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.
This lets us use fewer reallocations when parsing each line.
The current guess is set to the maximum fields in a line so far. This is
a free performance win in the common case where each line has the same
number of fields, but comes with some memory overhead in the case where
there is a line with lots of fields at the beginning of the file, and
fewer later, but each of these lines are typically not kept for very
long anyway.
Using indexes into the line instead of Vec<u8>s means we don't have to copy
the line to store the fields (indexes instead of slices because it avoids
self-referential structs). Using memchr also empirically saves a lot of
intermediate allocations.
Refactor the code for representing the `df` data table into `Header`
and `Row` structs. These structs live in a new module `table.rs`. When
combined with the `Options` struct, these structs can be
`Display`ed. Organizing the code this way makes it possible to test
the display settings independently of the machinery for getting the
filesystem data. New unit tests have been added to `table.rs` to
demonstrate this benefit.
Set the value of the `FsUsage.ffree` value to 0 on Windows, because
even though it is meaningless, it should not exceed the
`FsUsage.files` value so that client code can rely on the guarantee
that `FsUsage.ffree <= FsUsage.files`.
Show a warning if the `skip=N` command-line argument would cause `dd`
to skip past the end of the input. For example:
$ printf "abcd" | dd bs=1 skip=5 count=0 status=noxfer
'standard input': cannot skip to specified offset
0+0 records in
0+0 records out
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.
- consolidate configuration
- DRY improvements
- improve flexibility/robustness in the face of missing reference test info
- add reference test info IDs and additional logging to help diagnose testing failures
- includes parallel refactor of 'util/run-gnu-test.sh'
