1 /*
2  * Copyright (C) 2022 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.systemui.common.coroutine
18 
19 import kotlin.experimental.ExperimentalTypeInference
20 import kotlinx.coroutines.ExperimentalCoroutinesApi
21 import kotlinx.coroutines.channels.Channel
22 import kotlinx.coroutines.channels.ProducerScope
23 import kotlinx.coroutines.flow.Flow
24 import kotlinx.coroutines.flow.buffer
25 import kotlinx.coroutines.flow.callbackFlow
26 
27 object ConflatedCallbackFlow {
28 
29     /**
30      * A [callbackFlow] that uses a buffer [Channel] that is "conflated" meaning that, if
31      * backpressure occurs (if the producer that emits new values into the flow is faster than the
32      * consumer(s) of the values in the flow), the values are buffered and, if the buffer fills up,
33      * we drop the oldest values automatically instead of suspending the producer.
34      */
35     @Suppress("EXPERIMENTAL_IS_NOT_ENABLED")
36     @OptIn(ExperimentalTypeInference::class, ExperimentalCoroutinesApi::class)
37     fun <T> conflatedCallbackFlow(
38         @BuilderInference block: suspend ProducerScope<T>.() -> Unit,
39     ): Flow<T> = callbackFlow(block).buffer(capacity = Channel.CONFLATED)
40 }
41