324 lines
13 KiB
JavaScript
324 lines
13 KiB
JavaScript
import { bitsToBytes, bitsToInt, numberToBits, numberToBytes, numberToHex } from "./converters";
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import * as CRC from './CRC';
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let SEGMENT_DURATION = 30;
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let PACKET_SIZE_BITS = 8;
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let DATA_SIZE_BITS = 8;
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let DATA_SIZE_CRC_BITS = 8;
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let DATA_CRC_BITS = 8;
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let BITS_PER_SAMPLE = 1;
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let IS_ENCODED = false;
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let PACKET_ENCODED_BLOCK_SIZE = 1;
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let PACKET_DECODED_BLOCK_SIZE = 1;
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let ENCODING;
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let PACKET_CRC_BIT_COUNT = 0;
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let PACKET_SEQUENCE_NUMBER_BIT_COUNT = 0;
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export const changeConfiguration = (config) => {
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const {
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segmentDurationMilliseconds,
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packetSizeBitCount,
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dataSizeBitCount,
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dataSizeCrcBitCount,
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dataCrcBitCount,
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bitsPerSegment,
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packetEncoding,
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packetEncodingBitCount,
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packetDecodingBitCount,
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packetSequenceNumberBitCount,
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packetCrcBitCount
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} = config;
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SEGMENT_DURATION = segmentDurationMilliseconds;
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PACKET_SIZE_BITS = packetSizeBitCount;
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DATA_SIZE_BITS = dataSizeBitCount;
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DATA_SIZE_CRC_BITS = dataSizeCrcBitCount;
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DATA_CRC_BITS = dataCrcBitCount;
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BITS_PER_SAMPLE = bitsPerSegment;
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IS_ENCODED = packetEncoding;
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if(IS_ENCODED) {
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PACKET_ENCODED_BLOCK_SIZE = packetEncodingBitCount;
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PACKET_DECODED_BLOCK_SIZE = packetDecodingBitCount;
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} else {
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PACKET_ENCODED_BLOCK_SIZE = 1;
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PACKET_DECODED_BLOCK_SIZE = 1;
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}
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PACKET_CRC_BIT_COUNT = packetCrcBitCount;
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PACKET_SEQUENCE_NUMBER_BIT_COUNT = packetSequenceNumberBitCount;
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}
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export const setEncoding = (encoding) => {
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ENCODING = encoding;
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}
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const encodePacket = (packetBits) => IS_ENCODED ? ENCODING.encode(packetBits) : packetBits;
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const decodePacket = (packetBits) => IS_ENCODED ? ENCODING.decode(packetBits) : packetBits;
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export const getSegmentDurationMilliseconds = () => SEGMENT_DURATION;
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export const getPacketMaxByteCount = () => 2 ** PACKET_SIZE_BITS;
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export const getPacketMaxBitCount = () => (2 ** PACKET_SIZE_BITS) * 8;
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export const getDataMaxByteCount = () => 2 ** DATA_SIZE_BITS;
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export const getPacketEncodedBitCount = () => getPacketEncodingBlockCount() * PACKET_ENCODED_BLOCK_SIZE;
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export const getPacketEncodingBlockCount = () =>
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IS_ENCODED ? Math.floor(getPacketMaxBitCount() / PACKET_ENCODED_BLOCK_SIZE) : getPacketMaxBitCount();
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export const getPacketDataByteCount = () => {
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const availableBitCount = getPacketEncodedBitCount();
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const blocks = Math.floor(availableBitCount / PACKET_ENCODED_BLOCK_SIZE);
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let decodedBits = blocks * PACKET_DECODED_BLOCK_SIZE;
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decodedBits -= getPacketHeaderBitCount()
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// We only transfer full bytes within packets
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return Math.floor(decodedBits / 8);
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}
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export const getPacketDataBitCount = () => getPacketDataByteCount() * 8;
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export function fromByteCountGetPacketLastUnusedBitCount(byteCount) {
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const bitCount = byteCount * 8;
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const availableBits = getPacketMaxBitCount();
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const dataBitsPerPacket = getPacketDataBitCount();
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let bitsInLastPacket = bitCount % dataBitsPerPacket;
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let usedBits = bitsInLastPacket + getPacketHeaderBitCount() ;
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if(IS_ENCODED) {
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const blocks = Math.ceil(usedBits / PACKET_DECODED_BLOCK_SIZE)
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usedBits = blocks * PACKET_ENCODED_BLOCK_SIZE;
