Feature request for s2d: add option to ignore invalid input and print it as is

[alexbozhenko]

Hello.
I was wondering if you would be open to adding a flag that would allow s2d to print invalid input as is.
For example, if I have a stream of messages, some of them are encoded, and some of them are not.

What I currently see:

{ echo "encoded" | s2c - ; echo; echo "not_encoded"; }  | s2d -
encoded

ERROR: s2: unsupported input

What I would expect to see:

{ echo "encoded" | s2c - ; echo; echo "not_encoded"; }  | s2d --ignore-invalid -
encoded

not_encoded

[klauspost]

Not sure it is worth it for something that can be done pretty simple with a bash script...

#!/bin/bash

set -e

file="$1"

if head -c 10 "$file" | grep -q $'\xff\x06\x00\x00S2sTwO'; then
    ./s2d -c "$file"
else
    cat "$file"
fi

Or if you don't want a script, then this oneliner...

head -c 10 "$file" | grep -q $'^\xff\x06\x00\x00S2sTwO' \
  && ./s2d -c< "$file" \
  || cat < "$file"

[alexbozhenko]

Thank you for your prompt response!
I think the script example will work only if input is seekable. And since pipe is not seekable, it won't work if I want to just pipe input to s2d and get the uncompressed data.

For what it's worth, gzip and zstd have an option to achieve that.

gzip

# { echo "compressed" | gzip; echo "not_compressed"; } | gzip -d
compressed

gzip: stdin: decompression OK, trailing garbage ignored

# { echo "compressed" | gzip; echo "not_compressed"; } | gzip -d -f
compressed
not_compressed

zstd

# { echo "compressed" | zstd; echo "not_compressed"; } | zstd -d
compressed
zstd: /*stdin*\: unsupported format

# { echo "compressed" | zstd; echo "not_compressed"; } | zstd -d --pass-through
compressed
not_compressed