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
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
// Copyright 2019+ Klaus Post. All rights reserved.
// License information can be found in the LICENSE file.
// Based on work by Yann Collet, released under BSD License.
package zstd
import (
"errors"
"fmt"
"math/bits"
"runtime"
)
// DOption is an option for creating a decoder.
type DOption func(*decoderOptions) error
// options retains accumulated state of multiple options.
type decoderOptions struct {
lowMem bool
concurrent int
maxDecodedSize uint64
maxWindowSize uint64
dicts []*dict
ignoreChecksum bool
limitToCap bool
decodeBufsBelow int
}
func (o *decoderOptions) setDefault() {
*o = decoderOptions{
// use less ram: true for now, but may change.
lowMem: true,
concurrent: runtime.GOMAXPROCS(0),
maxWindowSize: MaxWindowSize,
decodeBufsBelow: 128 << 10,
}
if o.concurrent > 4 {
o.concurrent = 4
}
o.maxDecodedSize = 64 << 30
}
// WithDecoderLowmem will set whether to use a lower amount of memory,
// but possibly have to allocate more while running.
func WithDecoderLowmem(b bool) DOption {
return func(o *decoderOptions) error { o.lowMem = b; return nil }
}
// WithDecoderConcurrency sets the number of created decoders.
// When decoding block with DecodeAll, this will limit the number
// of possible concurrently running decodes.
// When decoding streams, this will limit the number of
// inflight blocks.
// When decoding streams and setting maximum to 1,
// no async decoding will be done.
// When a value of 0 is provided GOMAXPROCS will be used.
// By default this will be set to 4 or GOMAXPROCS, whatever is lower.
func WithDecoderConcurrency(n int) DOption {
return func(o *decoderOptions) error {
if n < 0 {
return errors.New("concurrency must be at least 1")
}
if n == 0 {
o.concurrent = runtime.GOMAXPROCS(0)
} else {
o.concurrent = n
}
return nil
}
}
// WithDecoderMaxMemory allows to set a maximum decoded size for in-memory
// non-streaming operations or maximum window size for streaming operations.
// This can be used to control memory usage of potentially hostile content.
// Maximum is 1 << 63 bytes. Default is 64GiB.
func WithDecoderMaxMemory(n uint64) DOption {
return func(o *decoderOptions) error {
if n == 0 {
return errors.New("WithDecoderMaxMemory must be at least 1")
}
if n > 1<<63 {
return errors.New("WithDecoderMaxmemory must be less than 1 << 63")
}
o.maxDecodedSize = n
return nil
}
}
// WithDecoderDicts allows to register one or more dictionaries for the decoder.
//
// Each slice in dict must be in the [dictionary format] produced by
// "zstd --train" from the Zstandard reference implementation.
//
// If several dictionaries with the same ID are provided, the last one will be used.
//
// [dictionary format]: https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#dictionary-format
func WithDecoderDicts(dicts ...[]byte) DOption {
return func(o *decoderOptions) error {
for _, b := range dicts {
d, err := loadDict(b)
if err != nil {
return err
}
o.dicts = append(o.dicts, d)
}
return nil
}
}
// WithDecoderDictRaw registers a dictionary that may be used by the decoder.
// The slice content can be arbitrary data.
func WithDecoderDictRaw(id uint32, content []byte) DOption {
return func(o *decoderOptions) error {
if bits.UintSize > 32 && uint(len(content)) > dictMaxLength {
return fmt.Errorf("dictionary of size %d > 2GiB too large", len(content))
}
o.dicts = append(o.dicts, &dict{id: id, content: content, offsets: [3]int{1, 4, 8}})
return nil
}
}
// WithDecoderMaxWindow allows to set a maximum window size for decodes.
// This allows rejecting packets that will cause big memory usage.
// The Decoder will likely allocate more memory based on the WithDecoderLowmem setting.
// If WithDecoderMaxMemory is set to a lower value, that will be used.
// Default is 512MB, Maximum is ~3.75 TB as per zstandard spec.
func WithDecoderMaxWindow(size uint64) DOption {
return func(o *decoderOptions) error {
if size < MinWindowSize {
return errors.New("WithMaxWindowSize must be at least 1KB, 1024 bytes")
}
if size > (1<<41)+7*(1<<38) {
return errors.New("WithMaxWindowSize must be less than (1<<41) + 7*(1<<38) ~ 3.75TB")
}
o.maxWindowSize = size
return nil
}
}
// WithDecodeAllCapLimit will limit DecodeAll to decoding cap(dst)-len(dst) bytes,
// or any size set in WithDecoderMaxMemory.
// This can be used to limit decoding to a specific maximum output size.
// Disabled by default.
func WithDecodeAllCapLimit(b bool) DOption {
return func(o *decoderOptions) error {
o.limitToCap = b
return nil
}
}
// WithDecodeBuffersBelow will fully decode readers that have a
// `Bytes() []byte` and `Len() int` interface similar to bytes.Buffer.
// This typically uses less allocations but will have the full decompressed object in memory.
// Note that DecodeAllCapLimit will disable this, as well as giving a size of 0 or less.
// Default is 128KiB.
func WithDecodeBuffersBelow(size int) DOption {
return func(o *decoderOptions) error {
o.decodeBufsBelow = size
return nil
}
}
// IgnoreChecksum allows to forcibly ignore checksum checking.
func IgnoreChecksum(b bool) DOption {
return func(o *decoderOptions) error {
o.ignoreChecksum = b
return nil
}
}
|
