forked from ngaut/unistore
-
Notifications
You must be signed in to change notification settings - Fork 0
/
compression.go
110 lines (97 loc) · 2.86 KB
/
compression.go
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
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
// Copyright 2019-present PingCAP, Inc.
//
// Licensed 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package rocksdb
import (
"math"
"github.com/pierrec/lz4"
"github.com/pingcap/errors"
)
var ErrDecompress = errors.New("Error during decompress")
func lz4Compress(input, dst []byte) []byte {
rawLen := len(input)
if rawLen > math.MaxUint32 {
return nil
}
var varintBuf [5]byte
decompressedSize := encodeVarint32(varintBuf[:], uint32(rawLen))
outputBound := lz4.CompressBlockBound(rawLen)
size := len(decompressedSize) + outputBound
if cap(dst) < size {
dst = make([]byte, size)
} else {
dst = dst[:size]
}
copy(dst, decompressedSize)
var ht [1 << 16]int
n, err := lz4.CompressBlock(input, dst[len(decompressedSize):], ht[:])
if err != nil || n == 0 {
return nil
}
return dst[:len(decompressedSize)+n]
}
func isGoodCompressionRatio(compressed, input []byte) bool {
cl, rl := len(compressed), len(input)
return cl < rl-(rl/8)
}
func CompressBlock(tp CompressionType, input, dst []byte) ([]byte, bool) {
var compressed []byte
switch tp {
case CompressionLz4:
compressed = lz4Compress(input, dst)
case CompressionNone:
return input, false
case CompressionSnappy:
panic("unsupported")
case CompressionZstd:
panic("unsupported")
}
if compressed == nil || !isGoodCompressionRatio(compressed, input) {
return input, false
}
return compressed, true
}
func lz4Decompress(input, dst []byte) ([]byte, error) {
size, n := decodeVarint32(input)
if n <= 0 {
return input, ErrDecompress
}
if uint32(cap(dst)) < size {
dst = make([]byte, size)
} else {
dst = dst[:size]
}
_, err := lz4.UncompressBlock(input[n:], dst)
return dst, err
}
func DecompressBlock(tp CompressionType, input, dst []byte) ([]byte, error) {
switch tp {
case CompressionLz4:
return lz4Decompress(input, dst)
case CompressionNone:
return input, nil
case CompressionSnappy:
panic("unsupported")
case CompressionZstd:
panic("unsupported")
default:
panic("unreachable branch")
}
}