/*
    * Copyright (C) 2008-2011, Google Inc.
    * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
    * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
   * SPDX-License-Identifier: BSD-3-Clause
   */
  
  package org.eclipse.jgit.internal.storage.dfs;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.zip.CRC32;
  import java.util.zip.DataFormatException;
  import java.util.zip.Inflater;
  
  import org.eclipse.jgit.internal.storage.pack.PackOutputStream;
  
  /** A cached slice of a {@link BlockBasedFile}. */
  final class DfsBlock {
  	final DfsStreamKey stream;
  	final long start;
  	final long end;
  	private final byte[] block;
  
  	DfsBlock(DfsStreamKey p, long pos, byte[] buf) {
  		stream = p;
  		start = pos;
  		end = pos + buf.length;
  		block = buf;
  	}
  
  	int size() {
  		return block.length;
  	}
  
  	ByteBuffer zeroCopyByteBuffer(int n) {
  		ByteBuffer b = ByteBuffer.wrap(block);
  		b.position(n);
  		return b;
  	}
  
  	boolean contains(DfsStreamKey want, long pos) {
  		return stream.equals(want) && start <= pos && pos < end;
  	}
  
  	int copy(long pos, byte[] dstbuf, int dstoff, int cnt) {
  		int ptr = (int) (pos - start);
  		return copy(ptr, dstbuf, dstoff, cnt);
  	}
  
  	int copy(int p, byte[] b, int o, int n) {
  		n = Math.min(block.length - p, n);
  		System.arraycopy(block, p, b, o, n);
  		return n;
  	}
  
  	int setInput(long pos, Inflater inf) throws DataFormatException {
  		int ptr = (int) (pos - start);
  		int cnt = block.length - ptr;
  		if (cnt <= 0) {
  			throw new DataFormatException(cnt + " bytes to inflate:" //$NON-NLS-1$
  					+ " at pos=" + pos //$NON-NLS-1$
  					+ "; block.start=" + start //$NON-NLS-1$
  					+ "; ptr=" + ptr //$NON-NLS-1$
  					+ "; block.length=" + block.length); //$NON-NLS-1$
  		}
  		inf.setInput(block, ptr, cnt);
  		return cnt;
  	}
  
  	void crc32(CRC32 out, long pos, int cnt) {
  		int ptr = (int) (pos - start);
  		out.update(block, ptr, cnt);
  	}
  
  	void write(PackOutputStream out, long pos, int cnt)
  			throws IOException {
  		out.write(block, (int) (pos - start), cnt);
  	}
  
  	void check(Inflater inf, byte[] tmp, long pos, int cnt)
  			throws DataFormatException {
  		// Unlike inflate() above the exact byte count is known by the caller.
  		// Push all of it in a single invocation to avoid unnecessary loops.
  		//
  		inf.setInput(block, (int) (pos - start), cnt);
  		while (inf.inflate(tmp, 0, tmp.length) > 0)
  			continue;
  	}
  }