commonMain.internal.BinaryNbtReader.kt Maven / Gradle / Ivy

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Minecraft NBT support for kotlinx.serialization
There is a newer version: 0.11.8
package net.benwoodworth.knbt.internal

import net.benwoodworth.knbt.*
import net.benwoodworth.knbt.internal.NbtTagType.*
import okio.Closeable
import okio.Source
import okio.buffer

@OptIn(OkioApi::class)
internal class BinaryNbtReader(nbt: Nbt, source: Source) : NbtReader, Closeable {
    private var compoundNesting = 0
    private var readRootEntry = false

    private val tagTypeStack = ArrayDeque()
    private val elementsRemainingStack = ArrayDeque()

    private val source: BinarySource

    init {
        val variant = nbt.configuration.variant
        val compression = nbt.configuration.compression

        val nonClosingSource = NonClosingSource(source).buffer()

        val detectedCompression = try {
            NbtCompression.detect(nonClosingSource)
        } catch (e: NbtDecodingException) {
            null
        }

        if (detectedCompression != null && compression != detectedCompression) {
            throw NbtDecodingException("Expected compression to be $compression, but was $detectedCompression")
        }

        this.source = variant.getBinarySource(
            compression.decompress(nonClosingSource).buffer()
        )
    }

    override fun close(): Unit = source.close()

    private fun  ArrayDeque.replaceLast(element: T): T = set(lastIndex, element)

    private fun BinarySource.readNbtTagType(): NbtTagType =
        NbtTagType.fromId(readByte())

    private fun checkTagType(expected: NbtTagType) {
        val actual = tagTypeStack.lastOrNull()
        if (expected != actual && actual != null) {
            throw NbtEncodingException("Expected $expected, but got $actual")
        }
    }

    override fun beginRootTag(): NbtReader.RootTagInfo =
        NbtReader.RootTagInfo(TAG_Compound)

    override fun beginCompound() {
        checkTagType(TAG_Compound)
        compoundNesting++
        tagTypeStack += TAG_End
    }

    override fun beginCompoundEntry(): NbtReader.CompoundEntryInfo {
        if (compoundNesting == 1) {
            if (readRootEntry) return NbtReader.CompoundEntryInfo.End
            readRootEntry = true
        }

        val type = source.readNbtTagType()
        return if (type == TAG_End) {
            NbtReader.CompoundEntryInfo.End
        } else {
            tagTypeStack.replaceLast(type)
            NbtReader.CompoundEntryInfo(type, source.readString())
        }
    }

    override fun endCompound() {
        if (compoundNesting == 1 && !readRootEntry) throw NbtDecodingException("The binary NBT format only supports $TAG_Compound with one entry")
        compoundNesting--
        tagTypeStack.removeLast()
    }

    private fun beginCollection(elementType: NbtTagType, size: Int) {
        tagTypeStack += elementType
        elementsRemainingStack += size
    }

    private fun beginCollectionEntry(): Boolean {
        val remaining = elementsRemainingStack.last()
        return if (remaining > 0) {
            elementsRemainingStack.replaceLast(remaining - 1)
            true
        } else {
            false
        }
    }

    private fun endCollection() {
        tagTypeStack.removeLast()
        elementsRemainingStack.removeLast()
    }

    override fun beginList(): NbtReader.ListInfo {
        checkTagType(TAG_List)

        val type = source.readNbtTagType()
        val size = source.readInt()
        beginCollection(type, size)

        return NbtReader.ListInfo(type, size)
    }

    override fun beginListEntry(): Boolean = beginCollectionEntry()

    override fun endList(): Unit = endCollection()

    override fun beginByteArray(): NbtReader.ArrayInfo {
        checkTagType(TAG_Byte_Array)

        val size = source.readInt()
        beginCollection(TAG_Byte, size)

        return NbtReader.ArrayInfo(size)
    }

    override fun beginByteArrayEntry(): Boolean = beginCollectionEntry()

    override fun endByteArray(): Unit = endCollection()

    override fun beginIntArray(): NbtReader.ArrayInfo {
        checkTagType(TAG_Int_Array)

        val size = source.readInt()
        beginCollection(TAG_Int, size)

        return NbtReader.ArrayInfo(size)
    }

    override fun beginIntArrayEntry(): Boolean = beginCollectionEntry()

    override fun endIntArray(): Unit = endCollection()

    override fun beginLongArray(): NbtReader.ArrayInfo {
        checkTagType(TAG_Long_Array)

        val size = source.readInt()
        beginCollection(TAG_Long, size)

        return NbtReader.ArrayInfo(size)
    }

    override fun beginLongArrayEntry(): Boolean = beginCollectionEntry()

    override fun endLongArray(): Unit = endCollection()

    override fun readByte(): Byte {
        checkTagType(TAG_Byte)
        return source.readByte()
    }

    override fun readShort(): Short {
        checkTagType(TAG_Short)
        return source.readShort()
    }

    override fun readInt(): Int {
        checkTagType(TAG_Int)
        return source.readInt()
    }

    override fun readLong(): Long {
        checkTagType(TAG_Long)
        return source.readLong()
    }

    override fun readFloat(): Float {
        checkTagType(TAG_Float)
        return Float.fromBits(source.readInt())
    }

    override fun readDouble(): Double {
        checkTagType(TAG_Double)
        return Double.fromBits(source.readLong())
    }

    override fun readString(): String {
        checkTagType(TAG_String)
        return source.readString()
    }
}