src/main/java/net/glowstone/io/anvil/RegionFile.java - glowstone - Rivoreo Source Code Repositories

 package net.glowstone.io.anvil;

 /*
  ** 2011 January 5
  **
  ** The author disclaims copyright to this source code.  In place of
  ** a legal notice, here is a blessing:
  **
  **    May you do good and not evil.
  **    May you find forgiveness for yourself and forgive others.
  **    May you share freely, never taking more than you give.
  **/

 /*
  * 2011 February 16
  *
  * This source code is based on the work of Scaevolus (see notice above).
  * It has been slightly modified by Mojang AB (constants instead of magic
  * numbers, a chunk timestamp header, and auto-formatted according to our
  * formatter template).
  *
  */

 /*
  * Later changes made by the Glowstone project.
  */

 // Interfaces with region files on the disk

 /*

  Region File Format

  Concept: The minimum unit of storage on hard drives is 4KB. 90% of Minecraft
  chunks are smaller than 4KB. 99% are smaller than 8KB. Write a simple
  container to store chunks in single files in runs of 4KB sectors.

  Each region file represents a 32x32 group of chunks. The conversion from
  chunk number to region number is floor(coord / 32): a chunk at (30, -3)
  would be in region (0, -1), and one at (70, -30) would be at (3, -1).
  Region files are named "r.x.z.data", where x and z are the region coordinates.

  A region file begins with a 4KB header that describes where chunks are stored
  in the file. A 4-byte big-endian integer represents sector offsets and sector
  counts. The chunk offset for a chunk (x, z) begins at byte 4*(x+z*32) in the
  file. The bottom byte of the chunk offset indicates the number of sectors the
  chunk takes up, and the top 3 bytes represent the sector number of the chunk.
  Given a chunk offset o, the chunk data begins at byte 4096*(o/256) and takes up
  at most 4096*(o%256) bytes. A chunk cannot exceed 1MB in size. If a chunk
  offset is 0, the corresponding chunk is not stored in the region file.

  Chunk data begins with a 4-byte big-endian integer representing the chunk data
  length in bytes, not counting the length field. The length must be smaller than
  4096 times the number of sectors. The next byte is a version field, to allow
  backwards-compatible updates to how chunks are encoded.

  A version of 1 represents a gzipped NBT file. The gzipped data is the chunk
  length - 1.

  A version of 2 represents a deflated (zlib compressed) NBT file. The deflated
  data is the chunk length - 1.

  */

 import net.glowstone.GlowServer;

 import java.io.*;
 import java.util.ArrayList;
 import java.util.zip.DeflaterOutputStream;
 import java.util.zip.GZIPInputStream;
 import java.util.zip.InflaterInputStream;

 public class RegionFile {

     private static final int VERSION_GZIP = 1;
     private static final int VERSION_DEFLATE = 2;

     private static final int SECTOR_BYTES = 4096;
     private static final int SECTOR_INTS = SECTOR_BYTES / 4;

     static final int CHUNK_HEADER_SIZE = 5;
     private static final byte emptySector[] = new byte[SECTOR_BYTES];

     private RandomAccessFile file;
     private final int offsets[];
     private final int chunkTimestamps[];
     private ArrayList<Boolean> sectorFree;
     private int sizeDelta;
     private long lastModified = 0;

     public RegionFile(File path) throws IOException {
         offsets = new int[SECTOR_INTS];
         chunkTimestamps = new int[SECTOR_INTS];

         sizeDelta = 0;

         if (path.exists()) {
             lastModified = path.lastModified();
         }

         file = new RandomAccessFile(path, "rw");

         // seek to the end to prepare size checking
         file.seek(file.length());

         // if the file size is under 8KB, grow it (4K chunk offset table, 4K timestamp table)
         if (file.length() < 2 * SECTOR_BYTES) {
             sizeDelta += 2 * SECTOR_BYTES - file.length();
             if (lastModified != 0) {
                 // only give a warning if the region file existed beforehand
                 GlowServer.logger.warning("Region \"" + path + "\" under 8K: " + file.length() + " increasing by " + (2 * SECTOR_BYTES - file.length()));
             }

             for (long i = file.length(); i < 2 * SECTOR_BYTES; ++i) {
                 file.write(0);
             }
         }

