true);
-    var sources = smc._sources = ArraySet.fromArray(aSourceMap._sources.toArray(), true);
-    smc.sourceRoot = aSourceMap._sourceRoot;
-    smc.sourcesContent = aSourceMap._generateSourcesContent(smc._sources.toArray(),
-                                                            smc.sourceRoot);
-    smc.file = aSourceMap._file;
-
-    // Because we are modifying the entries (by converting string sources and
-    // names to indices into the sources and names ArraySets), we have to make
-    // a copy of the entry or else bad things happen. Shared mutable state
-    // strikes again! See github issue #191.
-
-    var generatedMappings = aSourceMap._mappings.toArray().slice();
-    var destGeneratedMappings = smc.__generatedMappings = [];
-    var destOriginalMappings = smc.__originalMappings = [];
-
-    for (var i = 0, length = generatedMappings.length; i < length; i++) {
-      var srcMapping = generatedMappings[i];
-      var destMapping = new Mapping;
-      destMapping.generatedLine = srcMapping.generatedLine;
-      destMapping.generatedColumn = srcMapping.generatedColumn;
-
-      if (srcMapping.source) {
-        destMapping.source = sources.indexOf(srcMapping.source);
-        destMapping.originalLine = srcMapping.originalLine;
-        destMapping.originalColumn = srcMapping.originalColumn;
-
-        if (srcMapping.name) {
-          destMapping.name = names.indexOf(srcMapping.name);
-        }
+      that._computedColumnSpans = false;
+      that._mappingsPtr = 0;
+      that._wasm = null;
 
-        destOriginalMappings.push(destMapping);
-      }
+      return wasm().then(w => {
+        that._wasm = w;
+        return that;
+      });
+    });
+  }
 
-      destGeneratedMappings.push(destMapping);
+  /**
+   * Utility function to find the index of a source.  Returns -1 if not
+   * found.
+   */
+  _findSourceIndex(aSource) {
+    let relativeSource = aSource;
+    if (this.sourceRoot != null) {
+      relativeSource = util.relative(this.sourceRoot, relativeSource);
     }
 
-    quickSort(smc.__originalMappings, util.compareByOriginalPositions);
+    if (this._sources.has(relativeSource)) {
+      return this._sources.indexOf(relativeSource);
+    }
 
-    return smc;
-  };
+    // Maybe aSource is an absolute URL as returned by |sources|.  In
+    // this case we can't simply undo the transform.
+    for (let i = 0; i < this._absoluteSources.length; ++i) {
+      if (this._absoluteSources[i] == aSource) {
+        return i;
+      }
+    }
 
-/**
- * The version of the source mapping spec that we are consuming.
- */
-BasicSourceMapConsumer.prototype._version = 3;
+    return -1;
+  }
 
-/**
- * The list of original sources.
- */
-Object.defineProperty(BasicSourceMapConsumer.prototype, 'sources', {
-  get: function () {
-    return this._sources.toArray().map(function (s) {
-      return this.sourceRoot != null ? util.join(this.sourceRoot, s) : s;
-    }, this);
+  /**
+   * Create a BasicSourceMapConsumer from a SourceMapGenerator.
+   *
+   * @param SourceMapGenerator aSourceMap
+   *        The source map that will be consumed.
+   * @param String aSourceMapURL
+   *        The URL at which the source map can be found (optional)
+   * @returns BasicSourceMapConsumer
+   */
+  static fromSourceMap(aSourceMap, aSourceMapURL) {
+    return new BasicSourceMapConsumer(aSourceMap.toString());
   }
-});
 
-/**
- * Provide the JIT with a nice shape / hidden class.
- */
-function Mapping() {
-  this.generatedLine = 0;
-  this.generatedColumn = 0;
-  this.source = null;
-  this.originalLine = null;
-  this.originalColumn = null;
-  this.name = null;
-}
+  get sources() {
+    return this._absoluteSources.slice();
+  }
 
-/**
- * Parse the mappings in a string in to a data structure which we can easily
- * query (the ordered arrays in the `this.__generatedMappings` and
- * `this.__originalMappings` properties).
- */
-BasicSourceMapConsumer.prototype._parseMappings =
-  function SourceMapConsumer_parseMappings(aStr, aSourceRoot) {
-    var generatedLine = 1;
-    var previousGeneratedColumn = 0;
-    var previousOriginalLine = 0;
-    var previousOriginalColumn = 0;
-    var previousSource = 0;
-    var previousName = 0;
-    var length = aStr.length;
-    var index = 0;
-    var cachedSegments = {};
-    var temp = {};
-    var originalMappings = [];
-    var generatedMappings = [];
-    var mapping, str, segment, end, value;
-
-    while (index < length) {
-      if (aStr.charAt(index) === ';') {
-        generatedLine++;
-        index++;
-        previousGeneratedColumn = 0;
-      }
-      else if (aStr.charAt(index) === ',') {
-        index++;
+  _getMappingsPtr() {
+    if (this._mappingsPtr === 0) {
+      this._parseMappings(this._mappings, this.sourceRoot);
+    }
+
+    return this._mappingsPtr;
+  }
+
+  /**
+   * Parse the mappings in a string in to a data structure which we can easily
+   * query (the ordered arrays in the `this.__generatedMappings` and
+   * `this.__originalMappings` properties).
+   */
+  _parseMappings(aStr, aSourceRoot) {
+    const size = aStr.length;
+
+    const mappingsBufPtr = this._wasm.exports.allocate_mappings(size);
+    const mappingsBuf = new Uint8Array(this._wasm.exports.memory.buffer, mappingsBufPtr, size);
+    for (let i = 0; i < size; i++) {
+      mappingsBuf[i] = aStr.charCodeAt(i);
+    }
+
+    const mappingsPtr = this._wasm.exports.parse_mappings(mappingsBufPtr);
+
+    if (!mappingsPtr) {
+      const error = this._wasm.exports.get_last_error();
+      let msg = `Error parsing mappings (code ${error}): `;
+
+      // XXX: keep these error codes in sync with `fitzgen/source-map-mappings`.
+      switch (error) {
+        case 1:
+          msg += "the mappings contained a negative line, column, source index, or name index";
+          break;
+        case 2:
+          msg += "the mappings contained a number larger than 2**32";
+          break;
+        case 3:
+          msg += "reached EOF while in the middle of parsing a VLQ";
+          break;
+        case 4:
+          msg += "invalid base 64 character while parsing a VLQ";
+          break;
+        default:
+          msg += "unknown error code";
+          break;
       }
-      else {
-        mapping = new Mapping();
-        mapping.generatedLine = generatedLine;
-
-        // Because each offset is encoded relative to the previous one,
-        // many segments often have the same encoding. We can exploit this
-        // fact by caching the parsed variable length fields of each segment,
-        // allowing us to avoid a second parse if we encounter the same
-        // segment again.
-        for (end = index; end < length; end++) {
-          if (this._charIsMappingSeparator(aStr, end)) {
-            break;
-          }
-        }
-        str = aStr.slice(index, end);
-
-        segment = cachedSegments[str];
-        if (segment) {
-          index += str.length;
-        } else {
-          segment = [];
-          while (index < end) {
-            base64VLQ.decode(aStr, index, temp);
-            value = temp.value;
-            index = temp.rest;
-            segment.push(value);
-          }
 
