Use memory mapping and filter hidden files. (#44)

examples/codeviewer/common/src/commonMain/kotlin/org/jetbrains/codeviewer/platform/File.kt

@@ -11,5 +11,5 @@ interface File {
     val children: List<File>
     val hasChildren: Boolean
 
-    suspend fun readLines(backgroundScope: CoroutineScope): TextLines
+    fun readLines(scope: CoroutineScope): TextLines
 }

examples/codeviewer/common/src/commonMain/kotlin/org/jetbrains/codeviewer/ui/editor/Editor.kt

@@ -4,12 +4,13 @@ import androidx.compose.runtime.State
 import androidx.compose.runtime.mutableStateOf
 import kotlinx.coroutines.CoroutineScope
 import org.jetbrains.codeviewer.platform.File
+import org.jetbrains.codeviewer.util.EmptyTextLines
 import org.jetbrains.codeviewer.util.SingleSelection
 import org.jetbrains.codeviewer.util.afterSet
 
 class Editor(
     val fileName: String,
-    val lines: suspend (backgroundScope: CoroutineScope) -> Lines,
+    val lines: (backgroundScope: CoroutineScope) -> Lines,
 ) {
     var close: (() -> Unit)? = null
     lateinit var selection: SingleSelection
@@ -26,7 +27,7 @@ class Editor(
     interface Lines {
         val lineNumberDigitCount: Int get() = size.toString().length
         val size: Int
-        suspend fun get(index: Int): Line
+        fun get(index: Int): Line
     }
 
     class Content(val value: State<String>, val isCode: Boolean)
@@ -35,22 +36,24 @@ class Editor(
 fun Editor(file: File) = Editor(
     fileName = file.name
 ) { backgroundScope ->
-    val textLines = file.readLines(backgroundScope)
-    val indexToEditedText = mutableMapOf<Int, String>()
+    val textLines = try {
+        file.readLines(backgroundScope)
+    } catch (e: Throwable) {
+        e.printStackTrace()
+        EmptyTextLines
+    }
     val isCode = file.name.endsWith(".kt", ignoreCase = true)
 
-    suspend fun content(index: Int): Editor.Content {
-        val text = indexToEditedText[index] ?: textLines.get(index)
-        val state = mutableStateOf(text).afterSet {
-            indexToEditedText[index] = it
-        }
+    fun content(index: Int): Editor.Content {
+        val text = textLines.get(index)
+        val state = mutableStateOf(text)
         return Editor.Content(state, isCode)
     }
 
     object : Editor.Lines {
         override val size get() = textLines.size
 
-        override suspend fun get(index: Int) = Editor.Line(
+        override fun get(index: Int) = Editor.Line(
             number = index + 1,
             content = content(index)
         )

examples/codeviewer/common/src/commonMain/kotlin/org/jetbrains/codeviewer/util/Loadable.kt

@@ -5,12 +5,12 @@ import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.CoroutineScope
 
 @Composable
-fun <T : Any> loadable(load: suspend () -> T): MutableState<T?> {
+fun <T : Any> loadable(load: () -> T): MutableState<T?> {
     return loadableScoped { load() }
 }
 
 @Composable
-fun <T : Any> loadableScoped(load: suspend CoroutineScope.() -> T): MutableState<T?> {
+fun <T : Any> loadableScoped(load: CoroutineScope.() -> T): MutableState<T?> {
     val state: MutableState<T?> = remember { mutableStateOf(null) }
     LaunchedTask {
         try {

examples/codeviewer/common/src/commonMain/kotlin/org/jetbrains/codeviewer/util/TextLines.kt

@@ -2,5 +2,12 @@ package org.jetbrains.codeviewer.util
 
 interface TextLines {
     val size: Int
-    suspend fun get(index: Int): String
+    fun get(index: Int): String
+}
+
+object EmptyTextLines : TextLines {
+    override val size: Int
+        get() = 0
+
+    override fun get(index: Int): String = ""
 }

examples/codeviewer/common/src/jvmMain/kotlin/org/jetbrains/codeviewer/platform/JvmFile.kt

@@ -6,9 +6,11 @@ import androidx.compose.runtime.setValue
 import kotlinx.coroutines.*
 import org.jetbrains.codeviewer.util.TextLines
 import java.io.FileInputStream
+import java.io.FilenameFilter
 import java.io.IOException
 import java.io.RandomAccessFile
 import java.nio.channels.FileChannel
+import java.nio.charset.StandardCharsets
 
 fun java.io.File.toProjectFile(): File = object : File {
     override val name: String get() = this@toProjectFile.name
@@ -17,72 +19,67 @@ fun java.io.File.toProjectFile(): File = object : File {
 
     override val children: List<File>
         get() = this@toProjectFile
-            .listFiles()
+            .listFiles(FilenameFilter { _, name -> !name.startsWith(".")})
             .orEmpty()
             .map { it.toProjectFile() }
 
     override val hasChildren: Boolean
         get() = isDirectory && listFiles()?.size ?: 0 > 0
 