         // if the file size is not a multiple of 4KB, grow it
         if ((file.length() & 0xfff) != 0) {
             sizeDelta += SECTOR_BYTES - (file.length() & 0xfff);
             GlowServer.logger.warning("Region \"" + path + "\" not aligned: " + file.length() + " increasing by " + (SECTOR_BYTES - (file.length() & 0xfff)));

             for (long i = file.length() & 0xfff; i < SECTOR_BYTES; ++i) {
                 file.write(0);
             }
         }

         // set up the available sector map
         int nSectors = (int) (file.length() / SECTOR_BYTES);
         sectorFree = new ArrayList<>(nSectors);
         for (int i = 0; i < nSectors; ++i) {
             sectorFree.add(true);
         }

         sectorFree.set(0, false); // chunk offset table
         sectorFree.set(1, false); // for the last modified info

         // read offsets from offset table
         file.seek(0);
         for (int i = 0; i < SECTOR_INTS; ++i) {
             int offset = file.readInt();
             offsets[i] = offset;

             int startSector = (offset >> 8);
             int numSectors = (offset & 0xff);

             if (offset != 0 && startSector >= 0 && startSector + numSectors <= sectorFree.size()) {
                 for (int sectorNum = 0; sectorNum < numSectors; ++sectorNum) {
                     sectorFree.set(startSector + sectorNum, false);
                 }
             } else if (offset != 0) {
                 GlowServer.logger.warning("Region \"" + path + "\": offsets[" + i + "] = " + offset + " -> " + startSector + "," + numSectors + " does not fit");
             }
         }
         // read timestamps from timestamp table
         for (int i = 0; i < SECTOR_INTS; ++i) {
             chunkTimestamps[i] = file.readInt();
         }
     }

     /* the modification date of the region file when it was first opened */
     public long lastModified() {
         return lastModified;
     }

     /* gets how much the region file has grown since it was last checked */
     public int getSizeDelta() {
         int ret = sizeDelta;
         sizeDelta = 0;
         return ret;
     }

     /*
      * gets an (uncompressed) stream representing the chunk data returns null if
      * the chunk is not found or an error occurs
      */
     public DataInputStream getChunkDataInputStream(int x, int z) throws IOException {
         if (outOfBounds(x, z)) {
             throw new IndexOutOfBoundsException();
         }

         int offset = getOffset(x, z);
         if (offset == 0) {
             // does not exist
             return null;
         }

         int sectorNumber = offset >> 8;
         int numSectors = offset & 0xFF;

         if (sectorNumber + numSectors > sectorFree.size()) {
             throw new IOException("Invalid sector");
         }

         file.seek(sectorNumber * SECTOR_BYTES);
         int length = file.readInt();

         if (length > SECTOR_BYTES * numSectors) {
             throw new IOException("Invalid length");
         }

         byte version = file.readByte();
         if (version == VERSION_GZIP) {
             byte[] data = new byte[length - 1];
             file.read(data);
             DataInputStream ret = new DataInputStream(new GZIPInputStream(new ByteArrayInputStream(data)));
             return ret;
         } else if (version == VERSION_DEFLATE) {
             byte[] data = new byte[length - 1];
             file.read(data);
             DataInputStream ret = new DataInputStream(new InflaterInputStream(new ByteArrayInputStream(data)));
             return ret;
         }

         throw new IOException("Unknown version");
     }

     public DataOutputStream getChunkDataOutputStream(int x, int z) {
         if (outOfBounds(x, z)) return null;

         return new DataOutputStream(new DeflaterOutputStream(new ChunkBuffer(x, z)));
     }

