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refs #35 Lynon builtin compression

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This commit is contained in:
Sergey Chernov 2025-07-16 11:02:35 +03:00
parent 34bc7297bd
commit f3d766d1b1
14 changed files with 830 additions and 216 deletions
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60
lynglib/src/commonMain/kotlin/net/sergeych/lynon/BitInput.kt
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@ -1,36 +1,9 @@
package net.sergeych.lynon
abstract class BitInput {
interface BitInput {
data class DataByte(val data: Int,val bits: Int)
/**
* Return next byte, int in 0..255 range, or -1 if end of stream reached
*/
abstract fun getByte(): DataByte
private var accumulator = 0
var isEndOfStream: Boolean = false
private set
private var mask = 0
fun getBitOrNull(): Int? {
if (isEndOfStream) return null
if (mask == 0) {
val ab = getByte()
accumulator = ab.data
if (accumulator == -1) {
isEndOfStream = true
return null
}
mask = 1 shl (ab.bits - 1)
}
val result = if (0 == accumulator and mask) 0 else 1
mask = mask shr 1
return result
}
fun getBitOrNull(): Int?
fun getBitsOrNull(count: Int): ULong? {
var result = 0UL
@ -54,8 +27,11 @@ abstract class BitInput {
return getBitOrNull() ?: throw IllegalStateException("Unexpected end of stream")
}
fun unpackUnsigned(): ULong {
val tetrades = getBits(4).toInt()
fun unpackUnsigned(): ULong =
unpackUnsignedOrNull() ?: throw IllegalStateException("Unexpected end of stream")
fun unpackUnsignedOrNull(): ULong? {
val tetrades = getBitsOrNull(4)?.toInt() ?: return null
var result = 0UL
var shift = 0
for (i in 0.. tetrades) {
@ -84,5 +60,27 @@ abstract class BitInput {
}
return result
}
fun decompress(): ByteArray = decompressOrNull() ?: throw DecompressionException("Unexpected end of stream")
fun decompressOrNull(): ByteArray? {
val originalSize = unpackUnsignedOrNull()?.toInt() ?: return null
return if( getBit() == 1) {
// data is compressed
// val expectedCRC = getBits(32).toUInt()
val method = getBits(2).toInt()
if( method != 0) throw DecompressionException("Unknown compression method")
LZW.decompress(this, originalSize).asByteArray()
}
else {
getBytes(originalSize) ?: throw DecompressionException("Unexpected end of stream in uncompressed data")
}
}
@Suppress("unused")
fun decompressStringOrNull(): String? = decompressOrNull()?.decodeToString()
fun decompressString(): String = decompress().decodeToString()
}

34
lynglib/src/commonMain/kotlin/net/sergeych/lynon/BitList.kt Normal file
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@ -0,0 +1,34 @@
package net.sergeych.lynon
@Suppress("unused")
interface BitList {
operator fun get(bitIndex: Long): Int
operator fun set(bitIndex: Long,value: Int)
val size: Long
val indices: LongRange
fun toInput(): BitInput = object : BitInput {
private var index = 0L
override fun getBitOrNull(): Int? =
if( index < size) this@BitList[index++]
else null
}
}
fun bitListOf(vararg bits: Int): BitList {
return if( bits.size > 64) {
BitArray.ofBits(*bits)
}
else
TinyBits.of(*bits)
}
@Suppress("unused")
fun bitListOfSize(sizeInBits: Long): BitList {
return if( sizeInBits > 64) {
BitArray.withBitSize(sizeInBits)
}
else
TinyBits()
}

