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

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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: Andy 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andy Shevchenko 2021-06-30 18:55:17 -07:00 committed by Linus Torvalds
parent a080978335
commit 0362c27fb3
2 changed files with 17 additions and 4 deletions
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1
include/linux/string_helpers.h
View file

@ -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);

20
lib/string_helpers.c
View file

@ -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;