mirror of
https://github.com/dz0ny/meshcore-sar.git
synced 2026-07-02 09:31:36 +00:00
Janez T
619 lines
18 KiB
Dart
619 lines
18 KiB
Dart
import 'dart:typed_data';
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const int _maxCompanionFrameBytes = 172; // MeshCore MAX_FRAME_SIZE
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const int _cmdSendRawDataOverheadBytes = 2; // cmd + pathLen
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const int _maxMeshPacketPayloadBytes = 184; // MeshCore MAX_PACKET_PAYLOAD
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const int _meshPacketHeaderBytes = 2; // mesh header bytes before path/payload
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const int _imagePacketHeaderBytes = 6; // image packet binary header in payload
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const int _defaultLoRaSf = 10; // MeshCore companion defaults (SF10)
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const int _defaultLoRaCr = 5; // MeshCore companion defaults (4/5)
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const int _defaultLoRaBwHz = 250000; // MeshCore companion defaults (250kHz)
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const int _defaultLoRaPreambleSymbols = 8;
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const int _defaultLoRaCrcEnabled = 1;
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const int _defaultLoRaExplicitHeader = 1;
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const double _defaultAirtimeBudgetFactor = 1.0; // one half duty-cycle
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/// Compressed image format used in the image packet protocol.
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enum ImageFormat {
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avif(0, 'AVIF'),
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jpeg(1, 'JPEG');
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const ImageFormat(this.id, this.label);
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final int id;
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final String label;
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static ImageFormat fromId(int id) => ImageFormat.values.firstWhere(
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(f) => f.id == id,
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orElse: () => ImageFormat.avif,
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);
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}
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/// A single binary fragment of a compressed image.
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///
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/// Binary format (direct contacts, via pushRawData / cmdSendRawData):
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/// [0x49 'I'][sessionId:4B][idx:1B][imageData...]
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///
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/// Legacy default is 152 data bytes per fragment.
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class ImagePacket {
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final String sessionId; // 8 hex chars (4 bytes)
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final ImageFormat format;
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final int index; // 0-based
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final int total; // total fragment count (1..255)
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final Uint8List data;
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const ImagePacket({
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required this.sessionId,
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required this.format,
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required this.index,
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required this.total,
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required this.data,
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});
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static const int _magic = 0x49; // 'I'
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static const int _headerLen = 6; // magic(1)+session(4)+idx(1)
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static const int maxDataBytes =
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152; // Conservative default for compatibility.
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static bool isImageBinary(Uint8List payload) =>
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payload.isNotEmpty && payload[0] == _magic;
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static ImagePacket? tryParseBinary(Uint8List payload) {
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if (payload.length < _headerLen) return null;
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if (payload[0] != _magic) return null;
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try {
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final sessionId = payload
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.sublist(1, 5)
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.map((b) => b.toRadixString(16).padLeft(2, '0'))
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.join();
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final index = payload[5];
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final data = payload.sublist(_headerLen);
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return ImagePacket(
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sessionId: sessionId,
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format: ImageFormat.avif,
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index: index,
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total: 0,
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data: data,
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);
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} catch (_) {
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return null;
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}
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}
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Uint8List encodeBinary() {
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final sessionBytes = Uint8List(4);
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for (var i = 0; i < 4; i++) {
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sessionBytes[i] = int.parse(
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sessionId.substring(i * 2, i * 2 + 2),
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radix: 16,
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);
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}
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final out = Uint8List(_headerLen + data.length);
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out[0] = _magic;
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out.setRange(1, 5, sessionBytes);
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out[5] = index;
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out.setRange(_headerLen, out.length, data);
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return out;
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}
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@override
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String toString() {
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final suffix = total > 0 ? ' ${format.label} [$index/${total - 1}]' : ' [$index]';
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return 'ImagePacket($sessionId$suffix ${data.length}B)';
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}
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}
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/// Compute the maximum safe image data bytes for a direct route path.
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///
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/// This accounts for:
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/// - companion command-frame limit (MAX_FRAME_SIZE=172),
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/// - cmdSendRawData overhead (`cmd` + `pathLen`),
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/// - image packet binary header (8 bytes),
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/// - mesh packet payload limit (MAX_PACKET_PAYLOAD=184).
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///
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/// Path length follows Contact.outPathLen semantics: 0 = direct, 1+ = hops.
