Lz4: Add more oss-fuzz coverage

[terrelln]

@cmeister2 recently added oss-fuzz fuzzers to LZ4 in #739. I added some more fuzzer tests in #752. We still need more coverage. This is an (incomplete) list of fuzzers we still need:

• [x] Dictionary compression (extDict, prefix, attached, smaller than 64K prefix, etc)
• [x] LZ4HC
• [x] LZ4 frame (dictionary) compression
• [x] LZ4 frame (dictionary) decompression

[terrelln]

Added dictionary and streaming compression fuzzers in https://github.com/lz4/lz4/pull/757.

[terrelln]

Also added LZ4HC fuzzers to #757.

[cmeister2]

These Iook great BTW. Are they finding bugs yet? (I'm not on the cc list)

[terrelln]

Yeah, 3 bugs fixed by https://github.com/lz4/lz4/pull/756, the bug fixed in https://github.com/lz4/lz4/pull/759, and an off-by-one in the bug fix in https://github.com/lz4/lz4/pull/760. Either found by oss-fuzz or when creating the fuzzers.

[terrelln]

I added LZ4 frame fuzzers in https://github.com/lz4/lz4/pull/762.

I still have to add streaming LZ4 frame fuzzers to round_trip_stream_fuzzer, then we should have fairly complete coverage.

[Cyan4973]

Are there still more oss-fuzz tests to add ? Or is this action completed ?