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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: 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>
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@ -53,6 +53,7 @@ static inline int string_unescape_any_inplace(char *buf)
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#define ESCAPE_ANY_NP (ESCAPE_ANY | ESCAPE_NP)
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#define ESCAPE_HEX BIT(5)
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#define ESCAPE_NA BIT(6)
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#define ESCAPE_NAP BIT(7)
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int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
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unsigned int flags, const char *only);
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@ -454,9 +454,11 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
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*
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* 1. The character is not matched to the one from @only string and thus
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* must go as-is to the output.
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* 2. The character is matched to the printable or ASCII class, if asked,
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* 2. The character is matched to the printable and ASCII classes, if asked,
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* and in case of match it passes through to the output.
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* 3. The character is checked if it falls into the class given by @flags.
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* 3. The character is matched to the printable or ASCII class, if asked,
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* and in case of match it passes through to the output.
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* 4. The character is checked if it falls into the class given by @flags.
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* %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
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* character. Note that they actually can't go together, otherwise
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* %ESCAPE_HEX will be ignored.
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@ -489,11 +491,15 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
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* '\xHH' - byte with hexadecimal value HH (2 digits)
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* %ESCAPE_NA:
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* escape only non-ascii characters, checked by isascii()
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* %ESCAPE_NAP:
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* escape only non-printable or non-ascii characters
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*
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* One notable caveat, the %ESCAPE_NP and %ESCAPE_NA have higher priority
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* than the rest of the flags (%ESCAPE_NP is higher than %ESCAPE_NA).
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* One notable caveat, the %ESCAPE_NAP, %ESCAPE_NP and %ESCAPE_NA have the
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* higher priority than the rest of the flags (%ESCAPE_NAP is the highest).
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* It doesn't make much sense to use either of them without %ESCAPE_OCTAL
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* or %ESCAPE_HEX, because they cover most of the other character classes.
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* %ESCAPE_NAP can utilize %ESCAPE_SPACE or %ESCAPE_SPECIAL in addition to
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* the above.
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*
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* Return:
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* The total size of the escaped output that would be generated for
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@ -515,6 +521,8 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
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* Apply rules in the following sequence:
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* - the @only string is supplied and does not contain a
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* character under question
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* - the character is printable and ASCII, when @flags has
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* %ESCAPE_NAP bit set
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* - the character is printable, when @flags has
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* %ESCAPE_NP bit set
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* - the character is ASCII, when @flags has
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@ -528,6 +536,10 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
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escape_passthrough(c, &p, end))
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continue;
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if (isascii(c) && isprint(c) &&
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flags & ESCAPE_NAP && escape_passthrough(c, &p, end))
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continue;
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if (isprint(c) &&
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flags & ESCAPE_NP && escape_passthrough(c, &p, end))
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continue;
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