Added luasnap checkpointing mechanism

luprex/Makefile

@@ -11,6 +11,7 @@ CPP_FILES=\
 	cpp/globaldb.cpp\
 	cpp/table.cpp\
 	cpp/gui.cpp\
+	cpp/luasnap.cpp\
 	cpp/animqueue.cpp\
 	cpp/source.cpp\
 	cpp/world.cpp\

luprex/cpp/luasnap.cpp

@@ -0,0 +1,195 @@
+
+#include "luasnap.hpp"
+#include <iostream>
+#include <cassert>
+
+extern "C" {
+void      *lj_alloc_create();
+void      *lj_alloc_f(void *, void *, size_t, size_t);
+lua_State *lj_state_newstate(lua_Alloc f, void *ud);
+}
+
+static void *lsnap_create() {
+    return lj_alloc_create();
+}
+static lua_State *lsnap_newstate(lua_Alloc f, void *ud) {
+    return lj_state_newstate(f, ud);
+}
+static void *lsnap_malloc(void *mptr, size_t nsize) {
+    return lj_alloc_f(mptr, 0, 0, nsize);
+}
+static void *lsnap_realloc(void *mptr, void *ptr, size_t osize, size_t nsize) {
+    return lj_alloc_f(mptr, ptr, osize, nsize);
+}
+static void *lsnap_free(void *mptr, size_t osize, void *ptr) {
+    return lj_alloc_f(mptr, ptr, osize, 0);
+}
+
+struct BlockHeader {
+    BlockHeader *prev_;
+    BlockHeader *next_;
+    int32_t sanity_; // 0x12345678 only when linked.
+    size_t size_;
+    bool in_use_;
+    void *snapshot_;
+};
+
+size_t blocksize(size_t base) {
+    return base + sizeof(BlockHeader);
+}
+
+BlockHeader *pointer_to_header(void *ptr) {
+    return (BlockHeader*)(((char *)ptr) - sizeof(BlockHeader));
+}
+
+void *header_to_pointer(BlockHeader *blk) {
+    return (void *)(((char *)blk) + sizeof(BlockHeader));
+}
+
+class LuaSnapData {
+public:
+    lua_State *state_;
+    bool have_snapshot_;
+    void *lj_mstate_;
+    BlockHeader sentinel_;
+
+    LuaSnapData();
+    ~LuaSnapData();
+    lua_State *state() const { return state_; }
+    bool have_snapshot() const { return have_snapshot_; }
+    void snapshot();
+    void rollback();
+    void link(BlockHeader *blk);
+    void unlink(BlockHeader *blk);
+    void *allocf(void *ptr, size_t osize, size_t nsize);
+};
+
+void *lsd_alloc_f(void *lsd, void *ptr, size_t osize, size_t nsize) {
+    return ((LuaSnapData*)lsd)->allocf(ptr, osize, nsize);
+}
+
+LuaSnapData::LuaSnapData() {
+    sentinel_.prev_ = &sentinel_;
+    sentinel_.next_ = &sentinel_;
+    sentinel_.size_ = 0;
+    sentinel_.in_use_ = false;
+    sentinel_.snapshot_ = 0;
+    lj_mstate_ = lsnap_create();
+    have_snapshot_ = false;
+    state_ = lsnap_newstate(lsd_alloc_f, (void*)this);
+}
+
+LuaSnapData::~LuaSnapData() {
+    std::cerr << "LuaSnapData destructor not implemented." << std::endl;
+    exit(1);
+}
+
+void LuaSnapData::snapshot() {
+    assert(!have_snapshot_);
+    for (BlockHeader *blk = sentinel_.next_; blk != &sentinel_; blk = blk->next_) {
+        assert(blk->in_use_);
+        blk->snapshot_ = malloc(blk->size_);
+        memcpy(blk->snapshot_, header_to_pointer(blk), blk->size_);
+    }
+    have_snapshot_ = true;
+}
+
+void LuaSnapData::rollback() {
+    assert(have_snapshot_);
+    for (BlockHeader *blk = sentinel_.next_; blk != &sentinel_; ) {
+        BlockHeader *next = blk->next_;
+        if (blk->snapshot_) {
+            memcpy(header_to_pointer(blk), blk->snapshot_, blk->size_);
+            free(blk->snapshot_);
+            blk->snapshot_ = nullptr;
+            blk->in_use_ = true;
+        } else {
+            assert(blk->in_use_);
+            unlink(blk);
+            lsnap_free(lj_mstate_, blocksize(blk->size_), blk);
+        }
+        blk = next;
+    }
+    have_snapshot_ = false;
+}
+
+void LuaSnapData::link(BlockHeader *blk) {
+    blk->prev_ = sentinel_.prev_;
+    blk->next_ = &sentinel_;
+    blk->prev_->next_ = blk;
+    blk->next_->prev_ = blk;
+    blk->sanity_ = 0x12345678;
+}
+
+void LuaSnapData::unlink(BlockHeader *blk) {
+    blk->prev_->next_ = blk->next_;
+    blk->next_->prev_ = blk->prev_;
+    blk->prev_ = nullptr;
+    blk->next_ = nullptr;
+    blk->sanity_ = 0;
+}
+
+void *LuaSnapData::allocf(void *ptr, size_t osize, size_t nsize) {
+    if (nsize == 0) {
+        if (ptr == 0) return nullptr;
+        BlockHeader *blk = pointer_to_header(ptr);
+        assert(blk->sanity_ = 0x12345678);
+        assert(blk->in_use_);
+        if (blk->snapshot_ == nullptr) {
+            unlink(blk);
+            lsnap_free(lj_mstate_, blocksize(blk->size_), blk);
+        } else {
+            blk->in_use_ = false;
+        }
+        return nullptr;
+    } else if (ptr == NULL) {
+        BlockHeader *blk = (BlockHeader*)lsnap_malloc(lj_mstate_, blocksize(nsize));
+        link(blk);
+        blk->size_ = nsize;
+        blk->in_use_ = true;
+        blk->snapshot_ = nullptr;
+        return header_to_pointer(blk);
+    } else {
+        BlockHeader *blk = pointer_to_header(ptr);
+        assert(blk->sanity_ = 0x12345678);
+        assert(blk->in_use_);
+        if (blk->snapshot_ == nullptr) {
+            unlink(blk);
+            blk = (BlockHeader*)lsnap_realloc(lj_mstate_, blk, blocksize(blk->size_), blocksize(nsize));
+            blk->size_ = nsize;
+            link(blk);
+            return header_to_pointer(blk);
+        } else {
+            BlockHeader *nblk = (BlockHeader*)lsnap_malloc(lj_mstate_, blocksize(nsize));
+            memcpy(nblk, blk, (blk->size_ < nsize) ? blk->size_ : nsize);
+            blk->in_use_ = false;
+            link(nblk);
+            nblk->size_ = nsize;
+            nblk->in_use_ = true;
+            nblk->snapshot_ = nullptr;
+            return header_to_pointer(nblk);
+        }
+    }
+}
+
+
+LuaSnap::LuaSnap() {
+    data_ = new LuaSnapData;
+    state_ = data_->state();
+}
+
+LuaSnap::~LuaSnap() {
+    delete data_;
+}
+
+bool LuaSnap::have_snapshot() const {
+    return data_->have_snapshot();
+}
+
+void LuaSnap::snapshot() {
+    data_->snapshot();
+}
+
+void LuaSnap::rollback() {
+    data_->rollback();
+}

