mirror of
https://github.com/Dingo-Shenanigans/ReSkate.git
synced 2026-10-18 21:25:21 +02:00
207 lines
9.5 KiB
C++
207 lines
9.5 KiB
C++
#include "delta_codec.h"
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#include "pose_delta.h"
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#include "block_codec.h"
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#include <algorithm>
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namespace dingosdk::multiplayer {
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namespace {
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bool state_kind(PacketKind kind) {
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return kind == PacketKind::pose || kind == PacketKind::audio || kind == PacketKind::cosmetics;
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}
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bool magic(std::span<const std::uint8_t> b, const char *m) {
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return b.size() >= 4 && std::equal(b.begin(), b.begin() + 4, m);
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}
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void put(std::vector<std::uint8_t> &b, std::uint64_t value, unsigned n) {
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for (unsigned i = 0; i < n; ++i)
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b.push_back(static_cast<std::uint8_t>(value >> (8 * i)));
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}
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std::uint64_t get(std::span<const std::uint8_t> b, std::size_t at, unsigned n) {
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std::uint64_t value{};
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for (unsigned i = 0; i < n; ++i)
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value |= std::uint64_t{b[at + i]} << (8 * i);
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return value;
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}
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} // namespace
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WireUpdate DeltaSender::prepare(const Packet &p) const {
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const auto raw = encode(p, true);
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return prepare(p, raw, encode_wire_bytes(raw));
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}
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WireUpdate DeltaSender::prepare(const Packet &p, std::span<const std::uint8_t> raw,
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std::span<const std::uint8_t> wire) const {
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return build(p, raw, wire, nullptr);
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}
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WireUpdate DeltaSender::prepare(const Packet &p, std::span<const std::uint8_t> raw, std::span<const std::uint8_t> wire,
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DeltaCache &cache) const {
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return build(p, raw, wire, &cache);
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}
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WireUpdate DeltaSender::build(const Packet &p, std::span<const std::uint8_t> raw, std::span<const std::uint8_t> wire,
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DeltaCache *cache) const {
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WireUpdate out;
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if (!state_kind(p.kind)) {
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out.bytes.assign(wire.begin(), wire.end());
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return out;
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}
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const auto found = bases_.find({p.source, p.kind});
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if (found == bases_.end() || found->second.epoch != p.epoch || found->second.world != p.world || p.time_us < found->second.time ||
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(p.kind != PacketKind::cosmetics && p.time_us - found->second.time >= 2000000)) {
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if (wire.size() + 4 > max_packet)
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return out;
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out.bytes.assign(wire.begin(), wire.end());
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out.bytes.insert(out.bytes.begin(), {'R', 'M', 'B', '1'});
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out.baseline.assign(raw.begin(), raw.end());
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return out;
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}
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const auto &base = found->second;
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if (cache)
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for (const auto &entry : cache->entries)
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if (entry.sequence == base.sequence && *entry.reference == base.raw) {
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out.bytes = entry.bytes;
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return out;
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}
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std::size_t best = wire.size();
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if (p.kind == PacketKind::pose) {
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// Pose patches encode changed fields directly. Avoid also building and
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// compressing a full XOR candidate for every destination peer.
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const auto patch = pose_delta::encode(raw, base.raw);
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if (!patch.empty()) {
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std::vector<std::uint8_t> sparse{'R', 'M', 'S', '1'};
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put(sparse, p.source, 8);
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put(sparse, p.epoch, 8);
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put(sparse, static_cast<unsigned>(p.kind), 2);
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put(sparse, base.sequence, 4);
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put(sparse, raw.size(), 4);
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put(sparse, patch.size(), 4);
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auto compressed = compress_block(patch);
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if (34 + compressed.bytes.size() < best) {
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if (compressed.codec == BlockCodec::zstd) sparse[3] = '2';
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sparse.insert(sparse.end(), compressed.bytes.begin(), compressed.bytes.end());
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out.bytes = std::move(sparse);
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}
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}
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} else {
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std::vector<std::uint8_t> difference(raw.begin(), raw.end());
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for (std::size_t i = 0; i < std::min(raw.size(), base.raw.size()); ++i)
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difference[i] ^= base.raw[i];
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std::vector<std::uint8_t> delta{'R', 'M', 'D', '1'};
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put(delta, p.source, 8);
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put(delta, p.epoch, 8);
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put(delta, static_cast<unsigned>(p.kind), 2);
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put(delta, base.sequence, 4);
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put(delta, raw.size(), 4);
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auto block = compress_block(difference);
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if (30 + block.bytes.size() < best) {
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if (block.codec == BlockCodec::zstd) delta[3] = '2';
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delta.insert(delta.end(), block.bytes.begin(), block.bytes.end());
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out.bytes = std::move(delta);
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}
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}
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if (out.bytes.empty())
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out.bytes.assign(wire.begin(), wire.end());
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if (cache)
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cache->entries.push_back({base.sequence, &base.raw, out.bytes});
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return out;
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}
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void DeltaSender::sent(const Packet &p, WireUpdate &&update) {
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const StreamKey key{p.source, p.kind};
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if (!update.establishes_baseline()) {
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if (auto it = bases_.find(key); it != bases_.end())
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it->second.touched = ++clock_;
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return;
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}
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// A connection has at most seven active remote sources plus its sender.
