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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/. */
/**
* Module for reading Property Lists (.plist) files
* ------------------------------------------------
* This module functions as a reader for Apple Property Lists (.plist files).
* It supports both binary and xml formatted property lists. It does not
* support the legacy ASCII format. Reading of Cocoa's Keyed Archives serialized
* to binary property lists isn't supported either.
*
* Property Lists objects are represented by standard JS and Mozilla types,
* namely:
*
* XML type Cocoa Class Returned type(s)
* --------------------------------------------------------------------------
* <true/> / <false/> NSNumber TYPE_PRIMITIVE boolean
* <integer> / <real> NSNumber TYPE_PRIMITIVE number
* TYPE_INT64 String [1]
* Not Available NSNull TYPE_PRIMITIVE null [2]
* TYPE_PRIMITIVE undefined [3]
* <date/> NSDate TYPE_DATE Date
* <data/> NSData TYPE_UINT8_ARRAY Uint8Array
* <array/> NSArray TYPE_ARRAY Array
* Not Available NSSet TYPE_ARRAY Array [2][4]
* <dict/> NSDictionary TYPE_DICTIONARY Map
*
* Use PropertyListUtils.getObjectType to detect the type of a Property list
* object.
*
* -------------
* 1) Property lists supports storing U/Int64 numbers, while JS can only handle
* numbers that are in this limits of float-64 (±2^53). For numbers that
* do not outbound this limits, simple primitive number are always used.
* Otherwise, a String object.
* 2) About NSNull and NSSet values: While the xml format has no support for
* representing null and set values, the documentation for the binary format
* states that it supports storing both types. However, the Cocoa APIs for
* serializing property lists do not seem to support either types (test with
* NSPropertyListSerialization::propertyList:isValidForFormat). Furthermore,
* if an array or a dictionary (Map) contains a NSNull or a NSSet value, they cannot
* be serialized to a property list.
* As for usage within OS X, not surprisingly there's no known usage of
* storing either of these types in a property list. It seems that, for now,
* Apple is keeping the features of binary and xml formats in sync, probably as
* long as the XML format is not officially deprecated.
* 3) Not used anywhere.
* 4) About NSSet representation: For the time being, we represent those
* theoretical NSSet objects the same way NSArray is represented.
* While this would most certainly work, it is not the right way to handle
* it. A more correct representation for a set is a js generator, which would
* read the set lazily and has no indices semantics.
*/
"use strict";
var EXPORTED_SYMBOLS = ["PropertyListUtils"];
const lazy = {};
ChromeUtils.defineModuleGetter(
lazy,
"ctypes",
);
var PropertyListUtils = Object.freeze({
/**
* Asynchronously reads a file as a property list.
*
* @param aFile (Blob/nsIFile)
* the file to be read as a property list.
* @param aCallback
* If the property list is read successfully, aPropertyListRoot is set
* to the root object of the property list.
* Use getPropertyListObjectType to detect its type.
* If it's not read successfully, aPropertyListRoot is set to null.
* The reaon for failure is reported to the Error Console.
*/
read: function PLU_read(aFile, aCallback) {
if (!(aFile instanceof Ci.nsIFile || File.isInstance(aFile))) {
throw new Error("aFile is not a file object");
}
if (typeof aCallback != "function") {
throw new Error("Invalid value for aCallback");
}
// We guarantee not to throw directly for any other exceptions, and always
// call aCallback.
Services.tm.dispatchToMainThread(() => {
let self = this;
function readDOMFile(aFile) {
let fileReader = new FileReader();
let onLoadEnd = function() {
let root = null;
try {
fileReader.removeEventListener("loadend", onLoadEnd);
if (fileReader.readyState != fileReader.DONE) {
throw new Error(
"Could not read file contents: " + fileReader.error
);
}
root = self._readFromArrayBufferSync(fileReader.result);
} finally {
aCallback(root);
}
};
fileReader.addEventListener("loadend", onLoadEnd);
fileReader.readAsArrayBuffer(aFile);
}
try {
if (aFile instanceof Ci.nsIFile) {
if (!aFile.exists()) {
throw new Error("The file pointed by aFile does not exist");
}
File.createFromNsIFile(aFile).then(function(aFile) {
readDOMFile(aFile);
});
return;
}
readDOMFile(aFile);
} catch (ex) {
aCallback(null);
throw ex;
}
});
},
/**
* DO NOT USE ME. Once Bug 718189 is fixed, this method won't be public.
