diff --git a/luprex/core/Makefile b/luprex/core/Makefile
index 75775cc3..196af6b4 100644
--- a/luprex/core/Makefile
+++ b/luprex/core/Makefile
@@ -4,6 +4,8 @@ CXX=g++ -std=c++17 -Wall -g -Iinc -Icpp
 CPP_FILES=\
 	cpp/invocation.cpp\
 	cpp/spookyv2.cpp\
+	cpp/drivenengine.cpp\
+	cpp/driver.cpp\
 	cpp/util.cpp\
 	cpp/luastack.cpp\
 	cpp/traceback.cpp\
diff --git a/luprex/core/cpp/drivenengine.cpp b/luprex/core/cpp/drivenengine.cpp
index fad987ec..deebcd66 100644
--- a/luprex/core/cpp/drivenengine.cpp
+++ b/luprex/core/cpp/drivenengine.cpp
@@ -1 +1,175 @@
-#include "channel.hpp"
\ No newline at end of file
+#include "drivenengine.hpp"
+
+
+Channel::Channel(DrivenEngine *de, int chid, int port, const std::string &target) {
+    driven_ = de;
+    chid_ = chid;
+    sb_in_.reset(new StreamBuffer);
+    sb_out_.reset(new StreamBuffer);
+    port_ = port;
+    closed_ = false;
+    target_ = target;
+    assert(driven_->channels_[chid_] == nullptr);
+    driven_->channels_[chid_] = this;
+}
+
+Channel::~Channel() {
+    assert(driven_->channels_[chid_] == this);
+    driven_->channels_.erase(chid_);
+    if (driven_->recent_channel_ == this) {
+        driven_->recent_channel_ = driven_->stdio_channel_.get();
+    }
+}
+
+double DrivenEngine::get_clock() {
+    return clock_;
+}
+
+std::unique_ptr<Channel> DrivenEngine::new_outgoing_channel(const std::string &target) {
+    return std::unique_ptr<Channel>(new Channel(this, next_channel_id_++, 0, target));
+}
+
+std::unique_ptr<Channel> DrivenEngine::new_incoming_channel() {
+    if (accepted_channels_.empty()) {
+        return nullptr;
+    } else {
+        std::unique_ptr<Channel> result = std::move(accepted_channels_.back());
+        accepted_channels_.pop_back();
+        return std::move(result);
+    }
+}
+
+Channel *DrivenEngine::get_stdio_channel() {
+    return stdio_channel_.get();
+}
+
+std::unique_ptr<util::LuaSource> 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;
+}
+
+void DrivenEngine::drv_logmode_write(const std::string &filename, int64_t maxsize) {
+    // NOT IMPLEMENTED YET, but it's okay as a stub.
+}
+
+void DrivenEngine::drv_logmode_replay(const std::string &filename) {
+    // NOT IMPLEMENTED YET.
+    assert(false);
+}
+    
+void DrivenEngine::drv_logmode_none() {
+    // NOT IMPLEMENTED YET, but it's okay as a stub.
+}
+
+void DrivenEngine::drv_invoke_engine_init() {
+    init();
+}
+
+void DrivenEngine::drv_invoke_engine_update() {
+    update();
+}
+
+Channel *DrivenEngine::get_chid(int chid) {
+    // We cache the most recently used channel.
+    if (recent_channel_->chid_ != chid) {
+        auto iter = channels_.find(chid);
+        assert(iter != channels_.end());
+        recent_channel_ = iter->second;
+    }
+    return recent_channel_;
+}
+
+void DrivenEngine::drv_list_channels(std::vector<int> &channels) {
+    channels.clear();
+    for (const auto &p : channels_) {
+        if (!p.second->closed_) {
