Improve performance of JSON encoding

benchmark/src/jmh/kotlin/kotlinx/benchmarks/json/CitmBenchmark.kt

@@ -1,7 +1,10 @@
 package kotlinx.benchmarks.json
 
 import kotlinx.benchmarks.model.*
+import kotlinx.serialization.*
 import kotlinx.serialization.json.*
+import kotlinx.serialization.json.Json.Default.decodeFromString
+import kotlinx.serialization.json.Json.Default.encodeToString
 import org.openjdk.jmh.annotations.*
 import java.util.concurrent.*
 
@@ -16,8 +19,17 @@ open class CitmBenchmark {
      * For some reason Citm is kind of de-facto standard cross-language benchmark.
      * Order of magnitude: 200 ops/sec
      */
-    private val citm = CitmBenchmark::class.java.getResource("/citm_catalog.json").readBytes().decodeToString()
+    private val input = CitmBenchmark::class.java.getResource("/citm_catalog.json").readBytes().decodeToString()
+    private val citm = Json.decodeFromString(CitmCatalog.serializer(), input)
+
+    @Setup
+    fun init() {
+        require(citm == Json.decodeFromString(CitmCatalog.serializer(), Json.encodeToString(citm)))
+    }
+
+    @Benchmark
+    fun decodeCitm(): CitmCatalog = Json.decodeFromString(CitmCatalog.serializer(), input)
 
     @Benchmark
-    fun decodeCitm(): CitmCatalog = Json.decodeFromString(CitmCatalog.serializer(), citm)
+    fun encodeCitm(): String = Json.encodeToString(CitmCatalog.serializer(), citm)
 }

benchmark/src/jmh/kotlin/kotlinx/benchmarks/json/JacksonComparisonBenchmark.kt

@@ -33,7 +33,7 @@ open class JacksonComparisonBenchmark {
 
     private val objectMapper: ObjectMapper = jacksonObjectMapper()
 
-    private val data =  DefaultPixelEvent(
+    private val data = DefaultPixelEvent(
         version = 1,
         dateTime2 = System.currentTimeMillis().toString(),
         serverName = "some-endpoint-qwer",
@@ -48,15 +48,46 @@ open class JacksonComparisonBenchmark {
         cookies = "_ga=GA1.2.971852807.1546968515"
     )
 
-    private val stringData =  Json.encodeToString(DefaultPixelEvent.serializer(), data)
+    private val dataWithEscapes = DefaultPixelEvent(
+        version = 1,
+        dateTime2 = System.currentTimeMillis().toString(),
+        serverName = "some-endp\"oint-qwer",
+        domain = "<a href=\"some.domain.com\">",
+        method = "POST",
+        clientIp = "127.0.0.1",
+        queryString = "anxa=CASCative&anxv=13.901.16.34566&anxe=\"FoolbarActive\"&anxt=E7AFBF15-1761-4343-92C1-78167ED19B1C&anxtv=13.901.16.34566&anxp=%5ECQ6%5Expt292%5ES33656%5Eus&anxsi&anxd=2019-10-08T17%3A03%3A57.246Z&f=00400000&anxr=1571945992297&coid=\"66abafd0d49f42e58dc7536109395306\"&userSegment&cwsid=opgkcnbminncdgghighmimmphiooeohh",
+        userAgent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:70.0) Gecko/20100101 Firefox/70.0",
+        contentType = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
+        browserLanguage = "\"en\"-\"US\",en;\\q=0.5",
+        postData = "-",
+        cookies = "_ga=GA1.2.971852807.1546968515"
+    )
+
+    private val stringData = Json.encodeToString(DefaultPixelEvent.serializer(), data)
 
+    @Serializable
+    private class SmallDataClass(val id: Int, val name: String)
+
+    private val smallData = SmallDataClass(42, "Vincent")
 
     @Benchmark
     fun jacksonToString(): String = objectMapper.writeValueAsString(data)
 
+    @Benchmark
+    fun jacksonToStringWithEscapes(): String = objectMapper.writeValueAsString(dataWithEscapes)
+
+    @Benchmark
+    fun jacksonSmallToString(): String = objectMapper.writeValueAsString(smallData)
+
     @Benchmark
     fun kotlinToString(): String = Json.encodeToString(DefaultPixelEvent.serializer(), data)
 