*
* Synchronously read an ArrayBuffer contents as a property list.
*/
_readFromArrayBufferSync: function PLU__readFromArrayBufferSync(aBuffer) {
if (BinaryPropertyListReader.prototype.canProcess(aBuffer)) {
return new BinaryPropertyListReader(aBuffer).root;
}
// Convert the buffer into an XML tree.
let domParser = new DOMParser();
let bytesView = new Uint8Array(aBuffer);
try {
let doc = domParser.parseFromBuffer(bytesView, "application/xml");
return new XMLPropertyListReader(doc).root;
} catch (ex) {
throw new Error("aBuffer cannot be parsed as a DOM document: " + ex);
}
},
TYPE_PRIMITIVE: 0,
TYPE_DATE: 1,
TYPE_UINT8_ARRAY: 2,
TYPE_ARRAY: 3,
TYPE_DICTIONARY: 4,
TYPE_INT64: 5,
/**
* Get the type in which the given property list object is represented.
* Check the header for the mapping between the TYPE* constants to js types
* and objects.
*
* @return one of the TYPE_* constants listed above.
* @note this method is merely for convenience. It has no magic to detect
* that aObject is indeed a property list object created by this module.
*/
getObjectType: function PLU_getObjectType(aObject) {
if (aObject === null || typeof aObject != "object") {
return this.TYPE_PRIMITIVE;
}
// Given current usage, we could assume that aObject was created in the
// scope of this module, but in future, this util may be used as part of
// serializing js objects to a property list - in which case the object
// would most likely be created in the caller's scope.
let global = Cu.getGlobalForObject(aObject);
if (aObject instanceof global.Map) {
return this.TYPE_DICTIONARY;
}
if (Array.isArray(aObject)) {
return this.TYPE_ARRAY;
}
if (aObject instanceof global.Date) {
return this.TYPE_DATE;
}
if (aObject instanceof global.Uint8Array) {
return this.TYPE_UINT8_ARRAY;
}
if (aObject instanceof global.String && "__INT_64_WRAPPER__" in aObject) {
return this.TYPE_INT64;
}
throw new Error("aObject is not as a property list object.");
},
/**
* Wraps a 64-bit stored in the form of a string primitive as a String object,
* which we can later distiguish from regular string values.
* @param aPrimitive
* a number in the form of either a primitive string or a primitive number.
* @return a String wrapper around aNumberStr that can later be identified
* as holding 64-bit number using getObjectType.
*/
wrapInt64: function PLU_wrapInt64(aPrimitive) {
if (typeof aPrimitive != "string" && typeof aPrimitive != "number") {
throw new Error("aPrimitive should be a string primitive");
}
// The function converts string or number to object
// So eslint rule is disabled
// eslint-disable-next-line no-new-wrappers
let wrapped = new String(aPrimitive);
Object.defineProperty(wrapped, "__INT_64_WRAPPER__", { value: true });
return wrapped;
},
});
/**
* Here's the base structure of binary-format property lists.
* 1) Header - magic number
* - 6 bytes - "bplist"
* - 2 bytes - version number. This implementation only supports version 00.
* 2) Objects Table
* Variable-sized objects, see _readObject for how various types of objects
* are constructed.
* 3) Offsets Table
* The offset of each object in the objects table. The integer size is
* specified in the trailer.
* 4) Trailer
* - 6 unused bytes
* - 1 byte: the size of integers in the offsets table
* - 1 byte: the size of object references for arrays, sets and
* dictionaries.