     /*
      * lets chunk writing be multithreaded by not locking the whole file as a
      * chunk is serializing -- only writes when serialization is over
      */
     class ChunkBuffer extends ByteArrayOutputStream {
         private final int x, z;

         public ChunkBuffer(int x, int z) {
             super(8096); // initialize to 8KB
             this.x = x;
             this.z = z;
         }

         @Override
         public void close() throws IOException {
             try {
                 RegionFile.this.write(x, z, buf, count);
             } finally {
                 super.close();
             }
         }
     }

     /* write a chunk at (x,z) with length bytes of data to disk */
     protected void write(int x, int z, byte[] data, int length) throws IOException {
         int offset = getOffset(x, z);
         int sectorNumber = offset >> 8;
         int sectorsAllocated = offset & 0xFF;
         int sectorsNeeded = (length + CHUNK_HEADER_SIZE) / SECTOR_BYTES + 1;

         // maximum chunk size is 1MB
         if (sectorsNeeded >= 256) {
             return;
         }

         if (sectorNumber != 0 && sectorsAllocated == sectorsNeeded) {
             /* we can simply overwrite the old sectors */
             write(sectorNumber, data, length);
         } else {
             /* we need to allocate new sectors */

             /* mark the sectors previously used for this chunk as free */
             for (int i = 0; i < sectorsAllocated; ++i) {
                 sectorFree.set(sectorNumber + i, true);
             }

             /* scan for a free space large enough to store this chunk */
             int runStart = sectorFree.indexOf(true);
             int runLength = 0;
             if (runStart != -1) {
                 for (int i = runStart; i < sectorFree.size(); ++i) {
                     if (runLength != 0) {
                         if (sectorFree.get(i)) runLength++;
                         else runLength = 0;
                     } else if (sectorFree.get(i)) {
                         runStart = i;
                         runLength = 1;
                     }
                     if (runLength >= sectorsNeeded) {
                         break;
                     }
                 }
             }

             if (runLength >= sectorsNeeded) {
                 /* we found a free space large enough */
                 sectorNumber = runStart;
                 setOffset(x, z, (sectorNumber << 8) | sectorsNeeded);
                 for (int i = 0; i < sectorsNeeded; ++i) {
                     sectorFree.set(sectorNumber + i, false);
                 }
                 write(sectorNumber, data, length);
             } else {
                 /*
                  * no free space large enough found -- we need to grow the
                  * file
                  */
                 file.seek(file.length());
                 sectorNumber = sectorFree.size();
                 for (int i = 0; i < sectorsNeeded; ++i) {
                     file.write(emptySector);
                     sectorFree.add(false);
                 }
                 sizeDelta += SECTOR_BYTES * sectorsNeeded;

                 write(sectorNumber, data, length);
                 setOffset(x, z, (sectorNumber << 8) | sectorsNeeded);
             }
         }
         setTimestamp(x, z, (int) (System.currentTimeMillis() / 1000L));
         file.getChannel().force(true);
     }

     /* write a chunk data to the region file at specified sector number */
     private void write(int sectorNumber, byte[] data, int length) throws IOException {
         file.seek(sectorNumber * SECTOR_BYTES);
         file.writeInt(length + 1); // chunk length
         file.writeByte(VERSION_DEFLATE); // chunk version number
         file.write(data, 0, length); // chunk data
     }

     /* is this an invalid chunk coordinate? */
     private boolean outOfBounds(int x, int z) {
         return x < 0 || x >= 32 || z < 0 || z >= 32;
     }

     private int getOffset(int x, int z) {
         return offsets[x + z * 32];
     }

     public boolean hasChunk(int x, int z) {
         return getOffset(x, z) != 0;
     }

     private void setOffset(int x, int z, int offset) throws IOException {
         offsets[x + z * 32] = offset;
         file.seek((x + z * 32) * 4);
         file.writeInt(offset);
     }

     private void setTimestamp(int x, int z, int value) throws IOException {
         chunkTimestamps[x + z * 32] = value;
         file.seek(SECTOR_BYTES + (x + z * 32) * 4);
         file.writeInt(value);
     }

     public void close() throws IOException {
         file.getChannel().force(true);
         file.close();
     }
 }
	package net.glowstone.io.anvil;