95
lynglib/src/commonMain/kotlin/net/sergeych/lynon/BitOutput.kt
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@ -1,27 +1,6 @@
package net.sergeych.lynon
abstract class BitOutput {
abstract fun outputByte(byte: UByte)
private var accumulator = 0
/**
* Number of bits in accumulator. After output is closed by [close] this value is
* not changed and represents the number of bits in the last byte; this should
* be used to properly calculate end of the bit stream
*/
private var accumulatorBits = 0
private set
/**
* When [close] is called, represents the number of used bits in the last byte;
* bits after this number are the garbage and should be ignored
*/
val lastByteBits: Int get() {
if( !isClosed ) throw IllegalStateException("BitOutput is not closed")
return accumulatorBits
}
interface BitOutput {
fun putBits(bits: ULong, count: Int) {
require(count <= 64)
@ -41,13 +20,11 @@ abstract class BitOutput {
}
}
fun putBit(bit: Int) {
accumulator = (accumulator shl 1) or bit
if (++accumulatorBits >= 8) {
outputByte(accumulator.toUByte())
accumulator = accumulator shr 0
accumulatorBits = 0
}
fun putBit(bit: Int)
fun putBits(bitList: BitList) {
for (i in bitList.indices)
putBit(bitList[i])
}
fun packUnsigned(value: ULong) {
@ -71,23 +48,57 @@ abstract class BitOutput {
}
}
var isClosed = false
private set
fun close(): BitOutput {
if (!isClosed) {
if (accumulatorBits > 0) {
outputByte(accumulator.toUByte())
} else accumulatorBits = 8
isClosed = true
}
return this
}
fun putBytes(data: ByteArray) {
for (b in data) {
putBits(b.toULong(), 8)
}
}
/**
* Create compressed record with content and size check. Compression works with _bytes_.
*
* Structure:
*
* | size | meaning |
* |------|--------------------------------------------------|
* | packed unsigned | size of uncompressed content in bytes |
* | 1 | 0 - not compressed, 1 - compressed |
*
* __If compressed__, then:
*
* | size | meaning |
* |------|--------------------------------------|
* | 2 | 00 - LZW, other combinations reserved|
*
* After this header compressed bits follow.
*
* __If not compressed,__ then source data follows as bit stream.
*
* Compressed block overhead is 3 bits, uncompressed 1.
*/
fun compress(source: ByteArray) {
// size
packUnsigned(source.size.toULong())
// check compression is effective?
val compressed = LZW.compress(source.asUByteArray())
// check that compression is effective including header bits size:
if( compressed.size + 2 < source.size * 8L) {
println("write compressed")
putBit(1)
// LZW algorithm
putBits(0, 2)
// compressed data
putBits(compressed)
}
else {
putBit(0)
putBytes(source)
}
}
fun compress(source: String) {
compress(source.encodeToByteArray())
}
}

3
lynglib/src/commonMain/kotlin/net/sergeych/lynon/DecompressionException.kt Normal file
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@ -0,0 +1,3 @@
package net.sergeych.lynon
class DecompressionException(message: String) : IllegalArgumentException(message) {}

8
lynglib/src/commonMain/kotlin/net/sergeych/lynon/LynonDecoder.kt
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@ -28,10 +28,10 @@ open class LynonDecoder(val bin: BitInput,val settings: LynonSettings = LynonSet
return decodeCached { type.deserialize(scope, this) }
}
fun unpackBinaryData(): ByteArray? {
val size = bin.unpackUnsigned()
return bin.getBytes(size.toInt())
}
fun unpackBinaryData(): ByteArray = bin.decompress()
@Suppress("unused")
fun unpackBinaryDataOrNull(): ByteArray? = bin.decompressOrNull()
fun unpackBoolean(): Boolean {
return bin.getBit() == 1

3
lynglib/src/commonMain/kotlin/net/sergeych/lynon/LynonEncoder.kt
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@ -29,8 +29,7 @@ open class LynonEncoder(val bout: BitOutput,val settings: LynonSettings = LynonS
}
fun encodeBinaryData(data: ByteArray) {
bout.packUnsigned(data.size.toULong())
bout.putBytes(data)
bout.compress(data)
}
fun encodeSigned(value: Long) {

37
lynglib/src/commonMain/kotlin/net/sergeych/lynon/MemoryBitInput.kt
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@ -1,20 +1,39 @@
package net.sergeych.lynon
class MemoryBitInput(val packedBits: UByteArray,val lastByteBits: Int): BitInput() {
constructor(bout: MemoryBitOutput): this(bout.toUByteArray(), bout.lastByteBits)
class MemoryBitInput(val packedBits: UByteArray, val lastByteBits: Int) : BitInput {
constructor(ba: BitArray) : this(ba.bytes, ba.lastByteBits) {}
constructor(mba: MemoryBitOutput) : this(mba.toBitArray()) {}
private var index = 0
override fun getByte(): DataByte {
return if( index < packedBits.size ) {
DataByte(
packedBits[index++].toInt(),
if( index == packedBits.size ) lastByteBits else 8
)
/**
* Return next byte, int in 0..255 range, or -1 if end of stream reached
*/
private var accumulator = 0
private var isEndOfStream: Boolean = false
private set
private var mask = 0
override fun getBitOrNull(): Int? {
if (isEndOfStream) return null
if (mask == 0) {
if (index < packedBits.size) {
accumulator = packedBits[index++].toInt()
val n = if (index == packedBits.size) lastByteBits else 8
mask = 1 shl (n - 1)
} else {
DataByte(-1,0)
isEndOfStream = true
return null
}
}
val result = if (0 == accumulator and mask) 0 else 1
mask = mask shr 1
return result
}
}