* - 8 bytes: the number of objects in the objects table
* - 8 bytes: the index of the root object's offset in the offsets table.
* - 8 bytes: the offset of the offsets table.
*
* Note: all integers are stored in big-endian form.
*/
/**
* Reader for binary-format property lists.
*
* @param aBuffer
* ArrayBuffer object from which the binary plist should be read.
*/
function BinaryPropertyListReader(aBuffer) {
this._dataView = new DataView(aBuffer);
const JS_MAX_INT = Math.pow(2, 53);
this._JS_MAX_INT_SIGNED = lazy.ctypes.Int64(JS_MAX_INT);
this._JS_MAX_INT_UNSIGNED = lazy.ctypes.UInt64(JS_MAX_INT);
this._JS_MIN_INT = lazy.ctypes.Int64(-JS_MAX_INT);
try {
this._readTrailerInfo();
this._readObjectsOffsets();
} catch (ex) {
throw new Error("Could not read aBuffer as a binary property list");
}
this._objects = [];
}
BinaryPropertyListReader.prototype = {
/**
* Checks if the given ArrayBuffer can be read as a binary property list.
* It can be called on the prototype.
*/
canProcess: function BPLR_canProcess(aBuffer) {
return (
Array.from(new Uint8Array(aBuffer, 0, 8))
.map(c => String.fromCharCode(c))
.join("") == "bplist00"
);
},
get root() {
return this._readObject(this._rootObjectIndex);
},
_readTrailerInfo: function BPLR__readTrailer() {
// The first 6 bytes of the 32-bytes trailer are unused
let trailerOffset = this._dataView.byteLength - 26;
[
this._offsetTableIntegerSize,
this._objectRefSize,
] = this._readUnsignedInts(trailerOffset, 1, 2);
[
this._numberOfObjects,
this._rootObjectIndex,
this._offsetTableOffset,
] = this._readUnsignedInts(trailerOffset + 2, 8, 3);
},
_readObjectsOffsets: function BPLR__readObjectsOffsets() {
this._offsetTable = this._readUnsignedInts(
this._offsetTableOffset,
this._offsetTableIntegerSize,
this._numberOfObjects
);
},
_readSignedInt64: function BPLR__readSignedInt64(aByteOffset) {
let lo = this._dataView.getUint32(aByteOffset + 4);
let hi = this._dataView.getInt32(aByteOffset);
let int64 = lazy.ctypes.Int64.join(hi, lo);
if (
lazy.ctypes.Int64.compare(int64, this._JS_MAX_INT_SIGNED) == 1 ||
lazy.ctypes.Int64.compare(int64, this._JS_MIN_INT) == -1
) {
return PropertyListUtils.wrapInt64(int64.toString());
}
return parseInt(int64.toString(), 10);
},
_readReal: function BPLR__readReal(aByteOffset, aRealSize) {
if (aRealSize == 4) {
return this._dataView.getFloat32(aByteOffset);
}
if (aRealSize == 8) {
return this._dataView.getFloat64(aByteOffset);
}
throw new Error("Unsupported real size: " + aRealSize);
},
OBJECT_TYPE_BITS: {
SIMPLE: parseInt("0000", 2),
INTEGER: parseInt("0001", 2),
REAL: parseInt("0010", 2),
DATE: parseInt("0011", 2),
DATA: parseInt("0100", 2),
ASCII_STRING: parseInt("0101", 2),
UNICODE_STRING: parseInt("0110", 2),
UID: parseInt("1000", 2),
ARRAY: parseInt("1010", 2),
SET: parseInt("1100", 2),
DICTIONARY: parseInt("1101", 2),
},
ADDITIONAL_INFO_BITS: {
// Applies to OBJECT_TYPE_BITS.SIMPLE
NULL: parseInt("0000", 2),
FALSE: parseInt("1000", 2),
TRUE: parseInt("1001", 2),
FILL_BYTE: parseInt("1111", 2),
// Applies to OBJECT_TYPE_BITS.DATE
DATE: parseInt("0011", 2),
// Applies to OBJECT_TYPE_BITS.DATA, ASCII_STRING, UNICODE_STRING, ARRAY,
// SET and DICTIONARY.