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int safeImageDataBytesForPath(int pathLen) {
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final normalizedPathLen = pathLen.clamp(0, 64).toInt();
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final maxRawPayloadFromCommandFrame =
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_maxCompanionFrameBytes -
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_cmdSendRawDataOverheadBytes -
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normalizedPathLen;
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final maxRawPayloadFromMesh =
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_maxMeshPacketPayloadBytes - ImagePacket._headerLen;
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final maxRawPayload = maxRawPayloadFromCommandFrame < maxRawPayloadFromMesh
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? maxRawPayloadFromCommandFrame
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: maxRawPayloadFromMesh;
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final maxData = maxRawPayload - ImagePacket._headerLen;
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// Keep a safety margin below the theoretical direct-route ceiling.
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// Fragments at the absolute 172-byte command-frame limit have proven flaky
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// in practice, so cap to the conservative protocol default.
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return maxData.clamp(1, ImagePacket.maxDataBytes).toInt();
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}
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/// Approximate end-to-end transmit time for image fragments on MeshCore LoRa.
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///
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/// The estimate uses:
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/// - LoRa airtime math with MeshCore companion defaults (SF10/BW250/CR5),
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/// - MeshCore airtime budget pacing (default factor 1.0),
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/// - hop multiplier (`pathLen + 1`) for direct routed packets.
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Duration estimateImageTransmitDuration({
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required int fragmentCount,
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required int sizeBytes,
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int pathLen = 0,
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int? radioBw,
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int? radioSf,
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int? radioCr,
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}) {
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if (fragmentCount <= 0 || sizeBytes <= 0) return Duration.zero;
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final safePathLen = pathLen.clamp(0, 64);
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final hops = safePathLen + 1;
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final baseDataPerFragment = sizeBytes ~/ fragmentCount;
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final extraBytes = sizeBytes % fragmentCount;
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var totalMs = 0.0;
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for (var i = 0; i < fragmentCount; i++) {
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final fragmentDataBytes = baseDataPerFragment + (i < extraBytes ? 1 : 0);
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final loraLen =
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_meshPacketHeaderBytes +
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safePathLen +
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_imagePacketHeaderBytes +
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fragmentDataBytes;
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final airtimeMs = _estimateLoRaAirtimeMs(
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loraLen,
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radioBw: radioBw,
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radioSf: radioSf,
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radioCr: radioCr,
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);
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totalMs += airtimeMs * (1.0 + _defaultAirtimeBudgetFactor) * hops;
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}
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return Duration(milliseconds: totalMs.round());
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}
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double _estimateLoRaAirtimeMs(
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int payloadLenBytes, {
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int? radioBw,
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int? radioSf,
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int? radioCr,
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}) {
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final sf = _normalizeSf(radioSf);
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final bw = _resolveBandwidthHz(radioBw).toDouble();
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final cr = (_normalizeCr(radioCr) - 4).clamp(1, 4);
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final ih = _defaultLoRaExplicitHeader == 1 ? 0 : 1;
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final de = (sf >= 11 && _defaultLoRaBwHz <= 125000) ? 1 : 0;
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final symbolMs = ((1 << sf) / bw) * 1000.0;
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final preambleMs = (_defaultLoRaPreambleSymbols + 4.25) * symbolMs;
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final num =
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(8 * payloadLenBytes) -
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(4 * sf) +
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28 +
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(16 * _defaultLoRaCrcEnabled) -
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(20 * ih);
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final den = 4 * (sf - (2 * de));
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final payloadSymCoeff = den <= 0 ? 0 : (num / den).ceil();
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final payloadSymbols =
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8 + (payloadSymCoeff < 0 ? 0 : payloadSymCoeff) * (cr + 4);
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final payloadMs = payloadSymbols * symbolMs;
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return preambleMs + payloadMs;
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}
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int _normalizeSf(int? value) {
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if (value == null) return _defaultLoRaSf;
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if (value >= 5 && value <= 12) return value;
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return _defaultLoRaSf;
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}
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int _normalizeCr(int? value) {
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if (value == null) return _defaultLoRaCr;
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if (value >= 5 && value <= 8) return value;
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return _defaultLoRaCr;
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}
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int _resolveBandwidthHz(int? rawBw) {
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if (rawBw == null) return _defaultLoRaBwHz;
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if (rawBw > 1000) return rawBw;
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switch (rawBw) {
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case 0:
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return 7800;
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case 1:
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return 10400;
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case 2:
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return 15600;
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case 3:
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return 20800;
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case 4:
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return 31250;
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case 5:
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return 41700;
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case 6:
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return 62500;
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case 7:
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return 125000;
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case 8:
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return 250000;
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case 9:
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return 500000;
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default:
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return _defaultLoRaBwHz;
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}
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}
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/// Envelope announcing image availability (control plane).
