GitHub/SWCompression
1
0
Fork 0
mirror of https://github.com/tsolomko/SWCompression.git synced 2026-06-23 14:56:41 +00:00
Code Issues Packages Projects Releases Wiki Activity

A bit of refactoring in LZMADecoder.

Browse Source
This commit is contained in:
Timofey Solomko
2017-05-01 22:17:15 +03:00
parent 5c8fd61a0a
commit edbeb9adca
1 changed files with 25 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Sources/LZMADecoder.swift
+25 -20
View File
@@ -103,6 +103,8 @@ final class LZMADecoder {
self.repLenDecoder = LZMALenDecoder(&self.pointerData)
}
// MARK: LZMA2 related functions.
private func resetProperties() throws {
var properties = pointerData.alignedByte()
if properties >= (9 * 5 * 5) {
@@ -189,6 +191,8 @@ final class LZMADecoder {
else { throw LZMA2Error.WrongSizes }
}
// MARK: Main LZMA decoder function.
func decodeLZMA(_ uncompressedSize: inout Int) throws {
// First, we need to initialize Rande Decoder.
guard let rD = LZMARangeDecoder(&self.pointerData) else {
@@ -211,7 +215,7 @@ final class LZMADecoder {
// DECODE LITERAL:
/// Previous literal (zero, if there was none).
let prevByte = dictEnd == 0 ? 0 : out[1 <= dictEnd ? dictEnd - 1 : dictionarySize - 1 + dictEnd]
let prevByte = dictEnd == 0 ? 0 : self.byte(at: 1)
/// Decoded symbol. Initial value is 1.
var symbol = 1
/**
@@ -242,13 +246,8 @@ final class LZMADecoder {
symbol = (symbol << 1) | rangeDecoder.decode(bitWithProb: &literalProbs[litState][symbol])
}
let byte = (symbol - 0x100).toUInt8()
out.append(byte)
uncompressedSize -= 1
dictEnd += 1
if dictEnd - dictStart == dictionarySize {
dictStart += 1
}
self.put(byte)
// END.
// Finally, we need to update `state`.
@@ -273,13 +272,9 @@ final class LZMADecoder {
if rangeDecoder.decode(bitWithProb: &probabilities[241 + (state << LZMAConstants.numPosBitsMax) + posState]) == 0 {
// SHORT REP MATCH CASE
state = state < 7 ? 9 : 11
let byte = out[rep0 + 1 <= dictEnd ? dictEnd - rep0 - 1 : dictionarySize - rep0 - 1 + dictEnd]
out.append(byte)
let byte = self.byte(at: rep0 + 1)
uncompressedSize -= 1
dictEnd += 1
if dictEnd - dictStart == dictionarySize {
dictStart += 1
}
self.put(byte)
continue
}
} else { // REP MATCH CASE
@@ -361,15 +356,25 @@ final class LZMADecoder {
len += LZMAConstants.matchMinLen
if uncompressedSize > -1 && uncompressedSize < len { throw LZMAError.RepeatWillExceed }
for _ in 0..<len {
let byte = out[rep0 + 1 <= dictEnd ? dictEnd - rep0 - 1 : dictionarySize - rep0 - 1 + dictEnd]
out.append(byte)
let byte = self.byte(at: rep0 + 1)
uncompressedSize -= 1
dictEnd += 1
if dictEnd - dictStart == dictionarySize {
dictStart += 1
}
self.put(byte)
}
}
}
// MARK: Dictionary (out window) related functions.
private func put(_ byte: UInt8) {
out.append(byte)
dictEnd += 1
if dictEnd - dictStart == dictionarySize {
dictStart += 1
}
}
private func byte(at distance: Int) -> UInt8 {
return out[distance <= dictEnd ? dictEnd - distance : dictionarySize - distance + dictEnd]
}
}