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Subject[PATCH v1 4/6] lib: scanf: handle character ranges in %[...]
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Complete implementation isn't much bigger than present one.

This patch adds missing standard features:

%[a-z] - matches 'a'..'z'
%[][] - matches '[' and ']' (']' must be first)
%[_-] - matches '_' and '-' ('-' must be last)

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
lib/vsprintf.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 66debf42387a..5c27c5d18d4e 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -3019,7 +3019,6 @@ EXPORT_SYMBOL_GPL(bprintf);
* - memory-allocation "%m..."
* - pointer "%p", ptrdiff_t "%t...", intmax_t "%j..."
* - discaring of matching input "%*[...]"
- * - ranges or matching ']' in "%[...]"
* - positional assignment "%n$"
*
* Non-standatd features:
@@ -3160,11 +3159,8 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
/*
* Warning: This implementation of the '[' conversion specifier
* deviates from its glibc counterpart in the following ways:
- * (1) It does NOT support ranges i.e. '-' is NOT a special
- * character
- * (2) It cannot match the closing bracket ']' itself
- * (3) A field width is required
- * (4) '%*[' (discard matching input) is currently not supported
+ * (1) A field width is required
+ * (2) '%*[' (discard matching input) is currently not supported
*
* Example usage:
* ret = sscanf("00:0a:95","%2[^:]:%2[^:]:%2[^:]",
@@ -3176,7 +3172,6 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
{
char *s = (char *)va_arg(args, char *);
DECLARE_BITMAP(set, 256) = {0};
- unsigned int len = 0;
bool negate = (*fmt == '^');

/* field width is required */
@@ -3186,12 +3181,25 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
if (negate)
++fmt;

- for ( ; *fmt && *fmt != ']'; ++fmt, ++len)
- set_bit((u8)*fmt, set);
+ do {
+ /* no ']' found */
+ if (!*fmt)
+ return num;

- /* no ']' or no character set found */
- if (!*fmt || !len)
- return num;
+ /* '-' at last position is non-special */
+ if (*fmt == '-' && *(fmt + 1) != ']') {
+ u8 a = *(fmt - 1);
+ u8 b = *(fmt + 1);
+
+ if (a <= b)
+ bitmap_set(set, a, b - a + 1);
+ } else
+ set_bit((u8)*fmt, set);
+
+ /* ']' at first position is non-special */
+ } while (*++fmt != ']');
+
+ /* skip ']' */
++fmt;

if (negate) {
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