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Bug 397536 - "performance improvements for JSON.jsm" (optimize string serialization) [p=zeniko@gmail.com (Simon Bünzli) r=sspitzer sr=brendan a1.9=mconnor]

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This commit is contained in:
reed@reedloden.com 2007-09-27 09:50:29 -07:00
parent 3afd8639e0
commit c4a5cce285
1 changed files with 22 additions and 18 deletions
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40
js/src/xpconnect/loader/JSON.jsm
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@ -73,32 +73,36 @@ var JSON = {
* Note: aJSObject MUST not contain cyclic references.
*/
toString: function JSON_toString(aJSObject, aKeysToDrop) {
// these characters have a special escape notation
const charMap = { "\b": "\\b", "\t": "\\t", "\n": "\\n", "\f": "\\f",
"\r": "\\r", '"': '\\"', "\\": "\\\\" };
// we use a single string builder for efficiency reasons
var pieces = [];
// this recursive function walks through all objects and appends their
// JSON representation (in one or several pieces) to the string builder
function append_piece(aObj) {
if (typeof aObj == "boolean") {
if (typeof aObj == "string") {
aObj = aObj.replace(/[\\"\x00-\x1F\u0080-\uFFFF]/g, function($0) {
// use the special escape notation if one exists, otherwise
// produce a general unicode escape sequence
switch ($0) {
case "\b": return "\\b";
case "\t": return "\\t";
case "\n": return "\\n";
case "\f": return "\\f";
case "\r": return "\\r";
case '"': return '\\"';
case "\\": return "\\\\";
}
return "\\u" + ("0000" + $0.charCodeAt(0).toString(16)).slice(-4);
});
pieces.push('"' + aObj + '"')
}
else if (typeof aObj == "boolean") {
pieces.push(aObj ? "true" : "false");
}
else if (typeof aObj == "number" && isFinite(aObj)) {
// there is no representation for infinite numbers or for NaN!
pieces.push(aObj.toString());
}
else if (typeof aObj == "string") {
aObj = aObj.replace(/[\\"\x00-\x1F\u0080-\uFFFF]/g, function($0) {
// use the special escape notation if one exists, otherwise
// produce a general unicode escape sequence
return charMap[$0] ||
"\\u" + ("0000" + $0.charCodeAt(0).toString(16)).slice(-4);
});
pieces.push('"' + aObj + '"')
}
else if (aObj === null) {
pieces.push("null");
}
@ -109,10 +113,10 @@ var JSON = {
(aObj.length === 0 || aObj[aObj.length - 1] !== undefined)) {
pieces.push("[");
for (var i = 0; i < aObj.length; i++) {
append_piece(aObj[i]);
arguments.callee(aObj[i]);
pieces.push(",");
}
if (pieces[pieces.length - 1] == ",")
if (aObj.length > 0)
pieces.pop(); // drop the trailing colon
pieces.push("]");
}
@ -125,9 +129,9 @@ var JSON = {
if (aKeysToDrop && aKeysToDrop.indexOf(key) != -1)
continue;
append_piece(key.toString());
arguments.callee(key.toString());
pieces.push(":");
append_piece(aObj[key]);
arguments.callee(aObj[key]);
pieces.push(",");
}
if (pieces[pieces.length - 1] == ",")