luprex/cpp/luasnap.hpp

@@ -0,0 +1,60 @@
+////////////////////////////////////////////////////////////
+//
+// LUASNAP
+//
+// A lua interpreter that can be checkpointed (snapshotted).
+// This makes it possible to roll the entire interpreter back
+// to a previously-snapshotted state.
+//
+// To accomplish this, we take advantage of the 'allocf' parameter
+// to lua_newstate.  This lets us hook the lua allocator, which
+// in turn lets us find every block of memory currently in use by
+// lua.  To snapshot, we 'memcpy' every block of memory
+// that lua is using into a buffer.  To rollback, we just 'memcpy'
+// the data back.
+//
+// The current implementation is a proof-of-concept.  It's quite
+// wasteful of memory, roughly doubling the amount of RAM that
+// LUA uses. But it does demonstrate that this method of snapshot
+// and rollback is feasible.
+//
+////////////////////////////////////////////////////////////
+
+#ifndef LUASNAP_HPP
+#define LUASNAP_HPP
+
+#include "luastack.hpp"
+
+class LuaSnapData;
+class LuaSnap {
+private:
+    lua_State *state_;
+    LuaSnapData *data_;
+    
+public:
+    LuaSnap();
+    ~LuaSnap();
+
+    // Get the lua intepreter.
+    //
+    lua_State *state() const { return state_; }
+
+    // Return true if there's a saved snapshot.
+    //
+    bool have_snapshot() const;
+
+    // snapshot the state of the lua interpreter.
+    //
+    // If there is already a snapshot, this panics.
+    //
+    void snapshot();
+
+    // Rollback the lua intepreter to the snapshotted state.
+    //
+    // If there is no snapshot, this panics.
+    //
+    void rollback();
+};
+
+
+#endif // LUASNAP_HPP

