commonMain.kotlinx.serialization.json.internal.JsonIterator.kt Maven / Gradle / Ivy

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Kotlin multiplatform serialization runtime library
There is a newer version: 1.7.3
/*
 * Copyright 2017-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
 */

@file:Suppress("FunctionName")
@file:OptIn(ExperimentalSerializationApi::class)

package kotlinx.serialization.json.internal

import kotlinx.serialization.DeserializationStrategy
import kotlinx.serialization.ExperimentalSerializationApi
import kotlinx.serialization.json.*

internal fun  JsonIterator(
    mode: DecodeSequenceMode,
    json: Json,
    lexer: ReaderJsonLexer,
    deserializer: DeserializationStrategy
): Iterator = when (lexer.determineFormat(mode)) {
    DecodeSequenceMode.WHITESPACE_SEPARATED -> JsonIteratorWsSeparated(
        json,
        lexer,
        deserializer
    ) // Can be many WS-separated independent arrays
    DecodeSequenceMode.ARRAY_WRAPPED -> JsonIteratorArrayWrapped(
        json,
        lexer,
        deserializer
    )
    DecodeSequenceMode.AUTO_DETECT -> error("AbstractJsonLexer.determineFormat must be called beforehand.")
}


private fun AbstractJsonLexer.determineFormat(suggested: DecodeSequenceMode): DecodeSequenceMode = when (suggested) {
    DecodeSequenceMode.WHITESPACE_SEPARATED ->
        DecodeSequenceMode.WHITESPACE_SEPARATED // do not call consumeStartArray here so we don't confuse parser with stream of lists
    DecodeSequenceMode.ARRAY_WRAPPED ->
        if (tryConsumeStartArray()) DecodeSequenceMode.ARRAY_WRAPPED
        else fail(TC_BEGIN_LIST)
    DecodeSequenceMode.AUTO_DETECT ->
        if (tryConsumeStartArray()) DecodeSequenceMode.ARRAY_WRAPPED
        else DecodeSequenceMode.WHITESPACE_SEPARATED
}

private fun AbstractJsonLexer.tryConsumeStartArray(): Boolean {
    if (peekNextToken() == TC_BEGIN_LIST) {
        consumeNextToken(TC_BEGIN_LIST)
        return true
    }
    return false
}

private class JsonIteratorWsSeparated(
    private val json: Json,
    private val lexer: ReaderJsonLexer,
    private val deserializer: DeserializationStrategy
) : Iterator {
    override fun next(): T =
        StreamingJsonDecoder(json, WriteMode.OBJ, lexer, deserializer.descriptor, null)
            .decodeSerializableValue(deserializer)

    override fun hasNext(): Boolean = lexer.isNotEof()
}

private class JsonIteratorArrayWrapped(
    private val json: Json,
    private val lexer: ReaderJsonLexer,
    private val deserializer: DeserializationStrategy
) : Iterator {
    private var first = true

    override fun next(): T {
        if (first) {
            first = false
        } else {
            lexer.consumeNextToken(COMMA)
        }
        val input = StreamingJsonDecoder(json, WriteMode.OBJ, lexer, deserializer.descriptor, null)
        return input.decodeSerializableValue(deserializer)
    }

    /**
     * Note: if array separator (comma) is missing, hasNext() returns true, but next() throws an exception.
     */
    override fun hasNext(): Boolean {
        if (lexer.peekNextToken() == TC_END_LIST) {
            lexer.consumeNextToken(TC_END_LIST)
            if (lexer.isNotEof()) {
                if (lexer.peekNextToken() == TC_BEGIN_LIST) lexer.fail("There is a start of the new array after the one parsed to sequence. " +
                        "${DecodeSequenceMode.ARRAY_WRAPPED.name} mode doesn't merge consecutive arrays.\n" +
                        "If you need to parse a stream of arrays, please use ${DecodeSequenceMode.WHITESPACE_SEPARATED.name} mode instead.")
                lexer.expectEof()
            }
            return false
        }
        if (!lexer.isNotEof()) lexer.fail(TC_END_LIST)
        return true
    }
}