-          if (segment.length === 2) {
-            throw new Error('Found a source, but no line and column');
-          }
+      throw new Error(msg);
+    }
 
-          if (segment.length === 3) {
-            throw new Error('Found a source and line, but no column');
-          }
+    this._mappingsPtr = mappingsPtr;
+  }
 
-          cachedSegments[str] = segment;
-        }
+  eachMapping(aCallback, aContext, aOrder) {
+    const context = aContext || null;
+    const order = aOrder || SourceMapConsumer.GENERATED_ORDER;
+    const sourceRoot = this.sourceRoot;
+
+    this._wasm.withMappingCallback(
+      mapping => {
+        if (mapping.source !== null) {
+          mapping.source = this._sources.at(mapping.source);
+          mapping.source = util.computeSourceURL(sourceRoot, mapping.source, this._sourceMapURL);
 
-        // Generated column.
-        mapping.generatedColumn = previousGeneratedColumn + segment[0];
-        previousGeneratedColumn = mapping.generatedColumn;
-
-        if (segment.length > 1) {
-          // Original source.
-          mapping.source = previousSource + segment[1];
-          previousSource += segment[1];
-
-          // Original line.
-          mapping.originalLine = previousOriginalLine + segment[2];
-          previousOriginalLine = mapping.originalLine;
-          // Lines are stored 0-based
-          mapping.originalLine += 1;
-
-          // Original column.
-          mapping.originalColumn = previousOriginalColumn + segment[3];
-          previousOriginalColumn = mapping.originalColumn;
-
-          if (segment.length > 4) {
-            // Original name.
-            mapping.name = previousName + segment[4];
-            previousName += segment[4];
+          if (mapping.name !== null) {
+            mapping.name = this._names.at(mapping.name);
           }
         }
 
-        generatedMappings.push(mapping);
-        if (typeof mapping.originalLine === 'number') {
-          originalMappings.push(mapping);
+        aCallback.call(context, mapping);
+      },
+      () => {
+        switch (order) {
+        case SourceMapConsumer.GENERATED_ORDER:
+          this._wasm.exports.by_generated_location(this._getMappingsPtr());
+          break;
+        case SourceMapConsumer.ORIGINAL_ORDER:
+          this._wasm.exports.by_original_location(this._getMappingsPtr());
+          break;
+        default:
+          throw new Error("Unknown order of iteration.");
         }
       }
-    }
-
-    quickSort(generatedMappings, util.compareByGeneratedPositionsDeflated);
-    this.__generatedMappings = generatedMappings;
+    );
+  }
 
-    quickSort(originalMappings, util.compareByOriginalPositions);
-    this.__originalMappings = originalMappings;
-  };
+  allGeneratedPositionsFor(aArgs) {
+    let source = util.getArg(aArgs, "source");
+    const originalLine = util.getArg(aArgs, "line");
+    const originalColumn = aArgs.column || 0;
 
-/**
- * Find the mapping that best matches the hypothetical "needle" mapping that
- * we are searching for in the given "haystack" of mappings.
- */
-BasicSourceMapConsumer.prototype._findMapping =
-  function SourceMapConsumer_findMapping(aNeedle, aMappings, aLineName,
-                                         aColumnName, aComparator, aBias) {
-    // To return the position we are searching for, we must first find the
-    // mapping for the given position and then return the opposite position it
-    // points to. Because the mappings are sorted, we can use binary search to
-    // find the best mapping.
+    source = this._findSourceIndex(source);
+    if (source < 0) {
+      return [];
+    }
 
-    if (aNeedle[aLineName] <= 0) {
-      throw new TypeError('Line must be greater than or equal to 1, got '
-                          + aNeedle[aLineName]);
+    if (originalLine < 1) {
+      throw new Error("Line numbers must be >= 1");
     }
-    if (aNeedle[aColumnName] < 0) {
-      throw new TypeError('Column must be greater than or equal to 0, got '
-                          + aNeedle[aColumnName]);
+
+    if (originalColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
     }
 
-    return binarySearch.search(aNeedle, aMappings, aComparator, aBias);
-  };
+    const mappings = [];
 