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///
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/// Text format:
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/// IE4:{sid}:{fmt}:{total}:{w}:{h}:{bytes}
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/// Example:
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/// IE4:deadbeef:0:7:3k:3k:t6
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class ImageEnvelope {
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static const String _prefixV4 = 'IE4:';
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final String sessionId; // 8 hex chars
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final ImageFormat format;
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final int total; // total fragment count
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final int width;
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final int height;
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final int sizeBytes; // total compressed image size
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final int version;
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const ImageEnvelope({
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required this.sessionId,
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required this.format,
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required this.total,
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required this.width,
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required this.height,
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required this.sizeBytes,
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this.version = 4,
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});
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static bool isEnvelope(String text) => text.startsWith(_prefixV4);
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static ImageEnvelope? tryParse(String text) {
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if (!isEnvelope(text)) return null;
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final body = text.substring(_prefixV4.length);
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final parts = body.split(':');
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if (parts.length != 6) return null;
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try {
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final sid = _decodeSessionId(parts[0]);
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final fmtId = _parseInt(parts[1], base36: true);
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final total = _parseInt(parts[2], base36: true);
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final w = _parseInt(parts[3], base36: true);
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final h = _parseInt(parts[4], base36: true);
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final bytes = _parseInt(parts[5], base36: true);
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if (sid == null) return null;
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if (fmtId == null) return null;
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if (total == null || total < 1 || total > 255) return null;
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if (w == null || h == null || w < 1 || h < 1) return null;
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if (bytes == null || bytes < 1) return null;
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return ImageEnvelope(
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sessionId: sid,
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format: ImageFormat.fromId(fmtId),
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total: total,
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width: w,
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height: h,
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sizeBytes: bytes,
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version: 4,
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);
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} catch (_) {
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return null;
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}
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}
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String encode() =>
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'$_prefixV4${_encodeSessionId(sessionId)}:'
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'${_toBase36(format.id)}:${_toBase36(total)}:${_toBase36(width)}:'
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'${_toBase36(height)}:${_toBase36(sizeBytes)}';
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}
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/// Direct request to fetch image fragments (control plane).
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///
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/// Text format:
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/// IR4:{sid}:{want}:{requesterKey6}
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/// Example:
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/// IR4:deadbeef:a:aabbccddeeff
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class ImageFetchRequest {
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static const String _prefixV4 = 'IR4:';
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static const int _binaryMagic = 0x69; // 'i'
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final String sessionId;
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final String want; // 'all' or 'missing'
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final List<int> missingIndices;
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final String requesterKey6; // 12 hex chars
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final int version;
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const ImageFetchRequest({
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required this.sessionId,
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this.want = 'all',
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this.missingIndices = const [],
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required this.requesterKey6,
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this.version = 4,
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});
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static bool isRequest(String text) => text.startsWith(_prefixV4);
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static bool isRequestBinary(Uint8List payload) =>
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payload.isNotEmpty && payload[0] == _binaryMagic;
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static ImageFetchRequest? tryParse(String text) {
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if (!isRequest(text)) return null;
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final body = text.substring(_prefixV4.length);
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final parts = body.split(':');
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if (parts.length != 3) return null;
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try {
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final sid = _decodeSessionId(parts[0]);
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final wantToken = parts[1];
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final requesterKey6 = parts[2];
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final normalizedWant = wantToken == 'a'
