integration/luprex/core/cpp/luasnap.cpp

#include "luasnap.hpp"
#include "luastack.hpp"
#include <iostream>
#include <cassert>
#include <sstream>


LuaSnap::LuaSnap() {
    state_ = luaL_newstate();
    LuaStack LS(state_);
    LS.rawset(LuaRegistry, "persist", LuaNewTable);
    LS.rawset(LuaRegistry, "unpersist", LuaNewTable);
}

LuaSnap::~LuaSnap() {
    std::cerr << "LuaSnap destructor not implemented yet" << std::endl;
}

bool LuaSnap::have_snapshot() const {
    return !snapshot_.empty();
}

static void oss_writer(lua_State *L, const void *p, size_t sz, void *ud) {
    std::ostringstream *oss = (std::ostringstream *)ud;
    oss->write((const char *)p, sz);
}

void LuaSnap::snapshot() {
    // Snapshot and the lua stack should both be empty.
    assert(snapshot_.empty());
    assert(lua_gettop(state_) == 0);

    // lua variables that we'll need.
    LuaVar key, value;
    LuaRet permstable, regcopy;
    LuaStack LS(state_, permstable, regcopy, key, value);

    // Construct a copy of the registry table.
    LS.set(regcopy, LuaNewTable);
    LS.set(key, LuaNil);
    while (LS.next(LuaRegistry, key, value) != 0) {
        LS.rawset(regcopy, key, value);
    }

    // Remove certain things from the copy.
    LS.rawset(regcopy, LUA_RIDX_MAINTHREAD, LuaNil);
    LS.rawset(regcopy, "persist", LuaNil);
    LS.rawset(regcopy, "unpersist", LuaNil);
    LS.rawset(regcopy, "world", LuaNil);
    LS.rawset(regcopy, "gui", LuaNil);
    LS.result();

    // Get the permanents table from the registry.
    LS.rawget(permstable, LuaRegistry, "persist");

    // When we call 'LS.result', this should leave the
    // permstable and the regcopy on the stack.
    LS.result();
    assert(lua_gettop(state_) == 2);

    // Call eris to dump the state to an ostringstream,
    // then save the result.
    std::ostringstream oss;
    eris_dump(state_, oss_writer, (void *)&oss);
    snapshot_ = oss.str();
}

void LuaSnap::rollback() {
    assert(!snapshot_.empty());
}