LENGTH_INT_SIZE_FOLLOWS: parseInt("1111", 2),
},
/**
* Returns an object descriptor in the form of two integers: object type and
* additional info.
*
* @param aByteOffset
* the descriptor's offset.
* @return [objType, additionalInfo] - the object type and additional info.
* @see OBJECT_TYPE_BITS and ADDITIONAL_INFO_BITS
*/
_readObjectDescriptor: function BPLR__readObjectDescriptor(aByteOffset) {
// The first four bits hold the object type. For some types, additional
// info is held in the other 4 bits.
let byte = this._readUnsignedInts(aByteOffset, 1, 1)[0];
return [(byte & 0xf0) >> 4, byte & 0x0f];
},
_readDate: function BPLR__readDate(aByteOffset) {
// That's the reference date of NSDate.
let date = new Date("1 January 2001, GMT");
// NSDate values are float values, but setSeconds takes an integer.
date.setMilliseconds(this._readReal(aByteOffset, 8) * 1000);
return date;
},
/**
* Reads a portion of the buffer as a string.
*
* @param aByteOffset
* The offset in the buffer at which the string starts
* @param aNumberOfChars
* The length of the string to be read (that is the number of
* characters, not bytes).
* @param aUnicode
* Whether or not it is a unicode string.
* @return the string read.
*
* @note this is tested to work well with unicode surrogate pairs. Because
* all unicode characters are read as 2-byte integers, unicode surrogate
* pairs are read from the buffer in the form of two integers, as required
* by String.fromCharCode.
*/
_readString: function BPLR__readString(
aByteOffset,
aNumberOfChars,
aUnicode
) {
let codes = this._readUnsignedInts(
aByteOffset,
aUnicode ? 2 : 1,
aNumberOfChars
);
return codes.map(c => String.fromCharCode(c)).join("");
},
/**
* Reads an array of unsigned integers from the buffer. Integers larger than
* one byte are read in big endian form.
*
* @param aByteOffset
* The offset in the buffer at which the array starts.
* @param aIntSize
* The size of each int in the array.
* @param aLength
* The number of ints in the array.
* @param [optional] aBigIntAllowed (default: false)
* Whether or not to accept integers which outbounds JS limits for
* numbers (±2^53) in the form of a String.
* @return an array of integers (number primitive and/or Strings for large
* numbers (see header)).
* @throws if aBigIntAllowed is false and one of the integers in the array
* cannot be represented by a primitive js number.
*/
_readUnsignedInts: function BPLR__readUnsignedInts(
aByteOffset,
aIntSize,
aLength,
aBigIntAllowed
) {
let uints = [];
for (
let offset = aByteOffset;
offset < aByteOffset + aIntSize * aLength;
offset += aIntSize
) {
if (aIntSize == 1) {
uints.push(this._dataView.getUint8(offset));
} else if (aIntSize == 2) {
uints.push(this._dataView.getUint16(offset));
} else if (aIntSize == 3) {
let int24 = Uint8Array(4);
int24[3] = 0;
int24[2] = this._dataView.getUint8(offset);
int24[1] = this._dataView.getUint8(offset + 1);
int24[0] = this._dataView.getUint8(offset + 2);
uints.push(Uint32Array(int24.buffer)[0]);
} else if (aIntSize == 4) {
uints.push(this._dataView.getUint32(offset));
} else if (aIntSize == 8) {
let lo = this._dataView.getUint32(offset + 4);
let hi = this._dataView.getUint32(offset);
let uint64 = lazy.ctypes.UInt64.join(hi, lo);
if (
lazy.ctypes.UInt64.compare(uint64, this._JS_MAX_INT_UNSIGNED) == 1
) {
if (aBigIntAllowed === true) {
uints.push(PropertyListUtils.wrapInt64(uint64.toString()));
} else {
throw new Error("Integer too big to be read as float 64");
}
} else {
uints.push(parseInt(uint64, 10));
}
} else {
throw new Error("Unsupported size: " + aIntSize);
}
}
return uints;
},
/**
* Reads from the buffer the data object-count and the offset at which the
* first object starts.
