WrapperDataSource.kt
/*
* Copyright 2019 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 androidx.paging
import androidx.arch.core.util.Function
import java.util.IdentityHashMap
/**
* @param Key DataSource key type, same for original and wrapped.
* @param ValueFrom Value type of original DataSource.
* @param ValueTo Value type of new DataSource.
*/
internal open class WrapperDataSource<Key : Any, ValueFrom : Any, ValueTo : Any>(
private val source: DataSource<Key, ValueFrom>,
private val listFunction: Function<List<ValueFrom>, List<ValueTo>>
) : DataSource<Key, ValueTo>(source.type) {
private val keyMap = when (source.type) {
KeyType.ITEM_KEYED -> IdentityHashMap<ValueTo, Key>()
else -> null
}
override fun addInvalidatedCallback(onInvalidatedCallback: InvalidatedCallback) =
source.addInvalidatedCallback(onInvalidatedCallback)
override fun removeInvalidatedCallback(onInvalidatedCallback: InvalidatedCallback) =
source.removeInvalidatedCallback(onInvalidatedCallback)
override fun invalidate() = source.invalidate()
override val isInvalid
get() = source.isInvalid
override fun getKeyInternal(item: ValueTo): Key = when {
keyMap != null -> synchronized(keyMap) {
return keyMap[item]!!
}
// positional / page-keyed
else -> throw IllegalStateException("Cannot get key by item in non-item keyed DataSource")
}
@SuppressWarnings("WeakerAccess") /* synthetic access */
fun stashKeysIfNeeded(source: List<ValueFrom>, dest: List<ValueTo>) {
if (keyMap != null) {
synchronized(keyMap) {
for (i in dest.indices) {
@Suppress("DEPRECATION")
keyMap[dest[i]] = (this.source as ItemKeyedDataSource).getKey(source[i])
}
}
}
}
override suspend fun load(params: Params<Key>): BaseResult<ValueTo> {
val input = source.load(params)
val result = BaseResult.convert(input, listFunction)
stashKeysIfNeeded(input.data, result.data)
return result
}
}