├── .gitignore ├── .idea └── vcs.xml ├── LICENSE ├── README.md ├── build.gradle ├── coroutines-tutorial-basic-jvm.md ├── coroutines-tutorial-nio.md ├── gradle └── wrapper │ ├── gradle-wrapper.jar │ └── gradle-wrapper.properties ├── gradlew ├── gradlew.bat ├── local.properties ├── new_gradle_project_jvm.png ├── new_mvn_project_jvm.png ├── settings.gradle └── src ├── main └── kotlin │ └── kotlinx │ └── coroutines │ └── examples │ └── AsyncFileReadWrite.kt └── test ├── kotlin ├── CoroutinesTutorialTest.kt └── ForEachLineTest.kt └── resources └── example.txt /.gitignore: -------------------------------------------------------------------------------- 1 | *.class 2 | 3 | # Mobile Tools for Java (J2ME) 4 | .mtj.tmp/ 5 | 6 | # Package Files # 7 | *.jar 8 | *.war 9 | *.ear 10 | 11 | # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml 12 | hs_err_pid* 13 | -------------------------------------------------------------------------------- /.idea/vcs.xml: -------------------------------------------------------------------------------- 1 | 2 | 3 | 4 | 5 | 6 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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Introduction to Kotlin coroutines on the JVM 2 | 3 | Kotlin 1.1 introduced coroutines, a new way of writing asynchronous, non-blocking code (and much more). In this tutorial we will go through some basics of using Kotlin coroutines with the help of the `kotlinx.coroutines` library, which is a collection of helpers and wrappers for existing Java libraries. 4 | 5 | ## Setting up a project 6 | 7 | ### Gradle 8 | 9 | In IntelliJ IDEA go to *File -> New > Project...*: 10 | 11 | 12 | 13 | Then follow the wizard steps. You'll have a `build.gradle` file created with Kotlin configured according to [this tutorial](https://kotlinlang.org/docs/reference/using-gradle.html). Make sure it's configured for Kotlin 1.1 or higher. 14 | 15 | Since coroutines have the *experimental* status in Kotlin 1.1, by default the compiler reports a warning every time they are used. We can opt-in for the experimental feature and use it without a warning by adding this code to `build.gradle`: 16 | 17 | ```groovy 18 | apply plugin: 'kotlin' 19 | 20 | kotlin { 21 | experimental { 22 | coroutines 'enable' 23 | } 24 | } 25 | ``` 26 | 27 | Since we'll be using the [`kotlinx.corotuines`](https://github.com/Kotlin/kotlinx.coroutines), let's add it to our dependencies: 28 | 29 | ```groovy 30 | dependencies { 31 | ... 32 | compile "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.0" 33 | } 34 | ``` 35 | 36 | That's it, we are good to go and write code under `src/main/kotlin`. 37 | 38 | ### Maven 39 | 40 | In IntelliJ IDEA go to *File -> New > Project...* and check the *Create from archetype* box: 41 | 42 | 43 | 44 | Then follow the wizard steps. You'll have a `pom.xml` file created with Kotlin configured according to [this tutorial](https://kotlinlang.org/docs/reference/using-maven.html). Make sure it's configured for Kotlin 1.1 or higher. 45 | 46 | Since coroutines have the *experimental* status in Kotlin 1.1, by default the compiler reports a warning every time they are used. We can opt-in for the experimental feature and use it without a warning by adding this code to `pom.xml`: 47 | 48 | ```xml 49 | 50 | org.jetbrains.kotlin 51 | kotlin-maven-plugin 52 | ... 53 | 54 | 55 | -Xcoroutines=enable 56 | 57 | 58 | 59 | ``` 60 | 61 | Since we'll be using the [`kotlinx.corotuines`](https://github.com/Kotlin/kotlinx.coroutines), let's add it to our dependencies: 62 | 63 | ```xml 64 | 65 | ... 66 | 67 | org.jetbrains.kotlin 68 | kotlinx-coroutines-core 69 | 1.0 70 | 71 | 72 | ``` 73 | 74 | That's it, we are good to go and write code under `src/main/kotlin`. 75 | 76 | ## My first coroutine 77 | 78 | One can think of a coroutine as a light-weight thread. Like threads, coroutines can run in parallel, wait for each other and communicate. The biggest difference is that coroutines are very cheap, almost free: we can create thousands of them, and pay very little in terms of performance. True threads, on the other hand, expensive to start and keep around. A thousand threads can be a serious challenge for a modern machine. 79 | 80 | So, how do we start a coroutine? Let's use the `launch {}` function: 81 | 82 | ```kotlin 83 | launch(CommonPool) { 84 | ... 85 | } 86 | ``` 87 | 88 | This starts a new coroutine on a given thread pool. In this case we are using `CommonPool` that uses `ForkJoinPool.commonPool()`. Threads still exist in a program based on coroutines, but one thread can run many coroutines, so there's no need for too many threads. 