integration/luprex/cpp/core/drivenengine.cpp

#include "wrap-string.hpp"
#include "wrap-vector.hpp"
#include "util.hpp"
#include "drivenengine.hpp"

#include <string_view>
#include <utility>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <fstream>
#include <cassert>

DrivenEngineReg *DrivenEngineReg::All;

DrivenEngineReg::DrivenEngineReg(const char *n, DrivenEngineMaker fn) {
    name = n;
    maker = fn;
    next = All;
    All = this;
}

DrivenEngineInitializer DrivenEngineInitializerReg::func;

DrivenEngineInitializerReg::DrivenEngineInitializerReg(DrivenEngineInitializer fn) {
    assert(func == nullptr);
    func = fn;
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// DrivenEngine private methods
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

int DrivenEngine::find_unused_chid() {
    // Note: channel ID zero is special, it is never reused.
    for (int i = 0; i < DRV_MAX_CHAN; i++) {
        int id = next_unused_chid_++;
        if (next_unused_chid_ == DRV_MAX_CHAN) next_unused_chid_ = 1;
        if (channels_[id] == nullptr) return id;
    }
    assert(false);
    return 0;
}

Channel *DrivenEngine::get_chid(int chid) const {
    assert(unsigned(chid) < DRV_MAX_CHAN);
    assert(channels_[chid].get() != nullptr);
    return channels_[chid].get();
}

static DrivenEngine *make_engine(std::string_view kind) {
    for (auto reg = DrivenEngineReg::All; reg != nullptr; reg=reg->next) {
        if (kind == reg->name) {
            UniqueDrivenEngine result = reg->maker();
            return result.release();
        }
    }
    return nullptr;
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// Class Channel
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////


Channel::Channel(DrivenEngine *de, int chid, int port, const eng::string &target, bool stop) {
    chid_ = chid;
    port_ = port;
    closed_ = false;
    target_ = target;
    readline_lastc_ = 0;
    desired_prompt_ = "";
    stop_driver_ = stop;
    sb_in_ = eng::make_shared<StreamBuffer>();
    sb_out_ = eng::make_shared<StreamBuffer>();
    sb_drvout_ = sb_out_;
}

void Channel::erase_command() {
    int ccsize = current_prompt_.size() + current_command_.size();
    if (ccsize > 0) {
        sb_drvout_->write_bytes(util::repeat_string("\b \b", ccsize));
        current_prompt_ = "";
        current_command_ = "";
    }
}

void Channel::echo_command() {
    // If the prompt has changed, erase everything and start over.
    if (desired_prompt_ != current_prompt_) {
        int ccsize = current_prompt_.size() + current_command_.size();
        sb_drvout_->write_bytes(util::repeat_string("\b \b", ccsize));
        sb_drvout_->write_bytes(desired_prompt_);
        current_command_ = "";
        current_prompt_ = desired_prompt_;
    }

    // Find out how much of the command matches.
    int match = sv::common_prefix_length(current_command_, desired_command_);

    // Echo backspaces to remove the non-matching part.
    int remove = current_command_.size() - match;
    if (remove > 0) {
        sb_drvout_->write_bytes(util::repeat_string("\b \b", remove));
        current_command_ = current_command_.substr(0, match);
    }

    // Echo the new part.
    eng::string newpart = desired_command_.substr(current_command_.size());
    if (newpart != "") {
        sb_drvout_->write_bytes(newpart);
        current_command_ = desired_command_;
    }
}