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}
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return availableBits - usedBits;
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}
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export function getPacketLastSegmentUnusedBitCount() {
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return (BITS_PER_SAMPLE - (getPacketMaxBitCount() % BITS_PER_SAMPLE));
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}
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export const getBaud = () => {
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return Math.floor(BITS_PER_SAMPLE / getSegmentDurationSeconds());
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}
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export const getEffectiveBaud = () => {
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return Math.floor(getPacketDataBitCount() / getPacketDurationSeconds());
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}
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export const getEncodedPacketDataBitCount = () => {
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return IS_ENCODED ? getPacketEncodedBitCount() : 0;
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}
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export const getPacketUsedBitCount = () =>
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IS_ENCODED ? getPacketEncodedBitCount() : getPacketMaxBitCount();
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export const getPacketUnusedBitCount = () => getPacketMaxBitCount() - getPacketUsedBitCount();
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export const getMaxPackets = () =>
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Math.ceil((getDataMaxByteCount() * 8) / getPacketUsedBitCount());
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export const getMaxDurationMilliseconds = () => getMaxPackets() * getPacketDurationMilliseconds();
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export const canSendPacket = () => {
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let maxBits = getPacketMaxBitCount();
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// Need to be able to send at least 1 data bit with each packet
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if(maxBits - getPacketHeaderBitCount() < 1) return false;
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// Make sure we have enough encoding blocks within a packet
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return IS_ENCODED ? maxBits >= PACKET_ENCODED_BLOCK_SIZE : true;
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}
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export const getPacketizationHeaderBitCount = () => DATA_SIZE_BITS + DATA_SIZE_CRC_BITS + DATA_CRC_BITS;
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export const getPacketizationBitCountFromBitCount = (bitCount) => bitCount + getPacketizationHeaderBitCount();
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export const getPacketizationBitCountFromByteCount = (byteCount) =>
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getPacketizationBitCountFromBitCount(byteCount * 8);
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export const getPacketizationByteCountFromByteCount = (byteCount) =>
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Math.ceil(getPacketizationBitCountFromByteCount(byteCount) / 8);
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export const getPacketizationByteCountFromBitCount = bitCount =>
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Math.ceil(getPacketizationBitCountFromBitCount(bitCount) / 8);
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export const getDataTransferDurationMillisecondsFromByteCount = (byteCount) =>
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getDataTransferDurationMilliseconds(getPacketizationBitCountFromByteCount(byteCount));
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export const getDataTransferDurationSeconds = (bitCount) =>
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getDataTransferDurationMilliseconds(bitCount) / 1000;
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export const packetStats = byteCount => {
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const bitCount = byteCount * 8;
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const packetCount = getPacketCount(bitCount);
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return ({
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packetCount,
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sampleCount: packetCount * getPacketSegmentCount(),
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durationMilliseconds: packetCount * getPacketDurationMilliseconds(),
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totalBitCount: packetCount * getPacketMaxBitCount(),
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});
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};
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export const getPacketCount = (bitCount) =>
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canSendPacket() ? Math.ceil(bitCount / getPacketEncodedBitCount()) : 0;
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export const getDataTransferDurationMilliseconds = (bitCount) =>
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getPacketCount(bitCount) * getPacketDurationMilliseconds();
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export const getPacketDurationSeconds = () => getPacketDurationMilliseconds() / 1000;
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export const getSegmentDurationSeconds = () => getSegmentDurationMilliseconds() / 1000;
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export const getPacketSegmentCount = () => Math.ceil(getPacketMaxBitCount() / BITS_PER_SAMPLE);
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export const getPacketDurationMilliseconds = () =>
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getPacketSegmentCount() * getSegmentDurationMilliseconds();
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export const getPacketIndex = (transferStartedMilliseconds, time) =>
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Math.floor((time - transferStartedMilliseconds) / getPacketDurationMilliseconds());
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export function getPacketSegmentIndex(transferStartedMilliseconds, time) {
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return getTranserSegmentIndex(transferStartedMilliseconds, time) % getPacketSegmentCount();
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}
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export function getTranserSegmentIndex(transferStartedMilliseconds, time) {