+            channels.push_back(p.first);
+        }
+    }
+}
+
+const std::string &DrivenEngine::drv_get_target(int chid) {
+    return get_chid(chid)->target_;
+}
+
+void DrivenEngine::drv_peek_outgoing(int chid, int *nbytes, const char **bytes) {
+    Channel *ch = get_chid(chid);
+    *nbytes = ch->sb_out_->fill();
+    *bytes = ch->sb_out_->data();
+}
+
+void DrivenEngine::drv_sent_outgoing(int chid, int nbytes) {
+    get_chid(chid)->sb_out_->read_bytes(nbytes);
+}
+
+void DrivenEngine::drv_recv_incoming(int chid, int nbytes, char *bytes) {
+    get_chid(chid)->sb_in_->write_bytes(bytes, nbytes);
+}
+
+void DrivenEngine::drv_notify_close(int chid) {
+    get_chid(chid)->closed_ = true;
+}
+
+int DrivenEngine::drv_notify_accept(int port) {
+    int chid = next_channel_id_++;
+    accepted_channels_.emplace_back(new Channel(this, chid, port, ""));
+    return chid;
+}
+
+void DrivenEngine::drv_set_clock(double t) {
+    clock_ = t;
+}
+
+void DrivenEngine::drv_set_lua_source(const util::LuaSource &source) {
+    lua_source_.reset(new util::LuaSource(source));
+    rescan_lua_source_ = false;
+}
+
+bool DrivenEngine::drv_get_rescan_lua_source() {
+    return rescan_lua_source_;
+}
+
+bool DrivenEngine::drv_get_stop_driver() {
+    return stop_driver_;
+}
+
+bool DrivenEngine::drv_step_logfile() {
+    // NOT IMPLEMENTED
+    assert(false);
+    return false;
+}
+
+DrivenEngine::DrivenEngine() {
+    next_channel_id_ = 1;
+    stdio_channel_.reset(new Channel(this, 0, 0, ""));
+    recent_channel_ = stdio_channel_.get();
+    rescan_lua_source_ = true;
+    clock_ = 0.0;
+    stop_driver_ = false;
+}
+
+DrivenEngine::~DrivenEngine() {
+    // Delete the channels that we own.
+    stdio_channel_.reset();
+    accepted_channels_.clear();
+    // At this point, all channels should be gone.
+    assert(channels_.empty());
+}
+
+static DrivenEngine *engine_;
+
+void DrivenEngine::set(DrivenEngine *de) {
+    engine_ = de;
+}
+
+DrivenEngine *DrivenEngine::get() {
+    return engine_;
+}
+
diff --git a/luprex/core/cpp/drivenengine.hpp b/luprex/core/cpp/drivenengine.hpp
index 3583ad2d..89146f9b 100644
--- a/luprex/core/cpp/drivenengine.hpp
+++ b/luprex/core/cpp/drivenengine.hpp
@@ -73,6 +73,9 @@
 //
 //  * Repeat the following steps over and over:
 //
+//      - If the engine asked that the lua source be refreshed, read the source
+//        from disk and call 'drv_set_lua_source'.
+//
 //      - List all existing channels using drv_list_channels.
 //
 //      - If there are any new channels in the channel list, use
@@ -101,8 +104,7 @@
 //        drv_peek_outgoing, drv_sent_outgoing, and drv_recv_incoming in the
 //        same manner as you would for a socket.
 //
-//      - Use 'drv_invoke_engine_update' to invoke the engine's update
-//        callback.
+//      - Use 'drv_invoke_engine_update' to invoke the engine's update callback.
 //
 //////////////////////////////////////////////////////////////
 