void Channel::set_prompt(const eng::string &p) {
    desired_prompt_ = p;
}

void Channel::feed_readline(std::string_view data) {
    int nbytes = data.size();
    const char *bytes = data.data();
    for (int i = 0; i < nbytes; i++) {
        char c = bytes[i];
        if ((c == '\n') && (readline_lastc_ == '\r')) {
            // Ignore newline immediately after carriage return.
            // Otherwise, crlf produces two newlines.
        } else if ((c == '\r') || (c == '\n')) {
            echo_command();
            sb_drvout_->write_bytes(eng::string(" \n"));
            sb_in_->write_bytes(desired_command_);
            sb_in_->write_uint8('\n');
            desired_command_ = "";
            current_prompt_ = "";
            current_command_ = "";
        } else if ((c == '\b') || (c == 127)) {
            int len = desired_command_.size();
            if (len > 0) {
                desired_command_ = desired_command_.substr(0, len-1);
            }
        } else if (c >= 32) {
            int len = desired_command_.size();
            if (len < READLINE_MAX) {
                desired_command_ = desired_command_ + c;
            }
        }
        readline_lastc_ = c;
    }
}

std::string_view Channel::peek_outgoing() const {
    return sb_drvout_->view();
}

void Channel::pump_readline() {
    if (sb_drvout_ != sb_out_) {
        if (!sb_out_->empty()) {
            erase_command();
            sb_out_->transfer_into(sb_drvout_.get());
        }
        echo_command();
    }
}

void Channel::sent_outgoing(int nbytes) {
    sb_drvout_->read_bytes(nbytes);
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// DrivenEngine Client-Side API
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

void DrivenEngine::listen_port(int port) {
    assert(listen_ports_.size() < DRV_MAX_LISTEN_PORTS);
    listen_ports_.push_back(port);
}

double DrivenEngine::get_clock() {
    return clock_;
}

SharedChannel DrivenEngine::new_outgoing_channel(const eng::string &target) {
    int chid = find_unused_chid();
    new_outgoing_.push_back(chid);
    SharedChannel result = eng::make_shared<Channel>(this, chid, 0, target, stop_driver_);
    channels_[chid] = result;
    return result;
}

SharedChannel DrivenEngine::new_incoming_channel() {
    if (accepted_channels_.empty()) {
        return nullptr;
    } else {
        SharedChannel result = std::move(accepted_channels_.back());
        accepted_channels_.pop_back();
        return result;
    }
}

SharedChannel DrivenEngine::get_stdio_channel() {
    return stdio_channel_;
}

util::LuaSourcePtr DrivenEngine::get_lua_source() {
    return std::move(lua_source_);
}

void DrivenEngine::rescan_lua_source() {
    rescan_lua_source_ = true;
}

void DrivenEngine::stop_driver() {
    stop_driver_ = true;
    for (int i = 0; i < DRV_MAX_CHAN; i++) {
        if (channels_[i] != nullptr) {
            channels_[i]->stop_driver_ = true;
        }
    }
}

DrivenEngine::DrivenEngine() {
    next_unused_chid_ = 1;
    stdio_channel_ = eng::make_shared<Channel>(this, 0, 0, "", false);
    stdio_channel_->sb_drvout_ = eng::make_shared<StreamBuffer>();
    channels_[0] = stdio_channel_;
    rescan_lua_source_ = false;
    clock_ = 0.0;
    stop_driver_ = false;
}

DrivenEngine::~DrivenEngine() {}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// LOGFILE EVENT IDS.
//
// There's one event ID for each mutator, plus one for 'release'.
//
// There are no event IDs for getters, these aren't considered loggable events.
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

enum DrvAction {
    PLAY_INITIALIZE,
    PLAY_CLEAR_NEW_OUTGOING,
    PLAY_SENT_OUTGOING,
    PLAY_RECV_INCOMING,
    PLAY_NOTIFY_CLOSE,
    PLAY_NOTIFY_ACCEPT,
    PLAY_INVOKE_EVENT_UPDATE,
    PLAY_SET_LUA_SOURCE,
    PLAY_RELEASE,
};

