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https://github.com/PaperMC/Paper.git
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202 lines
8.8 KiB
Diff
202 lines
8.8 KiB
Diff
From 2be054a15c5fa8799a83dcdc6ae22305b6ea8421 Mon Sep 17 00:00:00 2001
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From: Spottedleaf <Spottedleaf@users.noreply.github.com>
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Date: Mon, 1 Apr 2019 18:57:32 -0700
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Subject: [PATCH] Make region files more reliable to write to
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Previously we would write to header before writing our chunk data,
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which opens a window for corruption (or we would overwrite entirely).
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Now the saving process has been changed to follow this chain of events:
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1. We always allocate a new space to write so we do not potentially
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overwrite and corrupt the current data
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2. Write the chunk data first (the order of the fields in
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the chunk data isn't relevant though)
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3. Flush to disk (if the launch flag is used)
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4. Write to the region header last
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5. Flush to disk (if the launch flag is used)
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6. Then we free the previous space allocated
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With this chain of events it is impossible for a chunk write to corrupt
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a region file, unless the operating system has lied and we have NOT flushed
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to disk.
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However server administrators are still recommended to continue performing
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regular backups.
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Note that when Mojang finally decides to change their region format
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to deal with oversized chunks this patch must be changed to deal with
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whatever system they decide to impose.
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If the paper.flush-on-save startup flag is set to true, then the
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steps 3 and 5 will make a call to sync() on the region file's fd,
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effectively flushing to disk.
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We also make use of two flushes to disk per chunk save (to ensure
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ordering and ensure data has gone to disk), so this will negatively
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affect save performance if the startup flag is used (especially on
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HDDs).
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diff --git a/src/main/java/net/minecraft/server/RegionFile.java b/src/main/java/net/minecraft/server/RegionFile.java
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index ed2ccebb23..2e14d84657 100644
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--- a/src/main/java/net/minecraft/server/RegionFile.java
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+++ b/src/main/java/net/minecraft/server/RegionFile.java
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@@ -29,7 +29,7 @@ public class RegionFile implements AutoCloseable {
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private final RandomAccessFile b; private RandomAccessFile getDataFile() { return this.b; } // Paper - OBFHELPER
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private final int[] c = new int[1024]; private int[] offsets = c; // Paper - OBFHELPER
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private final int[] d = new int[1024];private int[] timestamps = d; // Paper - OBFHELPER
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- private final List<Boolean> e;
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+ private final List<Boolean> e; private List<Boolean> getFreeSectors() { return this.e; } // Paper - OBFHELPER
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public RegionFile(File file) throws IOException {
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this.b = new RandomAccessFile(file, "rw");
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@@ -191,8 +191,8 @@ public class RegionFile implements AutoCloseable {
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protected synchronized void a(ChunkCoordIntPair chunkcoordintpair, byte[] abyte, int i) {
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try {
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int j = this.getOffset(chunkcoordintpair);
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- int k = j >> 8;
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- int l = j & 255;
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+ int k = j >> 8; final int oldSectorOffset = k; // Paper - store variable for later
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+ int l = j & 255; final int oldSectorCount; // Paper - store variable for later
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// Spigot start
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if (l == 255) {
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this.b.seek(k * 4096);
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@@ -200,6 +200,7 @@ public class RegionFile implements AutoCloseable {
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}
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// Spigot end
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int i1 = (i + 5) / 4096 + 1;
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+ oldSectorCount = l; // Paper - store variable for later (watch out for re-assignments of l)
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if (i1 >= 256) {
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// Spigot start
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@@ -209,14 +210,12 @@ public class RegionFile implements AutoCloseable {
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// Spigot end
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}
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- if (k != 0 && l == i1) {
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+ if (false && k != 0 && l == i1) { // Paper - We never want to overrite old data
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this.a(k, abyte, i);
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} else {
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int j1;
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- for (j1 = 0; j1 < l; ++j1) {
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- this.e.set(k + j1, true);
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- }
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+ // Paper - We do not free old sectors until we are done writing the new chunk data
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j1 = this.e.indexOf(true);
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int k1 = 0;
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@@ -243,13 +242,13 @@ public class RegionFile implements AutoCloseable {
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if (k1 >= i1) {
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k = j1;
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- this.a(chunkcoordintpair, j1 << 8 | (i1 > 255 ? 255 : i1)); // Spigot
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+ //this.a(chunkcoordintpair, j1 << 8 | (i1 > 255 ? 255 : i1)); // Spigot // Paper - We only write to header after we've written chunk data
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for (l1 = 0; l1 < i1; ++l1) {
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this.e.set(k + l1, false);
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}