133
lynglib/src/commonMain/kotlin/net/sergeych/lynon/MemoryBitOutput.kt
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@ -1,14 +1,135 @@
package net.sergeych.lynon
class MemoryBitOutput: BitOutput() {
private val buffer = mutableListOf<UByte>()
import kotlin.math.min
fun toUByteArray(): UByteArray {
close()
return buffer.toTypedArray().toUByteArray()
/**
* BitList implementation as fixed suze array of bits; indexing works exactly same as if
* [MemoryBitInput] is used with [MemoryBitInput.getBit].
*/
class BitArray(val bytes: UByteArray, val lastByteBits: Int) : BitList {
val bytesSize: Int get() = bytes.size
override val size by lazy { bytes.size * 8L - (8 - lastByteBits) }
override val indices by lazy { 0..<size }
/**
* @return [BitInput] that can be used to read from this array
*/
fun toBitInput(): BitInput = MemoryBitInput(bytes, lastByteBits)
private fun getIndexAndMask(bitIndex: Long): Pair<Int, Int> {
val byteIndex = (bitIndex / 8).toInt()
if (byteIndex !in bytes.indices)
throw IndexOutOfBoundsException("$bitIndex is out of bounds")
val i = (bitIndex % 8).toInt()
return byteIndex to (
if (byteIndex == bytes.lastIndex) {
if (i >= lastByteBits)
throw IndexOutOfBoundsException("$bitIndex is out of bounds (last)")
1 shl (lastByteBits - i - 1)
} else {
1 shl (7 - i)
}
)
}
override fun outputByte(byte: UByte) {
override operator fun get(bitIndex: Long): Int =
getIndexAndMask(bitIndex).let { (byteIndex, mask) ->
if (bytes[byteIndex].toInt() and mask == 0) 0 else 1
}
override operator fun set(bitIndex: Long, value: Int) {
require(value == 0 || value == 1)
val (byteIndex, mask) = getIndexAndMask(bitIndex)
if (value == 1)
bytes[byteIndex] = bytes[byteIndex] or mask.toUByte()
else
bytes[byteIndex] = bytes[byteIndex] and mask.inv().toUByte()
}
override fun toString(): String {
val result = StringBuilder()
val s = min(size, 64)
for (i in 0..<s) result.append(this[i])
if (s < size) result.append("…")
return result.toString()
}
companion object {
fun withBitSize(size: Long): BitArray {
val byteSize = ((size + 7) / 8).toInt()
val lastByteBits = size % 8
return BitArray(UByteArray(byteSize), lastByteBits.toInt())
}
fun ofBits(vararg bits: Int): BitArray {
return withBitSize(bits.size.toLong()).apply {
for (i in bits.indices) {
this[i.toLong()] = bits[i]
}
}
}
}
}
class MemoryBitOutput : BitOutput {
private val buffer = mutableListOf<UByte>()
private var accumulator = 0
/**
* Number of bits in accumulator. After output is closed by [close] this value is
* not changed and represents the number of bits in the last byte; this should
* be used to properly calculate end of the bit stream
*/
private var accumulatorBits = 0
private set
// /**
// * When [close] is called, represents the number of used bits in the last byte;
// * bits after this number are the garbage and should be ignored
// */
// val lastByteBits: Int
// get() {
// if (!isClosed) throw IllegalStateException("BitOutput is not closed")
// return accumulatorBits
// }
override fun putBit(bit: Int) {
accumulator = (accumulator shl 1) or bit
if (++accumulatorBits >= 8) {
outputByte(accumulator.toUByte())
accumulator = accumulator shr 8
accumulatorBits = 0
}
}
var isClosed = false
private set
fun close(): BitArray {
if (!isClosed) {
if (accumulatorBits > 0) {
outputByte(accumulator.toUByte())
} else accumulatorBits = 8
isClosed = true
}
return toBitArray()
}
fun toBitArray(): BitArray {
if (!isClosed) {
close()
}
return BitArray(buffer.toTypedArray().toUByteArray(), accumulatorBits)
}
fun toBitInput(): BitInput = toBitArray().toBitInput()
private fun outputByte(byte: UByte) {
buffer.add(byte)
}
}