inline static const char *action_string(DrvAction act) {
    switch(act) {
    case PLAY_INITIALIZE: return "PLAY_INITIALIZE";
    case PLAY_CLEAR_NEW_OUTGOING: return "PLAY_CLEAR_NEW_OUTGOING";
    case PLAY_SENT_OUTGOING: return "PLAY_SENT_OUTGOING";
    case PLAY_RECV_INCOMING: return "PLAY_RECV_INCOMING";
    case PLAY_NOTIFY_CLOSE: return "PLAY_NOTIFY_CLOSE";
    case PLAY_NOTIFY_ACCEPT: return "PLAY_NOTIFY_ACCEPT";
    case PLAY_SET_LUA_SOURCE: return "PLAY_SET_LUA_SOURCE";
    case PLAY_INVOKE_EVENT_UPDATE: return "PLAY_INVOKE_EVENT_UPDATE";
    case PLAY_RELEASE: return "PLAY_RELEASE";
    default: return "unknown";
    }
}
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// RLOG and WLOG, functions to read and write binary data to logfiles.
//
// After doing an rlog operation, you should check the stream
// for "good" to find out if there was any error.
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

class PlayLogfile : public std::ofstream { using std::ofstream::ofstream; };
class ReplayLogfile : public std::ifstream { using std::ifstream::ifstream; };

static uint8_t rlog_uint8(EngineWrapper *w) {
    uint8_t result;
    w->rlog->read((char *)&result, 1);
    if (!w->rlog->good()) return 0;
    return result;
}

static uint32_t rlog_uint32(EngineWrapper *w) {
    uint32_t result;
    w->rlog->read((char *)&result, 4);
    if (!w->rlog->good()) return 0;
    return result;
}

static uint64_t rlog_uint64(EngineWrapper *w) {
    uint64_t result;
    w->rlog->read((char *)&result, 8);
    if (!w->rlog->good()) return 0;
    return result;
}

static double rlog_double(EngineWrapper *w) {
    double result;
    w->rlog->read((char *)&result, 8);
    if (!w->rlog->good()) return 0.0;
    return result;
}

std::string_view rlog_short_string(EngineWrapper *w) {
    uint32_t len = rlog_uint8(w);
    if (len == 255) {
        len = rlog_uint32(w);
    }
    assert (len <= DRV_SHORTSTRING_SIZE);
    if (len > 0) w->rlog->read(w->databuffer, len);
    if (!w->rlog->good()) return std::string_view();
    return std::string_view(w->databuffer, len);
}

std::string rlog_string(EngineWrapper *w) {
    uint32_t len = rlog_uint8(w);
    if (len == 255) {
        len = rlog_uint32(w);
    }
    std::string result(len, ' ');
    if (len > 0) w->rlog->read(&result[0], len);
    if (!w->rlog->good()) return "";
    return result;
}

static void wlog_uint8(EngineWrapper *w, uint8_t v) {
    w->wlog->put((char)v);
}

static void wlog_uint32(EngineWrapper *w, uint32_t v) {
    w->wlog->write((const char *)&v, 4);
}

static void wlog_uint64(EngineWrapper *w, uint64_t v) {
    w->wlog->write((const char *)&v, 8);
}

static void wlog_double(EngineWrapper *w, double v) {
    w->wlog->write((const char *)&v, 8);
}

static void wlog_short_string(EngineWrapper *w, std::string_view v) {
    assert (v.size() <= DRV_SHORTSTRING_SIZE);
    if (v.size() >= 255) {
        wlog_uint8(w, 0xFF);
        wlog_uint32(w, v.size());
    } else {
        wlog_uint8(w, v.size());
    }
    w->wlog->write(v.data(), v.size());
}

static void wlog_string(EngineWrapper *w, std::string_view v) {
    if (v.size() >= 255) {
        wlog_uint8(w, 0xFF);
        wlog_uint32(w, v.size());
    } else {
        wlog_uint8(w, v.size());
    }
    w->wlog->write(v.data(), v.size());
}

static void wlog_cmd_hash(EngineWrapper *w, DrvAction act, uint32_t hash) {
    wlog_uint8(w, act);
    wlog_uint32(w, hash);
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// reset_wrapper
//
// Shut down a EngineWrapper, store an optional error message.
//
// release
//
// Shut down an EngineWrapper cleanly, with no error message, and
// log the step if the logfile is open.
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

