I took a look at this over the weekend.  Based on the existing code in hhvm only the json_decode pathway needs to be replaced.  encoding is implemented independently and shares a common pathway with a variety of other serializations.  I've gone ahead and done the initial work of porting over the linked pecl extension's json_decode into hhvm's codebase[1].  There are two issues that i'm not sure how to solve:

1) the json_encode pathway doesn't need to be replaced, but it does make a single method call[2] to a function from the previous library:

    void utf16_to_utf8(HPHP::StringBuffer &buf, unsigned short utf16);

I don't really know enough in this realm to go about re-implementing this. It takes the unsigned short and append its utf-8 representation to the buffer.  hhvm does have an intl_convert_utf16_to_utf8 method, but it works on full strings so passing it two bytes at a time would be undesirable.

2) hhvm has a special mode FB_LOOSE which allows invalid json.  json-c has a strict mode which i've only enabled when FB_LOOSE is not set, but this does not pass their unit tests of previously accepted invalid json.  I have not changed the method signatures between the json extension and the parser, rather implemented the existing method signatures with the json-c parser, so with a bit more work json-c could just be a compile time flag, but not sure i like that solution either.

Suggestions?

Erik B.

[1] https://github.com/ebernhardson/hiphop-php/commit/2619eb96c29f17e84ed0781f570de2b655ea75b2

[2] https://github.com/facebook/hhvm/blob/master/hphp/runtime/base/variable-serializer.cpp#L371

On Wed, Apr 16, 2014 at 3:42 PM, Ori Livneh <ori@wikimedia.org> wrote:

Hello,

One of the blockers for the effort to package HHVM for Debian is the licensing of the JSON extension. This is the same problem that has afflicted PHP (see <https://bugs.php.net/bug.php?id=63520>: "JSON extension includes a problematic license statement") and that we have discussed in the context of bug 47413 (<https://bugzilla.wikimedia.org/show_bug.cgi?id=47431>: "JSON extension dependency has a non-free component".

There is a drop-in replacement which is not encumbered with licensing issues: Remi Collet's pecl-json-c, available at <https://github.com/remicollet/pecl-json-c>. Paul Tarjan replied on the packaging thread (see <https://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg1208263.html>), saying that the HHVM team would be interested in swapping out the JSON library and replacing it with pecl-json-c, if someone were to port it. Since both extensions provide the same API, I imagine "porting" in this context means tweaking the include paths and the build configuration.

Are any of you interested in taking this on?