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const transferMs = time - transferStartedMilliseconds;
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const segmentMs = getSegmentDurationMilliseconds();
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return Math.floor(transferMs / segmentMs);
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}
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export function getPacketSegmentStartMilliseconds(transferStartedMilliseconds, packetIndex, segmentIndex) {
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const packetStart = getPacketStartMilliseconds(transferStartedMilliseconds, packetIndex);
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const segmentOffset = segmentIndex * getSegmentDurationMilliseconds();
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return packetStart + segmentOffset;
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}
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export function getPacketStartMilliseconds(transferStartedMilliseconds, packetIndex) {
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if(packetIndex < 0) return 0;
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if(packetIndex === 0) return transferStartedMilliseconds;
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return transferStartedMilliseconds + (packetIndex * getPacketDurationMilliseconds());
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}
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export function getPacketSegmentEndMilliseconds(transferStartedMilliseconds, packetIndex, segmentIndex) {
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return getPacketSegmentStartMilliseconds(transferStartedMilliseconds, packetIndex, segmentIndex + 1) - 0.1;
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}
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export const getPacketHeaderUnusedBitCount = () => 8 - (getPacketHeaderBitCount(false) % 8);
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export const getPacketHeaderBitCount = (padAsBytes = true) => {
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const bitCount = PACKET_CRC_BIT_COUNT +
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PACKET_SEQUENCE_NUMBER_BIT_COUNT +
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PACKET_SIZE_BITS;
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if(padAsBytes && bitCount % 8 !== 0) {
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return bitCount + (8 - (bitCount % 8))
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}
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return bitCount;
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}
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export const pack = (bits) => ({
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getBits: (packetIndex) => {
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// Returns a packet in the following order:
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// - [CRC]
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// - [Sequence Number]
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// - Data Length
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// - [Unused Bits (% 8 padding)]
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// - Data
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if(!canSendPacket()) return [];
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// How many data bits will be in our packet?
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let dataBitCount = getPacketDataBitCount();
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// grab our data
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const startIndex = packetIndex * dataBitCount;
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const endIndex = startIndex + dataBitCount;
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let packetBits = bits.slice(startIndex, endIndex);
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if(packetBits.length % 8 !== 0) {
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throw new Error('Attempted to create a packet with extra bits.');
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}
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// data byte count
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let byteCount = Math.ceil(packetBits.length / 8);
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const dataLengthBits = numberToBits(byteCount, PACKET_SIZE_BITS);
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let sequenceNumberBits = [];
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// sequence number
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if(PACKET_SEQUENCE_NUMBER_BIT_COUNT !== 0) {
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sequenceNumberBits = numberToBits(packetIndex, PACKET_SEQUENCE_NUMBER_BIT_COUNT);
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}
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// add our headers
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const headerBits = [
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...sequenceNumberBits,
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...dataLengthBits,
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...new Array(getPacketHeaderUnusedBitCount()).fill(0)
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]
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if(PACKET_CRC_BIT_COUNT !== 0) {
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// convert to bytes
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const crcCheckBits = [...headerBits, ...packetBits];
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console.log('crc check bits', crcCheckBits.length) // 136 bits
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const bytes = bitsToBytes(crcCheckBits);
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const crc = CRC.check(bytes, PACKET_CRC_BIT_COUNT);
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const crcBits = numberToBits(crc, PACKET_CRC_BIT_COUNT);
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if(packetIndex === 0) {
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console.log('header without crc was', headerBits.length)
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console.log('we did crc on this', crcCheckBits.join(''))
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}
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// CRC must be first
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headerBits.unshift(...crcBits);
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}
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packetBits.unshift(...headerBits);
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// encode our packet