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? 'all'
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: ((wantToken.startsWith('m')) ? 'missing' : wantToken);
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if (sid == null) return null;
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final missingIndices = <int>[];
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if (normalizedWant == 'missing') {
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final encoded = wantToken.substring(1);
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if (encoded.isEmpty) return null;
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missingIndices.addAll(_decodeMissingIndicesCompact(encoded));
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if (missingIndices.isEmpty) return null;
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} else if (normalizedWant != 'all') {
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return null;
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}
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if (!RegExp(r'^[0-9a-fA-F]{12}$').hasMatch(requesterKey6)) return null;
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return ImageFetchRequest(
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sessionId: sid,
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want: normalizedWant,
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missingIndices: missingIndices,
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requesterKey6: requesterKey6.toLowerCase(),
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version: 4,
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);
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} catch (_) {
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return null;
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}
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}
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static ImageFetchRequest? tryParseBinary(Uint8List payload) {
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if (!isRequestBinary(payload)) return null;
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if (payload.length < 13) return null; // magic+sid+flags+key6+count
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try {
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final sid = payload
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.sublist(1, 5)
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.map((b) => b.toRadixString(16).padLeft(2, '0'))
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.join()
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.toLowerCase();
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final flags = payload[5];
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final requesterKey6 = payload
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.sublist(6, 12)
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.map((b) => b.toRadixString(16).padLeft(2, '0'))
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.join()
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.toLowerCase();
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final missingCount = payload[12];
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if (payload.length != 13 + missingCount) return null;
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final wantMissing = (flags & 0x01) == 0x01;
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final missing = <int>[];
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for (var i = 0; i < missingCount; i++) {
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missing.add(payload[13 + i]);
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}
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return ImageFetchRequest(
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sessionId: sid,
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want: wantMissing ? 'missing' : 'all',
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missingIndices: missing,
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requesterKey6: requesterKey6,
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version: 4,
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);
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} catch (_) {
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return null;
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}
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}
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String encode() {
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final wantToken = want == 'missing' && missingIndices.isNotEmpty
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? 'm${_encodeMissingIndicesCompact(missingIndices)}'
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: (want == 'all' ? 'a' : want);
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return '$_prefixV4${_encodeSessionId(sessionId)}:$wantToken:${requesterKey6.toLowerCase()}';
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}
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Uint8List encodeBinary() {
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if (!RegExp(r'^[0-9a-fA-F]{8}$').hasMatch(sessionId)) {
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throw ArgumentError.value(sessionId, 'sessionId', 'Expected 8 hex chars');
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}
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if (!RegExp(r'^[0-9a-fA-F]{12}$').hasMatch(requesterKey6)) {
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throw ArgumentError.value(
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requesterKey6,
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'requesterKey6',
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'Expected 12 hex chars',
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);
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}
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final useMissing = want == 'missing' && missingIndices.isNotEmpty;
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final missing = useMissing
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? missingIndices.where((v) => v >= 0 && v <= 254).toList()
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: <int>[];
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final out = Uint8List(13 + missing.length);
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out[0] = _binaryMagic;
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for (var i = 0; i < 4; i++) {
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out[1 + i] = int.parse(sessionId.substring(i * 2, i * 2 + 2), radix: 16);
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}
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out[5] = useMissing ? 0x01 : 0x00;
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for (var i = 0; i < 6; i++) {
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out[6 + i] = int.parse(
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requesterKey6.substring(i * 2, i * 2 + 2),
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radix: 16,
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);
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}
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out[12] = missing.length;
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for (var i = 0; i < missing.length; i++) {
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out[13 + i] = missing[i];
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}
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return out;
