DfsBlock.java

/*
 * 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;
    }
}