static void reset_wrapper(EngineWrapper *w, const char *format, ...) {
    va_list argp;
    va_start(argp, format);
    memset(w->error, 0, DRV_ERRMSG_SIZE);
    vsnprintf(w->error, DRV_ERRMSG_SIZE, format, argp);
    w->error[DRV_ERRMSG_SIZE - 1] = 0;

    if (w->wlog != nullptr) {
        w->wlog->close();
        delete w->wlog;
        w->wlog = nullptr;
    }

    if (w->rlog != nullptr) {
        w->rlog->close();
        delete w->rlog;
        w->rlog = nullptr;
    }

    if (w->engine != nullptr) {
        delete w->engine;
        w->engine = nullptr;
    }
}

static void release(EngineWrapper *w) {
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_RELEASE, eng::memhash());
    }
    reset_wrapper(w, "");
};

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// DRIVER Methods: Getters
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

void DrivenEngine::drv_get_listen_ports(uint32_t *nports, const uint32_t **ports) const {
    *nports = listen_ports_.size();
    *ports = &listen_ports_[0];
}

void DrivenEngine::drv_get_new_outgoing(uint32_t *nchids, const uint32_t **chids) const {
    *nchids = new_outgoing_.size();
    *chids = &new_outgoing_[0];
}

const char *DrivenEngine::drv_get_target(uint32_t chid) const {
    return get_chid(chid)->target_.c_str();
}

bool DrivenEngine::drv_get_channel_released(uint32_t chid) const {
    return channels_[chid].use_count() == 1;
}

void DrivenEngine::drv_get_outgoing(uint32_t chid, uint32_t *len, const char **data) const {
    std::string_view v = get_chid(chid)->peek_outgoing();
    *len = v.size();
    *data = v.data();
}

bool DrivenEngine::drv_get_outgoing_empty(uint32_t chid) const {
    std::string_view v = get_chid(chid)->peek_outgoing();
    return (v.size() == 0);
}

double DrivenEngine::drv_get_clock() const {
    return clock_;
}

bool DrivenEngine::drv_get_rescan_lua_source() const {
    return rescan_lua_source_;
}

bool DrivenEngine::drv_get_stop_driver() const {
    return stop_driver_;
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// DRIVER Methods: Mutators
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

void DrivenEngine::drv_initialize(uint32_t srcpklen, const char *srcpk, int argc, char **argv) {
    drv_set_lua_source(srcpklen, srcpk);
    event_init(argc, argv);
    stdio_channel_->pump_readline();
}

void DrivenEngine::drv_clear_new_outgoing() {
    new_outgoing_.clear();
}

void DrivenEngine::drv_sent_outgoing(uint32_t chid, uint32_t nbytes) {
    return get_chid(chid)->sent_outgoing(nbytes);
}

void DrivenEngine::drv_recv_incoming(uint32_t chid, uint32_t nbytes, const char *bytes) {
    std::string_view sbytes(bytes, nbytes);
    if (nbytes > 0) {
        Channel *ch = get_chid(chid);
        if (ch->sb_drvout_ != ch->sb_out_) {
            ch->feed_readline(sbytes);
        } else {
            ch->sb_in_->write_bytes(sbytes);
        }
    }
}

void DrivenEngine::drv_notify_close(uint32_t chid, uint32_t len, const char *data) {
    Channel *ch = get_chid(chid);
    ch->closed_ = true;
    ch->error_ = std::string(data, len);
    channels_[chid].reset();
}

uint32_t DrivenEngine::drv_notify_accept(uint32_t port) {
    int chid = find_unused_chid();
    channels_[chid] = eng::make_shared<Channel>(this, chid, port, "", stop_driver_);
    accepted_channels_.push_back(channels_[chid]);
    return chid;
}

void DrivenEngine::drv_invoke_event_update(double clock) {
    clock_ = clock;
    event_update();
    stdio_channel_->pump_readline();
}