+    @Benchmark
+    fun kotlinToStringWithEscapes(): String = Json.encodeToString(DefaultPixelEvent.serializer(), dataWithEscapes)
+
+    @Benchmark
+    fun kotlinSmallToString(): String = Json.encodeToString(SmallDataClass.serializer(), smallData)
+
     @Benchmark
     fun jacksonFromString(): DefaultPixelEvent = objectMapper.readValue(stringData, DefaultPixelEvent::class.java)
 

benchmark/src/jmh/kotlin/kotlinx/benchmarks/json/TwitterBenchmark.kt

@@ -1,7 +1,10 @@
 package kotlinx.benchmarks.json
 
 import kotlinx.benchmarks.model.*
+import kotlinx.serialization.*
 import kotlinx.serialization.json.*
+import kotlinx.serialization.json.Json.Default.decodeFromString
+import kotlinx.serialization.json.Json.Default.encodeToString
 import org.openjdk.jmh.annotations.*
 import java.util.concurrent.*
 
@@ -20,8 +23,17 @@ open class TwitterBenchmark {
      * with Kotlin classes generated by Json2Kotlin plugin (and also manually adjusted)
      */
     private val input = TwitterBenchmark::class.java.getResource("/twitter.json").readBytes().decodeToString()
+    private val twitter = Json.decodeFromString(Twitter.serializer(), input)
+
+    @Setup
+    fun init() {
+        require(twitter == Json.decodeFromString(Twitter.serializer(), Json.encodeToString(Twitter.serializer(), twitter)))
+    }
 
     // Order of magnitude: 4-7 op/ms
     @Benchmark
-    fun parseTwitter() = Json.decodeFromString(Twitter.serializer(), input)
+    fun decodeTwitter() = Json.decodeFromString(Twitter.serializer(), input)
+
+    @Benchmark
+    fun encodeTwitter() = Json.encodeToString(Twitter.serializer(), twitter)
 }

benchmark/src/jmh/kotlin/kotlinx/benchmarks/json/TwitterFeedBenchmark.kt

@@ -1,7 +1,10 @@
 package kotlinx.benchmarks.json
 
 import kotlinx.benchmarks.model.*
+import kotlinx.serialization.*
 import kotlinx.serialization.json.*
+import kotlinx.serialization.json.Json.Default.decodeFromString
+import kotlinx.serialization.json.Json.Default.encodeToString
 import org.openjdk.jmh.annotations.*
 import java.util.concurrent.*
 
@@ -20,9 +23,17 @@ open class TwitterFeedBenchmark {
      * with Kotlin classes generated by Json2Kotlin plugin (and also manually adjusted)
      */
     private val input = TwitterFeedBenchmark::class.java.getResource("/twitter_macro.json").readBytes().decodeToString()
+    private val twitter = Json.decodeFromString(MacroTwitterFeed.serializer(), input)
 
+    @Setup
+    fun init() {
+        require(twitter == Json.decodeFromString(MacroTwitterFeed.serializer(), Json.encodeToString(MacroTwitterFeed.serializer(), twitter)))
+    }
 
     // Order of magnitude: ~400 op/s
     @Benchmark
-    fun parseTwitter() = Json.decodeFromString(MacroTwitterFeed.serializer(), input)
+    fun decodeTwitter() = Json.decodeFromString(MacroTwitterFeed.serializer(), input)
+
+    @Benchmark
+    fun encodeTwitter() = Json.encodeToString(MacroTwitterFeed.serializer(), twitter)
 }

formats/json/commonMain/src/kotlinx/serialization/json/Json.kt

@@ -64,14 +64,18 @@ public sealed class Json(internal val configuration: JsonConf) : StringFormat {
      * @throws [SerializationException] if the given value cannot be serialized to JSON.
      */
     public final override fun <T> encodeToString(serializer: SerializationStrategy<T>, value: T): String {
-        val result = StringBuilder()
-        val encoder = StreamingJsonEncoder(
-            result, this,
-            WriteMode.OBJ,
-            arrayOfNulls(WriteMode.values().size)
-        )
-        encoder.encodeSerializableValue(serializer, value)
-        return result.toString()
+        val result = JsonStringBuilder()
+        try {
+            val encoder = StreamingJsonEncoder(
+                result, this,
+                WriteMode.OBJ,
+                arrayOfNulls(WriteMode.values().size)
+            )
+            encoder.encodeSerializableValue(serializer, value)
+            return result.toString()
+        } finally {
+            result.release()
+        }
     }
 
