I could use gzoffset function in zlib to estimate the remaining uncompress file size. Is there a similar function in bzip2 library? If not, is there any trick that I can use?
Just track the amount of compressed data consumed. When you have processed xx% of the compressed data, you have generated approximately xx% of the uncompressed data.
gzoffset() does not tell you anything about the remaining uncompressed file size. It only tells you how many bytes you have uncompressed so far. You can get that simply by counting how many bytes you have uncompressed so far.