void DrivenEngine::drv_set_lua_source(uint32_t srcpklen, const char *srcpk) {
    StreamBuffer sb(srcpk, srcpklen);
    uint32_t nfiles = sb.read_uint32();
    lua_source_.reset(new util::LuaSourceVec);
    lua_source_->resize(nfiles);
    for (uint32_t i = 0; i < nfiles; i++) {
        (*lua_source_)[i].first = sb.read_string();
    }
    for (uint32_t i = 0; i < nfiles; i++) {
        (*lua_source_)[i].second = sb.read_string();
    }
    rescan_lua_source_ = false;
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// C Wrappers: Getters
//
// These wrappers make it possible to call the drv_get routines using C
// functions instead of methods.  This is important if the engine is compiled
// with one C++ compiler, but the driver is compiled with a different C++
// compiler.
//
// Some of these take parameter 'EngineWrapper', some take 'EngineWrapper',
// and some come in two versions.  This all depends on whether they are used
// during play, during replay, or both.
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

static void drv_get_listen_ports(EngineWrapper *w, uint32_t *nports, const uint32_t **ports) {
    return w->engine->drv_get_listen_ports(nports, ports);
}

static void drv_get_new_outgoing(EngineWrapper *w, uint32_t *nchanids, const uint32_t **chanids) {
    return w->engine->drv_get_new_outgoing(nchanids, chanids);
}

static const char *drv_get_target(EngineWrapper *w, uint32_t chid) {
    return w->engine->drv_get_target(chid);
}

static bool drv_get_channel_released(EngineWrapper *w, uint32_t chid) {
    return w->engine->drv_get_channel_released(chid);
}

static void drv_get_outgoing(EngineWrapper *w, uint32_t chid, uint32_t *len, const char **data) {
    return w->engine->drv_get_outgoing(chid, len, data);
}

static bool drv_get_outgoing_empty(EngineWrapper *w, uint32_t chid) {
    return w->engine->drv_get_outgoing_empty(chid);
}

static double drv_get_clock(EngineWrapper *w) {
    return w->engine->drv_get_clock();
}

static bool drv_get_rescan_lua_source(EngineWrapper *w) {
    return w->engine->drv_get_rescan_lua_source();
}

static bool drv_get_stop_driver(EngineWrapper *w) {
    return w->engine->drv_get_stop_driver();
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// C Wrappers: Mutators
//
// The wrapper for a mutator consists of two parts: the wrapper which is used at
// 'play' time, and the wrapper which is used at 'replay' time.  
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////


static void play_initialize(EngineWrapper *w, uint32_t argc, char **argv, uint32_t srcpklen, const char *srcpk, const char *logfn) {
    if (w->engine != nullptr) {
        return reset_wrapper(w, "Cannot initialize wrapper, it's already initialized.");
    }

    // Clear the error message.
    memset(w->error, 0, DRV_ERRMSG_SIZE);

    // Open the logfile, if any is specified.
    if ((logfn != nullptr) && (logfn[0] != 0)) {
        w->wlog = new PlayLogfile(logfn, std::ios_base::out | std::ios_base::binary | std::ios_base::trunc);
        if (!w->wlog->good()) {
            return reset_wrapper(w, "Could not open replay log for writing: %s", logfn);
        }
    } else {
        w->wlog = nullptr;
    }
    
    // If we have a logfile, then log this initialization.
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_INITIALIZE, eng::memhash());
        wlog_uint32(w, argc);
        for (uint32_t i = 0; i < argc; i++) {
            wlog_string(w, argv[i]);
        }
        wlog_string(w, std::string_view(srcpk, srcpklen));
        w->wlog->flush();
    }

    // Create the engine of the appropriate type.
    if (argc < 1) {
        std::ostringstream oss;
        oss << "Must pass an engine type on the command line.  Known types:\n";
        for (auto reg = DrivenEngineReg::All; reg != nullptr; reg=reg->next) {
            oss << "    " << reg->name << std::endl;
        }
        std::string err = oss.str();
        return reset_wrapper(w, err.c_str());
    }
    w->engine = make_engine(argv[0]);
    if (w->engine == nullptr) {
        return reset_wrapper(w, "No such driven engine type: %s", argv[0]);
    }