89 | 90 | Let's look at a full program that uses `launch`: 91 | 92 | 93 | ```kotlin 94 | import kotlinx.coroutines.experimental.* 95 | 96 | fun main(args: Array) { 97 | println("Start") 98 | 99 | // Start a coroutine 100 | launch(CommonPool) { 101 | delay(1000) 102 | println("Hello") 103 | } 104 | 105 | Thread.sleep(2000) // wait for 2 seconds 106 | println("Stop") 107 | } 108 | ``` 109 | 110 | Here we start a coroutine that waits for 1 second and prints `Hello`. 111 | 112 | We are using the `delay()` function that's like `Thread.sleep()`, but better: it _doesn't block a thread_, but only suspends the coroutine itself. The thread is returned to the pool while te coroutine is waiting, when the waiting is done, the coroutine resumes on some free thread in the pool. 113 | 114 | The main thread (that runs the `main()` function) must wait until our coroutine completes, otherwise the program ends before `Hello` is printed. 115 | 116 | _Exercise: try removing the `sleep()` from the program above and see the result._ 117 | 118 | If we try to use the same non-blocking `delay()` function directly inside `main()`, we'll get a compiler error: 119 | 120 | > Suspend functions are only allowed to be called from a coroutine or another suspend function 121 | 122 | This is because we are not inside any coroutine. We can use delay if we wrap it into `runBlocking {}` that starts a coroutine and waits until it's done: 123 | 124 | ```kotlin 125 | runBlocking { 126 | delay(2000) 127 | } 128 | ``` 129 | 130 | So, first the resulting program prints `Start`, then it runs a coroutine through `launch {}`, then it runs another one through `runBlocking {}` and blocks until it's done, then prints `Stop`. Meanwhile the first coroutine completes and prints `Hello`. Just like threads, we told you :) 131 | 132 | ## Let's run a lot of them 133 | 134 | Now, let's make sure that coroutines are really cheaper than threads. How a bout starting a million of them? Let's begin by start a million threads first: 135 | 136 | ```kotlin 137 | val c = AtomicInteger() 138 | 139 | for (i in 1..1_000_000) 140 | thread(start = true) { 141 | c.addAndGet(i) 142 | } 143 | 144 | println(c.get()) 145 | ``` 146 | 147 | This runs a 1'000'000 threads each of which adds to a common counter. My patience runs out before this program completes on my machine (definitely over a minute). 148 | 149 | Let's try the same with coroutines: 150 | 151 | ```kotlin 152 | val c = AtomicInteger() 153 | 154 | for (i in 1..1_000_000) 155 | launch(CommonPool) { 156 | c.addAndGet(i) 157 | } 158 | 159 | println(c.get()) 160 | ``` 161 | 162 | Completes in less than a second for me. But prints some arbitrary number, because some coroutines don't finish before `main()` prints the result. Let's fix that. 163 | 164 | We could use the same means of synchronization that are applicable to threads (a `CountDownLatch` is what crosses my mind in this case), but let's take a safer and cleaner path. 165 | 166 | 167 | ## Async: returning a value from a coroutine 168 | 169 | Another way of starting a coroutine is `async {}`. It is like `launch {}`, but returns an instance of `Deferred`, which has an `await()` function that return a result of the coroutine. `Deferred` is a very basic [future](https://en.wikipedia.org/wiki/Futures_and_promises) (fully-fledged JDK futures are also supported, but here we'll confine ourselves to `Deferred` for now). 170 | 171 | 172 | Let's create a million coroutines again, keeping their `Deferred` objects. Now there's no need in the atomic counter, as we can just return the numbers to be added from our coroutines: 173 | 174 | ```kotlin 175 | val deferred = (1..1_000_000).map { n -> 176 | async (CommonPool) { 177 | n 178 | } 179 | } 180 | ``` 181 | 182 | All these have already started, all we need is collect the results: 183 | 184 | ```kotlin 185 | val sum = deferred.sumBy { it.await() } 186 | ``` 187 | 188 | We simply take every coroutine and await its result here, then all results are added together by the standard library function `sumBy()`. But the compiler rightfully complains: 189 | 190 | > Suspend functions are only allowed to be called from a coroutine or another suspend function 191 | 192 | `await()` can not be called outside a coroutine, because it needs to suspend until the computation finishes, and only coroutines can suspend in a non-blocking way. So, let's put this inside a coroutine: 193 | 194 | ```kotlin 195 | runBlocking { 196 | val sum = deferred.sumBy { it.await() } 197 | println("Sum: $sum") 198 | } 199 | ``` 200 | 201 | Now it prints something sensible: `1784293664`, because all coroutines complete. 