*
* @param aObjectOffset
* the object's offset.
* @return [offset, count] - the offset in the buffer at which the first
* object in data starts, and the number of objects.
*/
_readDataOffsetAndCount: function BPLR__readDataOffsetAndCount(
aObjectOffset
) {
// The length of some objects in the data can be stored in two ways:
// * If it is small enough, it is stored in the second four bits of the
// object descriptors.
// * Otherwise, those bits are set to 1111, indicating that the next byte
// consists of the integer size of the data-length (also stored in the form
// of an object descriptor). The length follows this byte.
let [, maybeLength] = this._readObjectDescriptor(aObjectOffset);
if (maybeLength != this.ADDITIONAL_INFO_BITS.LENGTH_INT_SIZE_FOLLOWS) {
return [aObjectOffset + 1, maybeLength];
}
let [, intSizeInfo] = this._readObjectDescriptor(aObjectOffset + 1);
// The int size is 2^intSizeInfo.
let intSize = Math.pow(2, intSizeInfo);
let dataLength = this._readUnsignedInts(aObjectOffset + 2, intSize, 1)[0];
return [aObjectOffset + 2 + intSize, dataLength];
},
/**
* Read array from the buffer and wrap it as a js array.
* @param aObjectOffset
* the offset in the buffer at which the array starts.
* @param aNumberOfObjects
* the number of objects in the array.
* @return a js array.
*/
_wrapArray: function BPLR__wrapArray(aObjectOffset, aNumberOfObjects) {
let refs = this._readUnsignedInts(
aObjectOffset,
this._objectRefSize,
aNumberOfObjects
);
let array = new Array(aNumberOfObjects);
let readObjectBound = this._readObject.bind(this);
// Each index in the returned array is a lazy getter for its object.
Array.prototype.forEach.call(
refs,
function(ref, objIndex) {
Object.defineProperty(array, objIndex, {
get() {
delete array[objIndex];
return (array[objIndex] = readObjectBound(ref));
},
configurable: true,
enumerable: true,
});
},
this
);
return array;
},
/**
* Reads dictionary from the buffer and wraps it as a Map object.
* @param aObjectOffset
* the offset in the buffer at which the dictionary starts
* @param aNumberOfObjects
* the number of keys in the dictionary
* @return Map-style dictionary.
*/
_wrapDictionary(aObjectOffset, aNumberOfObjects) {
// A dictionary in the binary format is stored as a list of references to
// key-objects, followed by a list of references to the value-objects for
// those keys. The size of each list is aNumberOfObjects * this._objectRefSize.
let dict = new Proxy(new Map(), LazyMapProxyHandler());
if (aNumberOfObjects == 0) {
return dict;
}
let keyObjsRefs = this._readUnsignedInts(
aObjectOffset,
this._objectRefSize,
aNumberOfObjects
);
let valObjsRefs = this._readUnsignedInts(
aObjectOffset + aNumberOfObjects * this._objectRefSize,
this._objectRefSize,
aNumberOfObjects
);
for (let i = 0; i < aNumberOfObjects; i++) {
let key = this._readObject(keyObjsRefs[i]);
let readBound = this._readObject.bind(this, valObjsRefs[i]);
dict.setAsLazyGetter(key, readBound);
}
return dict;
},
/**
* Reads an object at the spcified index in the object table
* @param aObjectIndex
* index at the object table
* @return the property list object at the given index.