	/*
	** 2011 January 5
	**
	** The author disclaims copyright to this source code. In place of
	** a legal notice, here is a blessing:
	**
	** May you do good and not evil.
	** May you find forgiveness for yourself and forgive others.
	** May you share freely, never taking more than you give.
	**/

	/*
	* 2011 February 16
	*
	* This source code is based on the work of Scaevolus (see notice above).
	* It has been slightly modified by Mojang AB (constants instead of magic
	* numbers, a chunk timestamp header, and auto-formatted according to our
	* formatter template).
	*
	*/

	/*
	* Later changes made by the Glowstone project.
	*/

	// Interfaces with region files on the disk

	/*

	Region File Format

	Concept: The minimum unit of storage on hard drives is 4KB. 90% of Minecraft
	chunks are smaller than 4KB. 99% are smaller than 8KB. Write a simple
	container to store chunks in single files in runs of 4KB sectors.

	Each region file represents a 32x32 group of chunks. The conversion from
	chunk number to region number is floor(coord / 32): a chunk at (30, -3)
	would be in region (0, -1), and one at (70, -30) would be at (3, -1).
	Region files are named "r.x.z.data", where x and z are the region coordinates.

	A region file begins with a 4KB header that describes where chunks are stored
	in the file. A 4-byte big-endian integer represents sector offsets and sector
	counts. The chunk offset for a chunk (x, z) begins at byte 4(x+z32) in the
	file. The bottom byte of the chunk offset indicates the number of sectors the
	chunk takes up, and the top 3 bytes represent the sector number of the chunk.
	Given a chunk offset o, the chunk data begins at byte 4096*(o/256) and takes up
	at most 4096*(o%256) bytes. A chunk cannot exceed 1MB in size. If a chunk
	offset is 0, the corresponding chunk is not stored in the region file.

	Chunk data begins with a 4-byte big-endian integer representing the chunk data
	length in bytes, not counting the length field. The length must be smaller than
	4096 times the number of sectors. The next byte is a version field, to allow
	backwards-compatible updates to how chunks are encoded.

	A version of 1 represents a gzipped NBT file. The gzipped data is the chunk
	length - 1.

	A version of 2 represents a deflated (zlib compressed) NBT file. The deflated
	data is the chunk length - 1.

	*/

	import net.glowstone.GlowServer;

	import java.io.*;
	import java.util.ArrayList;
	import java.util.zip.DeflaterOutputStream;
	import java.util.zip.GZIPInputStream;
	import java.util.zip.InflaterInputStream;

	public class RegionFile {

	private static final int VERSION_GZIP = 1;
	private static final int VERSION_DEFLATE = 2;

	private static final int SECTOR_BYTES = 4096;
	private static final int SECTOR_INTS = SECTOR_BYTES / 4;

	static final int CHUNK_HEADER_SIZE = 5;
	private static final byte emptySector[] = new byte[SECTOR_BYTES];

	private RandomAccessFile file;
	private final int offsets[];
	private final int chunkTimestamps[];
	private ArrayList<Boolean> sectorFree;
	private int sizeDelta;
	private long lastModified = 0;

	public RegionFile(File path) throws IOException {
	offsets = new int[SECTOR_INTS];
	chunkTimestamps = new int[SECTOR_INTS];

	sizeDelta = 0;

	if (path.exists()) {
	lastModified = path.lastModified();
	}

	file = new RandomAccessFile(path, "rw");

	// seek to the end to prepare size checking
	file.seek(file.length());