    // Call the engine initialization sequence.
    w->engine->drv_initialize(srcpklen, srcpk, argc - 1, argv + 1);
}


static void replay_initialize(EngineWrapper *w) {
    assert(w->rlog != nullptr);
    std::vector<std::string> argvstr;
    uint32_t argc = rlog_uint32(w);
    for (uint32_t i = 0; i < argc; i++) {
        argvstr.push_back(rlog_string(w));
    }
    std::string srcpk = rlog_string(w);

    if (!w->rlog->good()) {
        return reset_wrapper(w, "replay log corrupt in replay_initialize");
    }

    // We need to convert the argument vector from an array
    // of C++ strings into the canonical argc, argv format.
    std::vector<char *> argvec;
    for (uint32_t i = 0; i < argc; i++) {
        argvec.push_back(&argvstr[i][0]);
    }
    char **argv = &argvec[0];

    // Create the engine.
    w->engine = make_engine(argv[0]);
    if (w->engine == nullptr) {
        return reset_wrapper(w, "No such driven engine type: %s", argvstr[0]);
    }


    w->engine->drv_initialize(srcpk.size(), srcpk.c_str(), argc - 1, argv + 1);
}


////////////////////////


static void play_clear_new_outgoing(EngineWrapper *w) {
    assert(w->rlog == nullptr);
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_CLEAR_NEW_OUTGOING, eng::memhash());
        w->wlog->flush();
    }
    w->engine->drv_clear_new_outgoing();
}

static void replay_clear_new_outgoing(EngineWrapper *w) {
    w->engine->drv_clear_new_outgoing();
}


////////////////////////


static void play_sent_outgoing(EngineWrapper *w, uint32_t chid, uint32_t nbytes) {
    assert(w->rlog == nullptr);
    if (w->wlog != nullptr) {
        uint32_t ndata; const char *data;
        w->engine->drv_get_outgoing(chid, &ndata, &data);
        assert(nbytes <= ndata);
        wlog_cmd_hash(w, PLAY_SENT_OUTGOING, eng::memhash());
        wlog_uint32(w, chid);
        wlog_uint32(w, nbytes);
        wlog_uint64(w, SpookyHash::QkHash64(data, nbytes));
        w->wlog->flush();
    }
    w->engine->drv_sent_outgoing(chid, nbytes);
}

static void replay_sent_outgoing(EngineWrapper *w) {
    uint32_t chid = rlog_uint32(w);
    uint32_t nbytes = rlog_uint32(w);
    uint64_t hash = rlog_uint64(w);

    if (!w->rlog->good()) {
        return reset_wrapper(w, "replay log corrupt in replay_sent_outgoing");
    }

    uint32_t ndata; const char *data;
    w->engine->drv_get_outgoing(chid, &ndata, &data);
    if ((nbytes > ndata) || (hash != SpookyHash::QkHash64(data, nbytes))) {
        return reset_wrapper(w, "nondeterministic in replay_sent_outgoing");
    }
    if (w->replay_cb_sent_outgoing != nullptr) {
        w->replay_cb_sent_outgoing(w->replay_cb_vp, chid, ndata, data);
    }
    w->engine->drv_sent_outgoing(chid, nbytes);
}


