akka.stream.impl.JsonObjectParser.scala Maven / Gradle / Ivy
/*
* Copyright (C) 2014-2020 Lightbend Inc.
*/
package akka.stream.impl
import akka.annotation.InternalApi
import akka.stream.scaladsl.Framing.FramingException
import akka.util.ByteString
import scala.annotation.switch
/**
* INTERNAL API: Use [[akka.stream.scaladsl.JsonFraming]] instead.
*/
@InternalApi private[akka] object JsonObjectParser {
final val SquareBraceStart = '['.toByte
final val SquareBraceEnd = ']'.toByte
final val CurlyBraceStart = '{'.toByte
final val CurlyBraceEnd = '}'.toByte
final val DoubleQuote = '"'.toByte
final val Backslash = '\\'.toByte
final val Comma = ','.toByte
final val LineBreak = 10 // '\n'
final val LineBreak2 = 13 // '\r'
final val Tab = 9 // '\t'
final val Space = 32 // ' '
def isWhitespace(b: Byte): Boolean = (b: @switch) match {
case Space => true
case LineBreak => true
case LineBreak2 => true
case Tab => true
case _ => false
}
}
/**
* INTERNAL API: Use [[akka.stream.scaladsl.JsonFraming]] instead.
*
* **Mutable** framing implementation that given any number of [[ByteString]] chunks, can emit JSON objects contained within them.
* Typically JSON objects are separated by new-lines or commas, however a top-level JSON Array can also be understood and chunked up
* into valid JSON objects by this framing implementation.
*
* Leading whitespace between elements will be trimmed.
*/
@InternalApi private[akka] class JsonObjectParser(maximumObjectLength: Int = Int.MaxValue) {
import JsonObjectParser._
private var buffer: ByteString = ByteString.empty
private var pos = 0 // latest position of pointer while scanning for json object end
private var trimFront = 0 // number of chars to drop from the front of the bytestring before emitting (skip whitespace etc)
private var depth = 0 // counter of object-nesting depth, once hits 0 an object should be emitted
private var completedObject = false
private var inStringExpression = false
private var isStartOfEscapeSequence = false
private var lastInput = 0.toByte
/**
* Appends input ByteString to internal byte string buffer.
* Use [[poll]] to extract contained JSON objects.
*/
def offer(input: ByteString): Unit =
buffer ++= input
def isEmpty: Boolean = buffer.isEmpty
/**
* Attempt to locate next complete JSON object in buffered ByteString and returns `Some(it)` if found.
* May throw a [[akka.stream.scaladsl.Framing.FramingException]] if the contained JSON is invalid or max object size is exceeded.
*/
def poll(): Option[ByteString] = {
val foundObject = seekObject()
if (!foundObject) None
else
(pos: @switch) match {
case -1 | 0 => None
case _ =>
val (emit, buf) = buffer.splitAt(pos)
buffer = buf.compact
pos = 0
val tf = trimFront
trimFront = 0
if (tf == 0) Some(emit)
else {
val trimmed = emit.drop(tf)
if (trimmed.isEmpty) None
else Some(trimmed)
}
}
}
/** @return true if an entire valid JSON object was found, false otherwise */
private def seekObject(): Boolean = {
completedObject = false
val bufSize = buffer.size
while (pos != -1 && (pos < bufSize && pos < maximumObjectLength) && !completedObject) proceed(buffer(pos))
if (pos >= maximumObjectLength)
throw new FramingException(s"""JSON element exceeded maximumObjectLength ($maximumObjectLength bytes)!""")
completedObject
}
private def proceed(input: Byte): Unit = {
if (input == SquareBraceStart && outsideObject) {
// outer object is an array
pos += 1
trimFront += 1
} else if (input == SquareBraceEnd && outsideObject) {
// outer array completed!
pos += 1
trimFront += 1
} else if (input == Comma && outsideObject) {
// do nothing
pos += 1
trimFront += 1
} else if (input == Backslash) {
if (lastInput == Backslash & isStartOfEscapeSequence) isStartOfEscapeSequence = false
else isStartOfEscapeSequence = true
pos += 1
} else if (input == DoubleQuote) {
if (!isStartOfEscapeSequence) inStringExpression = !inStringExpression
isStartOfEscapeSequence = false
pos += 1
} else if (input == CurlyBraceStart && !inStringExpression) {
isStartOfEscapeSequence = false
depth += 1
pos += 1
} else if (input == CurlyBraceEnd && !inStringExpression) {
isStartOfEscapeSequence = false
depth -= 1
pos += 1
if (depth == 0) completedObject = true
} else if (isWhitespace(input) && !inStringExpression) {
pos += 1
if (depth == 0) trimFront += 1
} else if (insideObject) {
isStartOfEscapeSequence = false
pos += 1
} else {
throw new FramingException(s"Invalid JSON encountered at position [$pos] of [$buffer]")
}
lastInput = input
}
@inline private final def insideObject: Boolean =
!outsideObject
@inline private final def outsideObject: Boolean =
depth == 0
}