-/**
- * Compute the last column for each generated mapping. The last column is
- * inclusive.
- */
-BasicSourceMapConsumer.prototype.computeColumnSpans =
-  function SourceMapConsumer_computeColumnSpans() {
-    for (var index = 0; index < this._generatedMappings.length; ++index) {
-      var mapping = this._generatedMappings[index];
-
-      // Mappings do not contain a field for the last generated columnt. We
-      // can come up with an optimistic estimate, however, by assuming that
-      // mappings are contiguous (i.e. given two consecutive mappings, the
-      // first mapping ends where the second one starts).
-      if (index + 1 < this._generatedMappings.length) {
-        var nextMapping = this._generatedMappings[index + 1];
-
-        if (mapping.generatedLine === nextMapping.generatedLine) {
-          mapping.lastGeneratedColumn = nextMapping.generatedColumn - 1;
-          continue;
+    this._wasm.withMappingCallback(
+      m => {
+        let lastColumn = m.lastGeneratedColumn;
+        if (this._computedColumnSpans && lastColumn === null) {
+          lastColumn = Infinity;
         }
+        mappings.push({
+          line: m.generatedLine,
+          column: m.generatedColumn,
+          lastColumn,
+        });
+      }, () => {
+        this._wasm.exports.all_generated_locations_for(
+          this._getMappingsPtr(),
+          source,
+          originalLine - 1,
+          "column" in aArgs,
+          originalColumn
+        );
       }
+    );
 
-      // The last mapping for each line spans the entire line.
-      mapping.lastGeneratedColumn = Infinity;
+    return mappings;
+  }
+
+  destroy() {
+    if (this._mappingsPtr !== 0) {
+      this._wasm.exports.free_mappings(this._mappingsPtr);
+      this._mappingsPtr = 0;
     }
-  };
+  }
 
-/**
- * Returns the original source, line, and column information for the generated
- * source's line and column positions provided. The only argument is an object
- * with the following properties:
- *
- *   - line: The line number in the generated source.
- *   - column: The column number in the generated source.
- *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
- *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
- *     closest element that is smaller than or greater than the one we are
- *     searching for, respectively, if the exact element cannot be found.
- *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
- *
- * and an object is returned with the following properties:
- *
- *   - source: The original source file, or null.
- *   - line: The line number in the original source, or null.
- *   - column: The column number in the original source, or null.
- *   - name: The original identifier, or null.
- */
-BasicSourceMapConsumer.prototype.originalPositionFor =
-  function SourceMapConsumer_originalPositionFor(aArgs) {
-    var needle = {
-      generatedLine: util.getArg(aArgs, 'line'),
-      generatedColumn: util.getArg(aArgs, 'column')
+  /**
+   * Compute the last column for each generated mapping. The last column is
+   * inclusive.
+   */
+  computeColumnSpans() {
+    if (this._computedColumnSpans) {
+      return;
+    }
+
+    this._wasm.exports.compute_column_spans(this._getMappingsPtr());
+    this._computedColumnSpans = true;
+  }
+
+  /**
+   * Returns the original source, line, and column information for the generated
+   * source's line and column positions provided. The only argument is an object
+   * with the following properties:
+   *
+   *   - line: The line number in the generated source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the generated source.  The column
+   *     number is 0-based.
+   *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
+   *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
+   *     closest element that is smaller than or greater than the one we are
+   *     searching for, respectively, if the exact element cannot be found.
+   *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - source: The original source file, or null.
+   *   - line: The line number in the original source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the original source, or null.  The
+   *     column number is 0-based.
+   *   - name: The original identifier, or null.
+   */
+  originalPositionFor(aArgs) {
+    const needle = {
+      generatedLine: util.getArg(aArgs, "line"),
+      generatedColumn: util.getArg(aArgs, "column")
     };
 
-    var index = this._findMapping(
-      needle,
-      this._generatedMappings,
-      "generatedLine",
-      "generatedColumn",
-      util.compareByGeneratedPositionsDeflated,
-      util.getArg(aArgs, 'bias', SourceMapConsumer.GREATEST_LOWER_BOUND)
-    );
+    if (needle.generatedLine < 1) {
+      throw new Error("Line numbers must be >= 1");
+    }
 
-    if (index >= 0) {
-      var mapping = this._generatedMappings[index];
+    if (needle.generatedColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
+    }
+
+    let bias = util.getArg(aArgs, "bias", SourceMapConsumer.GREATEST_LOWER_BOUND);
+    if (bias == null) {
+      bias = SourceMapConsumer.GREATEST_LOWER_BOUND;
+    }
 
+    let mapping;
+    this._wasm.withMappingCallback(m => mapping = m, () => {
+      this._wasm.exports.original_location_for(
+        this._getMappingsPtr(),
+        needle.generatedLine - 1,
+        needle.generatedColumn,
+        bias
+      );
+    });
+
+    if (mapping) {
       if (mapping.generatedLine === needle.generatedLine) {
-        var source = util.getArg(mapping, 'source', null);
+        let source = util.getArg(mapping, "source", null);
         if (source !== null) {
           source = this._sources.at(source);
-          if (this.sourceRoot != null) {
-            source = util.join(this.sourceRoot, source);
-          }
+          source = util.computeSourceURL(this.sourceRoot, source, this._sourceMapURL);
         }
-        var name = util.getArg(mapping, 'name', null);
+
+        let name = util.getArg(mapping, "name", null);
         if (name !== null) {
           name = this._names.at(name);
         }
+
         return {
-          source: source,
-          line: util.getArg(mapping, 'originalLine', null),
-          column: util.getArg(mapping, 'originalColumn', null),
-          name: name
+          source,
+          line: util.getArg(mapping, "originalLine", null),
+          column: util.getArg(mapping, "originalColumn", null),
+          name
         };
       }
     }
@@ -640,56 +525,56 @@ BasicSourceMapConsumer.prototype.originalPositionFor =
       column: null,
       name: null
     };
-  };
+  }
 
-/**
- * Return true if we have the source content for every source in the source
- * map, false otherwise.
- */
-BasicSourceMapConsumer.prototype.hasContentsOfAllSources =
-  function BasicSourceMapConsumer_hasContentsOfAllSources() {
+  /**
+   * Return true if we have the source content for every source in the source
+   * map, false otherwise.
+   */
+  hasContentsOfAllSources() {
     if (!this.sourcesContent) {
       return false;
     }
     return this.sourcesContent.length >= this._sources.size() &&
-      !this.sourcesContent.some(function (sc) { return sc == null; });
-  };
+      !this.sourcesContent.some(function(sc) { return sc == null; });
+  }
 
