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Commit af311506 authored by Juan Sebastian Martinez's avatar Juan Sebastian Martinez
Browse files

Using an efficient circular buffer as a logging structure. 

ArrayDequeue maintains an internal variable-size array that can grow
unnecessarily when adding elements. This could lead to performance
issues and crashes such as the ones reported in the bugs below. We can
avoid this overhead by implementing a minimal ring buffer to log MSDL
events.

Test: Unit tests
Flag: com.android.systemui.msdl_feedback
Bug: 421673110
Bug: 422056230
Change-Id: I54625ff7f1b2ebc4f78bc6329bd1a9790759d0e2
parent 5cc433e3

msdllib/src/com/google/android/msdl/logging/MSDLHistoryLogger.kt

+1 −1
Original line number Diff line number Diff line
@@ -34,7 +34,7 @@ interface MSDLHistoryLogger { 


    companion object {



        const val HISTORY_SIZE = 20

        const val HISTORY_SIZE = 50

        val DATE_FORMAT = SimpleDateFormat("MM-dd HH:mm:ss.SSS", Locale.US)

    }

}

msdllib/src/com/google/android/msdl/logging/MSDLHistoryLoggerImpl.kt

+14 −10
Original line number Diff line number Diff line
@@ -18,22 +18,26 @@ package com.google.android.msdl.logging 


import androidx.annotation.VisibleForTesting

import androidx.annotation.VisibleForTesting.Companion.PACKAGE_PRIVATE

import java.util.ArrayDeque

import java.util.Deque



@VisibleForTesting(otherwise = PACKAGE_PRIVATE)

class MSDLHistoryLoggerImpl(private val maxHistorySize: Int) : MSDLHistoryLogger {



    // Use an [ArrayDequeue] with a fixed size as the history structure

    private val history: Deque<MSDLEvent> = ArrayDeque(maxHistorySize)

    // Use an Array with a fixed size as the history structure. This will work as a ring buffer

    private val history: Array<MSDLEvent?> = arrayOfNulls(size = maxHistorySize)

    // The head will point to the next available position in the structure to add a new event

    private var head = 0



    override fun addEvent(event: MSDLEvent) {

        // Keep the history as a FIFO structure

        if (history.size == maxHistorySize) {

            history.removeFirst()

        }

        history.addLast(event)

        history[head] = event

        // Move the head pointer, wrapping if necessary

        head = (head + 1) % maxHistorySize

    }



    override fun getHistory(): List<MSDLEvent> = history.toList()

    override fun getHistory(): List<MSDLEvent> {

        val result = mutableListOf<MSDLEvent>()

        repeat(times = maxHistorySize) { i ->

            history[(i + head) % maxHistorySize]?.let { result.add(it) }

        }

        return result

    }

}