1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/hashing.h"
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/bit_util.h"
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/bitmap_reader.h"
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/macros.h"
namespace arrow20 {
namespace internal {
namespace {
/// \brief A hash function for bitmaps that can handle offsets and lengths in
/// terms of number of bits. The hash only depends on the bits actually hashed.
///
/// This implementation is based on 64-bit versions of MurmurHash2 by Austin Appleby.
///
/// It's the caller's responsibility to ensure that bits_offset + num_bits are
/// readable from the bitmap.
///
/// \param key The pointer to the bitmap.
/// \param seed The seed for the hash function (useful when chaining hash functions).
/// \param bits_offset The offset in bits relative to the start of the bitmap.
/// \param num_bits The number of bits after the offset to be hashed.
uint64_t MurmurHashBitmap64(const uint8_t* key, uint64_t seed, uint64_t bits_offset,
uint64_t num_bits) {
const uint64_t m = 0xc6a4a7935bd1e995LLU;
const int r = 47;
uint64_t h = seed ^ (num_bits * m);
BitmapWordReader<uint64_t> reader(key, bits_offset, num_bits);
auto nwords = reader.words();
while (nwords--) {
auto k = reader.NextWord();
k *= m;
k ^= k >> r;
k *= m;
h ^= k;
h *= m;
}
int valid_bits;
auto nbytes = reader.trailing_bytes();
if (nbytes) {
uint64_t k = 0;
do {
auto byte = reader.NextTrailingByte(valid_bits);
k = (k << 8) | static_cast<uint64_t>(byte);
} while (--nbytes);
h ^= k;
h *= m;
}
h ^= h >> r;
h *= m;
h ^= h >> r;
return h;
}
} // namespace
hash_t ComputeBitmapHash(const uint8_t* bitmap, hash_t seed, int64_t bits_offset,
int64_t num_bits) {
DCHECK_GE(bits_offset, 0);
DCHECK_GE(num_bits, 0);
return MurmurHashBitmap64(bitmap, seed, bits_offset, num_bits);
}
} // namespace internal
} // namespace arrow20
|
