-
Notifications
You must be signed in to change notification settings - Fork 16
Expand file tree
/
Copy pathLZ4.swift
More file actions
273 lines (229 loc) · 7.13 KB
/
LZ4.swift
File metadata and controls
273 lines (229 loc) · 7.13 KB
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
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Binary Parsing open source project
//
// Copyright (c) 2025 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
import BinaryParsing
import Foundation
// Using format information from:
// - https://github.com/lz4/lz4/blob/dev/doc/lz4_Block_format.md
// - https://github.com/lz4/lz4/blob/dev/doc/lz4_Frame_format.md
extension Int {
@inlinable
init(
parsingLZ4Sequence input: inout ParserSpan, token: UInt8, constant: UInt8
) throws {
self = Int(token) + Int(constant)
guard token == 0xf else { return }
while true {
let nextByte = try UInt8(parsing: &input)
try self.addThrowingOnOverflow(Int(nextByte))
if nextByte != 255 { break }
}
}
}
public struct LZ4 {
public var data: Data
public struct FrameHeader {
public enum MaxSize: UInt8 {
case size64KB = 0x40
case size256KB = 0x50
case size1MB = 0x60
case size4MB = 0x70
@usableFromInline
var bytes: Int {
switch self {
case .size64KB:
1 &<< 16
case .size256KB:
1 &<< 18
case .size1MB:
1 &<< 20
case .size4MB:
1 &<< 22
}
}
}
public struct Flags: RawRepresentable {
public var rawValue: UInt16
@usableFromInline
static let validationMask: UInt16 = 0b11001111_11000010
@usableFromInline
static let validationValue: UInt16 = 0b01000000_01000000
@inlinable
public init?(rawValue: UInt16) {
guard rawValue & Self.validationMask == Self.validationValue
else { return nil }
self.rawValue = rawValue
}
var blockIndependence: Bool {
rawValue & 0b00000000_00100000 != 0
}
var useBlockChecksum: Bool {
rawValue & 0b00000000_00010000 != 0
}
@usableFromInline
var useContentSize: Bool {
rawValue & 0b00000000_00001000 != 0
}
var useContentChecksum: Bool {
rawValue & 0b00000000_00000100 != 0
}
@usableFromInline
var useDictionaryID: Bool {
rawValue & 0b00000000_00000001 != 0
}
@usableFromInline
var blockMaximum: MaxSize? {
MaxSize(rawValue: UInt8(truncatingIfNeeded: rawValue >> 8))
}
}
@usableFromInline
var flags: Flags
@usableFromInline
var contentSize: UInt64
@usableFromInline
var dictionaryID: UInt32
@inlinable
init(flags: Flags, contentSize: UInt64, dictionaryID: UInt32) {
self.flags = flags
self.contentSize = contentSize
self.dictionaryID = dictionaryID
}
@inlinable
init(parsing input: inout ParserSpan) throws {
let magicNumber = try UInt32(parsingLittleEndian: &input)
guard magicNumber == 0x184D_2204 else {
throw TestError(description: "Invalid magic number")
}
self.flags = try Flags(parsingLittleEndian: &input)
self.contentSize =
if flags.useContentSize {
try UInt64(parsingLittleEndian: &input)
} else {
0
}
self.dictionaryID =
if flags.useDictionaryID {
try UInt32(parsingLittleEndian: &input)
} else {
0
}
_ = try UInt8(parsing: &input)
}
}
public struct Block {
public struct Size: RawRepresentable {
public var rawValue: UInt32
public init(rawValue: UInt32) {
self.rawValue = rawValue
}
static let compressionFlag: UInt32 = 0x8000_0000
@usableFromInline
var count: Int {
Int(rawValue & ~Self.compressionFlag)
}
public var isCompressed: Bool {
rawValue & Self.compressionFlag == 0
}
public var isTerminator: Bool {
rawValue == 0
}
}
}
@usableFromInline
struct CompressedSequence {
@usableFromInline
var literals: ParserRange
@usableFromInline
var offset: Int
@usableFromInline
var length: Int
@inlinable
init(parsing input: inout ParserSpan) throws {
let token = try UInt8(parsing: &input)
let (literalLengthToken, copyLengthToken) = (token &>> 4, token & 0xf)
let sequenceCount = try Int(
parsingLZ4Sequence: &input, token: literalLengthToken, constant: 0)
self.literals = try input.sliceRange(byteCount: sequenceCount)
// If we're at the end, the offset and length are zero
if input.isEmpty {
self.offset = 0
self.length = 0
} else {
// Otherwise, load them both
self.offset = try Int(
parsing: &input, storedAsLittleEndian: UInt16.self)
self.length = try Int(
parsingLZ4Sequence: &input, token: copyLengthToken, constant: 4)
guard offset != 0 else {
throw TestError(description: "2")
}
}
}
}
}
extension LZ4: ExpressibleByParsing {
@inlinable
public init(parsing input: inout ParserSpan) throws {
let header = try LZ4.FrameHeader(parsing: &input)
self.data = Data()
while !input.isEmpty {
let size = try Block.Size(parsingLittleEndian: &input)
let range = try input.sliceRange(byteCount: size.count)
if size.isTerminator {
break
}
if size.isCompressed {
guard let max = header.flags.blockMaximum else {
throw TestError(description: "Invalid block maximum in header flags")
}
// TODO: Switch to OutputSpan when we can implement a copying append
var blockData = Data(capacity: max.bytes)
var rangeSlice = try input.seeking(toRange: range)
while !rangeSlice.isEmpty {
let seq = try CompressedSequence(parsing: &rangeSlice)
try input.seeking(toRange: seq.literals).withUnsafeBytes {
blockData.append(contentsOf: $0)
}
guard seq.offset <= blockData.count else {
throw TestError(
description:
"Tried to offset too much: \(seq.offset) with count \(blockData.count)"
)
}
if seq.offset == 0 {
break
}
let (fullCopyCount, byteRemainder) =
seq.length.quotientAndRemainder(dividingBy: seq.offset)
let range = (blockData.count - seq.offset)..<blockData.count
let slice = Array(blockData[range])
for _ in 0..<fullCopyCount {
blockData.append(contentsOf: slice)
}
blockData.append(contentsOf: slice.prefix(byteRemainder))
}
data.append(contentsOf: blockData)
} else {
try input.seeking(toRange: range).withUnsafeBytes {
data.append(contentsOf: $0)
}
}
}
}
}
public func parseLZ4(_ data: some RandomAccessCollection<UInt8>) throws {
let lz4 = try LZ4(parsing: data)
print(
"""
Size at start: \(data.count) bytes
Decompressed: \(lz4.data.count) bytes
Compression rate: \(Double(lz4.data.count - data.count) / Double(lz4.data.count))
""")
}