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- this.a(k, abyte, i);
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+ this.writeChunk(chunkcoordintpair, j1 << 8 | (i1 > 255 ? 255 : i1), k, abyte, i); // Paper - Ensure we do not corrupt region files
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} else {
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this.b.seek(this.b.length());
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k = this.e.size();
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@@ -259,9 +258,14 @@ public class RegionFile implements AutoCloseable {
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this.e.add(false);
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}
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- this.a(k, abyte, i);
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- this.a(chunkcoordintpair, k << 8 | (i1 > 255 ? 255 : i1)); // Spigot
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+ this.writeChunk(chunkcoordintpair, k << 8 | (i1 > 255 ? 255 : i1), k, abyte, i); // Paper - Ensure we do not corrupt region files
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+ }
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+
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+ // Paper start - Now that we've written the new chunk we can free the old data
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+ for (int off = 0; off < oldSectorCount; ++off) {
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+ this.getFreeSectors().set(oldSectorOffset + off, true);
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}
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+ // Paper end
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}
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this.b(chunkcoordintpair, (int) (SystemUtils.getTimeMillis() / 1000L));
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@@ -271,10 +275,10 @@ public class RegionFile implements AutoCloseable {
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}
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+ private void writeChunkData(final int sectorOffset, final byte[] data, final int dataLength) throws IOException { this.a(sectorOffset, data, dataLength); } // Paper - OBFHELPER
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private void a(int i, byte[] abyte, int j) throws IOException {
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this.b.seek((long) (i * 4096));
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- this.b.writeInt(j + 1);
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- this.b.writeByte(2);
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+ this.writeIntAndByte(j + 1, (byte)2); // Paper - Avoid 4 io write calls
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this.b.write(abyte, 0, j);
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}
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@@ -286,12 +290,13 @@ public class RegionFile implements AutoCloseable {
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return this.getOffset(chunkcoordintpair) != 0;
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}
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+ private void updateChunkHeader(ChunkCoordIntPair chunkcoordintpair, final int offset) throws IOException { this.a(chunkcoordintpair, offset); } // Paper - OBFHELPER
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private void a(ChunkCoordIntPair chunkcoordintpair, int i) throws IOException {
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int j = this.f(chunkcoordintpair);
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this.c[j] = i;
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this.b.seek((long) (j * 4));
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- this.b.writeInt(i);
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+ this.writeInt(i); // Paper - Avoid 3 io write calls
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}
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private int f(ChunkCoordIntPair chunkcoordintpair) {
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@@ -303,7 +308,7 @@ public class RegionFile implements AutoCloseable {
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this.d[j] = i;
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this.b.seek((long) (4096 + j * 4));
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- this.b.writeInt(i);
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+ this.writeInt(i); // Paper - Avoid 3 io write calls
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}
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public void close() throws IOException {
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@@ -311,6 +316,40 @@ public class RegionFile implements AutoCloseable {
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}
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// Paper start
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+ private static final boolean FLUSH_ON_SAVE = Boolean.getBoolean("paper.flush-on-save");
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+ private void syncRegionFile() throws IOException {
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+ if (!FLUSH_ON_SAVE) {
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+ return;
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+ }
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+ this.getDataFile().getFD().sync(); // rethrow exception as we want to avoid corrupting a regionfile
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+ }
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+
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+ private final java.nio.ByteBuffer scratchBuffer = java.nio.ByteBuffer.allocate(8);
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+
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+ private void writeInt(final int value) throws IOException {
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+ synchronized (this.scratchBuffer) {
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+ this.scratchBuffer.putInt(0, value);
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+ this.getDataFile().write(this.scratchBuffer.array(), 0, 4);
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+ }
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+ }
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+
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+ // writes v1 then v2
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+ private void writeIntAndByte(final int v1, final byte v2) throws IOException {
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+ synchronized (this.scratchBuffer) {
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+ this.scratchBuffer.putInt(0, v1);
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+ this.scratchBuffer.put(4, v2);
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+ this.getDataFile().write(this.scratchBuffer.array(), 0, 5);
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+ }
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+ }
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+
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+ private void writeChunk(final ChunkCoordIntPair chunk, final int chunkHeaderData,
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+ final int chunkOffset, final byte[] chunkData, final int chunkDataLength) throws IOException {
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+ this.writeChunkData(chunkOffset, chunkData, chunkDataLength);
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+ this.syncRegionFile(); // Sync is required to ensure the previous data is written successfully
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+ this.updateChunkHeader(chunk, chunkHeaderData);
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+ this.syncRegionFile(); // Ensure header changes go through
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+ }
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+
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public synchronized void deleteChunk(int j1) {
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backup();
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int k = offsets[j1];
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--
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2.21.0
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