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Protocol Buffers 3 support for Kotlin Multiplatform

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package pro.felixo.protobuf.util

class PeekableIterator(
    private val base: Iterator
) : Iterator {
    private var peeked = ArrayDeque()

    override fun hasNext(): Boolean = peeked.isNotEmpty() || base.hasNext()

    override fun next(): T = peeked.removeFirstOrNull() ?: base.next()

    /**
     * Each call to this method peeks ahead one additional time without affecting the result of subsequent [next] calls.
     */
    fun peek(): T? = if (!base.hasNext()) null else base.next().also { peeked.add(it) }
}