Code/net/minecraft/util/datafix/fixes/BitStorageAlignFix.java

package net.minecraft.util.datafix.fixes;

import com.mojang.datafixers.DSL;
import com.mojang.datafixers.DataFix;
import com.mojang.datafixers.DataFixUtils;
import com.mojang.datafixers.OpticFinder;
import com.mojang.datafixers.TypeRewriteRule;
import com.mojang.datafixers.Typed;
import com.mojang.datafixers.schemas.Schema;
import com.mojang.datafixers.types.Type;
import com.mojang.datafixers.types.templates.List.ListType;
import com.mojang.datafixers.util.Pair;
import com.mojang.serialization.Dynamic;
import java.util.List;
import java.util.stream.LongStream;
import net.minecraft.util.Mth;

public class BitStorageAlignFix extends DataFix {
    private static final int BIT_TO_LONG_SHIFT = 6;
    private static final int SECTION_WIDTH = 16;
    private static final int SECTION_HEIGHT = 16;
    private static final int SECTION_SIZE = 4096;
    private static final int HEIGHTMAP_BITS = 9;
    private static final int HEIGHTMAP_SIZE = 256;

    public BitStorageAlignFix(Schema p_14736_) {
        super(p_14736_, false);
    }

    @Override
    protected TypeRewriteRule makeRule() {
        Type<?> type = this.getInputSchema().getType(References.CHUNK);
        Type<?> type1 = type.findFieldType("Level");
        OpticFinder<?> opticfinder = DSL.fieldFinder("Level", type1);
        OpticFinder<?> opticfinder1 = opticfinder.type().findField("Sections");
        Type<?> type2 = ((ListType)opticfinder1.type()).getElement();
        OpticFinder<?> opticfinder2 = DSL.typeFinder(type2);
        Type<Pair<String, Dynamic<?>>> type3 = DSL.named(References.BLOCK_STATE.typeName(), DSL.remainderType());
        OpticFinder<List<Pair<String, Dynamic<?>>>> opticfinder3 = DSL.fieldFinder("Palette", DSL.list(type3));
        return this.fixTypeEverywhereTyped(
            "BitStorageAlignFix",
            type,
            this.getOutputSchema().getType(References.CHUNK),
            p_14749_ -> p_14749_.updateTyped(opticfinder, p_145120_ -> this.updateHeightmaps(updateSections(opticfinder1, opticfinder2, opticfinder3, p_145120_)))
        );
    }

    private Typed<?> updateHeightmaps(Typed<?> p_14763_) {
        return p_14763_.update(
            DSL.remainderFinder(),
            p_14765_ -> p_14765_.update(
                "Heightmaps",
                p_145113_ -> p_145113_.updateMapValues(p_145110_ -> p_145110_.mapSecond(p_145123_ -> updateBitStorage(p_14765_, (Dynamic<?>)p_145123_, 256, 9)))
            )
        );
    }

    private static Typed<?> updateSections(OpticFinder<?> p_14751_, OpticFinder<?> p_14752_, OpticFinder<List<Pair<String, Dynamic<?>>>> p_14753_, Typed<?> p_14754_) {
        return p_14754_.updateTyped(
            p_14751_,
            p_14758_ -> p_14758_.updateTyped(
                p_14752_,
                p_145103_ -> {
                    int i = p_145103_.getOptional(p_14753_).map(p_145115_ -> Math.max(4, DataFixUtils.ceillog2(p_145115_.size()))).orElse(0);
                    return i != 0 && !Mth.isPowerOfTwo(i)
                        ? p_145103_.update(
                            DSL.remainderFinder(), p_145100_ -> p_145100_.update("BlockStates", p_145107_ -> updateBitStorage(p_145100_, p_145107_, 4096, i))
                        )
                        : p_145103_;
                }
            )
        );
    }

    private static Dynamic<?> updateBitStorage(Dynamic<?> p_14777_, Dynamic<?> p_14778_, int p_14779_, int p_14780_) {
        long[] along = p_14778_.asLongStream().toArray();
        long[] along1 = addPadding(p_14779_, p_14780_, along);
        return p_14777_.createLongList(LongStream.of(along1));
    }

    public static long[] addPadding(int p_14738_, int p_14739_, long[] p_14740_) {
        int i = p_14740_.length;
        if (i == 0) {
            return p_14740_;
        } else {
            long j = (1L << p_14739_) - 1L;
            int k = 64 / p_14739_;
            int l = (p_14738_ + k - 1) / k;
            long[] along = new long[l];
            int i1 = 0;
            int j1 = 0;
            long k1 = 0L;
            int l1 = 0;
            long i2 = p_14740_[0];
            long j2 = i > 1 ? p_14740_[1] : 0L;

            for (int k2 = 0; k2 < p_14738_; k2++) {
                int l2 = k2 * p_14739_;
                int i3 = l2 >> 6;
                int j3 = (k2 + 1) * p_14739_ - 1 >> 6;
                int k3 = l2 ^ i3 << 6;
                if (i3 != l1) {
                    i2 = j2;
                    j2 = i3 + 1 < i ? p_14740_[i3 + 1] : 0L;
                    l1 = i3;
                }

                long l3;
                if (i3 == j3) {
                    l3 = i2 >>> k3 & j;
                } else {
                    int i4 = 64 - k3;
                    l3 = (i2 >>> k3 | j2 << i4) & j;
                }

                int j4 = j1 + p_14739_;
                if (j4 >= 64) {
                    along[i1++] = k1;
                    k1 = l3;
                    j1 = p_14739_;
                } else {
                    k1 |= l3 << j1;
                    j1 = j4;
                }
            }

            if (k1 != 0L) {
                along[i1] = k1;
            }

            return along;
        }
    }
}