-/**
- * Returns the original source content. The only argument is the url of the
- * original source file. Returns null if no original source content is
- * available.
- */
-BasicSourceMapConsumer.prototype.sourceContentFor =
-  function SourceMapConsumer_sourceContentFor(aSource, nullOnMissing) {
+  /**
+   * Returns the original source content. The only argument is the url of the
+   * original source file. Returns null if no original source content is
+   * available.
+   */
+  sourceContentFor(aSource, nullOnMissing) {
     if (!this.sourcesContent) {
       return null;
     }
 
-    if (this.sourceRoot != null) {
-      aSource = util.relative(this.sourceRoot, aSource);
+    const index = this._findSourceIndex(aSource);
+    if (index >= 0) {
+      return this.sourcesContent[index];
     }
 
-    if (this._sources.has(aSource)) {
-      return this.sourcesContent[this._sources.indexOf(aSource)];
+    let relativeSource = aSource;
+    if (this.sourceRoot != null) {
+      relativeSource = util.relative(this.sourceRoot, relativeSource);
     }
 
-    var url;
+    let url;
     if (this.sourceRoot != null
         && (url = util.urlParse(this.sourceRoot))) {
       // XXX: file:// URIs and absolute paths lead to unexpected behavior for
       // many users. We can help them out when they expect file:// URIs to
       // behave like it would if they were running a local HTTP server. See
       // https://bugzilla.mozilla.org/show_bug.cgi?id=885597.
-      var fileUriAbsPath = aSource.replace(/^file:\/\//, "");
+      const fileUriAbsPath = relativeSource.replace(/^file:\/\//, "");
       if (url.scheme == "file"
           && this._sources.has(fileUriAbsPath)) {
-        return this.sourcesContent[this._sources.indexOf(fileUriAbsPath)]
+        return this.sourcesContent[this._sources.indexOf(fileUriAbsPath)];
       }
 
       if ((!url.path || url.path == "/")
-          && this._sources.has("/" + aSource)) {
-        return this.sourcesContent[this._sources.indexOf("/" + aSource)];
+          && this._sources.has("/" + relativeSource)) {
+        return this.sourcesContent[this._sources.indexOf("/" + relativeSource)];
       }
     }
 
@@ -700,68 +585,84 @@ BasicSourceMapConsumer.prototype.sourceContentFor =
     if (nullOnMissing) {
       return null;
     }
-    else {
-      throw new Error('"' + aSource + '" is not in the SourceMap.');
-    }
-  };
 
-/**
- * Returns the generated line and column information for the original source,
- * line, and column positions provided. The only argument is an object with
- * the following properties:
- *
- *   - source: The filename of the original source.
- *   - line: The line number in the original source.
- *   - column: The column number in the original source.
- *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
- *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
- *     closest element that is smaller than or greater than the one we are
- *     searching for, respectively, if the exact element cannot be found.
- *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
- *
- * and an object is returned with the following properties:
- *
- *   - line: The line number in the generated source, or null.
- *   - column: The column number in the generated source, or null.
- */
-BasicSourceMapConsumer.prototype.generatedPositionFor =
-  function SourceMapConsumer_generatedPositionFor(aArgs) {
-    var source = util.getArg(aArgs, 'source');
-    if (this.sourceRoot != null) {
-      source = util.relative(this.sourceRoot, source);
-    }
-    if (!this._sources.has(source)) {
+    throw new Error('"' + relativeSource + '" is not in the SourceMap.');
+  }
+
+  /**
+   * Returns the generated line and column information for the original source,
+   * line, and column positions provided. The only argument is an object with
+   * the following properties:
+   *
+   *   - source: The filename of the original source.
+   *   - line: The line number in the original source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the original source.  The column
+   *     number is 0-based.
+   *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
+   *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
+   *     closest element that is smaller than or greater than the one we are
+   *     searching for, respectively, if the exact element cannot be found.
+   *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - line: The line number in the generated source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the generated source, or null.
+   *     The column number is 0-based.
+   */
+  generatedPositionFor(aArgs) {
+    let source = util.getArg(aArgs, "source");
+    source = this._findSourceIndex(source);
+    if (source < 0) {
       return {
         line: null,
         column: null,
         lastColumn: null
       };
     }
-    source = this._sources.indexOf(source);
 
-    var needle = {
-      source: source,
-      originalLine: util.getArg(aArgs, 'line'),
-      originalColumn: util.getArg(aArgs, 'column')
+    const needle = {
+      source,
+      originalLine: util.getArg(aArgs, "line"),
+      originalColumn: util.getArg(aArgs, "column")
     };
 
-    var index = this._findMapping(
-      needle,
-      this._originalMappings,
-      "originalLine",
-      "originalColumn",
-      util.compareByOriginalPositions,
-      util.getArg(aArgs, 'bias', SourceMapConsumer.GREATEST_LOWER_BOUND)
-    );
+    if (needle.originalLine < 1) {
+      throw new Error("Line numbers must be >= 1");
+    }
 
-    if (index >= 0) {
-      var mapping = this._originalMappings[index];
+    if (needle.originalColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
+    }
+
+    let bias = util.getArg(aArgs, "bias", SourceMapConsumer.GREATEST_LOWER_BOUND);
+    if (bias == null) {
+      bias = SourceMapConsumer.GREATEST_LOWER_BOUND;
+    }
 