////////////////////////


static void play_recv_incoming(EngineWrapper *w, uint32_t chid, uint32_t len, const char *data) {
    assert(w->rlog == nullptr);
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_RECV_INCOMING, eng::memhash());
        wlog_uint32(w, chid);
        wlog_short_string(w, std::string_view(data, len));
        w->wlog->flush();
    }
    w->engine->drv_recv_incoming(chid, len, data);
}

static void replay_recv_incoming(EngineWrapper *w) {
    uint32_t chid = rlog_uint32(w);
    std::string_view data = rlog_short_string(w);

    if (!w->rlog->good()) {
        return reset_wrapper(w, "replay log corrupt in replay_recv_incoming");
    }

    w->engine->drv_recv_incoming(chid, data.size(), data.data());
}


////////////////////////


static void play_notify_close(EngineWrapper *w, uint32_t chid, uint32_t len, const char *data) {
    assert(w->rlog == nullptr);
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_NOTIFY_CLOSE, eng::memhash());
        wlog_uint32(w, chid);
        wlog_string(w, std::string_view(data, len));
        w->wlog->flush();
    }

    w->engine->drv_notify_close(chid, len, data);
}

static void replay_notify_close(EngineWrapper *w) {
    uint32_t chid = rlog_uint32(w);
    std::string message = rlog_string(w);

    if (!w->rlog->good()) {
        return reset_wrapper(w, "replay log corrupt in replay_notify_close");
    }

    w->engine->drv_notify_close(chid, message.size(), message.c_str());
}


////////////////////////


static uint32_t play_notify_accept(EngineWrapper *w, uint32_t port) {
    assert(w->rlog == nullptr);
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_NOTIFY_ACCEPT, eng::memhash());
        wlog_uint32(w, port);
        w->wlog->flush();
    }

    return w->engine->drv_notify_accept(port);
}

static void replay_notify_accept(EngineWrapper *w) {
    uint32_t port = rlog_uint32(w);
    
    if (!w->rlog->good()) {
        return reset_wrapper(w, "replay log corrupt in replay_notify_accept");
    }

    w->engine->drv_notify_accept(port);
}


////////////////////////


static void play_invoke_event_update(EngineWrapper *w, double clock) {
    assert(w->rlog == nullptr);
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_INVOKE_EVENT_UPDATE, eng::memhash());
        wlog_double(w, clock);
        w->wlog->flush();
    }

    w->engine->drv_invoke_event_update(clock);
}

static void replay_invoke_event_update(EngineWrapper *w) {
    double clock = rlog_double(w);

    if (!w->rlog->good()) {
        return reset_wrapper(w, "replay log corrupt in replay_event_update");
    }

    w->engine->drv_invoke_event_update(clock);
}


////////////////////////


void play_set_lua_source(EngineWrapper *w, uint32_t srcpklen, const char *srcpk) {
    assert(w->rlog == nullptr);
    if (w->wlog != nullptr) {
        wlog_cmd_hash(w, PLAY_SET_LUA_SOURCE, eng::memhash());
        wlog_string(w, std::string_view(srcpk, srcpklen));
        w->wlog->flush();
    }

    w->engine->drv_set_lua_source(srcpklen, srcpk);
}

void replay_set_lua_source(EngineWrapper *w) {
    std::string srcpack = rlog_string(w);

    if (!w->rlog->good()) {
        return reset_wrapper(w, "replay log corrupt in replay_set_lua_source");
    }

    w->engine->drv_set_lua_source(srcpack.size(), srcpack.c_str());
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// Replay Core
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////


static void replaycore_initialize(EngineWrapper *w, const char *logfn) {
    if (w->engine != nullptr) {
        return reset_wrapper(w, "Cannot initialize wrapper, it's already initialized.");
        return;
    }
    
    // Clear the error message.
    memset(w->error, 0, DRV_ERRMSG_SIZE);

    // Open the logfile.
    w->rlog = new ReplayLogfile(logfn, std::ios_base::in | std::ios_base::binary);
    if (!w->rlog->good()) {
        return reset_wrapper(w, "Could not open replay log for reading: %s", logfn);
    }

    // Read one step from the logfile, and make sure it's an initialize step.
    uint8_t code = rlog_uint8(w);
    int hash = rlog_uint32(w);
    if (!w->rlog->good()) {
        return reset_wrapper(w, "logfile corrupt in initial step");
    }
    if (hash != eng::memhash()) {
        return reset_wrapper(w, "nondeterminism detected in initial step");
    }
    if (code != PLAY_INITIALIZE) {
        return reset_wrapper(w, "replay log doesn't begin with initialize step");
    }