202 | 203 | Let's also make sure that our coroutines actually run in parallel. If we add a 1-second `delay()` to each of the `async`'s, the resulting program won't run for 1'000'000 seconds (over 11,5 days): 204 | 205 | ```kotlin 206 | val deferred = (1..1_000_000).map { n -> 207 | async (CommonPool) { 208 | delay(1000) 209 | n 210 | } 211 | } 212 | ``` 213 | 214 | This takes about 10 seconds on my machine, so yes, coroutines do run in parallel. 215 | 216 | ## Suspending functions 217 | 218 | Now, let's say we want to extract our _workload_ (which is "wait 1 second and return a number") into a separate function: 219 | 220 | ```kotlin 221 | fun workload(n: Int): Int { 222 | delay(1000) 223 | return n 224 | } 225 | ``` 226 | 227 | A familiar error pops up: 228 | 229 | > Suspend functions are only allowed to be called from a coroutine or another suspend function 230 | 231 | Let's dig a little into what it means. The biggest merit of coroutines is that they can _suspend_ without blocking a thread. The compiler has to emit some special code to make this possible, so we have to mark functions that _may suspend_ explicitly in the code. We use the `suspend` modifier for it: 232 | 233 | ```kotlin 234 | suspend fun workload(n: Int): Int { 235 | delay(1000) 236 | return n 237 | } 238 | ``` 239 | 240 | Now when we call `workload()` from a coroutine, the compiler knows that it may suspend and will prepare accordingly: 241 | 242 | ```kotlin 243 | async (CommonPool) { 244 | workload(n) 245 | } 246 | ``` 247 | 248 | Our `workload()` function can be called from a coroutine (or another suspending function), but _can not_ be called from outside a coroutine. Naturally, `delay()` and `await()` that we used above are themselves declared as `suspend`, and this is why we had to put them inside `runBlocking {}`, `launch {}` or `async {}`. 249 | -------------------------------------------------------------------------------- /coroutines-tutorial-nio.md: -------------------------------------------------------------------------------- 1 | # Tutorial. Introduction to NIO with Kotlin coroutines 2 | 3 | ## Setting up a project 4 | 5 | TODO 6 | 7 | Gradle, Maven, IntelliJ IDEA 8 | 9 | * enable coroutines 10 | * add dependency on kotlinx.coroutines 11 | 12 | 13 | Let's look at some common APIs. Java 7 added `AsynchronousFileChannel` and other non-blocking IO APIs. The `kotlinx-coroutines-nio` library wraps these APIs into coroutines making them nice and straightforward. 14 | 15 | Gradle: 16 | ```gradle 17 | compile 'org.jetbrains.kotlinx:kotlinx-coroutines-nio:0.6-rc' 18 | ``` 19 | 20 | Maven: TODO 21 | 22 | 23 | 24 | ## Non-blocking IO 25 | 26 | 27 | -------------------------------------------------------------------------------- /gradle/wrapper/gradle-wrapper.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/abreslav/kotlin-coroutines-tutorial/41d552bef87c75f17ea539c562c53930d4847614/gradle/wrapper/gradle-wrapper.jar -------------------------------------------------------------------------------- /gradle/wrapper/gradle-wrapper.properties: -------------------------------------------------------------------------------- 1 | #Wed Jan 25 15:39:32 MSK 2017 2 | distributionBase=GRADLE_USER_HOME 3 | distributionPath=wrapper/dists 4 | zipStoreBase=GRADLE_USER_HOME 5 | zipStorePath=wrapper/dists 6 | distributionUrl=https\://services.gradle.org/distributions/gradle-3.1-all.zip 7 | -------------------------------------------------------------------------------- /gradlew: -------------------------------------------------------------------------------- 1 | #!/usr/bin/env bash 2 | 3 | ############################################################################## 4 | ## 5 | ## Gradle start up script for UN*X 6 | ## 7 | ############################################################################## 8 | 9 | # Attempt to set APP_HOME 10 | # Resolve links: $0 may be a link 11 | PRG="$0" 12 | # Need this for relative symlinks. 13 | while [ -h "$PRG" ] ; do 14 | ls=`ls -ld "$PRG"` 15 | link=`expr "$ls" : '.*-> \(.*\)$'` 16 | if expr "$link" : '/.