/*
* Copyright (C) 2012 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.android.gallery3d.data;
import java.util.ArrayList;
// FilterDeleteSet filters a base MediaSet to remove some deletion items (we
// expect the number to be small). The user can use the following methods to
// add/remove deletion items:
//
// void addDeletion(Path path, int index);
// void removeDelection(Path path);
// void clearDeletion();
// int getNumberOfDeletions();
//
public class FilterDeleteSet extends MediaSet implements ContentListener {
@SuppressWarnings("unused")
private static final String TAG = "FilterDeleteSet";
private static final int REQUEST_ADD = 1;
private static final int REQUEST_REMOVE = 2;
private static final int REQUEST_CLEAR = 3;
private static class Request {
int type; // one of the REQUEST_* constants
Path path;
int indexHint;
public Request(int type, Path path, int indexHint) {
this.type = type;
this.path = path;
this.indexHint = indexHint;
}
}
private static class Deletion {
Path path;
int index;
public Deletion(Path path, int index) {
this.path = path;
this.index = index;
}
}
// The underlying MediaSet
private final MediaSet mBaseSet;
// Pending Requests
private ArrayList<Request> mRequests = new ArrayList<Request>();
// Deletions currently in effect, ordered by index
private ArrayList<Deletion> mCurrent = new ArrayList<Deletion>();
public FilterDeleteSet(Path path, MediaSet baseSet) {
super(path, INVALID_DATA_VERSION);
mBaseSet = baseSet;
mBaseSet.addContentListener(this);
}
@Override
public boolean isCameraRoll() {
return mBaseSet.isCameraRoll();
}
@Override
public String getName() {
return mBaseSet.getName();
}
@Override
public int getMediaItemCount() {
return mBaseSet.getMediaItemCount() - mCurrent.size();
}
// Gets the MediaItems whose (post-deletion) index are in the range [start,
// start + count). Because we remove some of the MediaItems, the index need
// to be adjusted.
//
// For example, if there are 12 items in total. The deleted items are 3, 5,
// 10, and the the requested range is [3, 7]:
//
// The original index: 0 1 2 3 4 5 6 7 8 9 A B C
// The deleted items: X X X
// The new index: 0 1 2 3 4 5 6 7 8 9
// Requested: * * * * *
//
// We need to figure out the [3, 7] actually maps to the original index 4,
// 6, 7, 8, 9.
//
// We can break the MediaItems into segments, each segment other than the
// last one ends in a deleted item. The difference between the new index and
// the original index increases with each segment:
//
// 0 1 2 X (new index = old index)
// 4 X (new index = old index - 1)
// 6 7 8 9 X (new index = old index - 2)
// B C (new index = old index - 3)
//
@Override
public ArrayList<MediaItem> getMediaItem(int start, int count) {
if (count <= 0) return new ArrayList<MediaItem>();
int end = start + count - 1;
int n = mCurrent.size();
// Find the segment that "start" falls into. Count the number of items
// not yet deleted until it reaches "start".
int i = 0;
for (i = 0; i < n; i++) {
Deletion d = mCurrent.get(i);
if (d.index - i > start) break;
}
// Find the segment that "end" falls into.
int j = i;
for (; j < n; j++) {
Deletion d = mCurrent.get(j);
if (d.index - j > end) break;
}
// Now get enough to cover deleted items in [start, end]
ArrayList<MediaItem> base = mBaseSet.getMediaItem(start + i, count + (j - i));
// Remove the deleted items.
for (int m = j - 1; m >= i; m--) {
Deletion d = mCurrent.get(m);
int k = d.index - (start + i);
base.remove(k);
}
return base;
}
// We apply the pending requests in the mRequests to construct mCurrent in reload().
@Override
public long reload() {
boolean newData = mBaseSet.reload() > mDataVersion;
synchronized (mRequests) {
if (!newData && mRequests.isEmpty()) {
return mDataVersion;
}
for (int i = 0; i < mRequests.size(); i++) {
Request r = mRequests.get(i);
switch (r.type) {
case REQUEST_ADD: {
// Add the path into mCurrent if there is no duplicate.
int n = mCurrent.size();
int j;
for (j = 0; j < n; j++) {
if (mCurrent.get(j).path == r.path) break;
}
if (j == n) {
mCurrent.add(new Deletion(r.path, r.indexHint));
}
break;
}
case REQUEST_REMOVE: {
// Remove the path from mCurrent.
int n = mCurrent.size();
for (int j = 0; j < n; j++) {
if (mCurrent.get(j).path == r.path) {
mCurrent.remove(j);
break;
}
}
break;
}
case REQUEST_CLEAR: {
mCurrent.clear();
break;
}
}
}
mRequests.clear();
}
if (!mCurrent.isEmpty()) {
// See if the elements in mCurrent can be found in the MediaSet. We
// don't want to search the whole mBaseSet, so we just search a
// small window that contains the index hints (plus some margin).
int minIndex = mCurrent.get(0).index;
int maxIndex = minIndex;
for (int i = 1; i < mCurrent.size(); i++) {
Deletion d = mCurrent.get(i);
minIndex = Math.min(d.index, minIndex);
maxIndex = Math.max(d.index, maxIndex);
}
int n = mBaseSet.getMediaItemCount();
int from = Math.max(minIndex - 5, 0);
int to = Math.min(maxIndex + 5, n);
ArrayList<MediaItem> items = mBaseSet.getMediaItem(from, to - from);
ArrayList<Deletion> result = new ArrayList<Deletion>();
for (int i = 0; i < items.size(); i++) {
MediaItem item = items.get(i);
if (item == null) continue;
Path p = item.getPath();
// Find the matching path in mCurrent, if found move it to result
for (int j = 0; j < mCurrent.size(); j++) {
Deletion d = mCurrent.get(j);
if (d.path == p) {
d.index = from + i;
result.add(d);
mCurrent.remove(j);
break;
}
}
}
mCurrent = result;
}
mDataVersion = nextVersionNumber();
return mDataVersion;
}
private void sendRequest(int type, Path path, int indexHint) {
Request r = new Request(type, path, indexHint);
synchronized (mRequests) {
mRequests.add(r);
}
notifyContentChanged();
}
@Override
public void onContentDirty() {
notifyContentChanged();
}
public void addDeletion(Path path, int indexHint) {
sendRequest(REQUEST_ADD, path, indexHint);
}
public void removeDeletion(Path path) {
sendRequest(REQUEST_REMOVE, path, 0 /* unused */);
}
public void clearDeletion() {
sendRequest(REQUEST_CLEAR, null /* unused */ , 0 /* unused */);
}
// Returns number of deletions _in effect_ (the number will only gets
// updated after a reload()).
public int getNumberOfDeletions() {
return mCurrent.size();
}
}