Byte, character, and line counting can all be done on the raw bytes
of the incoming stream without decoding the Unicode characters. This
fact was previously exploited in specific fast paths for counting
characters and counting lines. This change unifies those fast paths into
a single shared fast paths, using const generics to specialize the
function for each use case. This has the benefit of making sure that all
combinations of these Unicode-oblivious fast paths benefit from the same
optimization.
On my laptop, this speeds up `wc -clm odyssey1024.txt` from 840ms to
120ms. I experimented with using a filter loop for line counting, but
continuing to use the bytecount crate came out ahead by a significant
margin.
When wc is invoked with only the -m flag, we only need to count the
number of Unicode characters in the input. In order to do so, we don't
actually need to decode the input bytes into characters. Rather, we can
simply count the number of non-continuation bytes in the UTF-8 stream,
since every character will contain exactly one non-continuation byte.
On my laptop, this speeds up `wc -m odyssey1024.txt` from 745ms to
109ms.
* wc: specialize scanning loop on settings.
The primary computational loop in wc (iterating over all the
characters and computing word lengths, etc) is configured by a
number of boolean options that control the text-scanning behavior.
If we monomorphize the code loop for each possible combination of
scanning configurations, the rustc is able to generate better code
for each instantiation, at the least by removing the conditional
checks on each iteration, and possibly by allowing things like
vectorization.
On my computer (aarch64/macos), I am seeing at least a 5% performance
improvement in release builds on all wc flag configurations
(other than those that were already specialized) against
odyssey1024.txt, with wc -l showing the greatest improvement at 15%.
* Reduce the size of the wc dispatch table by half.
By extracting the handling of hand-written fast-paths to the
same dispatch as the automatic specializations, we can avoid
needing to pass `show_bytes` as a const generic to
`word_count_from_reader_specialized`. Eliminating this parameter
halves the number of arms in the dispatch.
* ls: handle looping symlinks infinite printing
* ls: better coloring and printing symlinks when dereferenced
* tests/ls: add dereferencing and symlink loop tests
* ls: reformat changed using rustfmt
* ls: follow clippy advice for cleaner code
* uucore/fs: fix FileInformation to open directory handles in Windows as
well
tee is supposed to exit when there is nothing left to write to. For
finite inputs, it can be hard to determine whether this functions
correctly, but for tee of infinite streams, it is very important to
exit when there is nothing more to write to.
This is part of fixing the tee tests. 'yes' is used by the GNU test
suite to identify what the SIGPIPE exit code is on the target
platform. By trapping SIGPIPE, it creates a requirement that other
utilities also trap SIGPIPE (and exit 0 after SIGPIPE). This is
sometimes at odds with their desired behaviour.
When the monitored process exits, the GNU version of timeout will
preserve its exit status, including the signal state.
This is a partial fix for timeout to enable the tee tests to pass. It
removes the default Rust trap for SIGPIPE, and kill itself with the
same signal as its child exited with to preserve the signal state.
This has the following behaviours. On Unix:
- The default is to exit on pipe errors, and warn on other errors.
- "--output-error=warn" means to warn on all errors
- "--output-error", "--output-error=warn-nopipe" and "-p" all mean
that pipe errors are suppressed, all other errors warn.
- "--output-error=exit" means to warn and exit on all errors.
- "--output-error=exit-nopipe" means to suppress pipe errors, and to
warn and exit on all other errors.
On non-Unix platforms, all pipe behaviours are ignored, so the default
is effectively "--output-error=warn" and "warn-nopipe" is identical.
The only meaningful option is "--output-error=exit" which is identical
to "--output-error=exit-nopipe" on these platforms.
Note that warnings give a non-zero exit code, but do not halt writing
to non-erroring targets.