*' > /dev/null; then 17 | PRG="$link" 18 | else 19 | PRG=`dirname "$PRG"`"/$link" 20 | fi 21 | done 22 | SAVED="`pwd`" 23 | cd "`dirname \"$PRG\"`/" >/dev/null 24 | APP_HOME="`pwd -P`" 25 | cd "$SAVED" >/dev/null 26 | 27 | APP_NAME="Gradle" 28 | APP_BASE_NAME=`basename "$0"` 29 | 30 | # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. 31 | DEFAULT_JVM_OPTS="" 32 | 33 | # Use the maximum available, or set MAX_FD != -1 to use that value. 34 | MAX_FD="maximum" 35 | 36 | warn ( ) { 37 | echo "$*" 38 | } 39 | 40 | die ( ) { 41 | echo 42 | echo "$*" 43 | echo 44 | exit 1 45 | } 46 | 47 | # OS specific support (must be 'true' or 'false'). 48 | cygwin=false 49 | msys=false 50 | darwin=false 51 | nonstop=false 52 | case "`uname`" in 53 | CYGWIN* ) 54 | cygwin=true 55 | ;; 56 | Darwin* ) 57 | darwin=true 58 | ;; 59 | MINGW* ) 60 | msys=true 61 | ;; 62 | NONSTOP* ) 63 | nonstop=true 64 | ;; 65 | esac 66 | 67 | CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar 68 | 69 | # Determine the Java command to use to start the JVM. 70 | if [ -n "$JAVA_HOME" ] ; then 71 | if [ -x "$JAVA_HOME/jre/sh/java" ] ; then 72 | # IBM's JDK on AIX uses strange locations for the executables 73 | JAVACMD="$JAVA_HOME/jre/sh/java" 74 | else 75 | JAVACMD="$JAVA_HOME/bin/java" 76 | fi 77 | if [ ! -x "$JAVACMD" ] ; then 78 | die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME 79 | 80 | Please set the JAVA_HOME variable in your environment to match the 81 | location of your Java installation." 82 | fi 83 | else 84 | JAVACMD="java" 85 | which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 86 | 87 | Please set the JAVA_HOME variable in your environment to match the 88 | location of your Java installation." 89 | fi 90 | 91 | # Increase the maximum file descriptors if we can. 92 | if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then 93 | MAX_FD_LIMIT=`ulimit -H -n` 94 | if [ $? -eq 0 ] ; then 95 | if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then 96 | MAX_FD="$MAX_FD_LIMIT" 97 | fi 98 | ulimit -n $MAX_FD 99 | if [ $? -ne 0 ] ; then 100 | warn "Could not set maximum file descriptor limit: $MAX_FD" 101 | fi 102 | else 103 | warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT" 104 | fi 105 | fi 106 | 107 | # For Darwin, add options to specify how the application appears in the dock 108 | if $darwin; then 109 | GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\"" 110 | fi 111 | 112 | # For Cygwin, switch paths to Windows format before running java 113 | if $cygwin ; then 114 | APP_HOME=`cygpath --path --mixed "$APP_HOME"` 115 | CLASSPATH=`cygpath --path --mixed "$CLASSPATH"` 116 | JAVACMD=`cygpath --unix "$JAVACMD"` 117 | 118 | # We build the pattern for arguments to be converted via cygpath 119 | ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null` 120 | SEP="" 121 | for dir in $ROOTDIRSRAW ; do 122 | ROOTDIRS="$ROOTDIRS$SEP$dir" 123 | SEP="|" 124 | done 125 | OURCYGPATTERN="(^($ROOTDIRS))" 126 | # Add a user-defined pattern to the cygpath arguments 127 | if [ "$GRADLE_CYGPATTERN" != "" ] ; then 128 | OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)" 129 | fi 130 | # Now convert the arguments - kludge to limit ourselves to /bin/sh 131 | i=0 132 | for arg in "$@" ; do 133 | CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -` 134 | CHECK2=`echo "$arg"|egrep -c "^-"` ### Determine if an option 135 | 136 | if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then ### Added a condition 137 | eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"` 138 | else 139 | eval `echo args$i`="\"$arg\"" 140 | fi 141 | i=$((i+1)) 142 | done 143 | case $i in 144 | (0) set -- ;; 145 | (1) set -- "$args0" ;; 146 | (2) set -- "$args0" "$args1" ;; 147 | (3) set -- "$args0" "$args1" "$args2" ;; 148 | (4) set -- "$args0" "$args1" "$args2" "$args3" ;; 149 | (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;; 150 | (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;; 151 | (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;; 152 | (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;; 153 | (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;; 154 | esac 155 | fi 156 | 157 | # Split up the JVM_OPTS And GRADLE_OPTS values into an array, following the shell quoting and substitution rules 158 | function splitJvmOpts() { 159 | JVM_OPTS=("$@") 160 | } 161 | eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS 162 | JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME" 163 | 164 | # by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong 165 | if [[ "$(uname)" == "Darwin" ]] && [[ "$HOME" == "$PWD" ]]; then 166 | cd "$(dirname "$0")" 167 | fi 168 | 169 | exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@" 170 | -------------------------------------------------------------------------------- /gradlew.bat: -------------------------------------------------------------------------------- 1 | @if "%DEBUG%" == "" @echo off 2 | @rem ########################################################################## 3 | @rem 4 | @rem Gradle startup script for Windows 5 | @rem 6 | @rem ########################################################################## 7 | 8 | @rem Set local scope for the variables with windows NT shell 9 | if "%OS%"=="Windows_NT" setlocal 10 | 11 | set DIRNAME=%~dp0 12 | if "%DIRNAME%" == "" set DIRNAME=. 13 | set APP_BASE_NAME=%~n0 14 | set APP_HOME=%DIRNAME% 15 | 16 | @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. 17 | set DEFAULT_JVM_OPTS= 18 | 19 | @rem Find java.exe 20 | if defined JAVA_HOME goto findJavaFromJavaHome 21 | 22 | set JAVA_EXE=java.exe 23 | %JAVA_EXE% -version >NUL 2>&1 24 | if "%ERRORLEVEL%" == "0" goto init 25 | 26 | echo. 27 | echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 28 | echo. 29 | echo Please set the JAVA_HOME variable in your environment to match the 30 | echo location of your Java installation. 31 | 32 | goto fail 33 | 34 | :findJavaFromJavaHome 35 | set JAVA_HOME=%JAVA_HOME:"=% 36 | set JAVA_EXE=%JAVA_HOME%/bin/java.exe 37 | 38 | if exist "%JAVA_EXE%" goto init 39 | 40 | echo. 41 | echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 42 | echo. 43 | echo Please set the JAVA_HOME variable in your environment to match the 44 | echo location of your Java installation. 45 | 46 | goto fail 47 | 48 | :init 49 | @rem Get command-line arguments, handling Windows variants 50 | 51 | if not "%OS%" == "Windows_NT" goto win9xME_args 52 | 53 | :win9xME_args 54 | @rem Slurp the command line arguments. 55 | set CMD_LINE_ARGS= 56 | set _SKIP=2 57 | 58 | :win9xME_args_slurp 59 | if "x%~1" == "x" goto execute 60 | 61 | set CMD_LINE_ARGS=%* 62 | 63 | :execute 64 | @rem Setup the command line 65 | 66 | set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar 67 | 68 | @rem Execute Gradle 69 | "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS% 70 | 71 | :end 72 | @rem End local scope for the variables with windows NT shell 73 | if "%ERRORLEVEL%"=="0" goto mainEnd 74 | 75 | :fail 76 | rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of 77 | rem the _cmd.exe /c_ return code! 78 | if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1 79 | exit /b 1 80 | 81 | :mainEnd 82 | if "%OS%"=="Windows_NT" endlocal 83 | 84 | :omega 85 | -------------------------------------------------------------------------------- /local.properties: -------------------------------------------------------------------------------- 1 | kotlin.coroutines=enable 2 | kotlin.incremental=true -------------------------------------------------------------------------------- /new_gradle_project_jvm.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/abreslav/kotlin-coroutines-tutorial/41d552bef87c75f17ea539c562c53930d4847614/new_gradle_project_jvm.png -------------------------------------------------------------------------------- /new_mvn_project_jvm.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/abreslav/kotlin-coroutines-tutorial/41d552bef87c75f17ea539c562c53930d4847614/new_mvn_project_jvm.png -------------------------------------------------------------------------------- /settings.gradle: -------------------------------------------------------------------------------- 1 | rootProject.name = 'kotlin-coroutines-tutorial' 2 | 3 | -------------------------------------------------------------------------------- /src/main/kotlin/kotlinx/coroutines/examples/AsyncFileReadWrite.kt: -------------------------------------------------------------------------------- 1 | package kotlinx.coroutines.examples 2 | 3 | import kotlinx.coroutines.experimental.nio.aRead 4 | import kotlinx.coroutines.experimental.nio.aWrite 5 | import java.nio.ByteBuffer 6 | import java.nio.CharBuffer 7 | import java.nio.channels.AsynchronousFileChannel 8 | import java.nio.charset.Charset 9 | import java.nio.charset.MalformedInputException 10 | import java.nio.file.Path 11 | import java.nio.file.StandardOpenOption 12 | import java.nio.file.attribute.FileAttribute 13 | import java.util.