@@ -111,25 +113,19 @@
 
 #include <memory>
 #include <string>
+#include <vector>
+#include <map>
 #include "streambuffer.hpp"
 #include "util.hpp"
 
+class DrivenEngine;
+
 class Channel {
-private:
-    int chid_;
-    std::unique_ptr<StreamBuffer> sb_in_;
-    std::unique_ptr<StreamBuffer> sb_out_;
-    int port_;
-    bool remote_closed_;
-    std::string target_;
-    
 public:
     // Get the buffers associated with this channel.
     //
-    StreamBuffer *out();
-    StreamBuffer *in();
-    const StreamBuffer *out() const;
-    const StreamBuffer *in() const;
+    StreamBuffer *out() { return sb_out_.get(); }
+    StreamBuffer *in() { return sb_in_.get(); }
 
     // If this is a socket connection, the receiver's port number.
     //
@@ -140,30 +136,32 @@ public:
 
     // True if the remote closed the connection, or a failure occurred.
     //
-    bool remote_closed() const { return remote_closed_; }
+    bool closed() const { return closed_; }
 
-    // If communications were closed by the remote, there may
-    // be an error message.
+    // You may delete any channel except for stdio.  This closes
+    // the channel.
     //
-    std::string errmsg() const { return errmsg_; }
+    ~Channel();
+    
+private:
+    // Constructor is deliberately private.  Use
+    // DrivenEngine::new_outgoing_channel to create outgoing socket channels.
+    //
+    Channel(DrivenEngine *de, int chid, int port, const std::string &target);
+
+private:
+    DrivenEngine *driven_;
+    int chid_;
+    std::unique_ptr<StreamBuffer> sb_in_;
+    std::unique_ptr<StreamBuffer> sb_out_;
+    int port_;
+    bool closed_;
+    std::string target_;
+    friend class DrivenEngine;
 };
 
 class DrivenEngine {
 public:
-    // Constructor.
-    //
-    // Most initialization is achieved by 'drv_xxx' functions, so
-    // this constructor takes no arguments.
-    //
-    DrivenEngine();
-
-    // Destructor.
-    //
-    // It is necessary to delete all channels before deleting the
-    // DrivenEngine.  The destructor will verify that this has been done.
-    //
-    ~DrivenEngine();
-
     //////////////////////////////////////////////////////////////
     //
     // The following methods are the 'engine' side of the pipe.
@@ -174,7 +172,7 @@ public:
     // This will be called to initialize the logic engine, shortly after the lua
     // source is loaded.
     //
-    virtual void init() { }
+    virtual void init() {}
 
     // The update function. You should override this in a subclass.  This will
     // be called to give the engine a chance to respond to new data.
@@ -195,7 +193,7 @@ public:
     // actually opening the connection and relaying data into the channel using
     // drv_get_target, drv_peek_outgoing, drv_sent_outgoing, drv_recv_incoming.
     //
-    std::unique_ptr<Channel> new_outgoing_channel(const std::string &target)
+    std::unique_ptr<Channel> new_outgoing_channel(const std::string &target);
 
     // Create a new channel from any pending incoming connection. If there is no
     // incoming connection, returns nullptr.
@@ -234,7 +232,7 @@ public:
     // periodically poll to see if the engine has called rescan_lua_source,
     // using drv_get_rescan
     //
-    std::unique_ptr<util::StringMap> get_lua_source();
+    std::unique_ptr<util::LuaSource> get_lua_source();
 
     // Rescan the lua source directory. The lua source directory is read once,
     // automatically, at engine creation time.  If you want to read it again,
@@ -245,6 +243,11 @@ public:
     //
     void rescan_lua_source();
 
+    // Stop the driver.  The engine should call this when it's done
+    // and there's nothing left to do.
+    //
+    void stop_driver();
+
     //////////////////////////////////////////////////////////////
     //
     // The following methods are the 'driver' side of the pipe.
@@ -293,7 +296,7 @@ public:
     // is supposed to be talking to.  Non-socket channels and incoming channels
     // have empty targets.
     //
-    std::string drv_get_target(int chid);
+    const std::string &drv_get_target(int chid);
 
     // Get a pointer to the bytes in the outgoing buffer.  The pointer returned
     // here is naturally only valid until the buffer is changed.  This function
@@ -338,7 +341,7 @@ public:
     // Set the lua source code.  The driver is expected to read the lua source
     // code and store it (using this function) once before invoking 
     //
-    void drv_set_lua_source(const util::StringMap &source);
+    void drv_set_lua_source(const util::LuaSource &source);
 
     // Check the 'rescan_lua_source' flag.  If this flag is set, it means
     // that the engine wants the driver to rescan the lua source code.
@@ -347,19 +350,59 @@ public:
     //
     bool drv_get_rescan_lua_source();
 
+    // If true, the engine is done.  Stop the driver.
+    //
+    bool drv_get_stop_driver();
+
     // In replay mode, perform a single step of the logfile.  Returns true
     // if the logfile was not empty.
     //
     bool drv_step_logfile();
 
