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import kotlin.math.pow
/**
* A 9P message with the given type, tag, and fields. The message size is calculated automatically.
*
* Important note: the field names in [fieldValuesInt] and [fieldValuesStr] (i.e. the keys of their maps) must be
* mutually exclusive and the union of these two maps' keys must result in a subset of (or a set equal to)
* [fieldNames]. Calling [write] when these conditions are not met throws an exception.
*
* @param type The 9P message type.
* @param tag The tag given to the message.
* @param fieldNames The names of the message fields, in the same order they are expected to be sent.
* @param fieldValuesInt A map of each field name into its value. This map only stores integer values.
* @param fieldValuesStr A map of each field name into its value. This map only stores string values.
*/
class NinePMessage(val type: NinePMessageType, val tag: UShort, val fieldNames: List<String>, val fieldValuesInt: Map<String, SizedMessageField>, val fieldValuesStr: Map<String, String>) {
/**
* Send the message using the given networking API.
*
* @param npt The networking API.
* @throws IllegalArgumentException if [fieldNames], [fieldValuesInt], and [fieldValuesStr] are incoherent.
*/
fun write(npt: NetworkPacketTransporter) {
// shorthands
val insecInts = fieldNames.intersect(fieldValuesInt.keys)
val insecStrs = fieldNames.intersect(fieldValuesStr.keys)
// check that names in fieldNames exist as keys in either fieldValuesInt or fieldValuesStr but not both
require(insecInts.size == fieldNames.size - insecStrs.size)
val totalSize = 4 + 1 + 2 + insecInts.sumOf { fieldValuesInt[it]!!.size } + insecStrs.sumOf { 2 + fieldValuesStr[it]!!.length }
writeMessageSizeType(npt, totalSize, type)
writeInteger(npt, SizedMessageField(2, tag.toInt().toBigInteger()))
for (field in fieldNames) {
if (field in insecInts) {
writeInteger(npt, fieldValuesInt[field]!!)
} else {
writeString(npt, fieldValuesStr[field]!!)
}
}
}
/**
* Write an integer number to the connection.
*
* In 9P, binary numbers (non-textual) are specified in little-endian order (least significant byte first).
*
* @param npt The networking API.
* @param value The number's value. [SizedMessageField] defines both its actual value and its size.
*/
private fun writeInteger(npt: NetworkPacketTransporter, value: SizedMessageField) {
npt.transmit(value.value.toByteArray().toList())
}
/**
* Write a string to the connection.
*
* In 9P, strings are represented as a 2-byte integer (the string's size) followed by the actual UTF-8 string. The
* null terminator is forbidden in 9P messages.
*
* @param npt The networking API.
* @param value The string.
* @throws IllegalArgumentException if the value of the string's size does not fit into 2 bytes.
*/
private fun writeString(npt: NetworkPacketTransporter, value: String) {
require(value.length <= 2.0.pow(16.0) - 1)
writeInteger(npt, SizedMessageField(2, value.length.toBigInteger()))
npt.transmit(value.toByteArray().toList())
}
/**
* Write the message size and type.
*
* @param npt The networking API.
* @param size The total message size, including the 4 bytes of this parameter and the type's byte.
* @param type The 9P message type as a [NinePMessageType] constant.
*/
private fun writeMessageSizeType(npt: NetworkPacketTransporter, size: Int, type: NinePMessageType) {
writeInteger(npt, SizedMessageField(4, size.toBigInteger()))
writeInteger(npt, SizedMessageField(1, type.value.toInt().toBigInteger()))
}
}
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