518475 - NPN_RequestRead fails with multiple byte ranges

Status: RESOLVED INCOMPLETE

(Core Graveyard :: Plug-ins, defect)

Description

[Jonathan Griffin (:jgriffin)]

When a plugin calls NPN_RequestRead and passes it a single byte range, the browser makes the appropriate request and calls NPP_Write as expected.  However, if the plugin calls NPN_RequestRead with two ranges in the rangeList parameter, the browser returns NPERR_NO_ERROR but never calls NPP_Write.

By turning on http logging I can see that the browser does in fact make the correct HTTP request and receive a response, but for some reason this is never tranlasted into any NPP_Write calls to the plugin.

To reproduce the passing case, you can load the following page:

http://people.mozilla.org/~jgriffin/npn_requestread/test_good.html

Note that when the passing case is run, the plugin populates the iframe with text, and produces the following debug output:

For application/x-test found plugin nptest.dll
NPP_NewStream
NPP_Write, offset=0, len=1024, end=3976
NPP_Write, offset=1024, len=1024, end=3976
NPP_Write, offset=2048, len=1024, end=3976
NPP_Write, offset=3072, len=904, end=3976
called NPN_RequestRead, return 0
NPP_Write, offset=100, len=100, end=3976
data matches!

It's the last NPP_Write call which was generated by the call to NPN_RequestRead, as the range passed to it was 100,100.

To reproduce the failing case, load the following page:

http://people.mozilla.org/~jgriffin/npn_requestread/test_fail.html

In this case, the iframe is never populated with data, and the debug output is:

For application/x-test found plugin nptest.dll
NPP_NewStream
NPP_Write, offset=0, len=1024, end=3976
NPP_Write, offset=1024, len=1024, end=3976
NPP_Write, offset=2048, len=1024, end=3976
NPP_Write, offset=3072, len=904, end=3976
called NPN_RequestRead, return 0

NPN_Write is never called following the call to NPN_RequestRead.  The call to NPN_RequestRead was made with two ranges in this case, 100,100 and 500,100.

Comment 1

[Benjamin Smedberg]

Perhaps NPN_RequestRead is being ignored because that data was already delivered? Typically NPN_RequestRead is called immediately from NPP_NewStream, which cancels the normal 'deliver all the content' behavior, I think...

Comment 2

[Jonathan Griffin (:jgriffin)]

Well, there is some uncertainty in the docs as to when NPN_RequestRead may be called.  All attempts I have made at calling it within NPP_NewStream always return NPERR_STREAM_NOT_SEEKABLE, even for nice seekable http streams.  Do you think this is a bug?

I also tried calling it from the first NPP_Write call (before the entire stream is consumed), but this results in the same behavior as the original description.

Comment 3

[Benjamin Smedberg]

Resolving old bugs which are likely not relevant any more, since NPAPI plugins are deprecated.