We've already checked that we are more than FASTLOOP_SAFE_DISTANCE
away from the end, so this branch can never be true, we will have
already jumped to the second decode loop.
Use LZ4_wildCopy16 for variable-length literals. For literal counts that
fit in the flag byte, copy directly. We can also omit oend checks for
roughly the same reason as the previous shortcut: We check once that both
match length and literal length fit in FASTLOOP_SAFE_DISTANCE, including
wildcopy distance.
Add an LZ4_wildCopy16, that will wildcopy, potentially smashing up
to 16 bytes, and use it for match copy. On x64, this avoids many
blocked loads due to store forwarding, similar to issue #411.
Copy the main loop, and change checks such that op is always less
than oend-SAFE_DISTANCE. Currently these are added for the literal
copy length check, and for the match copy length check.
Otherwise the first loop is exactly the same as the second. Follow on
diffs will optimize the first copy loop based on this new requirement.
I also tried instead making a separate inlineable function for the copy
loop (similar to existing partialDecode flags, etc), but I think the
changes might be significant enough to warrent doubling the code, instead
pulling out common functionality to separate functions.
This is the basic transformation that will allow several following optimisations.
Every 0xff byte in the compressed block corresponds to a length of 255 (not 256) in the input data. For long repeating sequences, using (length >> 8) may generate bad compressed blocks.
This commit adds a snapcraft.yaml file to allow lz4
to be distributed as a snap (see https://snapcraft.io/
for more info on snaps).
Building the Snap
-----------------
To build the snap simply install snapcraft and build the
snap e.g. on Ubuntu by doing:
$ sudo apt install snapcraft
$ cd contrib; snapcraft
This will build a snap that can be published [1] to
e.g. https://snapcraft.io/lz4
If you want to test the snap before publishing you
can do:
$ snap install <snapname>.snap --dangerous
And that will install it on your local host. You
will then have lz4 as a command to run.
Installing the Snap
-------------------
Once published and released in the snapstore your snap
can be installed on any platform that supports snaps
by doing:
snap install lz4
[1] https://docs.snapcraft.io/releasing-to-the-snap-store
