Change the interface provided by the `parse_size()` function to reduce
its responsibilities to just a single task: parsing a number of bytes
from a string of the form '123KB', etc. Previously, the function was
also responsible for deciding which mode truncate would operate in.
Furthermore, this commit simplifies the code for parsing the number and
unit to be less verbose and use less mutable state.
Finally, this commit adds some unit tests for the `parse_size()`
function.
The “GNU tests” task is routinely broken on `master`.
Broken CI is worse than no CI, as it teaches people to ignore errors.
This PR pins the versions of the GNU testsuite (and GNUlib) used,
to current stable versions, so this task stops breaking unexpectedly.
Presumably, someone will update `GNU.yml` when a new stable version
of the GNU coreutils is released, but I'm not volunteering.
Previous version would perform an amount of work proportional to `CHUNK_SIZE`,
so this wasn't a valid way to benchmark at multiple values of that constant.
The `TryInto` implementation for `&mut [T]` to `&mut [T; N]` relies on `const`
generics, and is available in (stable) Rust v1.51 and later.
Change the behavior of `head` to display an error for each problematic
file, instead of displaying an error message for the first problematic
file and terminating immediately at that point. This change now matches
the behavior of GNU `head`.
Before this commit, the first error caused the program to terminate
immediately:
$ head a b c
head: error: head: cannot open 'a' for reading: No such file or directory
After this commit:
$ head a b c
head: cannot open 'a' for reading: No such file or directory
head: cannot open 'b' for reading: No such file or directory
head: cannot open 'c' for reading: No such file or directory
Instead of using a BufReader and reading each line separately,
allocating a String for each one, we read to a chunk. Lines are
references to this chunk. This makes the allocator's job much easier
and yields performance improvements.
Chunks are read on a separate thread to further improve performance.
Fix a bug in which `head` failed to print headings for `stdin` inputs
when reading from multiple files, and fix another bug in which `head`
failed to print a blank line between the contents of a file and the
heading for the next file when reading multiple files. The output now
matches that of GNU `head`.
