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/*
* Copyright (C) 2017 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 android.arch.paging;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.annotation.RestrictTo;
import java.util.ArrayList;
import java.util.List;
/** @hide */
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
class PageArrayList<T> extends PagedList<T> {
// partial list of pages, doesn't include pages below the lowest accessed, or above the highest
final ArrayList<List<T>> mPages;
// to access page at index N, do mPages.get(N - mPageIndexOffset), but do bounds checking first!
int mPageIndexOffset;
final int mPageSize;
final int mCount;
final int mMaxPageCount;
PageArrayList(int pageSize, int count) {
mPages = new ArrayList<>();
mPageSize = pageSize;
mCount = count;
mMaxPageCount = (mCount + mPageSize - 1) / mPageSize;
}
private PageArrayList(PageArrayList<T> other) {
mPages = other.isImmutable() ? other.mPages : new ArrayList<>(other.mPages);
mPageIndexOffset = other.mPageIndexOffset;
mPageSize = other.mPageSize;
mCount = other.size();
mMaxPageCount = other.mMaxPageCount;
}
@Override
public T get(int index) {
if (index < 0 || index >= mCount) {
throw new IllegalArgumentException();
}
int localPageIndex = getLocalPageIndex(index);
List<T> page = getPage(localPageIndex);
if (page == null) {
// page empty
return null;
}
return page.get(index % mPageSize);
}
@Nullable
private List<T> getPage(int localPageIndex) {
if (localPageIndex < 0 || localPageIndex >= mPages.size()) {
// page not present
return null;
}
return mPages.get(localPageIndex);
}
private int getLocalPageIndex(int index) {
return index / mPageSize - mPageIndexOffset;
}
@Override
public void loadAround(int index) {
// do nothing - immutable, so no fetching will be done
}
@Override
public int size() {
return mCount;
}
@Override
public boolean isImmutable() {
return true;
}
boolean hasPage(int pageIndex) {
final int localPageIndex = pageIndex - mPageIndexOffset;
List<T> page = getPage(localPageIndex);
return page != null && page.size() != 0;
}
@Override
public PagedList<T> snapshot() {
if (isImmutable()) {
return this;
}
return new PageArrayList<>(this);
}
@Override
boolean isContiguous() {
return false;
}
@Override
public void addWeakCallback(@Nullable PagedList<T> previousSnapshot,
@NonNull Callback callback) {
// no op, immutable
}
@Override
public void removeWeakCallback(Callback callback) {
// no op, immutable
}
}
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