Rather than special-casing a check for `/dev/null`, this uses `stat()` to
avoid `chmod()`-ing any non-regular file. I believe this is the desirable
behavior. `UTIL_chmod()` is never called on directories at the moment, only
output files.
Instead of calling `stat()`, these functions accept the result of a previous
`stat()` call on the file in question, which will allow us to make multiple
decisions around a file without redundant `stat()` calls.
I want to introduce versions of many of these functions that take pre-
populated `stat_t` objects and use those rather than doing their own redundant
`stat()` internally. These functions will have `...Stat()` suffixes. So this
commit renames these existing functions into the active voice, to avoid
confusion.
new version easier to vectorize
leads to smaller code and faster execution
notably at the last recombination stage
(basically, fixed cost per block).
Assembly inspected with godbolt
On my laptop, with `clang` and `-mavx2` :
2K block : 1280 MB/s -> 1550 MB/s
8K block : 1750 MB/s -> 1860 MB/s
both `--long-commmand=arg` and `--long-command arg`
are supported by macro `NEXT_FIELD()`
so that the long-command only needs to be listed once.
This extends the syntax to support new syntaxes like
`-o=FILE` or `-D=dict`,
though there is no need to advertise this capability for the time being.
Also : added `NEXT_UINT32()`,
which is wrapper around `NEXT_FIELD()`
to read integer parameters.
Use the wrapper to new field, such as `--memlimit`
which can now support both syntaxes too.
for --patch-from origin
and --filelist list
Also : removed some constrained syntax tests,
as the new argument parsing syntax is more permissive.
For example :
zstd file -of dest
used to be disallowed.
It's now allowed, and understood as:
zstd file -o dest -f
this patch reduces complexity associated with
commands requiring a separated arguments
such as :
-o filename
-D dictionary
--output-dir-flat dir
--output-dir-mirror dir
It used to be a multi-stage process with explicit context,
it's now simplified as a single macro.
Thanks to this simplification,
separated arguments logic has also been extended to
--patch-from XXX
--filelist XXX
which extends existing capability using =XXX
--patch-from=XXX
--filelist=XXX
Separated argument is useful for filenames and directories,
as it benefits from shell expansion
such as ~/dir/file
where the ~ is automatically translated by the shell.
In contrast --long-command=FILE does not interpret FILE,
so ~/ is transmitted as is to the main() function,
generally resulting in incorrect file name.
