Replace `ByteSplitter` and `LineSplitter` with `ByteChunkWriter` and
`LineChunkWriter` respectively. This results in a more maintainable
design and an increase in the speed of splitting by lines.
Add the `ByteChunkWriter` and `LineChunkWriter` structs and
implementations, but don't use them yet. This structs offer an
alternative approach to writing chunks of output (contrasted with
`ByteSplitter` and `LineSplitter`). The main difference is that
control of which underlying file is being written is inside the writer
instead of outside.
Add some helper functions and adjust some error-handling to make the
`Output::dd_out()` method, containing the main loop of the `dd`
program, more concise. This commit also adds documentation and
comments describing the main loop procedure in more detail.
Add some structure to errors that can be created during parsing of
settings from command-line options. This commit creates
`StrategyError` and `SettingsError` enumerations to represent the
various parsing and other errors that can arise when transforming
`ArgMatches` into `Settings`.
Show a warning when a block size includes "0x" since this is
ambiguous: the user may have meant "multiply the next number by zero"
or they may have meant "the following characters should be interpreted
as a hexadecimal number".
When specifying `seek=N` and *not* specifying `conv=notrunc`, truncate
the output file to `N` blocks instead of truncating it to zero before
starting to write output. For example
$ printf "abc" > outfile
$ printf "123" | dd bs=1 skip=1 seek=1 count=1 status=noxfer of=outfile
1+0 records in
1+0 records out
$ cat outfile
a2
Fixes#3068.
This avoids hacking around the short options of these command line
arguments that have been introduced by clap. Additionally, we test and
correctly handle the combination of both version and help. The GNU
binary will ignore both arguments in this case while clap would perform
the first one. A test for this edge case was added.
Now treats recognized command line options and ignores unrecognized
command line options instead of returning a special exit status for
them.
There is one point of interest, which is related to an implementation
detail in GNU `true`. It may return a non-true exit status (in
particular EXIT_FAIL) if writing the diagnostics of a GNU specific
option fails. For example `true --version > /dev/full` would fail and
have exit status 1.
This behavior was acknowledged in gnu in commit
<9a6a486e6503520fd2581f2d3356b7149f1b225d>. No further
justification provided for keeping this quirk.
POSIX knows no such options, and requires an exit status of 0 in all
cases. We replicate GNU here which is a consistency improvement over the
prior implementation. Adds documentation to clarify the intended
behavior more properly.