71
lynglib/src/commonMain/kotlin/net/sergeych/lynon/TinyBits.kt Normal file
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@ -0,0 +1,71 @@
package net.sergeych.lynon
/**
* Bit size-aware code, short [BitList] implementation, up to 64 bits (efficiency tradeoff).
* E.g `Bits(0, 3) != Bits(0, 2). For longer, use [BitArray].
*
* Note that [bitListOf] creates [TinyBits] when possible.
*/
class TinyBits(initValue: ULong = 0U, override val size: Long = 0): BitList {
private var bits: ULong = initValue
constructor(value: ULong, size: Int): this(value, size.toLong()) {}
override val indices: LongRange by lazy { 0..<size }
override operator fun get(bitIndex: Long): Int {
if( bitIndex !in indices) throw IndexOutOfBoundsException("index out of bounds: $bitIndex")
val mask = 1UL shl (size - bitIndex - 1).toInt()
return if (bits and mask != 0UL) 1 else 0
}
override fun set(bitIndex: Long, value: Int) {
val mask = 1UL shl (size - bitIndex - 1).toInt()
if( value == 1)
bits = bits or mask
else
bits = bits and mask.inv()
}
override fun toString(): String {
val result = StringBuilder()
for (i in 0..<size) result.append(this[i])
return result.toString()
}
val value by ::bits
/**
* Add bit shifting value to the left and return _new instance_
*/
fun insertBit(bit: Int): TinyBits {
return TinyBits((bits shl 1) or bit.toULong(), size + 1)
}
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (other == null || this::class != other::class) return false
other as TinyBits
if (size != other.size) return false
if (bits != other.bits) return false
return true
}
override fun hashCode(): Int {
var result = size.hashCode()
result = 31 * result + bits.hashCode()
return result
}
companion object {
fun of(vararg bits: Int): TinyBits {
return TinyBits(0UL, bits.size).apply { bits.forEachIndexed { i, v -> this[i.toLong()] = v } }
}
}
}

