DataStore —— SharedPreferences 的替代者 ？

interface DataStore<T> {
    val dataFlow: Flow<T>
    suspend fun updateData(transform: suspend (t: T) -> T): T
    interface Serializer<T> {
        fun readFrom(input: InputStream): T
        fun writeTo(t: T, output: OutputStream)
        val defaultValue: T
    }
    // TODO(b/151635324): Add initializers.
    // TODO(b/151635324): Add exception handlers.
    // TODO(b/151635324): Consider adding snapshot API.
}
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class SingleProcessDataStore<T>(
    private val produceFile: () -> File,
    private val serializer: DataStore.Serializer<T>,
    private val scope: CoroutineScope = CoroutineScope(Dispatchers.IO + SupervisorJob())
) : DataStore<T> {
    ......
    private suspend fun readData(): T {
        // TODO(b/151635324): consider caching produceFile result.
        val file = produceFile()
        try {
            FileInputStream(file).use { stream ->
                return serializer.readFrom(stream)
            }
        } catch (ex: FileNotFoundException) {
            if (file.exists()) {
                throw ex
            }
            return serializer.defaultValue
        }
    }
    private fun writeData(newData: T) {
        // TODO(b/151635324): consider caching produceFile result.
        val file = produceFile()
        file.mkdirs()
        val scratchFile = File(file.absolutePath + SCRATCH_SUFFIX)
        try {
            FileOutputStream(scratchFile).use { stream ->
                serializer.writeTo(newData, stream)
                stream.fd.sync()
                // TODO(b/151635324): fsync the directory, otherwise a badly timed crash could
                //  result in reverting to a przuihouevious state.
            }
            scratchFile.renameTo(file)
        } catch (ex: IOException) {
            if (scratchFile.exists()) {
                scratchFile.delete()
            }
            throw ex
        }
    }
    ......
}
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