by triggering the prefetching decoder path
(which used to be dedicated to long-range offsets only).
Figures on my laptop :
no content prefetch : ~300 MB/s (for reference)
full content prefetch : ~325 MB/s (before this patch)
new prefetch path : ~375 MB/s (after this patch)
The benchmark speed is already significant,
but another side-effect is that this version
prefetch less data into memory,
since it only prefetches what's needed, instead of the full dictionary.
This is supposed to help highly active environments
such as active databases,
that can't be properly measured in benchmark environment (too clean).
Also :
fixed the largeNbDict test program
which was working improperly when setting nbBlocks > nbFiles.
not sure why it only triggers now,
this code has been around for a while.
Introduced a new error code : dstBuffer_null,
I couldn't express anything even remotely similar with existing error codes set.
changed workspace parameter convention
to always provide workspaceSize,
so that size can be explicitly checked.
Also, use more enum to make the meaning of some parameters more explicit.
isolate all logic associated with block decompression
into its own module.
zstd_decompress is still in charge
of context creation/destruction,
frames, headers, streaming, special blocks, etc.
Compressed blocks themselves are now handled within zstd_decompress_block .
fix#1385
decompressing into NULL was an automatic error.
It is now allowed, as long as the content of the frame is empty.
Seems to simplify things for `arrow`.
Maybe some other projects rely on this behavior ?
fix#1379
decodecorpus was generating one extraneous byte when `nbSeq==0`.
This is disallowed by the specification.
The reference decoder was just skipping the extraneous byte.
It is now stricter, and flag such situation as an error.
since corrupted bitstreams can generate too large values.
This slightly reduces the benefits from clang on my laptop.
gcc results and code generation are not affected.
while reviewing #1364,
I found a decompression speed improvement.
On my laptop, the new code decompresses +5-6% faster on clang
and +2-3% faster on gcc.
not bad for an accidental optimization...
Yann Collet