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.Deflater;
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;
private 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 getLastModified() {
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 {
checkBounds(x, z);
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: " + sectorNumber + "+" + numSectors + " > " + sectorFree.size());
}
file.seek(sectorNumber * SECTOR_BYTES);
int length = file.readInt();
if (length > SECTOR_BYTES * numSectors) {
throw new IOException("Invalid length: " + length + " > " + (SECTOR_BYTES * numSectors));
}
byte version = file.readByte();
if (version == VERSION_GZIP) {
byte[] data = new byte[length - 1];
file.read(data);
return new DataInputStream(new GZIPInputStream(new ByteArrayInputStream(data)));
} else if (version == VERSION_DEFLATE) {
byte[] data = new byte[length - 1];
file.read(data);
return new DataInputStream(new InflaterInputStream(new ByteArrayInputStream(data)));
}
throw new IOException("Unknown version: " + version);
}
public DataOutputStream getChunkDataOutputStream(int x, int z) {
checkBounds(x, z);
return new DataOutputStream(new DeflaterOutputStream(new ChunkBuffer(x, z), new Deflater(Deflater.BEST_SPEED)));
}
/*
* 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 void checkBounds(int x, int z) {
if (x < 0 || x >= 32 || z < 0 || z >= 32) {
throw new IllegalArgumentException("Chunk out of bounds: (" + x + ", " + z + ")");
}
}
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();
}
}