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}
|
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}
|
|
|
|
/// Per-fragment ACK for raw image payload packets.
|
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///
|
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/// Binary format:
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/// [0x6a 'j'][sessionId:4B][index:1B]
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class ImageFragmentAck {
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static const int _binaryMagic = 0x6a; // 'j'
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|
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final String sessionId; // 8 hex chars
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final int index; // 0..254
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|
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const ImageFragmentAck({required this.sessionId, required this.index});
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|
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static bool isImageFragmentAckBinary(Uint8List payload) =>
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payload.length == 6 && payload[0] == _binaryMagic;
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|
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static ImageFragmentAck? tryParseBinary(Uint8List payload) {
|
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if (!isImageFragmentAckBinary(payload)) return null;
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try {
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final sid = payload
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.sublist(1, 5)
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.map((b) => b.toRadixString(16).padLeft(2, '0'))
|
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.join()
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.toLowerCase();
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final idx = payload[5];
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return ImageFragmentAck(sessionId: sid, index: idx);
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} catch (_) {
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return null;
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}
|
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}
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|
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Uint8List encodeBinary() {
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if (!RegExp(r'^[0-9a-fA-F]{8}$').hasMatch(sessionId)) {
|
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throw ArgumentError.value(sessionId, 'sessionId', 'Expected 8 hex chars');
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}
|
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if (index < 0 || index > 254) {
|
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throw ArgumentError.value(index, 'index', 'Expected 0..254');
|
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}
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final out = Uint8List(6);
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out[0] = _binaryMagic;
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for (var i = 0; i < 4; i++) {
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out[1 + i] = int.parse(sessionId.substring(i * 2, i * 2 + 2), radix: 16);
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}
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out[5] = index;
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return out;
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}
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}
|
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|
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int? _parseInt(String token, {required bool base36}) =>
|
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int.tryParse(token, radix: base36 ? 36 : 10);
|
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|
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String _toBase36(int value) => value.toRadixString(36);
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|
|
String _encodeSessionId(String sessionIdHex) {
|
|
if (!RegExp(r'^[0-9a-fA-F]{8}$').hasMatch(sessionIdHex)) {
|
|
throw ArgumentError.value(
|
|
sessionIdHex,
|
|
'sessionIdHex',
|
|
'Expected 8 hex chars',
|
|
);
|
|
}
|
|
final value = int.parse(sessionIdHex, radix: 16);
|
|
return value.toRadixString(36);
|
|
}
|
|
|
|
String? _decodeSessionId(String token) {
|
|
if (!RegExp(r'^[0-9a-z]{1,7}$').hasMatch(token)) return null;
|
|
final value = int.tryParse(token, radix: 36);
|
|
if (value == null || value < 0 || value > 0xFFFFFFFF) return null;
|
|
return value.toRadixString(16).padLeft(8, '0');
|
|
}
|
|
|
|
String _encodeMissingIndicesCompact(List<int> indices) {
|
|
final sorted = indices.where((v) => v >= 0 && v <= 254).toSet().toList()
|
|
..sort();
|
|
if (sorted.isEmpty) return '';
|
|
final chunks = <String>[];
|
|
var start = sorted.first;
|
|
var prev = sorted.first;
|
|
for (var i = 1; i < sorted.length; i++) {
|
|
final curr = sorted[i];
|
|
if (curr == prev + 1) {
|
|
prev = curr;
|
|
continue;
|
|
}
|
|
chunks.add(
|
|
start == prev
|
|
? _toBase36(start)
|
|
: '${_toBase36(start)}-${_toBase36(prev)}',
|
|
);
|
|
start = curr;
|
|
prev = curr;
|
|
}
|
|
chunks.add(
|
|
start == prev ? _toBase36(start) : '${_toBase36(start)}-${_toBase36(prev)}',
|
|
);
|
|
return chunks.join('.');
|
|
}
|
|
|
|
List<int> _decodeMissingIndicesCompact(String encoded) {
|
|
final out = <int>[];
|
|
for (final token in encoded.split('.')) {
|
|
if (token.isEmpty) continue;
|
|
if (!token.contains('-')) {
|
|
final value = int.tryParse(token, radix: 36);
|
|
if (value == null || value < 0 || value > 254) return const [];
|
|
out.add(value);
|
|
continue;
|
|
}
|
|
final parts = token.split('-');
|
|
if (parts.length != 2) return const [];
|
|
final start = int.tryParse(parts[0], radix: 36);
|
|
final end = int.tryParse(parts[1], radix: 36);
|
|
if (start == null || end == null || start < 0 || end > 254 || start > end) {
|
|
return const [];
|
|
}
|
|
for (var i = start; i <= end; i++) {
|
|
out.add(i);
|
|
}
|
|
}
|
|
return out;
|
|
}
|
|
|
|
/// Fragment the compressed image bytes into [ImagePacket] list.
|
|
///
|
|
/// [sessionId] must be 8 lowercase hex chars.
|
|
/// [format] is the image format used.
|
|
/// Returns at most 255 packets; excess bytes are silently dropped.
|
|
List<ImagePacket> fragmentImage({
|
|
required String sessionId,
|
|
required ImageFormat format,
|
|
required Uint8List bytes,
|
|
int maxDataBytes = ImagePacket.maxDataBytes,
|
|
}) {
|
|
final chunkSize = maxDataBytes.clamp(1, 255).toInt();
|
|
final chunks = <Uint8List>[];
|
|
for (var offset = 0; offset < bytes.length; offset += chunkSize) {
|
|
final end = (offset + chunkSize).clamp(0, bytes.length);
|
|
chunks.add(bytes.sublist(offset, end));
|
|
if (chunks.length == 255) break; // protocol limit
|
|
}
|
|
final total = chunks.length;
|
|
return [
|
|
for (var i = 0; i < total; i++)
|
|
ImagePacket(
|
|
sessionId: sessionId,
|
|
format: format,
|
|
index: i,
|
|
total: total,
|
|
data: chunks[i],
|
|
),
|
|
];
|
|
}
|
|
|
|
/// Reassemble image bytes from received [packets].
|
|
///
|
|
/// Returns null if any fragment is missing.
|
|
Uint8List? reassembleImage(List<ImagePacket?> packets) {
|
|
if (packets.isEmpty) return null;
|
|
if (packets.any((p) => p == null)) return null;
|
|
final merged = <int>[];
|
|
for (final p in packets) {
|
|
merged.addAll(p!.data);
|
|
}
|
|
return Uint8List.fromList(merged);
|
|
}
|