mirror of https://github.com/M66B/FairEmail.git
101 lines
3.1 KiB
Java
101 lines
3.1 KiB
Java
/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package androidx.room;
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import androidx.annotation.RestrictTo;
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import androidx.sqlite.db.SupportSQLiteStatement;
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import java.util.concurrent.atomic.AtomicBoolean;
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/**
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* Represents a prepared SQLite state that can be re-used multiple times.
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* <p>
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* This class is used by generated code. After it is used, {@code release} must be called so that
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* it can be used by other threads.
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* <p>
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* To avoid re-entry even within the same thread, this class allows only 1 time access to the shared
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* statement until it is released.
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*
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* @hide
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*/
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@SuppressWarnings({"WeakerAccess", "unused"})
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@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP_PREFIX)
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public abstract class SharedSQLiteStatement {
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private final AtomicBoolean mLock = new AtomicBoolean(false);
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private final RoomDatabase mDatabase;
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private volatile SupportSQLiteStatement mStmt;
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/**
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* Creates an SQLite prepared statement that can be re-used across threads. If it is in use,
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* it automatically creates a new one.
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*
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* @param database The database to create the statement in.
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*/
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public SharedSQLiteStatement(RoomDatabase database) {
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mDatabase = database;
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}
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/**
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* Create the query.
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*
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* @return The SQL query to prepare.
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*/
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protected abstract String createQuery();
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protected void assertNotMainThread() {
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mDatabase.assertNotMainThread();
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}
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private SupportSQLiteStatement createNewStatement() {
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String query = createQuery();
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return mDatabase.compileStatement(query);
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}
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private SupportSQLiteStatement getStmt(boolean canUseCached) {
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final SupportSQLiteStatement stmt;
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if (canUseCached) {
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if (mStmt == null) {
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mStmt = createNewStatement();
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}
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stmt = mStmt;
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} else {
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// it is in use, create a one off statement
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stmt = createNewStatement();
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}
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return stmt;
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}
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/**
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* Call this to get the statement. Must call {@link #release(SupportSQLiteStatement)} once done.
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*/
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public SupportSQLiteStatement acquire() {
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assertNotMainThread();
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return getStmt(mLock.compareAndSet(false, true));
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}
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/**
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* Must call this when statement will not be used anymore.
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*
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* @param statement The statement that was returned from acquire.
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*/
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public void release(SupportSQLiteStatement statement) {
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if (statement == mStmt) {
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mLock.set(false);
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}
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}
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}
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