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[Qemu-devel] [PATCH 06/10] include: add xxhash.h
From: |
Emilio G. Cota |
Subject: |
[Qemu-devel] [PATCH 06/10] include: add xxhash.h |
Date: |
Tue, 5 Apr 2016 01:30:49 -0400 |
xxhash is a fast, high-quality hashing function. The appended
brings in the 32-bit version of it, with the small modification that
it assumes the data to be hashed is made of 32-bit chunks; this increases
speed slightly for the use-case we care about, i.e. tb-hash.
The original algorithm, as well as a 64-bit implementation, can be found at:
https://github.com/Cyan4973/xxHash
Signed-off-by: Emilio G. Cota <address@hidden>
---
include/qemu/xxhash.h | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 106 insertions(+)
create mode 100644 include/qemu/xxhash.h
diff --git a/include/qemu/xxhash.h b/include/qemu/xxhash.h
new file mode 100644
index 0000000..a13a665
--- /dev/null
+++ b/include/qemu/xxhash.h
@@ -0,0 +1,106 @@
+/*
+ * xxHash - Fast Hash algorithm
+ * Copyright (C) 2012-2016, Yann Collet
+ *
+ * BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * + Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * + Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * You can contact the author at :
+ * - xxHash source repository : https://github.com/Cyan4973/xxHash
+ */
+#ifndef QEMU_XXHASH_H
+#define QEMU_XXHASH_H
+
+#define PRIME32_1 2654435761U
+#define PRIME32_2 2246822519U
+#define PRIME32_3 3266489917U
+#define PRIME32_4 668265263U
+#define PRIME32_5 374761393U
+
+/*
+ * Note : although _rotl exists for minGW (GCC under windows), performance
+ * seems poor.
+ */
+#if defined(_MSC_VER)
+# define XXH_rotl32(x, r) _rotl(x, r)
+#else
+# define XXH_rotl32(x, r) ((x << r) | (x >> (32 - r)))
+#endif
+
+/* u32 hash of @n contiguous chunks of u32's */
+static inline uint32_t qemu_xxh32(const uint32_t *p, size_t n, uint32_t seed)
+{
+ const uint32_t *end = p + n;
+ uint32_t h32;
+
+ if (n >= 4) {
+ const uint32_t * const limit = end - 4;
+ uint32_t v1 = seed + PRIME32_1 + PRIME32_2;
+ uint32_t v2 = seed + PRIME32_2;
+ uint32_t v3 = seed + 0;
+ uint32_t v4 = seed - PRIME32_1;
+
+ do {
+ v1 += *p * PRIME32_2;
+ v1 = XXH_rotl32(v1, 13);
+ v1 *= PRIME32_1;
+ p++;
+ v2 += *p * PRIME32_2;
+ v2 = XXH_rotl32(v2, 13);
+ v2 *= PRIME32_1;
+ p++;
+ v3 += *p * PRIME32_2;
+ v3 = XXH_rotl32(v3, 13);
+ v3 *= PRIME32_1;
+ p++;
+ v4 += *p * PRIME32_2;
+ v4 = XXH_rotl32(v4, 13);
+ v4 *= PRIME32_1;
+ p++;
+ } while (p <= limit);
+ h32 = XXH_rotl32(v1, 1) + XXH_rotl32(v2, 7) + XXH_rotl32(v3, 12) +
+ XXH_rotl32(v4, 18);
+ } else {
+ h32 = seed + PRIME32_5;
+ }
+
+ h32 += n * sizeof(uint32_t);
+
+ while (p < end) {
+ h32 += *p * PRIME32_3;
+ h32 = XXH_rotl32(h32, 17) * PRIME32_4 ;
+ p++;
+ }
+
+ h32 ^= h32 >> 15;
+ h32 *= PRIME32_2;
+ h32 ^= h32 >> 13;
+ h32 *= PRIME32_3;
+ h32 ^= h32 >> 16;
+
+ return h32;
+}
+
+#endif /* QEMU_XXHASH_H */
--
2.5.0
- Re: [Qemu-devel] [PATCH 08/10] qht: QEMU's fast, resizable and scalable Hash Table, (continued)
- [Qemu-devel] [PATCH 04/10] seqlock: rename write_lock/unlock to write_begin/end, Emilio G. Cota, 2016/04/05
- [Qemu-devel] [PATCH 06/10] include: add xxhash.h,
Emilio G. Cota <=
- [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Emilio G. Cota, 2016/04/05
- Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Richard Henderson, 2016/04/05
- Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Paolo Bonzini, 2016/04/05
- Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Richard Henderson, 2016/04/05
- Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Emilio G. Cota, 2016/04/05
- Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Richard Henderson, 2016/04/05
- Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Emilio G. Cota, 2016/04/05
- Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash, Paolo Bonzini, 2016/04/06