244
lynglib/src/commonMain/kotlin/net/sergeych/lynon/huffman.kt Normal file
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@ -0,0 +1,244 @@
package net.sergeych.lynon
import net.sergeych.collections.SortedList
/**
* Experimental, reference implementation of Huffman trees and encoding.
*
* This is a reference huffman encoding implementation not yet ready;
* it was used to experiment with LZW, at the moment, LZW won the competition
* for compressed module format for its speed and sufficiently small size/
*
* This is byte-based compressor which makes it not too interesting.
*
* TODO: convert to use various source dictionary
*
* reason: version thant compress bytes is not too interesting; particular alphabets
* are often longer than byte bits and are often sparse, that requires another
* codes serialization implementation
*/
object Huffman {
sealed class Node(val freq: Int) : Comparable<Node> {
override fun compareTo(other: Node): Int {
return freq.compareTo(other.freq)
}
abstract fun decode(bin: BitInput): Int?
class Leaf(val value: Int, freq: Int) : Node(freq) {
override fun toString(): String {
return "[$value:$freq]"
}
override fun decode(bin: BitInput): Int {
return value//.also { println(": ${Char(value)}") }
}
}
class Internal(val left: Node, val right: Node) : Node(left.freq + right.freq) {
override fun toString(): String {
return "[${left.freq}<- :<$freq>: ->${right.freq}]"
}
override fun decode(bin: BitInput): Int? {
return when (bin.getBitOrNull().also { print("$it") }) {
1 -> left.decode(bin)
0 -> right.decode(bin)
else -> null
}
}
}
}
data class Code(val symbol: Int, val bits: TinyBits) {
val size by bits::size
override fun toString(): String {
return "[${Char(symbol)}:$size:$bits]"
}
}
private fun generateCanonicCodes(tree: Node): List<Code?> {
val codes = MutableList<Code?>(256) { null }
fun traverse(node: Node, code: TinyBits) {
when (node) {
is Node.Leaf ->
codes[node.value] = (Code(node.value, code))
is Node.Internal -> {
traverse(node.left, code.insertBit(1))
traverse(node.right, code.insertBit(0))
}
}
}
traverse(tree, TinyBits())
return makeCanonical(codes)
}
private fun makeCanonical(source: List<Code?>): List<Code?> {
val sorted = source.filterNotNull().sortedWith(canonicComparator)
val canonical = MutableList<Code?>(256) { null }
val first = sorted[0]
val prevValue = first.copy(bits = TinyBits(0UL, first.bits.size))
canonical[first.symbol] = prevValue
var prev = prevValue.bits
for (i in 1..<sorted.size) {
var bits = TinyBits(prev.value + 1U, prev.size)
val code = sorted[i]
while (code.bits.size > bits.size) {
bits = bits.insertBit(0)
}
canonical[code.symbol] = code.copy(bits = bits)//.also { println("$it") }
prev = bits
}
return canonical
}
private val canonicComparator = { a: Code, b: Code ->
if (a.bits.size == b.bits.size) {
a.symbol.compareTo(b.symbol)
} else {
a.bits.size.compareTo(b.bits.size)
}
}
private fun buildTree(data: UByteArray): Node {
// println(data.toDump())
val frequencies = Array(256) { 0 }
data.forEach { frequencies[it.toInt()]++ }
val list = SortedList<Node>(*frequencies.mapIndexed { index, i -> Node.Leaf(index, i) }.filter { it.freq > 0 }
.toTypedArray())
// build the tree
while (list.size > 1) {
val left = list.removeAt(0)
val right = list.removeAt(0)
list.add(Node.Internal(left, right))
}
return list[0]
}
fun decompressUsingCodes(bin: BitInput, codes: List<Code?>): UByteArray {
val result = mutableListOf<UByte>()
val table = codes.filterNotNull().associateBy { it.bits }
outer@ while (true) {
var input = TinyBits()
while (true) {
bin.getBitOrNull()?.let { input = input.insertBit(it) }
?: break@outer
val data = table[input]
if (data != null) {
// println("Code found: ${data.bits} -> [${data.symbol.toChar()}]")
result.add(data.symbol.toUByte())
break
}
}
}
return result.toUByteArray()
}
private fun serializeCanonicCodes(bout: BitOutput, codes: List<Code?>) {
var minSize: Int? = null
var maxSize: Int? = null
for (i in 1..<codes.size) {
val s = codes[i]?.size?.toInt() ?: continue
if (minSize == null || s < minSize) minSize = s
if (maxSize == null || s > maxSize) maxSize = s
}
val size = maxSize!! - minSize!! + 1
val sizeInBits = sizeInBits(size)
bout.packUnsigned(minSize.toULong())
bout.packUnsigned(sizeInBits.toULong())
for (c in codes) {
if (c != null)
bout.putBits(c.bits.size.toInt() - minSize + 1, sizeInBits)
else
bout.putBits(0, sizeInBits)
}
}
fun deserializeCanonicCodes(bin: BitInput): List<Code?> {
val minSize = bin.unpackUnsigned().toInt()
val sizeInBits = bin.unpackUnsigned().toInt()
val sorted = mutableListOf<Code>().also { codes ->
for (i in 0..<256) {
val s = bin.getBits(sizeInBits).toInt()
if (s > 0) {
codes.add(Code(i, TinyBits(0U, s - 1 + minSize)))
}
}
}.sortedWith(canonicComparator)
val result = MutableList<Code?>(256) { null }
var prev = sorted[0].copy(bits = TinyBits(0U, sorted[0].bits.size))
result[prev.symbol] = prev
for (i in 1..<sorted.size) {
val code = sorted[i]
var bits = TinyBits(prev.bits.value + 1u, prev.bits.size)
while (bits.size < code.bits.size) bits = bits.insertBit(0)
result[code.symbol] = code.copy(bits = bits).also {
prev = it
}
}
return result
}
fun compress(data: UByteArray): BitArray {
val root = buildTree(data)
val codes = generateCanonicCodes(root)
// serializa table
// test encode:
val bout = MemoryBitOutput()
serializeCanonicCodes(bout, codes)
for (i in data) {
val code = codes[i.toInt()]!!
// println(">> $code")
bout.putBits(code.bits)
}
// println(bout.toBitArray().bytes.toDump())
val compressed = bout.toBitArray()
// println("Size: ${compressed.bytes.size / data.size.toDouble() }")
// println("compression ratio: ${compressed.bytes.size / data.size.toDouble() }")
// test decompress
// val bin = MemoryBitInput(compressed)
// val codes2 = deserializeCanonicCodes(bin)
// for ((a, b) in codes.zip(codes2)) {
// if (a != b) {
// println("Codes mismatch: $a != $b")
// break
// }
// }
// require(codes == codes2)
// val result = decompressUsingCodes(bin, codes2)
//
//// println(result.toUByteArray().toDump())
// check(data contentEquals result.toUByteArray())
// if( !(data contentEquals result.toUByteArray()) )
// throw RuntimeException("Data mismatch")
// println(data.toDump())
//
return compressed
}
fun decompress(bin: BitInput): UByteArray {
val codes = deserializeCanonicCodes(bin)
return decompressUsingCodes(bin, codes)
}
}

