Optimize JSON object builder (#216)

* Add JSONValueBuilder
* Simplify JSONContext interface
* Rename to NullJSONContext
* Extract json benchmark to another project (only for Scala 2.12)

Author: xerial

airframe-json-benchmark/src/test/scala/wvlet/airframe/json/JSONBenchmark.scala

@@ -0,0 +1,83 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package wvlet.airframe.json
+
+import wvlet.airframe.AirframeSpec
+import wvlet.airframe.json.JSON.{JSONArray, JSONString}
+import wvlet.log.io.{IOUtil, Timer}
+
+import scala.util.Random
+
+/**
+  *
+  */
+class JSONBenchmark extends AirframeSpec with Timer {
+
+  def bench(benchName: String, json: String, N: Int = 5, B: Int = 2): Unit = {
+    val jsonSource = JSONSource.fromString(json)
+    time(benchName, repeat = N, blockRepeat = B) {
+      block("airframe      ") {
+        JSON.parse(jsonSource)
+      }
+      block("airframe scan ") {
+        JSONScanner.scan(jsonSource)
+      }
+      block("circe         ") {
+        io.circe.parser.parse(json)
+      }
+      block("jawn          ") {
+        new io.circe.jawn.JawnParser().parse(json)
+      }
+      block("json4s-jackson") {
+        org.json4s.jackson.JsonMethods.parse(json)
+      }
+      block("json4s-native ") {
+        org.json4s.native.JsonMethods.parse(json)
+      }
+      block("uJson         ") {
+        ujson.read(json)
+      }
+    }
+  }
+
+  lazy val twitterJson = IOUtil.readAsString("airframe-json/src/test/resources/twitter.json")
+
+  "JSONScannerBenchmarhk" should {
+    "parse twitter.json" taggedAs ("comparison") in {
+      bench("twitter.json", twitterJson)
+    }
+
+    "parse boolen arrays" taggedAs ("boolean-array") in {
+      val jsonArray = s"[${(0 until 10000).map(_ => Random.nextBoolean()).mkString(",")}]"
+      bench("boolean array", jsonArray)
+    }
+
+    "parse string arrays" taggedAs ("string-array") in {
+      // Extract JSON strings from twitter.json
+      val j = JSON.parse(twitterJson)
+      val b = IndexedSeq.newBuilder[JSONString]
+      JSONTraverser.traverse(j, new JSONVisitor {
+        override def visitKeyValue(k: String, v: JSON.JSONValue): Unit = {
+          b += JSONString(k)
+        }
+        override def visitString(v: JSON.JSONString): Unit = {
+          b += v
+        }
+      })
+      val jsonArray = JSONArray(b.result()).toJSON
+      bench("string array", jsonArray)
+    }
+  }
+
+}

airframe-json/.jvm/src/test/scala/wvlet/airframe/json/JSONScannerBenchmark.scala

@@ -0,0 +1,31 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package wvlet.airframe.json
+
+import wvlet.airframe.AirframeSpec
+import wvlet.log.io.IOUtil
+
+/**
+  *
+  */
+class TwitterJSONTest extends AirframeSpec {
+  lazy val twitterJson = IOUtil.readAsString("airframe-json/src/test/resources/twitter.json")
+
+  "JSONParser" should {
+    "parser twiter.json as JSONValue" in {
+      val j = JSON.parse(twitterJson)
+    }
+  }
+
+}

airframe-json/.jvm/src/test/scala/wvlet/airframe/json/TwitterJSONTest.scala

@@ -13,10 +13,12 @@
  */
 package wvlet.airframe.json
 
+import wvlet.log.LogSupport
+
 /**
   *
   */
-object JSON {
+object JSON extends LogSupport {
 
   def parse(s: String): JSONValue = {
     parse(JSONSource.fromString(s))
@@ -28,33 +30,37 @@ object JSON {
     parse(JSONSource.fromBytes(s, offset, length))
   }
   def parse(s: JSONSource): JSONValue = {
-    JSONParser.parse(s)
+    val b = new JSONValueBuilder().singleContext(s, 0)
+    JSONScanner.scan(s, b)
+    val j = b.result
+    j
   }
 
   sealed trait JSONValue {
     override def toString = toJSON
     def toJSON: String
   }
 
