Commit 0362c27f authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Linus Torvalds
Browse files

lib/string_helpers: introduce ESCAPE_NAP to escape non-ASCII and non-printable 

Some users may want to have an ASCII based filter for printable only
characters, provided by conjunction of isascii() and isprint() functions.

Here is the addition of a such.

Link: https://lkml.kernel.org/r/20210504180819.73127-6-andriy.shevchenko@linux.intel.com


Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a0809783

include/linux/string_helpers.h

+1 −0
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ static inline int string_unescape_any_inplace(char *buf) 
#define ESCAPE_ANY_NP		(ESCAPE_ANY | ESCAPE_NP)

#define ESCAPE_HEX		BIT(5)

#define ESCAPE_NA		BIT(6)

#define ESCAPE_NAP		BIT(7)



int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,

		unsigned int flags, const char *only);

lib/string_helpers.c

+16 −4
Original line number Diff line number Diff line
@@ -454,9 +454,11 @@ static bool escape_hex(unsigned char c, char **dst, char *end) 
 *

 *	1. The character is not matched to the one from @only string and thus

 *	   must go as-is to the output.

 *	2. The character is matched to the printable or ASCII class, if asked,

 *	2. The character is matched to the printable and ASCII classes, if asked,

 *	   and in case of match it passes through to the output.

 *	3. The character is checked if it falls into the class given by @flags.

 *	3. The character is matched to the printable or ASCII class, if asked,

 *	   and in case of match it passes through to the output.

 *	4. The character is checked if it falls into the class given by @flags.

 *	   %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any

 *	   character. Note that they actually can't go together, otherwise

 *	   %ESCAPE_HEX will be ignored.
@@ -489,11 +491,15 @@ static bool escape_hex(unsigned char c, char **dst, char *end) 
 *		'\xHH' - byte with hexadecimal value HH (2 digits)

 *	%ESCAPE_NA:

 *		escape only non-ascii characters, checked by isascii()

 *	%ESCAPE_NAP:

 *		escape only non-printable or non-ascii characters

 *

 * One notable caveat, the %ESCAPE_NP and %ESCAPE_NA have higher priority

 * than the rest of the flags (%ESCAPE_NP is higher than %ESCAPE_NA).

 * One notable caveat, the %ESCAPE_NAP, %ESCAPE_NP and %ESCAPE_NA have the

 * higher priority than the rest of the flags (%ESCAPE_NAP is the highest).

 * It doesn't make much sense to use either of them without %ESCAPE_OCTAL

 * or %ESCAPE_HEX, because they cover most of the other character classes.

 * %ESCAPE_NAP can utilize %ESCAPE_SPACE or %ESCAPE_SPECIAL in addition to

 * the above.

 *

 * Return:

 * The total size of the escaped output that would be generated for
@@ -515,6 +521,8 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz, 
		 * Apply rules in the following sequence:

		 *	- the @only string is supplied and does not contain a

		 *	  character under question

		 *	- the character is printable and ASCII, when @flags has

		 *	  %ESCAPE_NAP bit set

		 *	- the character is printable, when @flags has

		 *	  %ESCAPE_NP bit set

		 *	- the character is ASCII, when @flags has
@@ -528,6 +536,10 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz, 
					  escape_passthrough(c, &p, end))

			continue;



		if (isascii(c) && isprint(c) &&

		    flags & ESCAPE_NAP && escape_passthrough(c, &p, end))

			continue;



		if (isprint(c) &&

		    flags & ESCAPE_NP && escape_passthrough(c, &p, end))

			continue;