	// if the file size is under 8KB, grow it (4K chunk offset table, 4K timestamp table)
	if (file.length() < 2 * SECTOR_BYTES) {
	sizeDelta += 2 * SECTOR_BYTES - file.length();
	if (lastModified != 0) {
	// only give a warning if the region file existed beforehand
	GlowServer.logger.warning("Region \"" + path + "\" under 8K: " + file.length() + " increasing by " + (2 * SECTOR_BYTES - file.length()));
	}

	for (long i = file.length(); i < 2 * SECTOR_BYTES; ++i) {
	file.write(0);
	}
	}

	// if the file size is not a multiple of 4KB, grow it
	if ((file.length() & 0xfff) != 0) {
	sizeDelta += SECTOR_BYTES - (file.length() & 0xfff);
	GlowServer.logger.warning("Region \"" + path + "\" not aligned: " + file.length() + " increasing by " + (SECTOR_BYTES - (file.length() & 0xfff)));

	for (long i = file.length() & 0xfff; i < SECTOR_BYTES; ++i) {
	file.write(0);
	}
	}

	// set up the available sector map
	int nSectors = (int) (file.length() / SECTOR_BYTES);
	sectorFree = new ArrayList<>(nSectors);
	for (int i = 0; i < nSectors; ++i) {
	sectorFree.add(true);
	}

	sectorFree.set(0, false); // chunk offset table
	sectorFree.set(1, false); // for the last modified info

	// read offsets from offset table
	file.seek(0);
	for (int i = 0; i < SECTOR_INTS; ++i) {
	int offset = file.readInt();
	offsets[i] = offset;

	int startSector = (offset >> 8);
	int numSectors = (offset & 0xff);

	if (offset != 0 && startSector >= 0 && startSector + numSectors <= sectorFree.size()) {
	for (int sectorNum = 0; sectorNum < numSectors; ++sectorNum) {
	sectorFree.set(startSector + sectorNum, false);
	}
	} else if (offset != 0) {
	GlowServer.logger.warning("Region \"" + path + "\": offsets[" + i + "] = " + offset + " -> " + startSector + "," + numSectors + " does not fit");
	}
	}
	// read timestamps from timestamp table
	for (int i = 0; i < SECTOR_INTS; ++i) {
	chunkTimestamps[i] = file.readInt();
	}
	}

	/* the modification date of the region file when it was first opened */
	public long lastModified() {
	return lastModified;
	}

	/* gets how much the region file has grown since it was last checked */
	public int getSizeDelta() {
	int ret = sizeDelta;
	sizeDelta = 0;
	return ret;
	}

	/*
	* gets an (uncompressed) stream representing the chunk data returns null if
	* the chunk is not found or an error occurs
	*/
	public DataInputStream getChunkDataInputStream(int x, int z) throws IOException {
	if (outOfBounds(x, z)) {
	throw new IndexOutOfBoundsException();
	}

	int offset = getOffset(x, z);
	if (offset == 0) {
	// does not exist
	return null;
	}

	int sectorNumber = offset >> 8;
	int numSectors = offset & 0xFF;

	if (sectorNumber + numSectors > sectorFree.size()) {
	throw new IOException("Invalid sector");
	}

	file.seek(sectorNumber * SECTOR_BYTES);
	int length = file.readInt();

	if (length > SECTOR_BYTES * numSectors) {
	throw new IOException("Invalid length");
	}

	byte version = file.readByte();
	if (version == VERSION_GZIP) {
	byte[] data = new byte[length - 1];
	file.read(data);
	DataInputStream ret = new DataInputStream(new GZIPInputStream(new ByteArrayInputStream(data)));
	return ret;
	} else if (version == VERSION_DEFLATE) {
	byte[] data = new byte[length - 1];
	file.read(data);
	DataInputStream ret = new DataInputStream(new InflaterInputStream(new ByteArrayInputStream(data)));
	return ret;
	}

	throw new IOException("Unknown version");
	}

	public DataOutputStream getChunkDataOutputStream(int x, int z) {
	if (outOfBounds(x, z)) return null;

	return new DataOutputStream(new DeflaterOutputStream(new ChunkBuffer(x, z)));
	}

	/*
	* lets chunk writing be multithreaded by not locking the whole file as a
	* chunk is serializing -- only writes when serialization is over
	*/
	class ChunkBuffer extends ByteArrayOutputStream {
	private final int x, z;

	public ChunkBuffer(int x, int z) {
	super(8096); // initialize to 8KB
	this.x = x;
	this.z = z;
	}