-  case object JSONNull extends JSONValue {
+  final case object JSONNull extends JSONValue {
     override def toJSON: String = "null"
   }
 
-  case class JSONBoolean(val v: Boolean) extends JSONValue {
+  final case class JSONBoolean(val v: Boolean) extends JSONValue {
     override def toJSON: String = if (v) "true" else "false"
   }
 
   val JSONTrue  = JSONBoolean(true)
   val JSONFalse = JSONBoolean(false)
 
   trait JSONNumber extends JSONValue
-  case class JSONDouble(v: Double) extends JSONNumber {
+  final case class JSONDouble(v: Double) extends JSONNumber {
     override def toJSON: String = v.toString
   }
-  case class JSONLong(v: Long) extends JSONNumber {
+  final case class JSONLong(v: Long) extends JSONNumber {
     override def toJSON: String = v.toString
   }
-  case class JSONString(v: String) extends JSONValue {
+  final case class JSONString(v: String) extends JSONValue {
+    override def toString = v
     override def toJSON: String = {
       val s = new StringBuilder(v.length + 2)
       s.append("\"")
@@ -64,7 +70,7 @@ object JSON {
     }
   }
 
-  case class JSONObject(v: Seq[(String, JSONValue)]) extends JSONValue {
+  final case class JSONObject(v: Seq[(String, JSONValue)]) extends JSONValue {
     override def toJSON: String = {
       val s = new StringBuilder
       s.append("{")
@@ -83,7 +89,7 @@ object JSON {
       s.result()
     }
   }
-  case class JSONArray(v: Seq[JSONValue]) extends JSONValue {
+  final case class JSONArray(v: IndexedSeq[JSONValue]) extends JSONValue {
     override def toJSON: String = {
       val s = new StringBuilder
       s.append("[")

airframe-json/src/main/scala/wvlet/airframe/json/JSON.scala

@@ -13,16 +13,29 @@
  */
 package wvlet.airframe.json
 
-trait JSONEventHandler {
-  def startJson(s: JSONSource, start: Int): Unit
-  def endJson(s: JSONSource, start: Int): Unit
-  def startObject(s: JSONSource, start: Int): Unit
-  def endObject(s: JSONSource, start: Int, end: Int, numElem: Int)
-  def startArray(s: JSONSource, start: Int): Unit
-  def endArray(s: JSONSource, start: Int, end: Int, numElem: Int)
+trait JSONHandler[Expr] {
+  def singleContext(s: JSONSource, start: Int): JSONContext[Expr]
+  def objectContext(s: JSONSource, start: Int): JSONContext[Expr]
+  def arrayContext(s: JSONSource, start: Int): JSONContext[Expr]
+}
+
+/**
+  * A facade to build json ASTs while scanning json with JSONScanner
+  * @tparam Expr
+  */
+trait JSONContext[Expr] extends JSONHandler[Expr] {
+  def result: Expr
+  def isObjectContext: Boolean
+  private[json] final def endScannerState: Int = {
+    if (isObjectContext) JSONScanner.OBJECT_END
+    else JSONScanner.ARRAY_END
+  }
+
+  def add(v: Expr): Unit
+  def closeContext(s: JSONSource, end: Int): Unit
 
-  def nullValue(s: JSONSource, start: Int, end: Int): Unit
-  def stringValue(s: JSONSource, start: Int, end: Int): Unit
-  def numberValue(s: JSONSource, start: Int, end: Int, dotIndex: Int, expIndex: Int): Unit
-  def booleanValue(s: JSONSource, v: Boolean, start: Int, end: Int)
+  def addNull(s: JSONSource, start: Int, end: Int): Unit
+  def addString(s: JSONSource, start: Int, end: Int): Unit
+  def addNumber(s: JSONSource, start: Int, end: Int, dotIndex: Int, expIndex: Int): Unit
+  def addBoolean(s: JSONSource, v: Boolean, start: Int, end: Int)
 }