`swab(1)` - swap bytes #22

New Issue

Closed

opened 2023-12-30 15:36:22 +00:00 by trinity · 4 comments

trinity commented

2023-12-30 15:36:22 +00:00

Owner

This pertains to #23 in that it fulfills functionality offered in POSIX by dd(1p), specifically dd conv=swab.

Usage: swab (-w [word size])

swab(1) swaps bytes in standard input to standard output. The default word size is 2, as in two-byte words with the latter half of the word (in this case, one byte) being output before the former half of the word.

$ swab
hello world
ehll oowlrd

If there are remaining bytes less than the word size they're left unconverted. Word sizes up to 16 (128 bits) will be supported.

$ echo hello world | swab -w 8
o wohellrld

The usefulness of such a tool is limited but this should be small and easy to make, and would fill in more POSIX functionality in a way that is simpler than POSIX.

This pertains to #23 in that it fulfills functionality offered in POSIX by dd(1p), specifically `dd conv=swab`. ``` Usage: swab (-w [word size]) ``` swab(1) swaps bytes in standard input to standard output. The default word size is 2, as in two-byte words with the latter half of the word (in this case, one byte) being output before the former half of the word. ```sh $ swab hello world ehll oowlrd ``` If there are remaining bytes less than the word size they're left unconverted. Word sizes up to 16 (128 bits) will be supported. ```sh $ echo hello world | swab -w 8 o wohellrld ``` The usefulness of such a tool is limited but this should be small and easy to make, and would fill in more POSIX functionality in a way that is simpler than POSIX.

trinity referenced this issue

2023-12-30 15:44:13 +00:00

tests/posix: `dd(1p)` #23

trinity added the

enhancement

label 2023-12-30 16:00:34 +00:00

emma added the

help wanted

label 2023-12-30 21:39:42 +00:00

emma removed the

help wanted

label 2023-12-30 21:41:35 +00:00

emma changed title from ~~swab(1) - swap bytes~~ to `swab(1)` - swap bytes

2024-01-23 22:08:00 +00:00

trinity commented

2024-01-30 05:37:46 +00:00

Author

Owner

My current conundrum is that there are multiple useful types of byte reversal:

reversing bits in a byte
reversing bytes within a certain block size (e.g. "swabbing" - swapping bytes within a machine word - and the job of GNU tac(1), where all bytes in a file are reversed)
reversing bytes in blocks delimited by a certain byte sequence (e.g. GNU's rev(1), using '\n' or '\0')

The third should be relegated to a separate utility as it's higher level (plaintext) than endianness/bit order tomfoolery. Should the former two be separate utilities?

My current conundrum is that there are multiple useful types of byte reversal: - reversing bits in a byte - reversing bytes within a certain block size (e.g. "swabbing" - swapping bytes within a machine word - and the job of GNU tac(1), where all bytes in a file are reversed) - reversing bytes in blocks delimited by a certain byte sequence (e.g. GNU's rev(1), using '\n' or '\0') The third should be relegated to a separate utility as it's higher level (plaintext) than endianness/bit order tomfoolery. Should the former two be separate utilities?

emma added the

help wanted

label 2024-02-08 03:25:24 +00:00

emma referenced this issue

2024-02-08 03:38:19 +00:00

`rev(1)` – reverse data #48

emma commented

2024-02-08 03:39:14 +00:00

Owner

Ah, I didn’t realize GNU had a utility called rev already. Will come up with another name.

Ah, I didn’t realize GNU had a utility called `rev` already. Will come up with another name.

emma commented

2024-02-16 06:12:39 +00:00

Owner

On first consideration, I think it makes sense for all three to be separate utilities.

trinity removed the

help wanted

label 2024-02-24 03:50:24 +00:00

trinity self-assigned this 2024-02-24 03:50:29 +00:00

trinity commented

2024-02-24 03:54:11 +00:00

Author

Owner

swab(1) won't reverse bytes in a given word size but instead print the latter half of the word before the former half; actual reversal isn't relevant to the job, which is endianness in binary files.

I've started to implement this (with a lot of help from Emma and Mars as I am not used to Rust) and have a working but severely unpolished start.

swab(1) won't reverse bytes in a given word size but instead print the latter half of the word before the former half; actual reversal isn't relevant to the job, which is endianness in binary files. I've [started to implement this](https://git.tebibyte.media/bonsai/coreutils/commit/3f0d95fe8fe87cd3b3c6ba766e1ec643d6f7faa6) (with a lot of help from Emma and Mars as I am not used to Rust) and have a working but severely unpolished start.

trinity referenced this issue

2024-02-24 10:25:03 +00:00

swab(1) #73

emma referenced this issue from a commit

2024-03-19 02:54:47 +00:00

Merge branch 'swab' (closes #22)

emma closed this issue

2024-03-19 02:54:47 +00:00

trinity referenced this issue

2024-03-19 12:03:37 +00:00

Bonsai coreutils by Example #70