Encode/decode C-string literals

Question

I have a text file containing something that behaves like C-strings. For example:

something = "some text\nin two lines\tand tab";
somethingElse = "some text with \"quotes\"";

Fetching things between quotes is not a problem. Problem is that later I'm processing this string and slash escapes makes this hard.

I'd like to decode these strings, process them, then encode them back to C-string literals.

So from that raw input

some text\\with line wrap\nand \"quote\"

I need:

some text\with line wrap
and "quote"

and vice versa.

What I've tried:

I've found some API for processing Python string literals (string_escape), it is close to what I need, but since I'm processing C-strings it is useless. I've tried find other codecs to match my problem but no luck so far.

You're dealing with escape sequences, not text encoding. See http://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences — Pieter Witvoet, Nov 04 '14 at 11:01
`json.dumps` encodes Unicode characters to`\u` and this doesn't work for me :/. — Marek R, Nov 04 '14 at 11:33
OK loolks like `json.dumps(s, ensure_ascii=False)[1:][:-1]` do the work nicely, thanks a lot. — Marek R, Nov 04 '14 at 11:38

score 0 · Answer 1 · answered Dec 07 '19 at 12:15

I'm looking for a simple solution also, and json module seems to be the easiest solution. The following is my quick hack. Note that there are still issues if/when both the single (') and double quote (") appear in the same string... And I suspect you will have issues with unicode characters...

def c_decode(in_str:str) -> str:
    return json.loads(in_str.join('""' if '"' not in in_str else "''"))

def c_encode(in_str:str) -> str:
    """ Encode a string literal as per C"""
    return json.dumps(in_str)[1:-1]

Note also that if in_str is "AB\n\r\tYZ" ...

then we alternatively have: ("%r"%(in_str.join('""')))[2:-2]
giving: 'AB\\n\\r\\tYZ' # almost the same c_encode above.

Here's hoping that someone has a nicer solution.

Encode/decode C-string literals

1 Answers1