luprex/cpp/luastack.cpp

@@ -38,17 +38,20 @@ int LuaStack::collect_tagged_pointer(lua_State *L) {
 }
 
 void LuaStack::register_all_userdata(lua_State *L) {
-    LuaVar tab, lud;
-    LuaStack LS(L, tab, lud);
+    LuaVar tab, lud, classtab, classname;
+    LuaStack LS(L, tab, lud, classtab, classname);
     auto regs = LuaFunctionReg::all();
     for (const LuaFunctionReg *r : regs) {
         const std::string &name = util::tolower(r->get_name());
         lua_CFunction tag = r->get_func();
         std::string mode = r->get_mode();
+        LS.set(classname, name);
         if (mode.find('t') != std::string::npos) { // Register type
             LS.newtable(tab);
             LS.setfield(tab, "type", name);
             LS.setfield(tab, "__gc", collect_tagged_pointer);
+            LS.makeclass(classtab, classname);
+            LS.setfield(tab, "__index", classtab);
             LS.setlightuserdata(lud, (void *)tag);
             LS.rawset(LuaRegistry, lud, tab);
         }
@@ -202,6 +205,37 @@ void LuaStack::newtable(LuaSlot target) const {
     lua_replace(L_, target);
 }
 
+void LuaStack::makeclass(LuaSlot classtab, LuaSlot classname) const {
+    int top = lua_gettop(L_);
+    checkstring(classname);
+
+    // Special case: if the classname is _G, return global env.
+    lua_pushstring(L_, "_G");
+    int eqlg = lua_equal(L_, -1, classname.index());
+    lua_settop(L_, top);
+    if (eqlg) {
+        set(classtab, LuaGlobals);
+        return;
+    }
+    
+    // Get the classtab from the global environment.
+    // Create it if it doesn't exist.
+    rawget(classtab, LuaGlobals, classname);
+    if (isnil(classtab)) {
+        newtable(classtab);
+        rawset(LuaGlobals, classname, classtab);
+    }
+
+    // If the name isn't bound to a table, abort.
+    if (!istable(classtab)) {
+        luaL_error(L_, "%s is not a class", ckstring(classname).c_str());
+    }
+
+    // Repair the special fields.
+    setfield(classtab, "__index", classtab);
+    setfield(classtab, "__class", classname);
+}
+
 void LuaStack::setlightuserdata(LuaSlot target, void *p) const {
     lua_pushlightuserdata(L_, p);
     lua_replace(L_, target);

luprex/cpp/luastack.hpp

@@ -425,6 +425,9 @@ public:
     void checknometa(LuaSlot index) const;
 
     void newtable(LuaSlot target) const;
+
+    void makeclass(LuaSlot tab, LuaSlot name) const;
+
     void setlightuserdata(LuaSlot target, void *p) const;
 
     template <typename T>

luprex/cpp/source.cpp

@@ -34,42 +34,9 @@ util::stringvec read_control_lst(const std::string &path) {
 
 LuaDefine(source_makeclass, "f") {
     LuaArg classname;
-    LuaVar action, gname;
     LuaRet classtab;
-    LuaStack LS(L, classname, classtab, action, gname);
-
-    LS.checkstring(classname);
-
-    // Special case: if the classname is _G, return global env.
-    LS.set(gname, "_G");
-    if (LS.equal(classname, gname)) {
-        LS.set(classtab, LuaGlobals);
-        return LS.result();
-    }
-    
-    // Get the classtab from the global environment.
-    // Create it if it doesn't exist.
-    LS.rawget(classtab, LuaGlobals, classname);
-    if (LS.isnil(classtab)) {
-        LS.newtable(classtab);
-        LS.rawset(LuaGlobals, classname, classtab);
-    }
-
-    // If the name isn't bound to a table, abort.
-    if (!LS.istable(classtab)) {
-        luaL_error(L, "%s is not a class", LS.ckstring(classname).c_str());
-    }
-
-    // Repair the special fields.
-    LS.setfield(classtab, "__index", classtab);
-    LS.setfield(classtab, "__class", classname);
-
-    // Repair the action table.
-    LS.getfield(action, classtab, "action");
-    if (!LS.istable(action)) {
-        LS.setfield(classtab, "action", LuaNewTable);
-    }
-
+    LuaStack LS(L, classname, classtab);
+    LS.makeclass(classtab, classname);
     return LS.result();
 }
 