* 14 | import java.util.concurrent.ExecutorService 15 | 16 | 17 | internal const val DEFAULT_BLOCK_SIZE: Int = 4096 18 | internal const val MINIMUM_BLOCK_SIZE: Int = 512 19 | 20 | public fun Path.openChannel(vararg options: StandardOpenOption): AsynchronousFileChannel { 21 | return AsynchronousFileChannel.open(this, *options) 22 | } 23 | 24 | public fun Path.openChannel( 25 | options: Set, 26 | executor: ExecutorService? = null, 27 | vararg attrs: FileAttribute<*> 28 | ) = AsynchronousFileChannel.open(this, options, executor, *attrs) 29 | 30 | // NOT asynchronous enough: arrays are copied synchronously 31 | public suspend fun Path.aReadBytes(): ByteArray = openChannel(StandardOpenOption.READ).use { input -> 32 | var remaining = input.size().let { 33 | if (it > Int.MAX_VALUE) throw OutOfMemoryError("File $this is too big ($it bytes) to fit in memory.") else it 34 | }.toInt() 35 | val result = ByteArray(remaining) 36 | val buf = ByteBuffer.allocate(DEFAULT_BUFFER_SIZE) 37 | 38 | var offset = 0L 39 | while (remaining > 0) { 40 | val read = input.aRead(buf, offset) 41 | if (read < 0) break 42 | System.arraycopy(buf.array(), 0, result, offset.toInt(), read) 43 | remaining -= read 44 | offset += read 45 | } 46 | 47 | if (remaining == 0) result else result.copyOf(offset.toInt()) 48 | } 49 | 50 | public suspend fun Path.aWriteBytes(array: ByteArray): Unit = openChannel(StandardOpenOption.WRITE, StandardOpenOption.CREATE).use { 51 | it.aWrite(ByteBuffer.wrap(array), 0) 52 | } 53 | 54 | public suspend fun Path.aAppendBytes(array: ByteArray): Unit = openChannel(StandardOpenOption.APPEND).use { 55 | it.aWrite(ByteBuffer.wrap(array), 0) 56 | } 57 | 58 | public suspend fun Path.aReadText(charset: Charset = Charsets.UTF_8): String = aReadBytes().toString(charset) 59 | 60 | public suspend fun Path.aWriteText(text: String, charset: Charset = Charsets.UTF_8): Unit = aWriteBytes(text.toByteArray(charset)) 61 | 62 | public suspend fun Path.aAppendText(text: String, charset: Charset = Charsets.UTF_8): Unit = aAppendBytes(text.toByteArray(charset)) 63 | 64 | // TODO: ByteArray or ByteBuffer? 65 | public suspend fun Path.aForEachBlock(action: suspend (buffer: ByteArray, bytesRead: Int) -> Unit): Unit = aForEachBlock(DEFAULT_BLOCK_SIZE, action) 66 | 67 | public suspend fun Path.aForEachBlock(blockSize: Int, action: suspend (buffer: ByteArray, bytesRead: Int) -> Unit): Unit { 68 | val buf = ByteBuffer.allocate(blockSize.coerceAtLeast(MINIMUM_BLOCK_SIZE)) 69 | openChannel(StandardOpenOption.READ).use { 70 | channel -> 71 | var position = 0L 72 | while (true) { 73 | val read = channel.aRead(buf, position) 74 | if (read <= 0) { 75 | break 76 | } else { 77 | buf.flip() 78 | action(buf.array(), read) 79 | } 80 | position += read 81 | } 82 | } 83 | } 84 | 85 | public suspend fun Path.aForEachLine(charset: Charset = Charsets.UTF_8, action: suspend (line: String) -> Unit): Unit { 86 | val builder = StringBuilder() 87 | val decoder = charset.newDecoder() 88 | var chars = CharBuffer.allocate(DEFAULT_BLOCK_SIZE) 89 | var totalRead = 0 90 | // TODO: leftover bytes have to be prepended to the next buffer 91 | aForEachBlock { buffer, bytesRead -> 92 | chars.clear() 93 | if (bytesRead > chars.length) { 94 | chars = CharBuffer.allocate(bytesRead) 95 | } 96 | totalRead += bytesRead 97 | val result = decoder.decode(ByteBuffer.wrap(buffer, 0, bytesRead), chars, false /*no information, actually*/) 98 | if (result.isError) { 99 | throw MalformedInputException(totalRead) 100 | } 101 | chars.flip() 102 | 103 | var start = 0 104 | var pos = 0 105 | val length = chars.length 106 | 107 | fun trimCrLength(pos: Int) = pos - if (pos > 0 && chars[pos - 1] == '\r') 1 else 0 108 | fun substringWithBuilder(start: Int, end: Int): String { 109 | builder.append(chars, start, end) 110 | val substr = builder.toString() 111 | builder.setLength(0) 112 | return substr 113 | } 114 | 115 | while (pos < length) { 116 | val c = chars[pos] 117 | when (c) { 118 | '\n' -> { 119 | action(substringWithBuilder(start, trimCrLength(pos))) 120 | start = pos + 1 121 | 122 | } 123 | '\r' -> { 124 | val nextChar = if (pos + 1 < length) chars[pos + 1] else null 125 | 126 | action(substringWithBuilder(start, pos)) 127 | if (nextChar == '\n') { 128 | pos++ 129 | } 130 | start = pos + 1 131 | } 132 | } 133 | pos++ 134 | } 135 | 136 | if (start < length) { 137 | builder.append(chars, start, trimCrLength(length)) 138 | } 139 | } 140 | if (builder.isNotEmpty()) { 141 | action(builder.toString()) 142 | } 143 | } 144 | 145 | public suspend fun Path.aReadLines(charset: Charset = Charsets.UTF_8): List { 146 | val result = ArrayList() 147 | aForEachLine(charset) { result.add(it); } 148 | return result 149 | } 150 | 151 | //public fun AsynchronousFileChannel.lineSequence(): Sequence = LinesSequence(this).constrainOnce() 152 | 153 | -------------------------------------------------------------------------------- /src/test/kotlin/CoroutinesTutorialTest.kt: -------------------------------------------------------------------------------- 1 | 2 | import kotlinx.coroutines.examples.aForEachLine 3 | import kotlinx.coroutines.examples.openChannel 4 | import kotlinx.coroutines.experimental.