509678 - Performance improvement for built-in JSON parser

Status: RESOLVED FIXED

(Rhino Graveyard :: Core, enhancement)

Description

[Hannes Wallnoefer]

The parser for the built-in JSON object is currently based on regular expressions (see bug 505211). This is a hand written parser that should be quite a bit faster.

A few notes regarding numbers: I'm using java.lang.Double.valueOf() to parse numbers, as from empirical testing this does the right thing in most cases (except for leading zeroes, which I check for manually). 

Also, I removed the special handling for very large numbers using java.math.BigDecimal, so now 9999999999999999 is parsed as 10000000000000000 and 1.5e99999999 is parsed as positive Infinity. This matches the way numbers are parsed by the main Rhino parser, Spidermonkey, and V8, and I couln't find anything in the ES5 spec saying that JSON numbers should be parsed differently. I changed the unit test accordingly.

Comment 1

[Hannes Wallnoefer]

Attachment: Hand written replacement for native JSON parser

Comment 2

[Norris Boyd]

Attachment: A few small mods to patch: adding type params, formatting

Comment 3

[Hannes Wallnoefer]

I committed the last patch plus a minor fix in two of the tests I added, and removed the JsonLexer class which isn't used anymore.

Removing src/org/mozilla/javascript/json/JsonLexer.java;
/cvsroot/mozilla/js/rhino/src/org/mozilla/javascript/json/JsonLexer.java,v  <--  JsonLexer.java
new revision: delete; previous revision: 1.1
done
Checking in src/org/mozilla/javascript/json/JsonParser.java;
/cvsroot/mozilla/js/rhino/src/org/mozilla/javascript/json/JsonParser.java,v  <--  JsonParser.java
new revision: 1.2; previous revision: 1.1
done
Removing testsrc/org/mozilla/javascript/tests/json/JsonLexerTest.java;
/cvsroot/mozilla/js/rhino/testsrc/org/mozilla/javascript/tests/json/JsonLexerTest.java,v  <--  JsonLexerTest.java
new revision: delete; previous revision: 1.1
done
Checking in testsrc/org/mozilla/javascript/tests/json/JsonParserTest.java;
/cvsroot/mozilla/js/rhino/testsrc/org/mozilla/javascript/tests/json/JsonParserTest.java,v  <--  JsonParserTest.java
new revision: 1.2; previous revision: 1.1
done

Comment 4

[Norris Boyd]

Thanks so much for doing this!

Comment 5

[rspeyer]

Attachment: added \b as a valid escape character in JSON strings

Comment 6

[Hannes Wallnoefer]

Thanks Raphael, I committed your patch.

Comment 7

[rspeyer]

Attachment: make JSON.parse fail on invalid leading and trailing whitespace

Comment 8

[Norris Boyd]

Thanks, Raphael, this fixes a regression in the unit test. Patch committed:

Checking in src/org/mozilla/javascript/json/JsonParser.java;
/cvsroot/mozilla/js/rhino/src/org/mozilla/javascript/json/JsonParser.java,v  <--  JsonParser.java
new revision: 1.5; previous revision: 1.4
done