128
lynglib/src/commonMain/kotlin/net/sergeych/lynon/lzw.kt Normal file
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@ -0,0 +1,128 @@
package net.sergeych.lynon
import net.sergeych.bintools.ByteChunk
import kotlin.math.roundToInt
/**
* LZW lightweight pure kotlin compression.
*/
object LZW {
val MAX_CODE_SIZE = 17
val STOP_CODE = (1 shl MAX_CODE_SIZE) - 1
val MAX_DICT_SIZE = (STOP_CODE * 0.92).roundToInt()
fun compress(input: ByteArray, bitOutput: BitOutput)
= compress(input.asUByteArray(), bitOutput)
/**
* Compresses the input string using LZW algorithm
* @param input The string to compress
* @return List of compressed codes
*/
fun compress(input: UByteArray, bitOutput: BitOutput) {
// Initialize dictionary with all possible single characters
val dictionary = mutableMapOf<ByteChunk, Int>()
for (i in 0..255) {
// 23
dictionary[ByteChunk(ubyteArrayOf(i.toUByte()))] = i
}
var nextCode = 256
var current = ByteChunk(ubyteArrayOf())
// val result = mutableListOf<Int>()
for (char in input) {
val combined = current + char
if (dictionary.containsKey(combined)) {
current = combined
} else {
val size = sizeInBits(dictionary.size)
bitOutput.putBits(dictionary[current]!!, size)
if (dictionary.size >= MAX_DICT_SIZE) {
bitOutput.putBits(STOP_CODE, size)
dictionary.clear()
nextCode = 256
for (i in 0..255) {
dictionary[ByteChunk(ubyteArrayOf(i.toUByte()))] = i
}
} else
dictionary[combined] = nextCode++
current = ByteChunk(ubyteArrayOf(char))
}
}
if (current.size > 0) {
val size = sizeInBits(dictionary.size)
bitOutput.putBits(dictionary[current]!!, size)
}
}
fun compress(input: UByteArray): BitArray {
return MemoryBitOutput().apply {
compress(input, this)
}.toBitArray()
}
/**
* Decompresses a list of LZW codes back to the original string. Note that usage of apriori existing
* size is crucial: it let repeal explosion style attacks.
*
* @param compressed The list of compressed codes
* @param resultSize The expected size of the decompressed string
*
* @throws DecompressionException if something goes wrong
* @return The decompressed string
*/
fun decompress(compressed: BitInput, resultSize: Int): UByteArray {
// Initialize dictionary with all possible single characters
val dictionary = mutableMapOf<Int, UByteArray>()
for (i in 0..255) {
dictionary[i] = ubyteArrayOf(i.toUByte())
}
var nextCode = 256
val firstCode = compressed.getBits(9).toInt()
var previous = dictionary[firstCode]
?: throw DecompressionException("Invalid first compressed code: $firstCode")
val result = mutableListOf<UByte>()
result += previous
while (result.size < resultSize) {
val codeSize = sizeInBits(nextCode + 1)
val code = compressed.getBitsOrNull(codeSize)?.toInt() ?: break
if (code == STOP_CODE) {
nextCode = 256
dictionary.clear()
for (i in 0..255)
dictionary[i] = ubyteArrayOf(i.toUByte())
previous = dictionary[compressed.getBits(9).toInt()]!!
} else {
val current = if (code in dictionary) {
dictionary[code]!!
} else if (code == nextCode) {
// Special case for pattern like cScSc
previous + previous[0]
} else {
throw DecompressionException("Invalid compressed code: $code")
}
result += current
dictionary[nextCode++] = previous + current[0]
previous = current
}
}
if (result.size != resultSize)
throw DecompressionException("Decompressed size is not equal to expected: real/expected = ${result.size}/$resultSize")
return result.toTypedArray().toUByteArray()
}
}
private operator fun ByteChunk.plus(byte: UByte): ByteChunk {
return ByteChunk(data + byte)
}