    // Replay the initialize step from the logfile.
    // Doing this immediately, rather than waiting for the driver
    // to call 'step', enforces the invariant that after calling
    // initialize, there's an engine.
    replay_initialize(w);
}

static void replaycore_step(EngineWrapper *w) {
    if (w->rlog == nullptr) {
        return;
    }

    uint8_t code = rlog_uint8(w);
    if (w->rlog->eof()) {
        return reset_wrapper(w, "logfile terminated abruptly");
    }
    int hash = rlog_uint32(w);
    if (!w->rlog->good()) {
        return reset_wrapper(w, "logfile corrupt in replay step");
    }
    if (hash != eng::memhash()) {
        return reset_wrapper(w, "nondeterminism detected");
    }
    switch (code) {
    case PLAY_CLEAR_NEW_OUTGOING: replay_clear_new_outgoing(w); return;
    case PLAY_SENT_OUTGOING: replay_sent_outgoing(w); return;
    case PLAY_RECV_INCOMING: replay_recv_incoming(w); return;
    case PLAY_NOTIFY_CLOSE: replay_notify_close(w); return;
    case PLAY_NOTIFY_ACCEPT: replay_notify_accept(w); return;
    case PLAY_SET_LUA_SOURCE: replay_set_lua_source(w); return;
    case PLAY_INVOKE_EVENT_UPDATE: replay_invoke_event_update(w); return;
    case PLAY_RELEASE: release(w); return;
    default: return reset_wrapper(w, "Replay log corrupt in command dispatcher");
    }
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// General Mutators
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////



//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//
// Wrapper Initialization
//
// To access the engine across a DLL boundary, you first use
// GetProcAddress or dlsym to fetch the addresses of 'init_play_engine'
// and 'init_replay_engine'.  Then, you use those two functions to
// initialize a EngineWrapper or a EngineWrapper, which contain the addresses
// of all the other functions you need.  These are the only two functions
// marked 'DLLEXPORT', all other functions are exported from the DLL
// indirectly.
//
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

#if defined(__linux__)
  #define DLLEXPORT __attribute__((visibility("default")))
#elif defined(_WIN32)
  #define DLLEXPORT __declspec(dllexport)
#endif

static void init_engine_wrapper_helper(EngineWrapper *w) {
    static bool called_initializer;
    assert(DrivenEngineInitializerReg::func != nullptr);
    if (!called_initializer) {
        DrivenEngineInitializerReg::func();
        called_initializer = true;
    }

    memset(w, 0, sizeof(EngineWrapper));

    w->get_listen_ports = drv_get_listen_ports;
    w->get_new_outgoing = drv_get_new_outgoing;
    w->get_target = drv_get_target;
    w->get_channel_released = drv_get_channel_released;
    w->get_outgoing = drv_get_outgoing;
    w->get_outgoing_empty = drv_get_outgoing_empty;
    w->get_clock = drv_get_clock;
    w->get_rescan_lua_source = drv_get_rescan_lua_source;
    w->get_stop_driver = drv_get_stop_driver;

    w->play_initialize = play_initialize;
    w->play_clear_new_outgoing = play_clear_new_outgoing;
    w->play_sent_outgoing = play_sent_outgoing;
    w->play_recv_incoming = play_recv_incoming;
    w->play_notify_close = play_notify_close;
    w->play_notify_accept = play_notify_accept;
    w->play_invoke_event_update = play_invoke_event_update;
    w->play_set_lua_source = play_set_lua_source;

    w->replay_initialize = replaycore_initialize;
    w->replay_step = replaycore_step;

    w->hook_dprint = util::hook_dprint;
    w->release = release;
};

extern "C" {
DLLEXPORT void init_engine_wrapper(EngineWrapper *w) {
    init_engine_wrapper_helper(w);
}
}