	@Override
	public void close() throws IOException {
	try {
	RegionFile.this.write(x, z, buf, count);
	} finally {
	super.close();
	}
	}
	}

	/* write a chunk at (x,z) with length bytes of data to disk */
	protected void write(int x, int z, byte[] data, int length) throws IOException {
	int offset = getOffset(x, z);
	int sectorNumber = offset >> 8;
	int sectorsAllocated = offset & 0xFF;
	int sectorsNeeded = (length + CHUNK_HEADER_SIZE) / SECTOR_BYTES + 1;

	// maximum chunk size is 1MB
	if (sectorsNeeded >= 256) {
	return;
	}

	if (sectorNumber != 0 && sectorsAllocated == sectorsNeeded) {
	/* we can simply overwrite the old sectors */
	write(sectorNumber, data, length);
	} else {
	/* we need to allocate new sectors */

	/* mark the sectors previously used for this chunk as free */
	for (int i = 0; i < sectorsAllocated; ++i) {
	sectorFree.set(sectorNumber + i, true);
	}

	/* scan for a free space large enough to store this chunk */
	int runStart = sectorFree.indexOf(true);
	int runLength = 0;
	if (runStart != -1) {
	for (int i = runStart; i < sectorFree.size(); ++i) {
	if (runLength != 0) {
	if (sectorFree.get(i)) runLength++;
	else runLength = 0;
	} else if (sectorFree.get(i)) {
	runStart = i;
	runLength = 1;
	}
	if (runLength >= sectorsNeeded) {
	break;
	}
	}
	}

	if (runLength >= sectorsNeeded) {
	/* we found a free space large enough */
	sectorNumber = runStart;
	setOffset(x, z, (sectorNumber << 8) \| sectorsNeeded);
	for (int i = 0; i < sectorsNeeded; ++i) {
	sectorFree.set(sectorNumber + i, false);
	}
	write(sectorNumber, data, length);
	} else {
	/*
	* no free space large enough found -- we need to grow the
	* file
	*/
	file.seek(file.length());
	sectorNumber = sectorFree.size();
	for (int i = 0; i < sectorsNeeded; ++i) {
	file.write(emptySector);
	sectorFree.add(false);
	}
	sizeDelta += SECTOR_BYTES * sectorsNeeded;

	write(sectorNumber, data, length);
	setOffset(x, z, (sectorNumber << 8) \| sectorsNeeded);
	}
	}
	setTimestamp(x, z, (int) (System.currentTimeMillis() / 1000L));
	file.getChannel().force(true);
	}

	/* write a chunk data to the region file at specified sector number */
	private void write(int sectorNumber, byte[] data, int length) throws IOException {
	file.seek(sectorNumber * SECTOR_BYTES);
	file.writeInt(length + 1); // chunk length
	file.writeByte(VERSION_DEFLATE); // chunk version number
	file.write(data, 0, length); // chunk data
	}

	/* is this an invalid chunk coordinate? */
	private boolean outOfBounds(int x, int z) {
	return x < 0 \|\| x >= 32 \|\| z < 0 \|\| z >= 32;
	}

	private int getOffset(int x, int z) {
	return offsets[x + z * 32];
	}

	public boolean hasChunk(int x, int z) {
	return getOffset(x, z) != 0;
	}

	private void setOffset(int x, int z, int offset) throws IOException {
	offsets[x + z * 32] = offset;
	file.seek((x + z * 32) * 4);
	file.writeInt(offset);
	}

	private void setTimestamp(int x, int z, int value) throws IOException {
	chunkTimestamps[x + z * 32] = value;
	file.seek(SECTOR_BYTES + (x + z * 32) * 4);
	file.writeInt(value);
	}

	public void close() throws IOException {
	file.getChannel().force(true);
	file.close();
	}
	}