@@ -200,26 +167,17 @@ void SourceDB::update() {
 }
 
 // Delete everything from the global environment except
-// the class tables and the class action tables.
+// the class tables.
 //
 static void source_clear_globals(lua_State *L) {
-    LuaVar classname, classtab, action, key;
-    LuaStack LS(L, classname, classtab, action, key);
+    LuaVar classname, classtab, key;
+    LuaStack LS(L, classname, classtab, key);
 
     LS.setfield(LuaGlobals, "_G", LuaNil);
     LS.set(classname, LuaNil);
     while (LS.next(LuaGlobals, classname, classtab) != 0) {
         if (LS.istable(classtab)) {
-            bool keep_action = false;
-            LS.getfield(action, classtab, "action");
-            if (LS.istable(action)) {
-                LS.call(table_clear, action);
-                keep_action = true;
-            }
             LS.call(table_clear, classtab);
-            if (keep_action) {
-                LS.setfield(classtab, "action", action);
-            }
         } else {
             LS.rawset(LuaGlobals, classname, LuaNil);
         }
@@ -239,7 +197,7 @@ static void source_restore_builtins(lua_State *L) {
     LS.set(key, LuaNil);
     while (LS.next(snapshot, key, value) != 0) {
         LS.checktable(value);
-        LS.call(subglobal, source_makeclass, key);
+        LS.makeclass(subglobal, key);
         LS.set(skey, LuaNil);
         while (LS.next(value, skey, svalue) != 0) {
             LS.rawset(subglobal, skey, svalue);

luprex/cpp/textgame.cpp

@@ -43,9 +43,8 @@ static void l_message(const char *msg)
     fflush(stderr);
 }
 
-
 void TextGame::do_lua(const std::string &exp) {
-    lua_State *L = viewer_.get_lua_state();
+    lua_State *L = viewer_.state();
     int status = luaL_loadbuffer(L, exp.c_str(), exp.size(), "=stdin");
     assert(status == LUA_OK);
     globalL = L;
@@ -119,6 +118,22 @@ void TextGame::do_choose_command(const StringVec &cmd) {
     std::cerr << "Choose command (index " << index << ") not implemented yet." << std::endl;
 }
 
+void TextGame::do_snapshot_command(const StringVec &cmd) {
+    if (cmd.size() != 1) {
+        std::cerr << "s command (snapshot) takes no arguments" << std::endl;
+        return;
+    }
+    viewer_.snapshot();
+}
+
+void TextGame::do_rollback_command(const StringVec &cmd) {
+    if (cmd.size() != 1) {
+        std::cerr << "r command (rollback) takes no arguments" << std::endl;
+        return;
+    }
+    viewer_.rollback();
+}
+
 void TextGame::do_quit_command(const StringVec &cmd) {
     if (cmd.size() != 1) {
         std::cerr << "q command (quit) takes no arguments" << std::endl;
@@ -133,6 +148,8 @@ void TextGame::do_command(const StringVec &words) {
     case 'm': do_menu_command(words); break;
     case 'c': do_choose_command(words); break;
     case 'q': do_quit_command(words); break;
+    case 's': do_snapshot_command(words); break;
+    case 'r': do_rollback_command(words); break;
     default: 
         std::cerr << "Unknown command: " << words[0] << std::endl;
     }

luprex/cpp/textgame.hpp

@@ -17,7 +17,9 @@ private:
     void do_menu_command(const StringVec &cmd);
     void do_choose_command(const StringVec &cmd);
     void do_quit_command(const StringVec &cmd);
-
+    void do_snapshot_command(const StringVec &cmd);
+    void do_rollback_command(const StringVec &cmd);
+    
     void do_lua(const std::string &exp);
     void do_command(const StringVec &exp);
 public:

luprex/cpp/viewer.hpp

@@ -16,9 +16,13 @@ public:
     Viewer();
     ~Viewer();
 