+    //////////////////////////////////////////////////////////////
+    //
+    // Creation and Destruction.
+    //
+    //////////////////////////////////////////////////////////////
+
+    // Constructor.
+    //
+    // Most initialization is achieved by 'drv_xxx' functions, so
+    // this constructor takes no arguments.
+    //
+    DrivenEngine();
+
+    // Destructor.
+    //
+    // It is necessary to delete all channels before deleting the
+    // DrivenEngine.  The destructor will verify that this has been done.
+    //
+    virtual ~DrivenEngine();
+
+    // Set/Get Global Pointer.
+    //
+    // Normally, there is a single global "DrivenEngine" instance.
+    // We provide a global pointer to store this instance.  This is 
+    // a raw pointer, you must manually delete the DrivenEngine.
+    //
+    static void set(DrivenEngine *de);
+    static DrivenEngine *get();
+
 private:
-    Channel *stdio_channel_;
+    // Get a channel by channel ID.
+    Channel *get_chid(int chid);
+    
+private:
+    std::unique_ptr<Channel> stdio_channel_;
     int next_channel_id_;
     std::map<int, Channel *> channels_;
     Channel *recent_channel_;
-    std::vector<Channel*> accepted_channels_;
+    std::vector<std::unique_ptr<Channel>> accepted_channels_;
     bool rescan_lua_source_;
-    std::unique_ptr<util::StringMap> lua_source_;
+    std::unique_ptr<util::LuaSource> lua_source_;
+    double clock_;
+    bool stop_driver_;
+    friend class Channel;
 };
 
 #endif // DRIVENENGINE_HPP
diff --git a/luprex/core/cpp/driver.cpp b/luprex/core/cpp/driver.cpp
new file mode 100644
index 00000000..1e7e46ad
--- /dev/null
+++ b/luprex/core/cpp/driver.cpp
@@ -0,0 +1,32 @@
+
+#include "driver.hpp"
+#include <map>
+#include <iostream>
+#include <cstdio>
+#include <cstring>
+
+
+void driver_drive(DrivenEngine *de) {
+    const int MAXINPUT = 1000;
+    char buf[MAXINPUT];
+    int nbytes; const char *bytes;
+    DrivenEngine::set(de);
+    de->drv_logmode_none();
+    de->drv_set_lua_source(util::read_lua_source("lua"));
+    de->drv_invoke_engine_init();
+    while (!de->drv_get_stop_driver()) {
+        if (de->drv_get_rescan_lua_source()) {
+            de->drv_set_lua_source(util::read_lua_source("lua"));
+        }
+        de->drv_peek_outgoing(0, &nbytes, &bytes);
+        if (nbytes > 0) {
+            fwrite(bytes, 1, nbytes, stdout);
+        }
+        if (fgets(buf, MAXINPUT, stdin)) {
+            de->drv_recv_incoming(0, strlen(buf), buf);
+        }
+        de->drv_invoke_engine_update();
+    }
+    DrivenEngine::set(nullptr);
+}
+
diff --git a/luprex/core/cpp/driver.hpp b/luprex/core/cpp/driver.hpp
new file mode 100644
index 00000000..ed24bf48
--- /dev/null
+++ b/luprex/core/cpp/driver.hpp
@@ -0,0 +1,8 @@
+#ifndef DRIVER_HPP
+#define DRIVER_HPP
+
+#include "drivenengine.hpp"
+
+void driver_drive(DrivenEngine *de);
+
+#endif // DRIVER_HPP
diff --git a/luprex/core/cpp/main.cpp b/luprex/core/cpp/main.cpp
index 0ecdd19c..2ef99c9a 100644
--- a/luprex/core/cpp/main.cpp
+++ b/luprex/core/cpp/main.cpp
@@ -1,8 +1,9 @@
 
 #include "textgame.hpp"
+#include "driver.hpp"
 
 int main(int argc, char **argv)
 {
     TextGame tg;
-    tg.run();
+    driver_drive(&tg);
 }
diff --git a/luprex/core/cpp/source.cpp b/luprex/core/cpp/source.cpp
index 3aae50a8..d9e6e0a7 100644
--- a/luprex/core/cpp/source.cpp
+++ b/luprex/core/cpp/source.cpp
@@ -15,24 +15,6 @@
 #include "source.hpp"
 #include "luasnap.hpp"
 
