mirror of https://github.com/M66B/FairEmail.git
88 lines
2.7 KiB
Kotlin
88 lines
2.7 KiB
Kotlin
/*
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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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*
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* This class is used by generated code. After it is used, `release` must be called so that
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* it can be used by other threads.
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*
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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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* @constructor Creates an SQLite prepared statement that can be re-used across threads. If it is
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* in use, it automatically creates a new one.
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*
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*/
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@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP_PREFIX)
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abstract class SharedSQLiteStatement(private val database: RoomDatabase) {
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private val lock = AtomicBoolean(false)
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private val stmt: SupportSQLiteStatement by lazy {
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createNewStatement()
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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 fun createQuery(): String
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protected open fun assertNotMainThread() {
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database.assertNotMainThread()
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}
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private fun createNewStatement(): SupportSQLiteStatement {
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val query = createQuery()
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return database.compileStatement(query)
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}
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private fun getStmt(canUseCached: Boolean): SupportSQLiteStatement {
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val stmt = if (canUseCached) {
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stmt
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} else {
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// it is in use, create a one off statement
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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 [.release] once done.
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*/
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open fun acquire(): SupportSQLiteStatement {
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assertNotMainThread()
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return getStmt(lock.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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open fun release(statement: SupportSQLiteStatement) {
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if (statement === stmt) {
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lock.set(false)
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}
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}
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}
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