[PATCH v3 04/15] lib/string_helpers: Introduce ESCAPE_NA for escaping non-ASCII

Andy Shevchenko
2021-05-04T18:08:09Z

Some users may want to have an ASCII based filter, provided by
isascii() function. Here is the addition of a such.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
include/linux/string_helpers.h | 1 +
lib/string_helpers.c | 21 +++++++++++++++++----
2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index bf01e24edd89..d6cf6fe10f74 100644
--- a/include/linux/string_helpers.h
+++ b/include/linux/string_helpers.h
@@ -52,6 +52,7 @@ static inline int string_unescape_any_inplace(char *buf)
#define ESCAPE_NP BIT(4)
#define ESCAPE_ANY_NP (ESCAPE_ANY | ESCAPE_NP)
#define ESCAPE_HEX BIT(5)
+#define ESCAPE_NA BIT(6)

int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
unsigned int flags, const char *only);
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index e3ef9f86cc34..a963404b8c16 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -454,8 +454,8 @@ 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 class, if asked, and in
- * case of match it passes through to the output.
+ * 2. The character is matched to the printable or ASCII class, 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.
* %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
* character. Note that they actually can't go together, otherwise
@@ -463,7 +463,7 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
*
* Caller must provide valid source and destination pointers. Be aware that
* destination buffer will not be NULL-terminated, thus caller have to append
- * it if needs. The supported flags are::
+ * it if needs. The supported flags are::
*
* %ESCAPE_SPACE: (special white space, not space itself)
* '\f' - form feed
@@ -482,11 +482,18 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
* %ESCAPE_ANY:
* all previous together
* %ESCAPE_NP:
- * escape only non-printable characters (checked by isprint)
+ * escape only non-printable characters, checked by isprint()
* %ESCAPE_ANY_NP:
* all previous together
* %ESCAPE_HEX:
* '\xHH' - byte with hexadecimal value HH (2 digits)
+ * %ESCAPE_NA:
+ * escape only non-ascii characters, checked by isascii()
+ *
+ * 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).
+ * 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.
*
* Return:
* The total size of the escaped output that would be generated for
@@ -510,6 +517,8 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
* character under question
* - the character is printable, when @flags has
* %ESCAPE_NP bit set
+ * - the character is ASCII, when @flags has
+ * %ESCAPE_NA bit set
* - the character doesn't fall into a class of symbols
* defined by given @flags
* In these cases we just pass through a character to the
@@ -523,6 +532,10 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
flags & ESCAPE_NP && escape_passthrough(c, &p, end))
continue;

+ if (isascii(c) &&
+ flags & ESCAPE_NA && escape_passthrough(c, &p, end))
+ continue;
+
if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
continue;

--
2.30.2