package net.CyanWool.api.io;
/*
** 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).
*
*/
// 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 java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.GZIPInputStream;
import java.util.zip.InflaterInputStream;
public class RegionFile {
public static final String ANVIL_EXTENSION = ".mca";
public static final String MCREGION_EXTENSION = ".mcr";
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[4096];
private final File fileName;
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) {
offsets = new int[SECTOR_INTS];
chunkTimestamps = new int[SECTOR_INTS];
fileName = path;
debugln("REGION LOAD " + fileName);
sizeDelta = 0;
try {
if (path.exists()) {
lastModified = path.lastModified();
}
file = new RandomAccessFile(path, "rw");
if (file.length() < SECTOR_BYTES) {
/* we need to write the chunk offset table */
for (int i = 0; i < SECTOR_INTS; ++i) {
file.writeInt(0);
}
// write another sector for the timestamp info
for (int i = 0; i < SECTOR_INTS; ++i) {
file.writeInt(0);
}
sizeDelta += SECTOR_BYTES * 2;
}
if ((file.length() & 0xfff) != 0) {
/* the file size is not a multiple of 4KB, grow it */
for (int i = 0; i < (file.length() & 0xfff); ++i) {
file.write((byte) 0);
}
}
/* set up the available sector map */
int nSectors = (int) file.length() / SECTOR_BYTES;
sectorFree = new ArrayList<Boolean>(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
file.seek(0);
for (int i = 0; i < SECTOR_INTS; ++i) {
int offset = file.readInt();
offsets[i] = offset;
if (offset != 0 && (offset >> 8) + (offset & 0xFF) <= sectorFree.size()) {
for (int sectorNum = 0; sectorNum < (offset & 0xFF); ++sectorNum) {
sectorFree.set((offset >> 8) + sectorNum, false);
}
}
}
for (int i = 0; i < SECTOR_INTS; ++i) {
int lastModValue = file.readInt();
chunkTimestamps[i] = lastModValue;
}
} catch (IOException e) {
e.printStackTrace();
}
}
/* 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 synchronized int getSizeDelta() {
int ret = sizeDelta;
sizeDelta = 0;
return ret;
}
// various small debug printing helpers
private void debug(String in) {
System.out.print(in);
}
private void debugln(String in) {
debug(in + "\n");
}
private void debug(String mode, int x, int z, String in) {
debug("REGION " + mode + " " + fileName.getName() + "[" + x + "," + z + "] = " + in);
}
private void debug(String mode, int x, int z, int count, String in) {
debug("REGION " + mode + " " + fileName.getName() + "[" + x + "," + z + "] " + count + "B = " + in);
}
private void debugln(String mode, int x, int z, String in) {
debug(mode, x, z, in + "\n");
}
/*
* gets an (uncompressed) stream representing the chunk data returns null if
* the chunk is not found or an error occurs
*/
public synchronized DataInputStream getChunkDataInputStream(int x, int z) {
if (outOfBounds(x, z)) {
debugln("READ", x, z, "out of bounds");
return null;
}
try {
int offset = getOffset(x, z);
if (offset == 0) {
// debugln("READ", x, z, "miss");
return null;
}
int sectorNumber = offset >> 8;
int numSectors = offset & 0xFF;
if (sectorNumber + numSectors > sectorFree.size()) {
debugln("READ", x, z, "invalid sector");
return null;
}
file.seek(sectorNumber * SECTOR_BYTES);
int length = file.readInt();
if (length > SECTOR_BYTES * numSectors) {
debugln("READ", x, z, "invalid length: " + length + " > 4096 * " + numSectors);
return null;
}
byte version = file.readByte();
if (version == VERSION_GZIP) {
byte[] data = new byte[length - 1];
file.read(data);
DataInputStream ret = new DataInputStream(new BufferedInputStream(new GZIPInputStream(new ByteArrayInputStream(data))));
// debug("READ", x, z, " = found");
return ret;
} else if (version == VERSION_DEFLATE) {
byte[] data = new byte[length - 1];
file.read(data);
DataInputStream ret = new DataInputStream(new BufferedInputStream(new InflaterInputStream(new ByteArrayInputStream(data))));
// debug("READ", x, z, " = found");
return ret;
}
debugln("READ", x, z, "unknown version " + version);
return null;
} catch (IOException e) {
debugln("READ", x, z, "exception");
return null;
}
}
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 int x, z;
public ChunkBuffer(int x, int z) {
super(8096); // initialize to 8KB
this.x = x;
this.z = z;
}
@Override
public void close() {
RegionFile.this.write(x, z, buf, count);
}
}
/* write a chunk at (x,z) with length bytes of data to disk */
protected synchronized void write(int x, int z, byte[] data, int length) {
try {
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 */
debug("SAVE", x, z, length, "rewrite");
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 */
debug("SAVE", x, z, length, "reuse");
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
*/
debug("SAVE", x, z, length, "grow");
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));
} catch (IOException e) {
e.printStackTrace();
}
}
/* write a chunk data to the region file at specified sector number */
private void write(int sectorNumber, byte[] data, int length) throws IOException {
debugln(" " + sectorNumber);
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.close();
}
}