This changeset introduces new compile time switch macro LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION
which removes the following functions when it's defined.
```
// lz4.c
LZ4_createStream
LZ4_freeStream
LZ4_createStreamDecode
LZ4_freeStreamDecode
LZ4_create // legacy
// lz4hc.c
LZ4_createStreamHC(void)
LZ4_freeStreamHC
LZ4_createHC // legacy
LZ4_freeHC // legacy
```
These functions uses dynamic memory allocation functions such as malloc() and free().
It'll be useful for freestanding environment which doesn't have these allocation functions.
Since this change breaks API, this macro is only valid with lz4 as a static linked object.
This changeset introduces the following external macros.
- Add new macro LZ4_memset() which enables to inject external function as memset().
- Similar macro LZ4_memmove() for memmove().
- In same manner, LZ4_memcpy() also can be overriden by external macro.
makes it possible to replace at link time
malloc, calloc and free
by user-provided functions
which must be named LZ4_malloc(), LZ4_calloc() and LZ4_free().
answer #937
LZ4_compress_HC_destSize() had a tendency
to discard its last match when this match overflowed specified dstBuffer limit.
The impact is generally moderate,
but occasionally huge,
typically when this last match is very large
(such as compressing a bunch of zeroes).
Issue #784 fixed for both Chain and Opt implementations.
Added a unit test suggested by @remittor checking this topic.
when src ptr is in very low memory area (< 64K),
the virtual reference to data in dictionary
might end up in a very high memory address.
Since it's not a "real" memory address,
just a virtual one, to calculate distance,
it doesn't matter : only distance matters.
The assert was to restrictive.
Fixed.
When the match is very long and found quickly, we can do
matchLength * nbCompares iterations through the chain
swapping, which can really slow down compression.
It is important to continue to look backwards if the current pattern
reaches `lowPrefixPtr`. If the pattern detection doesn't go all the
way to the beginning of the pattern, or the end of the pattern it
slows down the search instead of speeding it up.
The slow unit in `round_trip_stream_fuzzer` used to take 12 seconds
to run with -O3, now it takes 0.2 seconds.
Credit to OSS-Fuzz
This diff fixes an issue in which we failed to clear the `dictCtx` in HC
compression. The `dictCtx` is not supposed to be used when an `extDict` is
present: matches found in the `dictCtx` do not account for the presence of an
`extDict` segment, and their offsets are therefore miscalculated when one is
present. This can lead to data corruption.
This diff clears the `dictCtx` whenever setting an `extDict`.
This issue was uncovered by @terrelln's fuzzing work.
