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From: Willy Tarreau <w@1wt.eu>
Date: Tue, 8 Aug 2023 15:23:19 +0200
Subject: MINOR: ist: add new function ist_find_range() to find a character
range
Origin: https://git.haproxy.org/?p=haproxy-2.6.git;a=commit;h=b375df60341c7f7a4904c2d8041a09c66115c754
This looks up the character range <min>..<max> in the input string and
returns a pointer to the first one found. It's essentially the equivalent
of ist_find_ctl() in that it searches by 32 or 64 bits at once, but deals
with a range.
(cherry picked from commit 197668de975e495f0c0f0e4ff51b96203fa9842d)
[ad: backported for following fix : BUG/MINOR: h2: reject more chars
from the :path pseudo header]
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
(cherry picked from commit 451ac6628acc4b9eed3260501a49c60d4e4d4e55)
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
(cherry picked from commit 3468f7f8e04c9c5ca5c985c7511e05e78fe1eded)
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
---
include/import/ist.h | 47 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)
diff --git a/include/import/ist.h b/include/import/ist.h
index 978fb3c72247..38fe9363c2a1 100644
--- a/include/import/ist.h
+++ b/include/import/ist.h
@@ -746,6 +746,53 @@ static inline const char *ist_find_ctl(const struct ist ist)
return NULL;
}
+/* Returns a pointer to the first character found <ist> that belongs to the
+ * range [min:max] inclusive, or NULL if none is present. The function is
+ * optimized for strings having no such chars by processing up to sizeof(long)
+ * bytes at once on architectures supporting efficient unaligned accesses.
+ * Despite this it is not very fast (~0.43 byte/cycle) and should mostly be
+ * used on low match probability when it can save a call to a much slower
+ * function. Will not work for characters 0x80 and above. It's optimized for
+ * min and max to be known at build time.
+ */
+static inline const char *ist_find_range(const struct ist ist, unsigned char min, unsigned char max)
+{
+ const union { unsigned long v; } __attribute__((packed)) *u;
+ const char *curr = (void *)ist.ptr - sizeof(long);
+ const char *last = curr + ist.len;
+ unsigned long l1, l2;
+
+ /* easier with an exclusive boundary */
+ max++;
+
+ do {
+ curr += sizeof(long);
+ if (curr > last)
+ break;
+ u = (void *)curr;
+ /* add 0x<min><min><min><min>..<min> then subtract
+ * 0x<max><max><max><max>..<max> to the value to generate a
+ * carry in the lower byte if the byte contains a lower value.
+ * If we generate a bit 7 that was not there, it means the byte
+ * was min..max.
+ */
+ l2 = u->v;
+ l1 = ~l2 & ((~0UL / 255) * 0x80); /* 0x808080...80 */
+ l2 += (~0UL / 255) * min; /* 0x<min><min>..<min> */
+ l2 -= (~0UL / 255) * max; /* 0x<max><max>..<max> */
+ } while ((l1 & l2) == 0);
+
+ last += sizeof(long);
+ if (__builtin_expect(curr < last, 0)) {
+ do {
+ if ((unsigned char)(*curr - min) < (unsigned char)(max - min))
+ return curr;
+ curr++;
+ } while (curr < last);
+ }
+ return NULL;
+}
+
/* looks for first occurrence of character <chr> in string <ist> and returns
* the tail of the string starting with this character, or (ist.end,0) if not
* found.
--
2.43.0
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