-// Read control.lst
-//
-// - trim all lines
-// - remove blank lines
-// - remove comment lines
-//
-util::StringVec read_control_lst(const std::string &path) {
-    util::StringVec lines = util::get_file_lines(path);
-    util::StringVec result;
-    for (int i = 0; i < int(lines.size()); i++) {
-        std::string trimmed = util::trim(lines[i]);
-        if ((trimmed.size() > 0) && (trimmed[0] != '#')) {
-            result.push_back(trimmed);
-        }
-    }
-    return result;
-}
-
 LuaDefine(source_makeclass, "f") {
     LuaArg classname;
     LuaRet classtab;
@@ -155,17 +137,7 @@ static void source_updatefile(LuaStack &LS0, LuaSlot source, LuaSlot fn, LuaSlot
         old_fingerprint = LS.ckstring(fingerprint);
     }
     // std::cerr << "Probing " << cfn << std::endl;
-    std::string new_fingerprint = util::get_file_fingerprint("lua/" + cfn);
-    if ((old_fingerprint == "") || (old_fingerprint != new_fingerprint)) {
-        std::cerr << "Rereading " << cfn << std::endl;
-        std::string code;
-        if (new_fingerprint != "") code = util::get_file_contents("lua/" + cfn);
-        LS.rawset(info, "name", fn);
-        LS.rawset(info, "fingerprint", new_fingerprint);
-        LS.rawset(info, "code", code);
-        LS.rawset(info, "hash", util::hash_to_hex(util::hash_string(code)));
-        calculate_loadresult(LS, info, cfn, code);
-    }
+
     LS.result();
 }
 
@@ -295,39 +267,31 @@ std::string SourceDB::get(const std::string &fn) {
     return oss.str(); 
 }
 
-void SourceDB::update() {
+void SourceDB::update(const util::LuaSource &source) {
     lua_State *L = lua_state_;
-    LuaVar sourcedb, newdb, info, fn, seq;
-    LuaStack LS(L, newdb, sourcedb, info, fn, seq);
+    LuaVar sourcedb, info;
+    LuaStack LS(L, sourcedb, info);
 
-    // Get the (old) source database.
+    // Get and clear the source database.
     LS.rawget(sourcedb, LuaRegistry, "sourcedb");
     if (!LS.istable(sourcedb)) {
         LS.newtable(sourcedb);
+        LS.rawset(LuaRegistry, "sourcedb", sourcedb);
     }
+    LS.cleartable(sourcedb);
 
-    // Read the list of filenames.
-    util::StringVec filenames = read_control_lst("lua/control.lst");
-    if (filenames.empty()) {
-        luaL_error(L, "cannot read source database control.lst");
+    for (int i = 0; i < int(source.size()); i++) {
+        const std::string &file = source[i].first;
+        const std::string &code = source[i].second;
+        std::cerr << "Compiling " << file << std::endl;
+        LS.newtable(info);
+        LS.rawset(info, "name", file);
+        LS.rawset(info, "code", code);
+        LS.rawset(info, "hash", util::hash_to_hex(util::hash_string(code)));
+        LS.rawset(info, "sequence", i + 1);
+        calculate_loadresult(LS, info, file, code);
+        LS.rawset(sourcedb, file, info);
     }
-
-    // Process the files one by one.
-    LS.newtable(newdb);
-    for (int i = 0; i < int(filenames.size()); i++) {
-        LS.set(fn, filenames[i]);
-
-        // Call source_updatefile to get the updated info for one file.
-        source_updatefile(LS, sourcedb, fn, info);
-
-        // Insert the sequence number and put finalized info into the new database.
-        LS.set(seq, i + 1);
-        LS.rawset(info, "sequence", seq);
-        LS.rawset(newdb, fn, info);
-    }
-
-    // Store the new source db.
-    LS.rawset(LuaRegistry, "sourcedb", newdb);
     LS.result();
 }
 
diff --git a/luprex/core/cpp/source.hpp b/luprex/core/cpp/source.hpp
index 35558546..d6bbb9f5 100644
--- a/luprex/core/cpp/source.hpp
+++ b/luprex/core/cpp/source.hpp
@@ -132,12 +132,10 @@ public:
     
     // Update
     //
-    // Read all the lua source files from disk and store them in the
-    // source database.  Also compiles these files using lua's "load"
-    // function.  Efficient: if a source file is already in the database
-    // and hasn't been modified, it is not reloaded.
+    // Update the database using the specified lua source code.
+    // Compiles these files using lua's "load" function.
     //
-    void update();
+    void update(const util::LuaSource &source);
 