* 5 | import kotlinx.coroutines.experimental.nio.aRead 6 | import org.junit.Test 7 | import java.lang.StringBuilder 8 | import java.nio.ByteBuffer 9 | import java.nio.channels.AsynchronousFileChannel 10 | import java.nio.file.Paths 11 | import java.nio.file.StandardOpenOption 12 | import java.util.concurrent.CountDownLatch 13 | import java.util.concurrent.atomic.AtomicInteger 14 | import kotlin.concurrent.thread 15 | 16 | class CoroutinesTutorialTest { 17 | @Test 18 | fun launchWithThreadSleep() { 19 | println("Start") 20 | 21 | // Start a coroutine 22 | launch(CommonPool) { 23 | delay(1000) 24 | println("Hello") 25 | } 26 | 27 | Thread.sleep(2000) // wait for 2 seconds 28 | println("Stop") 29 | } 30 | 31 | @Test 32 | fun launchWithRunBlocking() { 33 | println("Start") 34 | 35 | // Start a coroutine 36 | launch(CommonPool) { 37 | delay(1000) 38 | println("Hello") 39 | } 40 | 41 | runBlocking { 42 | delay(2000) 43 | } 44 | println("Stop") 45 | } 46 | 47 | @Test 48 | fun thousandThreads() { 49 | val c = AtomicInteger() 50 | 51 | for (i in 1..1_000) 52 | thread(start = true) { 53 | c.addAndGet(i) 54 | } 55 | 56 | println(c.get()) 57 | } 58 | 59 | @Test 60 | fun thousandLaunches() { 61 | val c = AtomicInteger() 62 | 63 | for (i in 1..1_000) 64 | launch(CommonPool) { 65 | c.addAndGet(i) 66 | } 67 | 68 | println(c.get()) 69 | } 70 | 71 | @Test 72 | fun millionThreads() { 73 | val c = AtomicInteger() 74 | 75 | for (i in 1..1_000_000) 76 | thread(start = true) { 77 | c.addAndGet(i) 78 | } 79 | 80 | println(c.get()) 81 | } 82 | 83 | @Test 84 | fun millionLaunches() { 85 | val c = AtomicInteger() 86 | 87 | for (i in 1..1_000_000) 88 | launch(CommonPool) { 89 | c.addAndGet(i) 90 | } 91 | 92 | println(c.get()) 93 | } 94 | 95 | @Test 96 | fun millionLaunchesLatch() { 97 | val c = AtomicInteger() 98 | val latch = CountDownLatch(1_000_000) 99 | 100 | for (i in 1..1_000_000) 101 | launch(CommonPool) { 102 | c.addAndGet(i) 103 | latch.countDown() 104 | } 105 | 106 | latch.await() 107 | println(c.get()) 108 | } 109 | 110 | @Test 111 | fun millionDefers() { 112 | val deferred = (1..1_000_000).map { n -> 113 | defer (CommonPool) { 114 | n 115 | } 116 | } 117 | 118 | runBlocking { 119 | val sum = deferred.sumBy { it.await() } 120 | println("Sum: $sum") 121 | } 122 | } 123 | 124 | @Test 125 | fun millionDefersWithDelay() { 126 | val deferred = (1..1_000_000).map { n -> 127 | defer (CommonPool) { 128 | delay(1000) 129 | n 130 | } 131 | } 132 | 133 | runBlocking { 134 | val sum = deferred.sumBy { it.await() } 135 | println("Sum: $sum") 136 | } 137 | } 138 | 139 | suspend fun workload(n: Int): Int { 140 | delay(1000) 141 | return n 142 | } 143 | 144 | @Test 145 | fun millionDefersWithDelayExtractFun() { 146 | val deferred = (1..1_000_000).map { n -> 147 | defer (CommonPool) { 148 | workload(n) 149 | } 150 | } 151 | 152 | runBlocking { 153 | val sum = deferred.sumBy { it.await() } 154 | println("Sum: $sum") 155 | } 156 | } 157 | 158 | @Test 159 | fun readFile() { 160 | val file = Paths.get("src/test/resources/example.txt").openChannel(StandardOpenOption.READ) 161 | val buf = ByteBuffer.allocate(64) 162 | 163 | runBlocking { 164 | var position = 0L 165 | 166 | while (true) { 167 | val count = file.aRead(buf, position) 168 | if (count < 0) break 169 | position += count 170 | buf.flip() 171 | 172 | print(String(buf.array(), 0, count)) 173 | } 174 | 175 | } 176 | 177 | file.close() 178 | } 179 | 180 | suspend fun AsynchronousFileChannel.aReadBytes(bufferSize: Int = 1024, handleChunk: (ByteBuffer, Int) -> Unit) { 181 | val buf = ByteBuffer.allocate(bufferSize) 182 | var position = 0L 183 | 184 | while (true) { 185 | val count = aRead(buf, position) 186 | if (count < 0) break 187 | position += count 188 | buf.flip() 189 | 190 | handleChunk(buf, count) 191 | } 192 | } 193 | 194 | @Test 195 | fun aReadBytes() { 196 | val file = Paths.get("src/test/resources/example.txt").openChannel(StandardOpenOption.READ) 197 | runBlocking { 198 | file.aReadBytes(64) { buf, count -> 199 | println(String(buf.array(), 0, count)) 200 | } 201 | } 202 | } 203 | 204 | suspend fun AsynchronousFileChannel.aReadText( 205 | bufferSize: Int = 1024, 206 | builder: StringBuilder = StringBuilder() 207 | ): CharSequence { 208 | aReadBytes(bufferSize) { buf, count -> 209 | builder.append(String(buf.array(), 0, count)) 210 | } 211 | return builder 212 | } 213 | 214 | @Test 215 | fun aReadText() { 216 | val file = Paths.get("src/test/resources/example.txt").openChannel(StandardOpenOption.READ) 217 | runBlocking { 218 | println(file.aReadText()) 219 | } 220 | } 221 | 222 | @Test 223 | fun forEachLine() { 224 | val file = Paths.get("src/test/resources/example.txt") 225 | runBlocking { 226 | file.aForEachLine { 227 | println("|$it|") 228 | } 229 | } 230 | } 231 | } -------------------------------------------------------------------------------- /src/test/kotlin/ForEachLineTest.kt: -------------------------------------------------------------------------------- 1 | 2 | import kotlinx.coroutines.examples.aForEachLine 3 | import kotlinx.coroutines.experimental.runBlocking 4 | import org.junit.Assert 5 | import org.junit.Test 6 | import org.junit.runner.RunWith 7 | import org.junit.runners.Parameterized 8 | import java.io.StringReader 9 | 10 | @RunWith(Parameterized::class) 11 | class ForEachLineTest(val multiplier: Int) { 12 | companion object { 13 | @JvmStatic 14 | @Parameterized.Parameters(name = "String size multiplier = {0}") 15 | fun data(): Collection> { 16 | return listOf( 17 | arrayOf(1), 18 | arrayOf(1024), 19 | arrayOf(4 * 1024), 20 | arrayOf(8 * 1024), 21 | arrayOf(16 * 1024), 22 | arrayOf(239239) 23 | ) 24 | } 25 | } 26 | 27 | fun doTest(text: String) = runBlocking { 28 | val preparedText = if (multiplier > 1) { 29 | buildString { 30 | for (c in text) { 31 | if (c !in "\r\n") { 32 | append("$c".repeat(multiplier)) 33 | } else { 34 | append(c) 35 | } 36 | } 37 | } 38 | } else { 39 | text 40 | } 41 | 42 | 43 | val tempFile = createTempFile("tmp") 44 | try { 45 | tempFile.writeText(preparedText) 46 | val lines = arrayListOf() 47 | tempFile.toPath().aForEachLine { 48 | lines.add(it) 49 | } 50 | 51 | val expected = StringReader(preparedText).readLines() 52 | 53 | Assert.assertEquals(expected, lines) 54 | } finally { 55 | tempFile.deleteOnExit() 56 | } 57 | } 58 | 59 | @Test 60 | fun empty() { 61 | doTest("") 62 | } 63 | 64 | @Test 65 | fun lf() { 66 | doTest("\n") 67 | } 68 | 69 | @Test 70 | fun cr() { 71 | doTest("\r") 72 | } 73 | 74 | @Test 75 | fun crlf() { 76 | doTest("\r\n") 77 | } 78 | 79 | @Test 80 | fun lfcr() { 81 | doTest("\n\r") 82 | } 83 | 84 | @Test 85 | fun crcr() { 86 | doTest("\r\r") 87 | } 88 | 89 | @Test 90 | fun lflf() { 91 | doTest("\n\n") 92 | } 93 | 94 | @Test 95 | fun singleChar() { 96 | doTest("a") 97 | } 98 | 99 | @Test 100 | fun singleLine() { 101 | doTest("abc") 102 | } 103 | 104 | @Test 105 | fun singleLineLf() { 106 | doTest("abc\n") 107 | } 108 | 109 | @Test 110 | fun singleLineCr() { 111 | doTest("abc\r") 112 | } 113 | 114 | @Test 115 | fun singleLineCrLf() { 116 | doTest("abc\r\n") 117 | } 118 | 119 | @Test 120 | fun multiLine() { 121 | doTest("abc\ndef") 122 | } 123 | 124 | @Test 125 | fun multiLineCrSep() { 126 | doTest("abc\rdef") 127 | } 128 | 129 | @Test 130 | fun multiLineCrLfSep() { 131 | doTest("abc\n\rdef") 132 | } 133 | 134 | @Test 135 | fun multiLineLf() { 136 | doTest("abc\ndef\n") 137 | } 138 | 139 | @Test 140 | fun multiLineCr() { 141 | doTest("abc\ndef\r") 142 | } 143 | 144 | @Test 145 | fun multiLineCrLf() { 146 | doTest("abc\ndef\r\n") 147 | } 148 | 149 | @Test 150 | fun lfStart() { 151 | doTest("\nabc") 152 | } 153 | 154 | @Test 155 | fun crStart() { 156 | doTest("\rabc") 157 | } 158 | 159 | @Test 160 | fun crlfStart() { 161 | doTest("\r\nabc") 162 | } 163 | 164 | @Test 165 | fun lfcrStart() { 166 | doTest("\n\rabc") 167 | } 168 | 169 | @Test 170 | fun manyLines() { 171 | doTest("abc\nabc\rabc\r\nabc\n\nabc\r\rabc\n\rabc\r\n\r\nabc\n\n\n\nabc") 172 | } 173 | } -------------------------------------------------------------------------------- /src/test/resources/example.txt: -------------------------------------------------------------------------------- 1 | Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. 2 | Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. 3 | Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. 4 | Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. --------------------------------------------------------------------------------