+    // Snapshot/rollback the lua state (temporary hack)
+    void snapshot() { world_->lua_snap_.snapshot(); }
+    void rollback() { world_->lua_snap_.rollback(); }
+    
     // Get the lua state for interaction.
     //
-    lua_State *get_lua_state() { return world_->get_lua_state(); }
+    lua_State *state() { return world_->state(); }
 
     // Get the player ID of the current player.
     //

luprex/cpp/world.cpp

@@ -15,22 +15,15 @@ World::~World() {
 }
 
 World::World() {
-    // Create the lua state.
-    lua_state_ = lua_open();
-    if (lua_state_ == nullptr) {
-        std::cerr << "Cannot create lua state." << std::endl;
-        exit(1);
-    }
-
     // Initialize the userdata metatables.
-    LuaStack::register_all_userdata(lua_state_);
+    LuaStack::register_all_userdata(state());
     
     // Initialize the ID allocator in master mode.
     id_global_pool_.init_master(10);
 
     // Prepare to manipulate the lua state.
     LuaVar world;
-    LuaStack LS(lua_state_, world);
+    LuaStack LS(state(), world);
 
     // Put the world pointer into the lua registry.
     LS.newpointer(world, this, false);
@@ -40,11 +33,11 @@ World::World() {
     LS.setfield(LuaRegistry, "tangibles", LuaNewTable);
 
     // Initialize the SourceDB
-    source_db_.initialize(lua_state_);
+    source_db_.initialize(state());
     source_db_.rebuild();
 
     LS.result();
-    assert (lua_gettop(lua_state_) == 0);
+    assert (lua_gettop(state()) == 0);
 }
 
 void Tangible::be_a_player() {
@@ -53,6 +46,16 @@ void Tangible::be_a_player() {
 
         anim_queue_.add(world_->id_global_pool_.get_one(), "");
         anim_queue_.set_graphic("player");
+
+        LuaVar classtab, mt, place, tangibles;
+        LuaStack LS(world_->state(), classtab, mt, place, tangibles);
+
+        LS.call(classtab, source_makeclass, "player");
+        LS.getfield(tangibles, LuaRegistry, "tangibles");
+        LS.rawget(place, tangibles, anim_queue_.get_id());
+        LS.getmetatable(mt, place);
+        LS.setfield(mt, "__index", classtab);
+        LS.result();
     }
 }
 
@@ -65,7 +68,7 @@ void World::init_standalone() {
     source_db_.run_unittests();
 
     // Create the player tangible.
-    Tangible *player = tangible_make(lua_state_, 1, false);
+    Tangible *player = tangible_make(state(), 1, false);
     player->be_a_player();
 }
 
@@ -135,7 +138,7 @@ World *World::fetch(lua_State *L) {
 
 void World::update_gui(int64_t actor_id, int64_t place_id, Gui *gui) {
     gui->clear();
-    lua_State *L = get_lua_state();
+    lua_State *L = state();
 
     LuaVar actor, place, ugui, func, tangibles;
     LuaStack LS(L, actor, place, ugui, func, tangibles);
@@ -179,8 +182,6 @@ void World::update_gui(int64_t actor_id, int64_t place_id, Gui *gui) {
     LS.result();
 }
     
-
-
 LuaDefine(tangible_get, "c") {
     LuaArg id;
     LuaRet database;

luprex/cpp/world.hpp

@@ -8,6 +8,7 @@
 #include "animqueue.hpp"
 #include "source.hpp"
 #include "gui.hpp"
+#include "luasnap.hpp"
 #include <memory>
 #include <unordered_map>
 
@@ -43,10 +44,10 @@ public:
 
 class World {
 public:
-    // A pointer to the lua State.
+    // A lua intepreter with snapshot function.
     //
-    lua_State *lua_state_;
-
+    LuaSnap lua_snap_;
+    
     // The Global ID Pool.
     //
     IdGlobalPool id_global_pool_;
@@ -81,7 +82,7 @@ public:
     //
     // Get the lua interpreter associated with this world model.
     //
-    lua_State *get_lua_state() { return lua_state_; }
+    lua_State *state() { return lua_snap_.state(); }
 
     // get_near
     //