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// Evict old departed streams without allowing unbounded retained cosmetics.
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if (!bases_.contains(key) && bases_.size() >= max_players * 3) {
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const auto oldest = std::min_element(bases_.begin(), bases_.end(), [](const auto &a, const auto &b) {
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return a.second.touched < b.second.touched;
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});
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bases_.erase(oldest);
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}
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bases_[key] = {std::move(update.baseline), p.epoch, p.world, p.time_us, ++clock_, p.sequence};
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}
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bool DeltaReceiver::holds(std::uint64_t source, PacketKind kind, std::uint64_t epoch,
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std::uint32_t sequence) const noexcept {
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const auto stream = streams_.find({source, kind});
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return stream != streams_.end() &&
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std::any_of(stream->second.bases.begin(), stream->second.bases.end(),
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[&](const auto &b) { return b.epoch == epoch && b.sequence == sequence; });
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}
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std::optional<Packet> DeltaReceiver::receive(std::span<const std::uint8_t> bytes, bool &missing,
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std::uint64_t accepted_world) noexcept {
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missing = false;
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try {
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if (bytes.size() > max_packet)
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return {};
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if (magic(bytes, "RMB1")) {
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const auto raw = decode_wire_bytes(bytes.subspan(4));
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auto p = raw ? decode(*raw) : std::nullopt;
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if (!p || !state_kind(p->kind))
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return {};
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// Late snapshots must not evict references for the current world.
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if (accepted_world && p->world != accepted_world)
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return p;
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const StreamKey key{p->source, p->kind};
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if (!streams_.contains(key) && streams_.size() >= max_players * 3) {
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const auto oldest =
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std::min_element(streams_.begin(), streams_.end(), [](const auto &a, const auto &b) {
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return a.second.touched < b.second.touched;
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});
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streams_.erase(oldest);
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}
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auto &stream = streams_[key];
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stream.touched = ++clock_;
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// Re-encoding a decoded quaternion can change its last quantized bit.
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// Cache the exact packed bytes, never regenerated native transforms.
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if (stream.bases.empty() || stream.bases.back().epoch != p->epoch)
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stream.bases.clear();
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if (std::none_of(stream.bases.begin(), stream.bases.end(),
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[&](const auto &b) { return b.sequence == p->sequence; }))
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stream.bases.push_back({*raw, p->epoch, p->world, p->session, p->map, p->sequence});
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while (stream.bases.size() > 3)
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stream.bases.pop_front();
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return p;
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}
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const bool sparse = magic(bytes, "RMS1") || magic(bytes, "RMS2");
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if (!sparse && !magic(bytes, "RMD1") && !magic(bytes, "RMD2"))
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return decode_wire(bytes);
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if (bytes.size() <= (sparse ? 34U : 30U))
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return {};
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const StreamKey key{get(bytes, 4, 8), static_cast<PacketKind>(get(bytes, 20, 2))};
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const auto epoch = get(bytes, 12, 8), sequence = get(bytes, 22, 4), size = get(bytes, 26, 4);
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if (!state_kind(key.second) || !epoch || size < packet_header_size || size > max_packet || bytes.size() >= size)
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return {};
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const auto stream = streams_.find(key);
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if (stream == streams_.end()) {
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missing = true;
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return {};
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}
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const auto base =
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std::find_if(stream->second.bases.begin(), stream->second.bases.end(),
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[&](const auto &b) { return b.epoch == epoch && b.sequence == sequence; });
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if (base == stream->second.bases.end()) {
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missing = true;
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return {};
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}
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const auto header = sparse ? 34U : 30U;
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const auto unpacked = sparse ? get(bytes, 30, 4) : size;
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if (sparse && (key.second != PacketKind::pose || unpacked < packet_header_size + 6 ||
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unpacked > max_packet + 1024)) return {};
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std::vector<std::uint8_t> raw(static_cast<std::size_t>(unpacked));
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if (!decompress_block(bytes.subspan(header), raw,
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bytes[3] == '2' ? BlockCodec::zstd : BlockCodec::lz4)) return {};
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if (sparse)
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raw = pose_delta::decode(raw, base->raw, static_cast<std::size_t>(size));
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else
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for (std::size_t i = 0; i < std::min(raw.size(), base->raw.size()); ++i)
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raw[i] ^= base->raw[i];
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auto p = decode(raw);
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if (!p || p->source != key.first || p->kind != key.second || p->epoch != epoch ||
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p->world != base->world || p->session != base->session || p->map != base->map)
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return {};
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stream->second.touched = ++clock_;
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return p;
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} catch (...) {
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return {};
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}
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}
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} // namespace dingosdk::multiplayer
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