     // Rebuild
     //
diff --git a/luprex/core/cpp/streambuffer.cpp b/luprex/core/cpp/streambuffer.cpp
index 2dd7f067..86538a12 100644
--- a/luprex/core/cpp/streambuffer.cpp
+++ b/luprex/core/cpp/streambuffer.cpp
@@ -111,6 +111,19 @@ void StreamBuffer::clear() {
     lua_reader_size_ = 0;
 }
 
+std::string StreamBuffer::readline() {
+    char *p = read_cursor_;
+    while ((p < write_cursor_) && (*p != '\n')) p++;
+    if (p == write_cursor_) {
+        return "";
+    } else {
+        p++;
+        std::string result(read_cursor_, p - read_cursor_);
+        read_cursor_ = p;
+        return result;
+    }
+}
+
 // These routines return true if you can losslessly cast the
 // specified value to the specified type.
 
diff --git a/luprex/core/cpp/streambuffer.hpp b/luprex/core/cpp/streambuffer.hpp
index a34512e7..a1163dd4 100644
--- a/luprex/core/cpp/streambuffer.hpp
+++ b/luprex/core/cpp/streambuffer.hpp
@@ -266,6 +266,11 @@ public:
     // Frees up as much space as possible.
     void clear();
 
+    // Attempt to do a "readline".  If there is no newline in
+    // the buffer, returns empty string.  If there is a newline,
+    // returns a block of text that ends in newline.
+    std::string readline();
+
     // Write block of bytes into the buffer.
     //
     // Caution: this function doesn't write the length!  
diff --git a/luprex/core/cpp/textgame.cpp b/luprex/core/cpp/textgame.cpp
index dd233022..bd9c0d32 100644
--- a/luprex/core/cpp/textgame.cpp
+++ b/luprex/core/cpp/textgame.cpp
@@ -144,6 +144,7 @@ void TextGame::do_quit_command(const StringVec &cmd) {
         return;
     }
     actor_id_ = 0;
+    stop_driver();
 }
 
 void TextGame::do_command(const StringVec &words) {
@@ -169,18 +170,28 @@ void TextGame::check_redirects() {
     }
 }
 
-void TextGame::run()
+void TextGame::init()
 {
     world_.reset(new World(util::WORLD_TYPE_STANDALONE));
-    world_->update_source();
+    std::unique_ptr<util::LuaSource> lsource = get_lua_source();
+    world_->update_source(*lsource);
     world_->run_unittests();
     actor_id_ = world_->create_login_actor();
     std::cerr << "Login actor ID: " << actor_id_ << std::endl;
     console_.clear();
+}
+
+void TextGame::update() {
+    check_redirects();
+    if (actor_id_ == 0) {
+        stop_driver();
+        return;
+    }
+    // Process lines from stdin.
     while (true) {
-        check_redirects();
-        if (actor_id_ == 0) break;
-        console_.add_stdin();
+        std::string line = get_stdio_channel()->in()->readline();
+        if (line == "") break;
+        console_.add(line);
         int action = console_.action();
         if (action == LuaConsole::DO_LUA) {
             do_lua(console_.lua_expression());
@@ -190,5 +201,8 @@ void TextGame::run()
             std::cerr << console_.syntax() << std::endl;
         }
     }
+    // Process lua source if available.
+    std::unique_ptr<util::LuaSource> source = get_lua_source();
+    if (source != nullptr) world_->update_source(*source);
 }
 
diff --git a/luprex/core/cpp/textgame.hpp b/luprex/core/cpp/textgame.hpp
index 7cd2baa3..3b4ff258 100644
--- a/luprex/core/cpp/textgame.hpp
+++ b/luprex/core/cpp/textgame.hpp
@@ -4,9 +4,10 @@
 
 #include "luaconsole.hpp"
 #include "world.hpp"
+#include "drivenengine.hpp"
 #include <memory>
 
-class TextGame {
+class TextGame : public DrivenEngine {
 private:
     using StringVec = LuaConsole::StringVec;
     std::unique_ptr<World> world_;
@@ -27,7 +28,8 @@ private:
 
     void check_redirects();
 public:
-    void run();
+    virtual void init();
+    virtual void update();
 };
 