     /**

formats/json/commonMain/src/kotlinx/serialization/json/internal/Composers.kt

@@ -0,0 +1,62 @@
+package kotlinx.serialization.json.internal
+
+import kotlinx.serialization.json.*
+import kotlin.jvm.*
+
+internal open class Composer(@JvmField internal val sb: JsonStringBuilder, @JvmField internal val json: Json) {
+    private var level = 0
+    var writingFirst = true
+        private set
+
+    fun indent() {
+        writingFirst = true
+        level++
+    }
+
+    fun unIndent() {
+        level--
+    }
+
+    fun nextItem() {
+        writingFirst = false
+        if (json.configuration.prettyPrint) {
+            print("\n")
+            repeat(level) { print(json.configuration.prettyPrintIndent) }
+        }
+    }
+
+    fun space() {
+        if (json.configuration.prettyPrint)
+            print(' ')
+    }
+
+    fun print(v: Char) = sb.append(v)
+    fun print(v: String) = sb.append(v)
+    open fun print(v: Float) = sb.append(v.toString())
+    open fun print(v: Double) = sb.append(v.toString())
+    open fun print(v: Byte) = sb.append(v.toLong())
+    open fun print(v: Short) = sb.append(v.toLong())
+    open fun print(v: Int) = sb.append(v.toLong())
+    open fun print(v: Long) = sb.append(v)
+    open fun print(v: Boolean) = sb.append(v.toString())
+    fun printQuoted(value: String): Unit = sb.appendQuoted(value)
+}
+
+@ExperimentalUnsignedTypes
+internal class ComposerForUnsignedNumbers(sb: JsonStringBuilder, json: Json) : Composer(sb, json) {
+    override fun print(v: Int) {
+        return super.print(v.toUInt().toString())
+    }
+
+    override fun print(v: Long) {
+        return super.print(v.toULong().toString())
+    }
+
+    override fun print(v: Byte) {
+        return super.print(v.toUByte().toString())
+    }
+
+    override fun print(v: Short) {
+        return super.print(v.toUShort().toString())
+    }
+}

formats/json/commonMain/src/kotlinx/serialization/json/internal/JsonStringBuilder.kt

@@ -0,0 +1,10 @@
+package kotlinx.serialization.json.internal
+
+internal expect class JsonStringBuilder constructor() {
+    fun append(value: Long)
+    fun append(ch: Char)
+    fun append(string: String)
+    fun appendQuoted(string: String)
+    override fun toString(): String
+    fun release()
+}

formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonEncoder.kt

@@ -36,11 +36,11 @@ internal class StreamingJsonEncoder(
 ) : JsonEncoder, AbstractEncoder() {
 
     internal constructor(
-        output: StringBuilder, json: Json, mode: WriteMode,
+        output: JsonStringBuilder, json: Json, mode: WriteMode,
         modeReuseCache: Array<JsonEncoder?>
     ) : this(Composer(output, json), json, mode, modeReuseCache)
 
-    public override val serializersModule: SerializersModule = json.serializersModule
+    override val serializersModule: SerializersModule = json.serializersModule
     private val configuration = json.configuration
 
     // Forces serializer to wrap all values into quotes
@@ -152,7 +152,7 @@ internal class StreamingJsonEncoder(
         return if (inlineDescriptor.isUnsignedNumber) StreamingJsonEncoder(
             ComposerForUnsignedNumbers(
                 composer.sb,
-                composer.json
+                json
             ), json, mode, null
         )
         else this
@@ -207,61 +207,4 @@ internal class StreamingJsonEncoder(
     override fun encodeEnum(enumDescriptor: SerialDescriptor, index: Int) {
         encodeString(enumDescriptor.getElementName(index))
     }
-
-    internal open class Composer(@JvmField internal val sb: StringBuilder, @JvmField internal val json: Json) {
-        private var level = 0
-        var writingFirst = true
-            private set
-
-        fun indent() {
-            writingFirst = true; level++
-        }
-
-        fun unIndent() {
-            level--
-        }
-
-        fun nextItem() {
-            writingFirst = false
-            if (json.configuration.prettyPrint) {
-                print("\n")
-                repeat(level) { print(json.configuration.prettyPrintIndent) }
-            }
-        }
-
-        fun space() {
-            if (json.configuration.prettyPrint)
-                print(' ')
-        }
-
-        open fun print(v: Char) = sb.append(v)
-        open fun print(v: String) = sb.append(v)
-        open fun print(v: Float) = sb.append(v)
-        open fun print(v: Double) = sb.append(v)
-        open fun print(v: Byte) = sb.append(v)
-        open fun print(v: Short) = sb.append(v)
-        open fun print(v: Int) = sb.append(v)
-        open fun print(v: Long) = sb.append(v)
-        open fun print(v: Boolean) = sb.append(v)
-        open fun printQuoted(value: String): Unit = sb.printQuoted(value)
-    }
-
-    @ExperimentalUnsignedTypes
-    internal class ComposerForUnsignedNumbers(sb: StringBuilder, json: Json) : Composer(sb, json) {
-        override fun print(v: Int): StringBuilder {
-            return super.print(v.toUInt().toString())
-        }
-
-        override fun print(v: Long): StringBuilder {
-            return super.print(v.toULong().toString())
-        }
-
-        override fun print(v: Byte): StringBuilder {
-            return super.print(v.toUByte().toString())
-        }
-
-        override fun print(v: Short): StringBuilder {
-            return super.print(v.toUShort().toString())
-        }
-    }
 }