Re: [PATCH 2/6] lib / string_helpers: introduce string_escape_mem()

[Andrew Morton <akpm@linux-foundation.org>]

On Wed,  2 Jul 2014 16:20:25 +0300 Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> This is almost the opposite function to string_unescape(). Nevertheless it
> handles \0 and could be used for any byte buffer.
> 
> The documentation is supplied together with the function prototype.
> 
> The test cases covers most of the scenarios and would be expanded later on.
> 
> ...
>
> --- a/include/linux/string_helpers.h
> +++ b/include/linux/string_helpers.h
> @@ -71,4 +71,87 @@ static inline int string_unescape_any_inplace(char *buf)
>  	return string_unescape_any(buf, buf, 0);
>  }
>  
> +#define ESCAPE_SPACE		0x01
> +#define ESCAPE_SPECIAL		0x02
> +#define ESCAPE_NULL		0x04
> +#define ESCAPE_OCTAL		0x08
> +#define ESCAPE_ANY		\
> +	(ESCAPE_SPACE | ESCAPE_OCTAL | ESCAPE_SPECIAL | ESCAPE_NULL)
> +#define ESCAPE_NP		0x10
> +#define ESCAPE_ANY_NP		(ESCAPE_ANY | ESCAPE_NP)
> +#define ESCAPE_HEX		0x20
> +
> +/**
> + * string_escape_mem - quote characters in the given memory buffer

It drive me nuts when the kerneldoc is in the .h file.  Who thinks of
looking there?  I realise that string_unescape() already did that, but
I'd prefer that we fix string_unescape() rather than imitate it.

> --- a/lib/string_helpers.c
> +++ b/lib/string_helpers.c

This is a lot of code!  Adds nearly a kbyte.  I'm surprised that
escaping a string is so verbose.

I wonder if the implementation really needs to be so comprehensive?

Would a table-driven approach be more compact?

>  static int __init test_string_helpers_init(void)
>  {
>  	unsigned int i;
> @@ -112,6 +315,16 @@ static int __init test_string_helpers_init(void)
>  	test_string_unescape("unescape inplace",
>  			     get_random_int() % (UNESCAPE_ANY + 1), true);
>  
> +	/* Without dictionary */
> +	for (i = 0; i < (ESCAPE_ANY_NP | ESCAPE_HEX) + 1; i++)
> +		test_string_escape("escape 0", escape0, i, TEST_STRING_2_DICT_0);
> +
> +	/* With dictionary */
> +	for (i = 0; i < (ESCAPE_ANY_NP | ESCAPE_HEX) + 1; i++)
> +		test_string_escape("escape 1", escape1, i, TEST_STRING_2_DICT_1);
> +
> +	test_string_escape_nomem();
> +
>  	return -EINVAL;
>  }

I wonder why this returns -EINVAL.