 #endif // TEXTGAME_HPP
diff --git a/luprex/core/cpp/util.cpp b/luprex/core/cpp/util.cpp
index 6ea043cc..4e6a35bd 100644
--- a/luprex/core/cpp/util.cpp
+++ b/luprex/core/cpp/util.cpp
@@ -8,6 +8,7 @@
 #include <cmath>
 #include <iostream>
 #include <iomanip>
+#include <cassert>
 
 #ifndef WIN32
 #include <unistd.h>
@@ -206,36 +207,34 @@ double distance_squared(double x1, double y1, double x2, double y2) {
     return dx*dx + dy*dy;
 }
 
-std::string get_file_contents(const std::string &fn) {
+static std::string get_file_contents(const std::string &fn) {
     std::ifstream fs(fn);
     std::stringstream buffer;
     buffer << fs.rdbuf();
     return buffer.str();
 }
 
-StringVec get_file_lines(const std::string &path) {
-    StringVec result;
-    std::ifstream f;
-    f.open(path);
-    if (f) {
-        std::string line;
-        while (std::getline(f, line)) {
-            result.push_back(line);
+static StringVec read_control_lst(const std::string &path) {
+    StringVec lines = split(get_file_contents(path), '\n');
+    util::StringVec result;
+    for (int i = 0; i < int(lines.size()); i++) {
+        std::string trimmed = trim(lines[i]);
+        if ((trimmed.size() > 0) && (trimmed[0] != '#')) {
+            result.push_back(trimmed);
         }
-        f.close();
     }
     return result;
 }
 
-std::string get_file_fingerprint(const std::string &fn) {
-    struct stat result;
-    if(stat(fn.c_str(), &result)==0)
-    {
-        std::stringstream ss;
-        ss << result.st_mtime;
-        return ss.str();
+LuaSource read_lua_source(const std::string &dir) {
+    StringVec files = read_control_lst(dir + "/control.lst");
+    assert (!files.empty());
+    LuaSource result;
+    for (const std::string &file : files) {
+        std::string data = get_file_contents(dir + "/" + file);
+        result.emplace_back(file, data);
     }
-    return "";
+    return result;
 }
 
 std::string XYZ::debug_string() const {
diff --git a/luprex/core/cpp/util.hpp b/luprex/core/cpp/util.hpp
index b90fb498..4a69f3e1 100644
--- a/luprex/core/cpp/util.hpp
+++ b/luprex/core/cpp/util.hpp
@@ -3,6 +3,7 @@
 
 #include <string>
 #include <set>
+#include <map>
 #include <algorithm>
 #include <sstream>
 #include <ostream>
@@ -21,7 +22,8 @@ enum WorldType {
 };
 
 using StringVec = std::vector<std::string>;
-using StringMap = std::map<std::string, std::string>;
+using StringPair = std::pair<std::string, std::string>;
+using LuaSource = std::vector<StringPair>;
 using HashValue = std::pair<uint64_t, uint64_t>;
 using IdVector = std::vector<int64_t>;
 
@@ -73,14 +75,8 @@ std::string trim(std::string s);
 // Calculate distance between two points
 double distance_squared(double x1, double y1, double x2, double y2);
 
-// Read a file as one big string.
-std::string get_file_contents(const std::string &path);
-
-// Read a file as a vector of lines.
-StringVec   get_file_lines(const std::string &path);
-
-// Get a file's fingerprint - ie, size and modification time.
-std::string get_file_fingerprint(const std::string &path);
+// Read the lua source code from the specified directory.
+LuaSource read_lua_source(const std::string &directory);
 
 // An XYZ coordinate, general purpose.
 struct XYZ {
diff --git a/luprex/core/cpp/world.hpp b/luprex/core/cpp/world.hpp
index ffd8753f..03a1bd7c 100644
--- a/luprex/core/cpp/world.hpp
+++ b/luprex/core/cpp/world.hpp
@@ -174,7 +174,7 @@ public:
 
     // Update the source database from disk.
     //
-    void update_source() { source_db_.update(); source_db_.rebuild(true); }
+    void update_source(const util::LuaSource &source) { source_db_.update(source); source_db_.rebuild(true); }
 
     // Run all unit tests.
     //