Reviewers: kpreid2,
Description:
At https://github.com/drses/weak-map/pull/3/files Kris Kowal sped up
WeakMaps by using the hiddenRecord directly as the array-like, indexed
by a per-map unique index.
I kept the old defProp that explicitly enumerates the writable,
enumerable, configurable attributes that should default to false
anyway, out of general paranoia about remaining undiagnosed bugs in
Object.defineProperty.
Please review this at https://codereview.appspot.com/54750043/
Affected files (+30, -57 lines):
M src/com/google/caja/ses/WeakMap.js
Index: src/com/google/caja/ses/WeakMap.js
===================================================================
--- src/com/google/caja/ses/WeakMap.js (revision 5656)
+++ src/com/google/caja/ses/WeakMap.js (working copy)
@@ -310,14 +310,10 @@
// Weak map must brute force, as explained in doc-comment above.
return void 0;
}
- var gets = [];
- var vals = [];
- hiddenRecord = {
- key: key, // self pointer for quick own check above.
- gets: gets, // get___ methods identifying weak maps
- vals: vals // values associated with this key in each
- // corresponding weak map.
- };
+ var hiddenRecord = Object.create(null);
+ // For quickly verifying that this hidden record is an own property,
not
+ // a hidden record from up the prototype chain.
+ hiddenRecord.key = key;
defProp(key, HIDDEN_NAME, {
value: hiddenRecord,
writable: false,
@@ -378,10 +374,7 @@
}
}
- // Right now (12/25/2012) the histogram supports the current
- // representation. We should check this occasionally, as a true
- // constant time representation is easy.
- // var histogram = [];
+ var nextId = 0;
var OurWeakMap = function() {
if (!(this instanceof OurWeakMap)) { // approximate test for new ...()
@@ -391,73 +384,52 @@
// We are currently (12/25/2012) never encountering any prematurely
// non-extensible keys.
var keys = []; // brute force for prematurely non-extensible keys.
- var vals = []; // brute force for corresponding values.
+ var values = []; // brute force for corresponding values.
+ var id = nextId++;
function get___(key, opt_default) {
- var hr = getHiddenRecord(key);
- var i, vs;
- if (hr) {
- i = hr.gets.indexOf(get___);
- vs = hr.vals;
+ var index;
+ var hiddenRecord = getHiddenRecord(key);
+ if (hiddenRecord) {
+ return id in hiddenRecord ? hiddenRecord[id] : opt_default;
} else {
- i = keys.indexOf(key);
- vs = vals;
+ index = keys.indexOf(key);
+ return index >= 0 ? values[index] : opt_default;
}
- return (i >= 0) ? vs[i] : opt_default;
}
function has___(key) {
- var hr = getHiddenRecord(key);
- var i;
- if (hr) {
- i = hr.gets.indexOf(get___);
+ var hiddenRecord = getHiddenRecord(key);
+ if (hiddenRecord) {
+ return id in hiddenRecord;
} else {
- i = keys.indexOf(key);
+ return keys.indexOf(key) >= 0;
}
- return i >= 0;
}
function set___(key, value) {
- var hr = getHiddenRecord(key);
- var i;
- if (hr) {
- i = hr.gets.indexOf(get___);
- if (i >= 0) {
- hr.vals[i] = value;
- } else {
-// i = hr.gets.length;
-// histogram[i] = (histogram[i] || 0) + 1;
- hr.gets.push(get___);
- hr.vals.push(value);
- }
+ var index;
+ var hiddenRecord = getHiddenRecord(key);
+ if (hiddenRecord) {
+ hiddenRecord[id] = value;
} else {
- i = keys.indexOf(key);
- if (i >= 0) {
- vals[i] = value;
+ index = keys.indexOf(key);
+ if (index >= 0) {
+ values[index] = value;
} else {
keys.push(key);
- vals.push(value);
+ values.push(value);
}
}
}
function delete___(key) {
- var hr = getHiddenRecord(key);
- var i;
- if (hr) {
- i = hr.gets.indexOf(get___);
- if (i >= 0) {
- hr.gets.splice(i, 1);
- hr.vals.splice(i, 1);
- }
+ var hiddenRecord = getHiddenRecord(key);
+ if (hiddenRecord) {
+ delete hiddenRecord[id];
} else {
- i = keys.indexOf(key);
- if (i >= 0) {
- keys.splice(i, 1);
- vals.splice(i, 1);
- }
+ return keys.indexOf(key) >= 0;
}
- return true;
}
return Object.create(OurWeakMap.prototype, {
@@ -467,6 +439,7 @@
delete___: { value: constFunc(delete___) }
});
};
+
OurWeakMap.prototype = Object.create(Object.prototype, {
get: {
/**
--
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