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- /*
- ** 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.*;
- import java.util.ArrayList;
- import java.util.zip.*;
- 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[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 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 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;
- }
- 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();
- }
- }
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