+    let mapping;
+    this._wasm.withMappingCallback(m => mapping = m, () => {
+      this._wasm.exports.generated_location_for(
+        this._getMappingsPtr(),
+        needle.source,
+        needle.originalLine - 1,
+        needle.originalColumn,
+        bias
+      );
+    });
+
+    if (mapping) {
       if (mapping.source === needle.source) {
+        let lastColumn = mapping.lastGeneratedColumn;
+        if (this._computedColumnSpans && lastColumn === null) {
+          lastColumn = Infinity;
+        }
         return {
-          line: util.getArg(mapping, 'generatedLine', null),
-          column: util.getArg(mapping, 'generatedColumn', null),
-          lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
+          line: util.getArg(mapping, "generatedLine", null),
+          column: util.getArg(mapping, "generatedColumn", null),
+          lastColumn,
         };
       }
     }
@@ -771,8 +672,10 @@ BasicSourceMapConsumer.prototype.generatedPositionFor =
       column: null,
       lastColumn: null
     };
-  };
+  }
+}
 
+BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;
 exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
 
 /**
@@ -781,7 +684,7 @@ exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
  * that it takes "indexed" source maps (i.e. ones with a "sections" field) as
  * input.
  *
- * The only parameter is a raw source map (either as a JSON string, or already
+ * The first parameter is a raw source map (either as a JSON string, or already
  * parsed to an object). According to the spec for indexed source maps, they
  * have the following attributes:
  *
@@ -818,114 +721,197 @@ exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
  *    }],
  *  }
  *
+ * The second parameter, if given, is a string whose value is the URL
+ * at which the source map was found.  This URL is used to compute the
+ * sources array.
+ *
  * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit#heading=h.535es3xeprgt
  */
-function IndexedSourceMapConsumer(aSourceMap) {
-  var sourceMap = aSourceMap;
-  if (typeof aSourceMap === 'string') {
-    sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
+class IndexedSourceMapConsumer extends SourceMapConsumer {
+  constructor(aSourceMap, aSourceMapURL) {
+    return super(INTERNAL).then(that => {
+      let sourceMap = aSourceMap;
+      if (typeof aSourceMap === "string") {
+        sourceMap = util.parseSourceMapInput(aSourceMap);
+      }
+
+      const version = util.getArg(sourceMap, "version");
+      const sections = util.getArg(sourceMap, "sections");
+
+      if (version != that._version) {
+        throw new Error("Unsupported version: " + version);
+      }
+
+      that._sources = new ArraySet();
+      that._names = new ArraySet();
+      that.__generatedMappings = null;
+      that.__originalMappings = null;
+      that.__generatedMappingsUnsorted = null;
+      that.__originalMappingsUnsorted = null;
+
+      let lastOffset = {
+        line: -1,
+        column: 0
+      };
+      return Promise.all(sections.map(s => {
+        if (s.url) {
+          // The url field will require support for asynchronicity.
+          // See https://github.com/mozilla/source-map/issues/16
+          throw new Error("Support for url field in sections not implemented.");
+        }
+        const offset = util.getArg(s, "offset");
+        const offsetLine = util.getArg(offset, "line");
+        const offsetColumn = util.getArg(offset, "column");
+
+        if (offsetLine < lastOffset.line ||
+            (offsetLine === lastOffset.line && offsetColumn < lastOffset.column)) {
+          throw new Error("Section offsets must be ordered and non-overlapping.");
+        }
+        lastOffset = offset;
+
+        const cons = new SourceMapConsumer(util.getArg(s, "map"), aSourceMapURL);
+        return cons.then(consumer => {
+          return {
+            generatedOffset: {
+              // The offset fields are 0-based, but we use 1-based indices when
+              // encoding/decoding from VLQ.
+              generatedLine: offsetLine + 1,
+              generatedColumn: offsetColumn + 1
+            },
+            consumer
+          };
+        });
+      })).then(s => {
+        that._sections = s;
+        return that;
+      });
+    });
   }
 
-  var version = util.getArg(sourceMap, 'version');
-  var sections = util.getArg(sourceMap, 'sections');
+  // `__generatedMappings` and `__originalMappings` are arrays that hold the
+  // parsed mapping coordinates from the source map's "mappings" attribute. They
+  // are lazily instantiated, accessed via the `_generatedMappings` and
+  // `_originalMappings` getters respectively, and we only parse the mappings
+  // and create these arrays once queried for a source location. We jump through
+  // these hoops because there can be many thousands of mappings, and parsing
+  // them is expensive, so we only want to do it if we must.
+  //
+  // Each object in the arrays is of the form:
+  //
+  //     {
+  //       generatedLine: The line number in the generated code,
+  //       generatedColumn: The column number in the generated code,
+  //       source: The path to the original source file that generated this
+  //               chunk of code,
+  //       originalLine: The line number in the original source that
+  //                     corresponds to this chunk of generated code,
+  //       originalColumn: The column number in the original source that
+  //                       corresponds to this chunk of generated code,
+  //       name: The name of the original symbol which generated this chunk of
+  //             code.
+  //     }
+  //
+  // All properties except for `generatedLine` and `generatedColumn` can be
+  // `null`.
+  //
+  // `_generatedMappings` is ordered by the generated positions.
+  //
+  // `_originalMappings` is ordered by the original positions.
+  get _generatedMappings() {
+    if (!this.__generatedMappings) {
+      this._sortGeneratedMappings();
+    }
 
-  if (version != this._version) {
-    throw new Error('Unsupported version: ' + version);
+    return this.__generatedMappings;
   }
 
-  this._sources = new ArraySet();
-  this._names = new ArraySet();
-
-  var lastOffset = {
-    line: -1,
-    column: 0
-  };
-  this._sections = sections.map(function (s) {
-    if (s.url) {
-      // The url field will require support for asynchronicity.
-      // See https://github.com/mozilla/source-map/issues/16
-      throw new Error('Support for url field in sections not implemented.');
+  get _originalMappings() {
+    if (!this.__originalMappings) {
+      this._sortOriginalMappings();
     }
-    var offset = util.getArg(s, 'offset');
-    var offsetLine = util.getArg(offset, 'line');
-    var offsetColumn = util.getArg(offset, 'column');
 