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const encodedBits = encodePacket(packetBits);
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if(encodedBits.length > 2 ** PACKET_SIZE_BITS * 8) {
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throw new Error(`Attempted to create packet exceeding ${2 ** PACKET_SIZE_BITS * 8} bits with ${encodedBits.length} bits.`);
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}
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return encodedBits;
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}
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});
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export const unpack = (bits) => ({
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getPacketFromBits: (packetBits, packetIndex) => {
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const unpacked = {
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crc: CRC.INVALID,
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actualCrc: CRC.INVALID,
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packetIndex,
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sequence: -1,
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bytes: [],
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size: -1
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};
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if(packetBits.length === 0) return unpacked;
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// Remove the extra bits not used by the packet
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packetBits = packetBits.slice(0, getPacketMaxBitCount());
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// Remove extra bits not used by encoding
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if(IS_ENCODED) {
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packetBits.splice(getPacketEncodedBitCount());// before or after... i thik we need encoded. 144 is too small for 256 available
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packetBits = decodePacket(packetBits);
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}
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const headerBitCount = getPacketHeaderBitCount();
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// Get data size
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const sizeBits = packetBits.slice(
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PACKET_CRC_BIT_COUNT + PACKET_SEQUENCE_NUMBER_BIT_COUNT,
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PACKET_CRC_BIT_COUNT + PACKET_SEQUENCE_NUMBER_BIT_COUNT + PACKET_SIZE_BITS
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);
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const dataSizeByteCount = bitsToInt(sizeBits, PACKET_SIZE_BITS);
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unpacked.size = dataSizeByteCount;
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// Get sequence number
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if(PACKET_SEQUENCE_NUMBER_BIT_COUNT === 0) {
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unpacked.sequence = packetIndex;
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} else {
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const sequenceBits = packetBits.slice(
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PACKET_CRC_BIT_COUNT,
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PACKET_CRC_BIT_COUNT + PACKET_SEQUENCE_NUMBER_BIT_COUNT
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);
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const sequence = bitsToInt(sequenceBits, PACKET_SEQUENCE_NUMBER_BIT_COUNT);
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unpacked.sequence = sequence;
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}
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// Get CRC Header
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if(PACKET_CRC_BIT_COUNT !== 0) {
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const crcBits = packetBits.slice(0, PACKET_CRC_BIT_COUNT);
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const expectedCrc = bitsToInt(crcBits, PACKET_CRC_BIT_COUNT);
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unpacked.crc = expectedCrc;
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// Run CRC on all bits except CRC header
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const bitCountToCheck = (headerBitCount - PACKET_CRC_BIT_COUNT) + (dataSizeByteCount * 8);
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const crcCopy = packetBits.slice(PACKET_CRC_BIT_COUNT, PACKET_CRC_BIT_COUNT + bitCountToCheck);
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// check the crc is valid
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const bytes = bitsToBytes(crcCopy);
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unpacked.actualCrc = CRC.check(bytes, PACKET_CRC_BIT_COUNT);
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}
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// Get data bits
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packetBits = packetBits.slice(headerBitCount, headerBitCount + unpacked.size * 8);
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// convert to bytes
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unpacked.bytes = bitsToBytes(packetBits);
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return unpacked;
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},
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getPacket: (packetIndex) => {
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const unpacked = {
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crc: CRC.INVALID,
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actualCrc: CRC.INVALID,
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sequence: -1,
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bytes: [],
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size: -1
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};
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if(!canSendPacket()) return unpacked;
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// Get bits associated with the packet
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const packetBitCount = getPacketSegmentCount() + BITS_PER_SAMPLE;
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const offset = packetIndex * packetBitCount;
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const packetBits = bits.slice(offset, offset + packetBitCount);
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if(packetBits.length === 0) return unpacked;
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return this.getPacketFromBits(packetBits, packetIndex);
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}
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}); |