*/
_readObject: function BPLR__readObject(aObjectIndex) {
// If the object was previously read, return the cached object.
if (this._objects[aObjectIndex] !== undefined) {
return this._objects[aObjectIndex];
}
let objOffset = this._offsetTable[aObjectIndex];
let [objType, additionalInfo] = this._readObjectDescriptor(objOffset);
let value;
switch (objType) {
case this.OBJECT_TYPE_BITS.SIMPLE: {
switch (additionalInfo) {
case this.ADDITIONAL_INFO_BITS.NULL:
value = null;
break;
case this.ADDITIONAL_INFO_BITS.FILL_BYTE:
value = undefined;
break;
case this.ADDITIONAL_INFO_BITS.FALSE:
value = false;
break;
case this.ADDITIONAL_INFO_BITS.TRUE:
value = true;
break;
default:
throw new Error("Unexpected value!");
}
break;
}
case this.OBJECT_TYPE_BITS.INTEGER: {
// The integer is sized 2^additionalInfo.
let intSize = Math.pow(2, additionalInfo);
// For objects, 64-bit integers are always signed. Negative integers
// are always represented by a 64-bit integer.
if (intSize == 8) {
value = this._readSignedInt64(objOffset + 1);
} else {
value = this._readUnsignedInts(objOffset + 1, intSize, 1, true)[0];
}
break;
}
case this.OBJECT_TYPE_BITS.REAL: {
// The real is sized 2^additionalInfo.
value = this._readReal(objOffset + 1, Math.pow(2, additionalInfo));
break;
}
case this.OBJECT_TYPE_BITS.DATE: {
if (additionalInfo != this.ADDITIONAL_INFO_BITS.DATE) {
throw new Error("Unexpected value");
}
value = this._readDate(objOffset + 1);
break;
}
case this.OBJECT_TYPE_BITS.DATA: {
let [offset, bytesCount] = this._readDataOffsetAndCount(objOffset);
value = new Uint8Array(this._readUnsignedInts(offset, 1, bytesCount));
break;
}
case this.OBJECT_TYPE_BITS.ASCII_STRING: {
let [offset, charsCount] = this._readDataOffsetAndCount(objOffset);
value = this._readString(offset, charsCount, false);
break;
}
case this.OBJECT_TYPE_BITS.UNICODE_STRING: {
let [offset, unicharsCount] = this._readDataOffsetAndCount(objOffset);
value = this._readString(offset, unicharsCount, true);
break;
}
case this.OBJECT_TYPE_BITS.UID: {
// UIDs are only used in Keyed Archives, which are not yet supported.
throw new Error("Keyed Archives are not supported");
}
case this.OBJECT_TYPE_BITS.ARRAY:
case this.OBJECT_TYPE_BITS.SET: {
// Note: For now, we fallback to handle sets the same way we handle
// arrays. See comments in the header of this file.
// The bytes following the count are references to objects (indices).
// Each reference is an unsigned int with size=this._objectRefSize.
let [offset, objectsCount] = this._readDataOffsetAndCount(objOffset);
value = this._wrapArray(offset, objectsCount);
break;
}
case this.OBJECT_TYPE_BITS.DICTIONARY: {
let [offset, objectsCount] = this._readDataOffsetAndCount(objOffset);
value = this._wrapDictionary(offset, objectsCount);
break;
}
default: {
throw new Error("Unknown object type: " + objType);
}
}
return (this._objects[aObjectIndex] = value);
},
};
/**
* Reader for XML property lists.
*
* @param aDOMDoc
* the DOM document to be read as a property list.
*/
function XMLPropertyListReader(aDOMDoc) {
let docElt = aDOMDoc.documentElement;
if (!docElt || docElt.localName != "plist" || !docElt.firstElementChild) {
throw new Error("aDoc is not a property list document");
}
this._plistRootElement = docElt.firstElementChild;
}
XMLPropertyListReader.prototype = {
get root() {
return this._readObject(this._plistRootElement);
},
/**
* Convert a dom element to a property list object.
* @param aDOMElt
* a dom element in a xml tree of a property list.
* @return a js object representing the property list object.