-    if (offsetLine < lastOffset.line ||
-        (offsetLine === lastOffset.line && offsetColumn < lastOffset.column)) {
-      throw new Error('Section offsets must be ordered and non-overlapping.');
+    return this.__originalMappings;
+  }
+
+  get _generatedMappingsUnsorted() {
+    if (!this.__generatedMappingsUnsorted) {
+      this._parseMappings(this._mappings, this.sourceRoot);
     }
-    lastOffset = offset;
 
-    return {
-      generatedOffset: {
-        // The offset fields are 0-based, but we use 1-based indices when
-        // encoding/decoding from VLQ.
-        generatedLine: offsetLine + 1,
-        generatedColumn: offsetColumn + 1
-      },
-      consumer: new SourceMapConsumer(util.getArg(s, 'map'))
+    return this.__generatedMappingsUnsorted;
+  }
+
+  get _originalMappingsUnsorted() {
+    if (!this.__originalMappingsUnsorted) {
+      this._parseMappings(this._mappings, this.sourceRoot);
     }
-  });
-}
 
-IndexedSourceMapConsumer.prototype = Object.create(SourceMapConsumer.prototype);
-IndexedSourceMapConsumer.prototype.constructor = SourceMapConsumer;
+    return this.__originalMappingsUnsorted;
+  }
 
-/**
- * The version of the source mapping spec that we are consuming.
- */
-IndexedSourceMapConsumer.prototype._version = 3;
+  _sortGeneratedMappings() {
+    const mappings = this._generatedMappingsUnsorted;
+    mappings.sort(util.compareByGeneratedPositionsDeflated);
+    this.__generatedMappings = mappings;
+  }
 
-/**
- * The list of original sources.
- */
-Object.defineProperty(IndexedSourceMapConsumer.prototype, 'sources', {
-  get: function () {
-    var sources = [];
-    for (var i = 0; i < this._sections.length; i++) {
-      for (var j = 0; j < this._sections[i].consumer.sources.length; j++) {
+  _sortOriginalMappings() {
+    const mappings = this._originalMappingsUnsorted;
+    mappings.sort(util.compareByOriginalPositions);
+    this.__originalMappings = mappings;
+  }
+
+  /**
+   * The list of original sources.
+   */
+  get sources() {
+    const sources = [];
+    for (let i = 0; i < this._sections.length; i++) {
+      for (let j = 0; j < this._sections[i].consumer.sources.length; j++) {
         sources.push(this._sections[i].consumer.sources[j]);
       }
     }
     return sources;
   }
-});
 
-/**
- * Returns the original source, line, and column information for the generated
- * source's line and column positions provided. The only argument is an object
- * with the following properties:
- *
- *   - line: The line number in the generated source.
- *   - column: The column number in the generated source.
- *
- * and an object is returned with the following properties:
- *
- *   - source: The original source file, or null.
- *   - line: The line number in the original source, or null.
- *   - column: The column number in the original source, or null.
- *   - name: The original identifier, or null.
- */
-IndexedSourceMapConsumer.prototype.originalPositionFor =
-  function IndexedSourceMapConsumer_originalPositionFor(aArgs) {
-    var needle = {
-      generatedLine: util.getArg(aArgs, 'line'),
-      generatedColumn: util.getArg(aArgs, 'column')
+  /**
+   * Returns the original source, line, and column information for the generated
+   * source's line and column positions provided. The only argument is an object
+   * with the following properties:
+   *
+   *   - line: The line number in the generated source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the generated source.  The column
+   *     number is 0-based.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - source: The original source file, or null.
+   *   - line: The line number in the original source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the original source, or null.  The
+   *     column number is 0-based.
+   *   - name: The original identifier, or null.
+   */
+  originalPositionFor(aArgs) {
+    const needle = {
+      generatedLine: util.getArg(aArgs, "line"),
+      generatedColumn: util.getArg(aArgs, "column")
     };
 
     // Find the section containing the generated position we're trying to map
     // to an original position.
-    var sectionIndex = binarySearch.search(needle, this._sections,
-      function(needle, section) {
-        var cmp = needle.generatedLine - section.generatedOffset.generatedLine;
+    const sectionIndex = binarySearch.search(needle, this._sections,
+      function(aNeedle, section) {
+        const cmp = aNeedle.generatedLine - section.generatedOffset.generatedLine;
         if (cmp) {
           return cmp;
         }
 
-        return (needle.generatedColumn -
+        return (aNeedle.generatedColumn -
                 section.generatedOffset.generatedColumn);
       });
-    var section = this._sections[sectionIndex];
+    const section = this._sections[sectionIndex];
 
     if (!section) {
       return {
@@ -945,30 +931,28 @@ IndexedSourceMapConsumer.prototype.originalPositionFor =
          : 0),
       bias: aArgs.bias
     });
-  };
+  }
 
-/**
- * Return true if we have the source content for every source in the source
- * map, false otherwise.
- */
-IndexedSourceMapConsumer.prototype.hasContentsOfAllSources =
-  function IndexedSourceMapConsumer_hasContentsOfAllSources() {
-    return this._sections.every(function (s) {
+  /**
+   * Return true if we have the source content for every source in the source
+   * map, false otherwise.
+   */
+  hasContentsOfAllSources() {
+    return this._sections.every(function(s) {
       return s.consumer.hasContentsOfAllSources();
     });
-  };
+  }
 
-/**
- * Returns the original source content. The only argument is the url of the
- * original source file. Returns null if no original source content is
- * available.
- */
-IndexedSourceMapConsumer.prototype.sourceContentFor =
-  function IndexedSourceMapConsumer_sourceContentFor(aSource, nullOnMissing) {
-    for (var i = 0; i < this._sections.length; i++) {
-      var section = this._sections[i];
+  /**
+   * Returns the original source content. The only argument is the url of the
+   * original source file. Returns null if no original source content is
+   * available.
+   */
+  sourceContentFor(aSource, nullOnMissing) {
+    for (let i = 0; i < this._sections.length; i++) {
+      const section = this._sections[i];
 