114
lynglib/src/commonMain/kotlin/net/sergeych/lynon/lzw0.kt
View File

@ -1,114 +0,0 @@
package net.sergeych.lynon
import net.sergeych.bintools.ByteChunk
import kotlin.math.roundToInt
/**
* LZW compression algorithm: work in progress.
*
* Uses Lyng but input/output. Uses automatic code size.
*/
class LZW {
companion object {
val MAX_CODE_SIZE = 17
val STOP_CODE = (1 shl MAX_CODE_SIZE) - 1
val MAX_DICT_SIZE = (STOP_CODE * 0.92).roundToInt()
/**
* Compresses the input string using LZW algorithm
* @param input The string to compress
* @return List of compressed codes
*/
fun compress(input: UByteArray,bitOutput: BitOutput) {
// Initialize dictionary with all possible single characters
val dictionary = mutableMapOf<ByteChunk, Int>()
for (i in 0..255) {
// 23
dictionary[ByteChunk(ubyteArrayOf(i.toUByte()))] = i
}
var nextCode = 256
var current = ByteChunk(ubyteArrayOf())
// val result = mutableListOf<Int>()
for (char in input) {
val combined = current + char
if (dictionary.containsKey(combined)) {
current = combined
} else {
val size = sizeInBits(dictionary.size)
bitOutput.putBits(dictionary[current]!!,size)
if( dictionary.size >= MAX_DICT_SIZE ) {
bitOutput.putBits(STOP_CODE,size)
dictionary.clear()
nextCode = 256
for (i in 0..255) {
dictionary[ByteChunk(ubyteArrayOf(i.toUByte()))] = i
}
}
else
dictionary[combined] = nextCode++
current = ByteChunk(ubyteArrayOf(char))
}
}
if (current.size > 0) {
val size = sizeInBits(dictionary.size)
bitOutput.putBits(dictionary[current]!!,size)
}
}
/**
* Decompresses a list of LZW codes back to the original string
* @param compressed The list of compressed codes
* @return The decompressed string
*/
fun decompress(compressed: BitInput): UByteArray {
// Initialize dictionary with all possible single characters
val dictionary = mutableMapOf<Int, UByteArray>()
for (i in 0..255) {
dictionary[i] = ubyteArrayOf(i.toUByte())
}
var nextCode = 256
var previous = dictionary[compressed.getBits(9).toInt()]!!
val result = mutableListOf<UByte>()
while( !compressed.isEndOfStream ) {
val codeSize = sizeInBits(nextCode + 1)
val code = compressed.getBitsOrNull(codeSize)?.toInt() ?: break
if( code == STOP_CODE ) {
nextCode = 256
dictionary.clear()
for (i in 0..255)
dictionary[i] = ubyteArrayOf(i.toUByte())
previous = dictionary[compressed.getBits(9).toInt()]!!
}
else {
val current = if (code in dictionary) {
dictionary[code]!!
} else if (code == nextCode) {
// Special case for pattern like cScSc
previous + previous[0]
} else {
throw IllegalArgumentException("Invalid compressed code: $code")
}
result += current
dictionary[nextCode++] = previous + current[0]
previous = current
}
}
return result.toTypedArray().toUByteArray()
}
}
}
private operator fun ByteChunk.plus(byte: UByte): ByteChunk {
return ByteChunk(data + byte)
}

2
lynglib/src/commonMain/kotlin/net/sergeych/lynon/tools.kt
View File

@ -11,5 +11,5 @@ class LynonPacker(bout: MemoryBitOutput = MemoryBitOutput(), settings: LynonSett
* Variant of [LynonDecoder] that reads from a given `source` using [MemoryBitInput]
*/
class LynonUnpacker(source: BitInput) : LynonDecoder(source) {
constructor(packer: LynonPacker) : this(MemoryBitInput(packer.bout as MemoryBitOutput))
constructor(packer: LynonPacker) : this((packer.bout as MemoryBitOutput).toBitInput())
}

