Co-authored-by: vtorri <vincent.torri@gmail.com>

Add --single-thread to zstd --help

[cmake] Add playTests.sh as a test

Fix the c99/cmake build under Cygwin/MSYS2

Super blocks must never violate the zstd block bound of input_size + ZSTD_blockHeaderSize. The individual sub-blocks may, but not the super block. If the superblock violates the block bound we are liable to violate ZSTD_compressBound(), which we must not do. Whenever the super block violates the block bound we instead emit an uncompressed block.

This means we increase the latency because of the single uncompressed block. I fix this by enabling streaming an uncompressed block, so the latency of an uncompressed block is 1 byte. This doesn't reduce the latency of the buffer-less API, but I don't think we really care.

* I added a test case that verifies that the decompression has 1 byte latency.
* I rely on existing zstreamtest / fuzzer / libfuzzer regression tests for correctness. During development I had several correctness bugs, and they easily caught them.
* The added assert that the superblock doesn't violate the block bound will help us discover any missed conditions (though I think I got them all).

Credit to OSS-Fuzz.

When building zst under cygwin or msys2 with std=c99 the build would fail because
of an undefined fileno()/_fileno(), which is used by the IS_CONSOLE() macro.

When building with -std=c99 (gcc otherwise defaults to gnu, which implies POSIX),
which is the default of the cmake build, then including unistd.h wont define
_POSIX_VERSION and all other headers also wont expose POSIX API.

To fix this make sure to define _POSIX_C_SOURCE with the version we want before including
unistd.h and so that _POSIX_VERSION is set to the version provided by the system.

Since Cygwin/MSYS2 just follow POSIX we can also remove their special cases for
defining IS_CONSOLE().

And, for completeness, also explicitly include stdio.h which is what actually declares fileno().

Tested with the normal make file and cmake under MSYS2 and Cygwin.

* Adding new cli endpoint --diff-from=

* Appveyor conversion nit

* Using bool set trick instead of direct set

* Removing --diff-from and only leaving --diff-from=#

* Throwing error when both dictFileName vars are set

* Clean up syntax

* Renaming diff-from to patch-from

* Revering comma separated syntax clean up

* Updating playtests with patch-from

* Uncommenting accidentally commented

* Updating remaining docs and var names to be patch-from instead of diff-from

* Constifying

* Using existing log2 function and removing newly created one

* Argument order (moving prefs to end)

* Using comma separated syntax

* Moving to outside #ifndef

* Allow zero sized buffers in `stream_decompress`. Ensure that we never have two
  zero sized buffers in a row so we guarantee forwards progress.
* Make case 4 in `stream_round_trip` do a zero sized buffers call followed by
  a full call to guarantee forwards progress.
* Fix `limitCopy()` in legacy decoders.
* Fix memcpy in `zstdmt_compress.c`.

Catches the bug fixed in PR #1939 

The `numFiles` variable wasn't updated, so the fuzzer didn't do anything.
I did two things to fix this:

1. Remove the `numFiles` variable entirely.
2. Error if we can't open a file and print the number of files tested.

Cygwin currently uses the fallback implementation which just returns 1 every time,
which leads to bad performance when zstd is called with -T0 for example.

Instead use the POSIX implementation used for the BSDs which works just fine under Cygwin.

Tested under Cygwin and MSYS2.

one missing item in v1.4.4

* Initial revised automated benchmarking script

* Updating nb_iterations and making loop infinite

* Allowing benchmarking params to be changed from cli

* Renaming old speed test

* Removing numpy dependency for cli

* Change filename and benchmakr on pr level

* Moving build outside loop and adding iterations param

* Moving benchmarking to seperate travis ci test

* Fixing typo and using unused variable

* Added mode labels and updated README accordingly

* Adding new mode 'current' that compraes facebook:dev against current hash

* Typo

* Reverting previous accidental diff

* Typo

* Adding frequency config variable to prevent github from blacklisting

* Added new argument for frequency of fetching new prs

* Updating documentation

* Adding fail logging for superblock flow

* Dividing by targetCBlockSize instead of blockSize

* Adding new const and using more acurate formula for nbBlocks

* Only do dstCapacity check if using superblock

* Remvoing disabling logic

* Updating test to make it catch more extreme case of previou bug

* Also updating comment

* Only taking compressEnd shortcut on non-superblock

* Adding -M# operation modifier documentation

* Adding long name, typo and update desc

Use statbuf->st_mtim Again

[fuzz] Adding bool to check if there is enough room to emit noCompress Superblocks

Add Support for Dictionaries in Corruption Diagnosis Tool

added ppc64le tests on travis

on real hardware