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/**
* @author Aleksey Terzi
*
*/
package com.encrox.instancedregions.chunkmap;
import java.io.IOException;
public class ChunkReader {
private byte[] data;
private int bitsPerBlock;
private long maxValueMask;
private int byteIndex;
private int bitIndex;
private long buffer;
public ChunkReader(byte[] data) {
this.data = data;
this.byteIndex = 0;
this.bitIndex = 0;
}
public int getByteIndex() {
return this.byteIndex;
}
public void skip(int count) {
this.byteIndex += count;
this.bitIndex = 0;
}
public void setBitsPerBlock(int bitsPerBlock) {
this.bitsPerBlock = bitsPerBlock;
this.maxValueMask = (1L << this.bitsPerBlock) - 1;
}
public int readBlockBits() throws IOException {
if(this.bitIndex == 0 || this.bitIndex >= 64) {
readLong();
this.bitIndex = 0;
}
int leftBits = 64 - this.bitIndex;
long result = this.buffer >>> this.bitIndex;
if(leftBits >= this.bitsPerBlock) {
this.bitIndex += this.bitsPerBlock;
} else {
readLong();
result |= this.buffer << leftBits;
this.bitIndex = this.bitsPerBlock - leftBits;
}
return (int)(result & this.maxValueMask);
}
private void readLong() throws IOException {
if(this.byteIndex + 7 >= this.data.length) {
throw new IOException("No data to read.");
}
this.buffer = ((this.data[this.byteIndex] & 0xffL) << 56)
| ((this.data[this.byteIndex + 1] & 0xffL) << 48)
| ((this.data[this.byteIndex + 2] & 0xffL) << 40)
| ((this.data[this.byteIndex + 3] & 0xffL) << 32)
| ((this.data[this.byteIndex + 4] & 0xffL) << 24)
| ((this.data[this.byteIndex + 5] & 0xffL) << 16)
| ((this.data[this.byteIndex + 6] & 0xffL) << 8)
| (this.data[this.byteIndex + 7] & 0xffL);
this.byteIndex += 8;
}
public int readVarInt() throws IOException {
int value = 0;
int size = 0;
int b;
while(((b = readByte()) & 0x80) == 0x80) {
value |= (b & 0x7F) << (size++ * 7);
if(size > 5) {
throw new IOException("Invalid VarInt.");
}
}
return value | ((b & 0x7F) << (size * 7));
}
public int readByte() throws IOException {
if(this.byteIndex >= this.data.length) {
throw new IOException("No data to read.");
}
return this.data[this.byteIndex++] & 0xff;
}
}
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