110
lynglib/src/jvmTest/kotlin/LynonTests.kt
View File

@ -6,7 +6,7 @@ import net.sergeych.lynon.*
import java.nio.file.Files
import java.nio.file.Path
import kotlin.test.Test
import kotlin.test.assertContentEquals
class LynonTests {
@Test
@ -210,11 +210,13 @@ class LynonTests {
assertEquals(null, bin.getBitsOrNull(3))
}
val original = Files.readString(Path.of("../sample_texts/dikkens_hard_times.txt"))
@Test
fun testLzw() {
// Example usage
// val original = "TOBEORNOTTOBEORTOBEORNOT"
val original = Files.readString(Path.of("../sample_texts/dikkens_hard_times.txt"))
// println("Original: $original")
println("Length: ${original.length}")
@ -222,14 +224,112 @@ class LynonTests {
val out = MemoryBitOutput()
LZW.compress(original.encodeToByteArray().toUByteArray(), out)
// println("\nCompressed codes: ${out.toUByteArray().toDump()}")
println("Number of codes: ${out.toUByteArray().size}")
println("Number of codes: ${out.toBitArray().bytesSize}")
println("Copression rate: ${out.toBitArray().bytesSize.toDouble() / original.length.toDouble()}")
// // Decompress
val decompressed = LZW.decompress(MemoryBitInput(out)).toByteArray().decodeToString()
val decompressed = LZW.decompress(MemoryBitInput(out), original.length).toByteArray().decodeToString()
// println("\nDecompressed: $decompressed")
println("Length: ${decompressed.length}")
// Verification
println("\nOriginal and decompressed match: ${original == decompressed}")
assertEquals(original, decompressed)
}
@Test
fun testTinyBits() {
var a0 = TinyBits()
assertEquals(a0, a0)
a0 = a0.insertBit(0)
a0 = a0.insertBit(1)
a0 = a0.insertBit(1)
a0 = a0.insertBit(1)
a0 = a0.insertBit(0)
a0 = a0.insertBit(1)
// println(a0)
assertEquals("011101", a0.toString())
val bin = MemoryBitInput(MemoryBitOutput().apply { putBits(a0) })
var result = TinyBits()
for( i in a0.indices) result = result.insertBit(bin.getBit())
assertEquals(a0, result)
}
@Test
fun testHuffman() {
val x = original.encodeToByteArray().toUByteArray()
// val x ="hello, world!".toByteArray().asUByteArray()// original.encodeToByteArray().toUByteArray()
println("Original : ${x.size}")
val lzw = LZW.compress(x).bytes
println("LZW : ${lzw.size}")
val ba = Huffman.compress(x)
val huff = ba.bytes
println("Huffman : ${huff.size}")
val lzwhuff = Huffman.compress(lzw).bytes
println("LZW+HUFF : ${lzwhuff.size}")
val compressed = Huffman.compress(x)
val decompressed = Huffman.decompress(compressed.toBitInput())
assertContentEquals(x, decompressed)
}
@Test
fun testBitListSmall() {
var t = TinyBits()
for( i in listOf(1, 1, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1) )
t = t.insertBit(i)
assertEquals(1, t[0])
assertEquals(1, t[1])
assertEquals(0, t[2])
assertEquals("1101000111101",t.toString())
t[0] = 0
t[1] = 0
t[2] = 1
assertEquals("0011000111101",t.toString())
t[12] = 0
t[11] = 1
assertEquals("0011000111110",t.toString())
}
@Test
fun testBitListSerialization() {
// this also tests bitArray with first and last bytes
val bout = MemoryBitOutput()
assertEquals("1101", bitListOf(1, 1, 0, 1).toString())
bout.putBits(bitListOf(1, 1, 0, 1))
bout.putBits(bitListOf( 0, 0))
bout.putBits(bitListOf( 0, 1, 1, 1, 1, 0, 1))
val x = bout.toBitArray()
assertEquals("1101000111101",x.toString())
}
@Test
fun testCompressionWithOffsets() {
val src = "to be or not to be or not to be or not to be or not to be"
val bout = MemoryBitOutput()
bout.packUnsigned(1571UL)
LZW.compress(src.encodeToByteArray(), bout)
bout.packUnsigned(157108UL)
val bin = bout.toBitInput()
assertEquals(1571UL, bin.unpackUnsigned())
assertEquals(src, LZW.decompress(bin, src.length).asByteArray().decodeToString())
assertEquals(157108UL, bin.unpackUnsigned())
}
@Test
fun testCompressionRecord() {
val bout = MemoryBitOutput()
val src = "to be or not to be or not to be or not to be or not to be"
val src2 = "to be or not to be"
val src3 = "ababababab"
bout.compress(src)
bout.compress(src2)
bout.compress(src3)
val bin = bout.toBitInput()
assertEquals(src, bin.decompressString())
assertEquals(src2, bin.decompressString())
assertEquals(src3, bin.decompressString())
}
}