Move to kernel style SPDX license identifiers

[lttng-ust.git] / liblttng-ust / jhash.h

diff --git a/liblttng-ust/jhash.h b/liblttng-ust/jhash.h
index da1e7dd02c7b994bbdda9e5f8f7ce6eae27d4f5b..91993e8bf64ea6d5c6a45ae210a4bd1f4145b3ad 100644 (file)
--- a/liblttng-ust/jhash.h
+++ b/liblttng-ust/jhash.h
@@ -1,21 +1,11 @@
 /*
- * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation;
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+ * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  */
 
+#include <stddef.h>
+#include <stdint.h>
 #include <urcu/compiler.h>
 #include <lttng/ust-endian.h>
 
@@ -63,19 +53,19 @@ do { \
  * Returns a 32-bit value.  Every bit of the key affects every bit of
  * the return value.  Two keys differing by one or two bits will have
  * totally different hash values.
- * 
+ *
  * The best hash table sizes are powers of 2.  There is no need to do
  * mod a prime (mod is sooo slow!).  If you need less than 32 bits,
  * use a bitmask.  For example, if you need only 10 bits, do
  *   h = (h & hashmask(10));
  * In which case, the hash table should have hashsize(10) elements.
- * 
+ *
  * If you are hashing n strings (uint8_t **)k, do it like this:
  *   for (i = 0, h = 0; i < n; ++i) h = hashlittle(k[i], len[i], h);
- * 
+ *
  * By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
  * code any way you wish, private, educational, or commercial.  It's free.
- * 
+ *
  * Use for hash table lookup, or anything where one collision in 2^^32 is
  * acceptable.  Do NOT use for cryptographic purposes.
  */
@@ -106,34 +96,14 @@ uint32_t hashlittle(const void *key, size_t length, uint32_t initval)
                }
 
                /*----------------------------- handle the last (probably partial) block */
-               /* 
-                * "k[2]&0xffffff" actually reads beyond the end of the string, but
-                * then masks off the part it's not allowed to read.    Because the
-                * string is aligned, the masked-off tail is in the same word as the
-                * rest of the string.  Every machine with memory protection I've seen
-                * does it on word boundaries, so is OK with this.      But VALGRIND will
-                * still catch it and complain. The masking trick does make the hash
-                * noticably faster for short strings (like English words).
+               /*
+                * The original jhash.h reads beyond the end of string, and implements
+                * a special code path for VALGRIND. It seems to make ASan unhappy too
+                * though, so considering that hashing event names is not a fast-path
+                * in lttng-ust, remove the "fast" code entirely and use the slower
+                * but verifiable VALGRIND version of the code which does not issue
+                * out-of-bound reads.
                 */
-#ifndef VALGRIND
-
-               switch (length) {
-               case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
-               case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
-               case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
-               case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
-               case 8 : b+=k[1]; a+=k[0]; break;
-               case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
-               case 6 : b+=k[1]&0xffff; a+=k[0]; break;
-               case 5 : b+=k[1]&0xff; a+=k[0]; break;
-               case 4 : a+=k[0]; break;
-               case 3 : a+=k[0]&0xffffff; break;
-               case 2 : a+=k[0]&0xffff; break;
-               case 1 : a+=k[0]&0xff; break;
-               case 0 : return c;              /* zero length strings require no mixing */
-               }
-
-#else /* make valgrind happy */
                {
                        const uint8_t *k8;
 
@@ -154,7 +124,6 @@ uint32_t hashlittle(const void *key, size_t length, uint32_t initval)
                        case 0 : return c;
                        }
                }
-#endif /* !valgrind */
 
        } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
                const uint16_t *k = (const uint16_t *) key;     /* read 16-bit chunks */