*/
_readObject: function XPLR__readObject(aDOMElt) {
switch (aDOMElt.localName) {
case "true":
return true;
case "false":
return false;
case "string":
case "key":
return aDOMElt.textContent;
case "integer":
return this._readInteger(aDOMElt);
case "real": {
let number = parseFloat(aDOMElt.textContent.trim());
if (isNaN(number)) {
throw new Error("Could not parse float value");
}
return number;
}
case "date":
return new Date(aDOMElt.textContent);
case "data":
// Strip spaces and new lines.
let base64str = aDOMElt.textContent.replace(/\s*/g, "");
let decoded = atob(base64str);
return new Uint8Array(Array.from(decoded, c => c.charCodeAt(0)));
case "dict":
return this._wrapDictionary(aDOMElt);
case "array":
return this._wrapArray(aDOMElt);
default:
throw new Error("Unexpected tagname");
}
},
_readInteger: function XPLR__readInteger(aDOMElt) {
// The integer may outbound js's max/min integer value. We recognize this
// case by comparing the parsed number to the original string value.
// In case of an outbound, we fallback to return the number as a string.
let numberAsString = aDOMElt.textContent.toString();
let parsedNumber = parseInt(numberAsString, 10);
if (isNaN(parsedNumber)) {
throw new Error("Could not parse integer value");
}
if (parsedNumber.toString() == numberAsString) {
return parsedNumber;
}
return PropertyListUtils.wrapInt64(numberAsString);
},
_wrapDictionary: function XPLR__wrapDictionary(aDOMElt) {
// <dict>
// <key>my true bool</key>
// <true/>
// <key>my string key</key>
// <string>My String Key</string>
// </dict>
if (aDOMElt.children.length % 2 != 0) {
throw new Error("Invalid dictionary");
}
let dict = new Proxy(new Map(), LazyMapProxyHandler());
for (let i = 0; i < aDOMElt.children.length; i += 2) {
let keyElem = aDOMElt.children[i];
let valElem = aDOMElt.children[i + 1];
if (keyElem.localName != "key") {
throw new Error("Invalid dictionary");
}
let keyName = this._readObject(keyElem);
let readBound = this._readObject.bind(this, valElem);
dict.setAsLazyGetter(keyName, readBound);
}
return dict;
},
_wrapArray: function XPLR__wrapArray(aDOMElt) {
// <array>
// <string>...</string>
// <integer></integer>
// <dict>
// ....
// </dict>
// </array>
// Each element in the array is a lazy getter for its property list object.
let array = [];
let readObjectBound = this._readObject.bind(this);
Array.prototype.forEach.call(aDOMElt.children, function(elem, elemIndex) {
Object.defineProperty(array, elemIndex, {
get() {
delete array[elemIndex];
return (array[elemIndex] = readObjectBound(elem));
},
configurable: true,
enumerable: true,
});
});
return array;
},
};
/**
* Simple handler method to proxy calls to dict/Map objects to implement the
* setAsLazyGetter API. With this, a value can be set as a function that will
* evaluate its value and only be called when it's first retrieved.
* @member _lazyGetters
* Set() object to hold keys invoking LazyGetter.
* @method get
* Trap for getting property values. Ensures that if a lazyGetter is present
* as value for key, then the function is evaluated, the value is cached,
* and its value will be returned.
* @param target
* Target object. (dict/Map)
* @param name
* Name of operation to be invoked on target.
* @param key
* Key to be set, retrieved or deleted. Keys are checked for laziness.
* @return Returns value of "name" property of target by default. Otherwise returns
* updated target.
*/
function LazyMapProxyHandler() {
return {
_lazyGetters: new Set(),
get(target, name) {
switch (name) {
case "setAsLazyGetter":
return (key, value) => {
this._lazyGetters.add(key);
target.set(key, value);
};
case "get":
return key => {
if (this._lazyGetters.has(key)) {
target.set(key, target.get(key)());
this._lazyGetters.delete(key);
}
return target.get(key);
};
case "delete":
return key => {
if (this._lazyGetters.has(key)) {
this._lazyGetters.delete(key);
}
return target.delete(key);
};
case "has":
return key => target.has(key);
default:
return target[name];
}
},
};
}