-      var content = section.consumer.sourceContentFor(aSource, true);
+      const content = section.consumer.sourceContentFor(aSource, true);
       if (content) {
         return content;
       }
@@ -976,38 +960,39 @@ IndexedSourceMapConsumer.prototype.sourceContentFor =
     if (nullOnMissing) {
       return null;
     }
-    else {
-      throw new Error('"' + aSource + '" is not in the SourceMap.');
-    }
-  };
+    throw new Error('"' + aSource + '" is not in the SourceMap.');
+  }
 
-/**
- * Returns the generated line and column information for the original source,
- * line, and column positions provided. The only argument is an object with
- * the following properties:
- *
- *   - source: The filename of the original source.
- *   - line: The line number in the original source.
- *   - column: The column number in the original source.
- *
- * and an object is returned with the following properties:
- *
- *   - line: The line number in the generated source, or null.
- *   - column: The column number in the generated source, or null.
- */
-IndexedSourceMapConsumer.prototype.generatedPositionFor =
-  function IndexedSourceMapConsumer_generatedPositionFor(aArgs) {
-    for (var i = 0; i < this._sections.length; i++) {
-      var section = this._sections[i];
+  /**
+   * Returns the generated line and column information for the original source,
+   * line, and column positions provided. The only argument is an object with
+   * the following properties:
+   *
+   *   - source: The filename of the original source.
+   *   - line: The line number in the original source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the original source.  The column
+   *     number is 0-based.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - line: The line number in the generated source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the generated source, or null.
+   *     The column number is 0-based.
+   */
+  generatedPositionFor(aArgs) {
+    for (let i = 0; i < this._sections.length; i++) {
+      const section = this._sections[i];
 
       // Only consider this section if the requested source is in the list of
       // sources of the consumer.
-      if (section.consumer.sources.indexOf(util.getArg(aArgs, 'source')) === -1) {
+      if (section.consumer._findSourceIndex(util.getArg(aArgs, "source")) === -1) {
         continue;
       }
-      var generatedPosition = section.consumer.generatedPositionFor(aArgs);
+      const generatedPosition = section.consumer.generatedPositionFor(aArgs);
       if (generatedPosition) {
-        var ret = {
+        const ret = {
           line: generatedPosition.line +
             (section.generatedOffset.generatedLine - 1),
           column: generatedPosition.column +
@@ -1023,40 +1008,45 @@ IndexedSourceMapConsumer.prototype.generatedPositionFor =
       line: null,
       column: null
     };
-  };
+  }
 
-/**
- * Parse the mappings in a string in to a data structure which we can easily
- * query (the ordered arrays in the `this.__generatedMappings` and
- * `this.__originalMappings` properties).
- */
-IndexedSourceMapConsumer.prototype._parseMappings =
-  function IndexedSourceMapConsumer_parseMappings(aStr, aSourceRoot) {
-    this.__generatedMappings = [];
-    this.__originalMappings = [];
-    for (var i = 0; i < this._sections.length; i++) {
-      var section = this._sections[i];
-      var sectionMappings = section.consumer._generatedMappings;
-      for (var j = 0; j < sectionMappings.length; j++) {
-        var mapping = sectionMappings[j];
-
-        var source = section.consumer._sources.at(mapping.source);
-        if (section.consumer.sourceRoot !== null) {
-          source = util.join(section.consumer.sourceRoot, source);
-        }
+  /**
+   * Parse the mappings in a string in to a data structure which we can easily
+   * query (the ordered arrays in the `this.__generatedMappings` and
+   * `this.__originalMappings` properties).
+   */
+  _parseMappings(aStr, aSourceRoot) {
+    const generatedMappings = this.__generatedMappingsUnsorted = [];
+    const originalMappings = this.__originalMappingsUnsorted = [];
+    for (let i = 0; i < this._sections.length; i++) {
+      const section = this._sections[i];
+
+      const sectionMappings = [];
+      section.consumer.eachMapping(m => sectionMappings.push(m));
+
+      for (let j = 0; j < sectionMappings.length; j++) {
+        const mapping = sectionMappings[j];
+
+        // TODO: test if null is correct here.  The original code used
+        // `source`, which would actually have gotten used as null because
+        // var's get hoisted.
+        // See: https://github.com/mozilla/source-map/issues/333
+        let source = util.computeSourceURL(section.consumer.sourceRoot, null, this._sourceMapURL);
         this._sources.add(source);
         source = this._sources.indexOf(source);
 
-        var name = section.consumer._names.at(mapping.name);
-        this._names.add(name);
-        name = this._names.indexOf(name);
+        let name = null;
+        if (mapping.name) {
+          this._names.add(mapping.name);
+          name = this._names.indexOf(mapping.name);
+        }
 
         // The mappings coming from the consumer for the section have
         // generated positions relative to the start of the section, so we
         // need to offset them to be relative to the start of the concatenated
         // generated file.
-        var adjustedMapping = {
-          source: source,
+        const adjustedMapping = {
+          source,
           generatedLine: mapping.generatedLine +
             (section.generatedOffset.generatedLine - 1),
           generatedColumn: mapping.generatedColumn +
@@ -1065,18 +1055,183 @@ IndexedSourceMapConsumer.prototype._parseMappings =
             : 0),
           originalLine: mapping.originalLine,
           originalColumn: mapping.originalColumn,
-          name: name
+          name
         };
 
-        this.__generatedMappings.push(adjustedMapping);
-        if (typeof adjustedMapping.originalLine === 'number') {
-          this.__originalMappings.push(adjustedMapping);
+        generatedMappings.push(adjustedMapping);
+        if (typeof adjustedMapping.originalLine === "number") {
+          originalMappings.push(adjustedMapping);
         }
       }
     }
+  }
 
-    quickSort(this.__generatedMappings, util.compareByGeneratedPositionsDeflated);
-    quickSort(this.__originalMappings, util.compareByOriginalPositions);
-  };
+  eachMapping(aCallback, aContext, aOrder) {
+    const context = aContext || null;
+    const order = aOrder || SourceMapConsumer.GENERATED_ORDER;
 
