tree c3cb87afe1b1e5b944a734441dd9b52f349e6e4c
parent 822a1d64e9c3cc602df1b3debe0532a2fe6f2848
author K. Moon <kmoon@chromium.org> 1649741853 +0000
committer Pdfium LUCI CQ <pdfium-scoped@luci-project-accounts.iam.gserviceaccount.com> 1649741853 +0000

[xfa] Fix GIF decode continuation

Fixes the GIF decoder to continue decoding across various boundaries.
The old logic only works for a single scanline within a single image
data sub-block, which obviously doesn't hold for real GIF images.

Critically, the existing logic fails to recover from source buffer
underflow and destination buffer overflow correctly. To fix this:

1. LZWDecompressor::Decode() doesn't discard previously-decoded state.
2. ProgressiveDecoder incrementally feeds LZWDecompressor new data.

Note that ProgressiveDecoder.BUG_895009 does not contain a valid GIF,
which the fixed decoder correctly fails to decode; the test expectations
have been updated accordingly.

Fixed: pdfium:904, pdfium:1337
Change-Id: I79db5c8962ff40a9b47e680f5e34e62950c1d495
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/92390
Auto-Submit: K. Moon <kmoon@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>