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Add an accumulator that builds an AST directly
Inspired by the `Facade` abstraction from jawn, we can build the AST directly, without emitting intermediate tokens, which makes it faster.
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147 changes: 147 additions & 0 deletions
147
json/src/main/scala/fs2/data/json/internal/BuilderChunkAccumulator.scala
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * Copyright 2023 Lucas Satabin | ||
| * | ||
| * 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. | ||
| */ | ||
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| package fs2 | ||
| package data | ||
| package json | ||
| package internals | ||
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| import scala.collection.immutable.{TreeMap, VectorBuilder} | ||
| import scala.collection.mutable.ListBuffer | ||
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| import ast.Builder | ||
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| /** A chunk accumulator that allows for building a stream of AST values | ||
| * for the provided [[ast.Builder Builder]]. | ||
| * | ||
| * The design is inspired by the jawn `Facade` and `FContext`. | ||
| */ | ||
| private[json] final class BuilderChunkAccumulator[Json](builder: Builder[Json]) extends ChunkAccumulator[Json] { | ||
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| private[this] final val chunkAcc: VectorBuilder[Json] = new VectorBuilder | ||
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| private trait Context { | ||
| def string(s: String): Unit | ||
| def value(v: Json): Unit | ||
| def finish(): Json | ||
| } | ||
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| private def toplevelContext(): Context = | ||
| new Context { | ||
| override def string(s: String): Unit = chunkAcc.addOne(builder.makeString(s)) | ||
| override def value(v: Json): Unit = chunkAcc.addOne(v) | ||
| override def finish(): Json = builder.makeNull | ||
| } | ||
| private def arrayContext(): Context = | ||
| new Context { | ||
| private[this] val vs = ListBuffer.empty[Json] | ||
| override def string(s: String): Unit = vs.addOne(builder.makeString(s)) | ||
| override def value(v: Json): Unit = vs.addOne(v) | ||
| override def finish(): Json = builder.makeArray(vs) | ||
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| } | ||
| private def objectContext(): Context = | ||
| new Context { | ||
| private[this] var key: String = null | ||
| private[this] var vs = TreeMap.empty[String, Json] | ||
| override def string(s: String): Unit = key = s | ||
| override def value(v: Json): Unit = { | ||
| vs = vs.updated(key, v) | ||
| key = null | ||
| } | ||
| override def finish(): Json = builder.makeObject(vs) | ||
| } | ||
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| private[this] var context: Context = toplevelContext() | ||
| private[this] var stack: List[Context] = Nil | ||
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| override def startObject(): this.type = { | ||
| stack = context :: stack | ||
| context = objectContext() | ||
| this | ||
| } | ||
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| override def key(key: String): this.type = { | ||
| context.string(key) | ||
| this | ||
| } | ||
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| override def endObject(): this.type = | ||
| if (stack.isEmpty) { | ||
| chunkAcc.addOne(context.finish()) | ||
| context = toplevelContext() | ||
| this | ||
| } else { | ||
| val v = context.finish() | ||
| context = stack.head | ||
| context.value(v) | ||
| stack = stack.tail | ||
| this | ||
| } | ||
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| override def startArray(): this.type = { | ||
| stack = context :: stack | ||
| context = arrayContext() | ||
| this | ||
| } | ||
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| override def endArray(): this.type = | ||
| if (stack.isEmpty) { | ||
| chunkAcc.addOne(context.finish()) | ||
| context = toplevelContext() | ||
| this | ||
| } else { | ||
| val v = context.finish() | ||
| context = stack.head | ||
| context.value(v) | ||
| stack = stack.tail | ||
| this | ||
| } | ||
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| override def nullValue(): this.type = { | ||
| context.value(builder.makeNull) | ||
| this | ||
| } | ||
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| override def trueValue(): this.type = { | ||
| context.value(builder.makeTrue) | ||
| this | ||
| } | ||
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| override def falseValue(): this.type = { | ||
| context.value(builder.makeFalse) | ||
| this | ||
| } | ||
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| override def numberValue(value: String): this.type = { | ||
| context.value(builder.makeNumber(value)) | ||
| this | ||
| } | ||
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| override def stringValue(value: String): this.type = { | ||
| context.value(builder.makeString(value)) | ||
| this | ||
| } | ||
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| override def chunk(): Chunk[Json] = | ||
| Chunk.vector(chunkAcc.result()) | ||
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| override def flush(): this.type = { | ||
| chunkAcc.clear() | ||
| this | ||
| } | ||
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| } |
16 changes: 16 additions & 0 deletions
16
json/src/main/scala/fs2/data/json/internal/ChunkAccumulator.scala
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