src/main/java/com/google/gerrit/server/patch/DiffCacheContent.java

// Copyright (C) 2009 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.gerrit.server.patch;

import org.spearce.jgit.diff.Edit;
import org.spearce.jgit.lib.FileMode;
import org.spearce.jgit.patch.CombinedFileHeader;
import org.spearce.jgit.patch.FileHeader;
import org.spearce.jgit.patch.Patch;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public final class DiffCacheContent implements Serializable {
  // Note: If we modify our version, also modify DiffCacheKey, so
  // the on disk cache is fully destroyed and recreated when the
  // schema has changed.
  //
  private static final long serialVersionUID = DiffCacheKey.serialVersionUID;

  public static DiffCacheContent create(final FileHeader file) {
    return new DiffCacheContent(file);
  }

  public static DiffCacheContent createEmpty() {
    return new DiffCacheContent();
  }

  private transient FileHeader header;
  private transient List<Edit> edits;

  private DiffCacheContent() {
    header = null;
    edits = Collections.emptyList();
  }

  private DiffCacheContent(final FileHeader h) {
    header = compact(h);

    if (h == null || h instanceof CombinedFileHeader || h.getHunks().isEmpty()
        || h.getOldMode() == FileMode.GITLINK
        || h.getNewMode() == FileMode.GITLINK) {
      edits = Collections.emptyList();
    } else {
      edits = Collections.unmodifiableList(h.toEditList());
    }
  }

  public FileHeader getFileHeader() {
    return header;
  }

  public List<Edit> getEdits() {
    return edits;
  }

  private void writeObject(final ObjectOutputStream out) throws IOException {
    if (header != null) {
      final int hdrLen = end(header) - header.getStartOffset();
      out.writeInt(hdrLen);
      out.write(header.getBuffer(), header.getStartOffset(), hdrLen);
    } else {
      out.writeInt(0);
    }

    out.writeInt(edits.size());
    for (final Edit e : edits) {
      out.writeInt(e.getBeginA());
      out.writeInt(e.getEndA());
      out.writeInt(e.getBeginB());
      out.writeInt(e.getEndB());
    }
  }

  private void readObject(final ObjectInputStream in) throws IOException {
    final int hdrLen = in.readInt();
    if (hdrLen > 0) {
      final byte[] buf = new byte[hdrLen];
      in.readFully(buf);
      header = parse(buf);
    } else {
      header = null;
    }

    final int editCount = in.readInt();
    if (editCount > 0) {
      final Edit[] editArray = new Edit[editCount];
      for (int i = 0; i < editCount; i++) {
        final int beginA = in.readInt();
        final int endA = in.readInt();
        final int beginB = in.readInt();
        final int endB = in.readInt();
        editArray[i] = new Edit(beginA, endA, beginB, endB);
      }
      edits = Collections.unmodifiableList(Arrays.asList(editArray));
    } else {
      edits = Collections.emptyList();
    }
  }

  private static FileHeader parse(final byte[] buf) {
    final Patch p = new Patch();
    p.parse(buf, 0, buf.length);
    return p.getFiles().get(0);
  }

  private static FileHeader compact(final FileHeader h) {
    final int end = end(h);
    if (h.getStartOffset() == 0 && end == h.getBuffer().length) {
      return h;
    }

    final byte[] buf = new byte[end - h.getStartOffset()];
    System.arraycopy(h.getBuffer(), h.getStartOffset(), buf, 0, buf.length);
    return parse(buf);
  }

  private static int end(final FileHeader h) {
    if (h instanceof CombinedFileHeader) {
      return h.getEndOffset();
    }
    if (!h.getHunks().isEmpty()) {
      return h.getHunks().get(0).getStartOffset();
    }
    return h.getEndOffset();
  }
}