Comments on: AMF – Errata and other ramblings

By: Tim

Tim — Tue, 14 Oct 2008 21:30:02 +0000

I don’t know about windows, but in PHP you need to reverse the 8 byte string before unpacking the data.

$s = “\x3F\xF3\xAE\x14\x7A\xE1\x47\xAE”;
$d = current( unpack(‘d’, strrev($s) ) );
var_dump( $d ); // float(1.23)

By: umberto21

umberto21 — Tue, 14 Oct 2008 04:05:28 +0000

There is also something weird I noticed with the REAL/DOUBLE : it isn’t bit coded correctly on Win32/VS2008 : you can’t just case a DOUBLE into 8 bytes. there is some other coding mechanism where they split the decimal part and the integer part.. I am trying to work it out. They have the same AMF coded DOuble in the headers of FLV files (open one with HexEditor and try to work out the video time duration in {millisec.nanosec} ).

By: Tim

Tim — Tue, 14 Oct 2008 04:02:47 +0000

536870912 possible values includes 0, so max is 536870911.
likewise with unsigned; -268435456 to +268435455

By: umberto21

umberto21 — Tue, 14 Oct 2008 04:01:52 +0000

14 Oct 2008

I agree : they must have a typo in the 13 page doc on AMF3
the range of their weird INT encoding is from 0 to 536870912 .. or from -268435456 to +268435456

REF :

http://cvs.savannah.gnu.org/viewvc/*checkout*/gnash/libamf/amf.cpp?root=gnash

http://myt.ag/URLWeb.aspx?email=steve@fooworks.com&url=http://cvs.savannah.gnu.org/viewcvs/gnash/libamf/amf.cpp%3fcvsroot%3dgnash%26r1%3d1.15%26r2%3d1.16&sn=

http://cvs.savannah.gnu.org/viewvc/*checkout*/gnash/libamf/amfutf8.h?root=gnash