-    override suspend fun readLines(backgroundScope: CoroutineScope): TextLines {
-        // linePositions can be very big, so we are using IntList instead of List<Long>
-        val linePositions = IntList()
+
+    override fun readLines(scope: CoroutineScope): TextLines {
+        var byteBufferSize: Int
+        val byteBuffer = RandomAccessFile(this@toProjectFile, "r").use { file ->
+            byteBufferSize = file.length().toInt()
+            file.channel
+                .map(FileChannel.MapMode.READ_ONLY, 0, file.length())
+        }
+
+        val lineStartPositions = IntList()
+
         var size by mutableStateOf(0)
 
-        val refreshJob = backgroundScope.launch {
+        val refreshJob = scope.launch {
             delay(100)
-            size = linePositions.size
+            size = lineStartPositions.size
             while (true) {
                 delay(1000)
-                size = linePositions.size
+                size = lineStartPositions.size
             }
         }
 
-        backgroundScope.launch {
-            readLinePositions(linePositions)
+        scope.launch(Dispatchers.IO) {
+            readLinePositions(lineStartPositions)
             refreshJob.cancel()
-            size = linePositions.size
+            size = lineStartPositions.size
         }
 
         return object : TextLines {
             override val size get() = size
 
-            override suspend fun get(index: Int): String {
-                return withContext(Dispatchers.IO) {
-                    val position = linePositions[index]
-                    try {
-                        RandomAccessFile(this@toProjectFile, "rws").use {
-                            it.seek(position.toLong())
-                            // NOTE: it isn't efficient, but simple
-                            String(
-                                it.readLine()
-                                    .toCharArray()
-                                    .map(Char::toByte)
-                                    .toByteArray(),
-                                Charsets.UTF_8
-                            )
-                        }
-                    } catch (e: IOException) {
-                        e.printStackTrace()
-                        "<Error on opening the file>"
-                    }
-                }
+            override fun get(index: Int): String {
+                val startPosition = lineStartPositions[index]
+                val length = if (index + 1 < size) lineStartPositions[index + 1] - startPosition else
+                    byteBufferSize - startPosition
+                // Only JDK since 13 has slice() method we need, so do ugly for now.
+                byteBuffer.position(startPosition)
+                val slice = byteBuffer.slice()
+                slice.limit(length)
+                return StandardCharsets.UTF_8.decode(slice).toString()
             }
         }
     }
 }
 
-@Suppress("BlockingMethodInNonBlockingContext")
-private suspend fun java.io.File.readLinePositions(list: IntList) = withContext(Dispatchers.IO) {
+private fun java.io.File.readLinePositions(
+    starts: IntList
+) {
     require(length() <= Int.MAX_VALUE) {
         "Files with size over ${Int.MAX_VALUE} aren't supported"
     }
 
     val averageLineLength = 200
-    list.clear(length().toInt() / averageLineLength)
-
-    var isBeginOfLine = true
-    var position = 0L
+    starts.clear(length().toInt() / averageLineLength)
 
     try {
         FileInputStream(this@readLinePositions).use {
@@ -90,22 +87,25 @@ private suspend fun java.io.File.readLinePositions(list: IntList) = withContext(
             val ib = channel.map(
                 FileChannel.MapMode.READ_ONLY, 0, channel.size()
             )
+            var isBeginOfLine = true
+            var position = 0L
             while (ib.hasRemaining()) {
                 val byte = ib.get()
                 if (isBeginOfLine) {
-                    list.add(position.toInt())
+                    starts.add(position.toInt())
                 }
                 isBeginOfLine = byte.toChar() == '\n'
                 position++
             }
+            channel.close()
         }
     } catch (e: IOException) {
         e.printStackTrace()
-        list.clear(1)
-        list.add(0)
+        starts.clear(1)
+        starts.add(0)
     }
 
-    list.compact()
+    starts.compact()
 }
 
 /**

examples/codeviewer/desktop/src/jvmMain/kotlin/org/jetbrains/codeviewer/main.kt

@@ -6,15 +6,21 @@ import androidx.compose.ui.unit.IntSize
 import org.jetbrains.codeviewer.ui.MainView
 import java.awt.image.BufferedImage
 import javax.imageio.ImageIO
+import javax.swing.SwingUtilities.invokeLater
 
 @OptIn(ExperimentalLayout::class)
-fun main() = Window(
+fun main() {
+    invokeLater {
+        Window(
             title = "Code Viewer",
             size = IntSize(1280, 768),
             icon = loadImageResource("ic_launcher.png")
         ) {
             MainView()
         }
+    }
+}
+
 
 @Suppress("SameParameterValue")
 private fun loadImageResource(path: String): BufferedImage {