#208 fig2dev truncates PostScript image data when deflate stream size is exactly a multiple of 16384 bytes

[Fabiano Baroni]

I encountered a bug in the export of an imported raster image.

XFig displays the image correctly, but fig2dev produces a PostScript file in which the bottom part of the image is missing.

The problem is in fig2dev/dev/encode.c, in deflate_ascii85encode(). The output buffer is 16384 bytes, and the code ends with:

if (ret == Z_STREAM_END && strm.avail_out != 0)
    ascii85encode(out, buf, sizeof buf - strm.avail_out);

For this offending image, the deflate stream is exactly 81920 bytes (5 × 16384). Thus deflate() returns Z_STREAM_END with strm.avail_out == 0, and the final 16384-byte buffer is not written. Only 65536 bytes are output.

Changing the condition to:

if (ret == Z_STREAM_END)
    ascii85encode(out, buf, sizeof buf - strm.avail_out);

appears to fix the problem. This seems to be an edge case where the final deflate output buffer is exactly full.

Thank you, best regards

[tkl]

Awesome! The proposed patch fixes the problem, and does not seem to create other bugs. I am still writing a test for the issue.