Opened 10 years ago

Closed 10 years ago

Last modified 8 months ago

#8988 closed patch

New IFF parser

Reported by: peres Owned by: peres
Priority: normal Component: --Other--
Keywords: Cc:


I was extending the ILBM format decoder for Big Red Adventure when I ran into a better implementation of the underlying IFF parser (in Kyra).

The current IFF parser only allows sequential access to the chunks, whereas the one in the patch doesn't have this limitation. As a result, client code can effectively search for the chunks it needs instead of scanning all the file accumulating state.

The ILBM decoder I was working on came out so much better without switch()'s, that I ended up ditching the whole current IFFParser and adapted its users: ILBMDecoder, PBMDecoder and A8SVXDecoder.

The patch contains the related changes, together with adaptations to Parallaction (for A8SVXDecoder), and a one-liner in Saga (for PBMDecoder).

Ticket imported from: #2704062. Ticket imported from: patches/1093.

Attachments (2)

iff001.patch (25.0 KB) - added by peres 10 years ago.
New IFF parser and related classes. (5.7 KB) - added by peres 10 years ago.
A IFF parser using a ReadStream, and its ILBMDecoder companion.

Download all attachments as: .zip

Change History (14)

Changed 10 years ago by peres

Attachment: iff001.patch added

New IFF parser and related classes.

comment:1 Changed 10 years ago by fingolfin

While being able to arbitrarily switch between chunks certainly simplifies the parsing code, the drawback is that now you suddenly must read from a seekable stream. This can affect performance quite negatively. Esp. on low end devices. It is also annoying if one wants to read data from a compressed stream.

comment:2 Changed 10 years ago by peres

If being able to read a seekable stream is not acceptable for the parser, I can switch it back to work on a ReadStream.

I am going to submit another patch based a bit on the iffparse library in AmigaOS. This shouldn't require more than a ReadStream, but also provide an interface that looks like the one in the patch.

comment:3 Changed 10 years ago by bluegr

The patch looks good to me, apart from the issue that fingolfin pointed out already. The new code looks cleaner and more organized.
Something quite minor: there are a lot of newlnes at the end of graphics/iff.cpp

comment:4 Changed 10 years ago by peres

Here is a new implementation of the parser. I changed the underlying stream to a ReadStream, as it is currently in trunk.

The client has to tell the parser which chunks are needed before the process starts. The parser will then scan the file and store the requested chunk in memory, from where they can be retrieved by the client when parsing is over.

The client can also instruct the parser to pause when a certain chunk is found, and obtain a ReadStream* to the data. This may be useful when a big chunk of data must be analyzed, but can't used verbatim (e.g., a packed bitmap).

The usage is shown in the ILBMDecoder included in the zip file.

Changed 10 years ago by peres

Attachment: added

A IFF parser using a ReadStream, and its ILBMDecoder companion.

comment:5 Changed 10 years ago by sev-

Peres, please, commit it. I can provide you the ITE demo which makes use of PBM images, so you can doublecheck it works well.

Only remark: As I understand, we are talking about moving this parser from common/parallacion to graphics/? Because your last patch contained files from engines/parallaction directory only.

comment:6 Changed 10 years ago by peres

Owner: set to peres

comment:7 Changed 10 years ago by peres

Thank you for the feedback. As you understood, although the attached patch is on engine/parallaction, the parser will be moved into common/, with changes to related iff files in graphics/ and sound/.
I'm working to adapt the current patch and will post a followup and commit as soon as it's done.

About the ITE demo, I have one; I just need to know where I have to go to trigger the loading of a PBM resource.

comment:8 Changed 10 years ago by sev-

- Skip intro.
- Leave the tent (click either of the sites)
- Follow the yellow road until you leave the village. The path is straight
- You fill wind yourself on the world map
- Then all but one location display static PBM images:
o Boar castle, right down
o Elk's forest, on the left
o Rat's cave left top
o Tycho's house, top right
o Ferret's village, down
o Sanctuary, in the center, slightly right

comment:9 Changed 10 years ago by lordhoto

What's the status of this item? I thought it was (at least partially) committed?

comment:10 Changed 10 years ago by peres

The parser was committed and related code updated. I'm thus closing the ticket.

comment:11 Changed 10 years ago by peres

Status: newclosed

comment:12 Changed 8 months ago by digitall

Component: --Other--
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