+    let mappings;
+    switch (order) {
+    case SourceMapConsumer.GENERATED_ORDER:
+      mappings = this._generatedMappings;
+      break;
+    case SourceMapConsumer.ORIGINAL_ORDER:
+      mappings = this._originalMappings;
+      break;
+    default:
+      throw new Error("Unknown order of iteration.");
+    }
+
+    const sourceRoot = this.sourceRoot;
+    mappings.map(function(mapping) {
+      let source = null;
+      if (mapping.source !== null) {
+        source = this._sources.at(mapping.source);
+        source = util.computeSourceURL(sourceRoot, source, this._sourceMapURL);
+      }
+      return {
+        source,
+        generatedLine: mapping.generatedLine,
+        generatedColumn: mapping.generatedColumn,
+        originalLine: mapping.originalLine,
+        originalColumn: mapping.originalColumn,
+        name: mapping.name === null ? null : this._names.at(mapping.name)
+      };
+    }, this).forEach(aCallback, context);
+  }
+
+  /**
+   * Find the mapping that best matches the hypothetical "needle" mapping that
+   * we are searching for in the given "haystack" of mappings.
+   */
+  _findMapping(aNeedle, aMappings, aLineName,
+              aColumnName, aComparator, aBias) {
+    // To return the position we are searching for, we must first find the
+    // mapping for the given position and then return the opposite position it
+    // points to. Because the mappings are sorted, we can use binary search to
+    // find the best mapping.
+
+    if (aNeedle[aLineName] <= 0) {
+      throw new TypeError("Line must be greater than or equal to 1, got "
+                          + aNeedle[aLineName]);
+    }
+    if (aNeedle[aColumnName] < 0) {
+      throw new TypeError("Column must be greater than or equal to 0, got "
+                          + aNeedle[aColumnName]);
+    }
+
+    return binarySearch.search(aNeedle, aMappings, aComparator, aBias);
+  }
+
+  allGeneratedPositionsFor(aArgs) {
+    const line = util.getArg(aArgs, "line");
+
+    // When there is no exact match, BasicSourceMapConsumer.prototype._findMapping
+    // returns the index of the closest mapping less than the needle. By
+    // setting needle.originalColumn to 0, we thus find the last mapping for
+    // the given line, provided such a mapping exists.
+    const needle = {
+      source: util.getArg(aArgs, "source"),
+      originalLine: line,
+      originalColumn: util.getArg(aArgs, "column", 0)
+    };
+
+    needle.source = this._findSourceIndex(needle.source);
+    if (needle.source < 0) {
+      return [];
+    }
+
+    if (needle.originalLine < 1) {
+      throw new Error("Line numbers must be >= 1");
+    }
+
+    if (needle.originalColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
+    }
+
+    const mappings = [];
+
+    let index = this._findMapping(needle,
+                                  this._originalMappings,
+                                  "originalLine",
+                                  "originalColumn",
+                                  util.compareByOriginalPositions,
+                                  binarySearch.LEAST_UPPER_BOUND);
+    if (index >= 0) {
+      let mapping = this._originalMappings[index];
+
+      if (aArgs.column === undefined) {
+        const originalLine = mapping.originalLine;
+
+        // Iterate until either we run out of mappings, or we run into
+        // a mapping for a different line than the one we found. Since
+        // mappings are sorted, this is guaranteed to find all mappings for
+        // the line we found.
+        while (mapping && mapping.originalLine === originalLine) {
+          let lastColumn = mapping.lastGeneratedColumn;
+          if (this._computedColumnSpans && lastColumn === null) {
+            lastColumn = Infinity;
+          }
+          mappings.push({
+            line: util.getArg(mapping, "generatedLine", null),
+            column: util.getArg(mapping, "generatedColumn", null),
+            lastColumn,
+          });
+
+          mapping = this._originalMappings[++index];
+        }
+      } else {
+        const originalColumn = mapping.originalColumn;
+
+        // Iterate until either we run out of mappings, or we run into
+        // a mapping for a different line than the one we were searching for.
+        // Since mappings are sorted, this is guaranteed to find all mappings for
+        // the line we are searching for.
+        while (mapping &&
+               mapping.originalLine === line &&
+               mapping.originalColumn == originalColumn) {
+          let lastColumn = mapping.lastGeneratedColumn;
+          if (this._computedColumnSpans && lastColumn === null) {
+            lastColumn = Infinity;
+          }
+          mappings.push({
+            line: util.getArg(mapping, "generatedLine", null),
+            column: util.getArg(mapping, "generatedColumn", null),
+            lastColumn,
+          });
+
+          mapping = this._originalMappings[++index];
+        }
+      }
+    }
+
+    return mappings;
+  }
+
+  destroy() {
+    for (let i = 0; i < this._sections.length; i++) {
+      this._sections[i].consumer.destroy();
+    }
+  }
+}
 exports.IndexedSourceMapConsumer = IndexedSourceMapConsumer;
+
+/*
+ * Cheat to get around inter-twingled classes.  `factory()` can be at the end
+ * where it has access to non-hoisted classes, but it gets hoisted itself.
+ */
+function _factory(aSourceMap, aSourceMapURL) {
+  let sourceMap = aSourceMap;
+  if (typeof aSourceMap === "string") {
+    sourceMap = util.parseSourceMapInput(aSourceMap);
+  }
+
+  const consumer = sourceMap.sections != null
+      ? new IndexedSourceMapConsumer(sourceMap, aSourceMapURL)
+      : new BasicSourceMapConsumer(sourceMap, aSourceMapURL);
+  return Promise.resolve(consumer);
+}
+
+function _factoryBSM(aSourceMap, aSourceMapURL) {
+  return BasicSourceMapConsumer.fromSourceMap(aSourceMap, aSourceMapURL);
+}