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Diffstat (limited to 'src/main/kotlin/Message.kt')
| -rw-r--r-- | src/main/kotlin/Message.kt | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/src/main/kotlin/Message.kt b/src/main/kotlin/Message.kt new file mode 100644 index 0000000..5007c26 --- /dev/null +++ b/src/main/kotlin/Message.kt @@ -0,0 +1,104 @@ +import java.math.BigInteger +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 Message(val type: NinePMessageType, val tag: UShort, val fieldNames: List<String>, val fieldValuesInt: Map<String, BigInteger>, val fieldValuesStr: Map<String, String>, val maxSize: UInt) { + /** + * Intersection between [fieldNames] and [fieldValuesInt]. In other words: the amount of integer fields that are + * going to be used when writing the message. + */ + private val insecInts = fieldNames.intersect(fieldValuesInt.keys) + /** + * Intersection between [fieldNames] and [fieldValuesStr]. In other words: the amount of string fields that are + * going to be used when writing the message. + */ + private val insecStrs = fieldNames.intersect(fieldValuesStr.keys) + + /** + * Send the message using the given networking API. + * + * @param tl The networking API. + * @throws IllegalArgumentException if [fieldNames], [fieldValuesInt], and [fieldValuesStr] are incoherent or the + * final size of the message exceeds the negotiated value. + */ + fun write(tl: TransportLayer) { + // 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 = size() + if (totalSize > this.maxSize) { + throw IllegalArgumentException("Message size exceeded.") + } + writeMessageSizeType(tl, totalSize, type) + writeInteger(tl, tag.toInt().toBigInteger()) + for (field in fieldNames) { + if (field in insecInts) { + writeInteger(tl, fieldValuesInt[field]!!) + } else { + writeString(tl, fieldValuesStr[field]!!) + } + } + } + + // TODO: Add size that the value is required to fit in + /** + * Write an integer number to the connection. + * + * In 9P, binary numbers (non-textual) are specified in little-endian order (least significant byte first). + * + * @param tl The networking API. + * @param value The number's value. + */ + private fun writeInteger(tl: TransportLayer, value: BigInteger) { + val bytes = value.toByteArray() + tl.transmit(Array(bytes.size) { i -> bytes[i].toUByte() }) + } + + /** + * 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 tl 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(tl: TransportLayer, value: String) { + require(value.length <= 2.0.pow(16.0) - 1) + writeInteger(tl, value.length.toBigInteger()) + val bytes = value.toByteArray() + tl.transmit(Array(bytes.size) { i -> bytes[i].toUByte() }) + } + + /** + * Write the message size and type. + * + * @param tl 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(tl: TransportLayer, size: UInt, type: NinePMessageType) { + writeInteger(tl, size.toInt().toBigInteger()) + writeInteger(tl, type.value.toInt().toBigInteger()) + } + + /** + * Calculate the expected size of the message. + */ + fun size(): UInt { + return 4u + 1u + 2u + this.insecInts.sumOf { this.fieldValuesInt[it]!!.bitLength().toUInt() } + this.insecStrs.sumOf { 2u + this.fieldValuesStr[it]!!.length.toUInt() } + } +}
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