From 7abf31ea821a0bbddb836adb1a63d0fec2ceee4f Mon Sep 17 00:00:00 2001
From: Leonard Kugis <leonard@kug.is>
Date: Mon, 25 Apr 2022 18:41:24 +0200
Subject: Initial commit

---
 .../instancedregions/chunkmap/ChunkReader.java     | 100 +++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100755 src/main/java/com/encrox/instancedregions/chunkmap/ChunkReader.java

(limited to 'src/main/java/com/encrox/instancedregions/chunkmap/ChunkReader.java')

diff --git a/src/main/java/com/encrox/instancedregions/chunkmap/ChunkReader.java b/src/main/java/com/encrox/instancedregions/chunkmap/ChunkReader.java
new file mode 100755
index 0000000..a05fa7a
--- /dev/null
+++ b/src/main/java/com/encrox/instancedregions/chunkmap/ChunkReader.java
@@ -0,0 +1,100 @@
+/**
+ * @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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