dfhack/library/LuaTypes.cpp

/*
https://github.com/peterix/dfhack
Copyright (c) 2009-2011 Petr Mrázek (peterix@gmail.com)

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any
damages arising from the use of this software.

Permission is granted to anyone to use this software for any
purpose, including commercial applications, and to alter it and
redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must
not claim that you wrote the original software. If you use this
software in a product, an acknowledgment in the product documentation
would be appreciated but is not required.

2. Altered source versions must be plainly marked as such, and
must not be misrepresented as being the original software.

3. This notice may not be removed or altered from any source
distribution.
*/

#include "Internal.h"

#include <string>
#include <vector>
#include <map>

#include "MemAccess.h"
#include "Core.h"
#include "VersionInfo.h"
#include "tinythread.h"
// must be last due to MS stupidity
#include "DataDefs.h"
#include "DataIdentity.h"
#include "LuaWrapper.h"
#include "DataFuncs.h"

#include "MiscUtils.h"

#include <lua.h>
#include <lauxlib.h>

using namespace DFHack;
using namespace DFHack::LuaWrapper;

/**************************************
 * Identity object read/write methods *
 **************************************/

void function_identity_base::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    field_error(state, fname_idx, "executable code", "read");
}

void function_identity_base::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    field_error(state, fname_idx, "executable code", "write");
}

void constructed_identity::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    push_object_internal(state, this, ptr);
}

void constructed_identity::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    field_error(state, fname_idx, "complex object", "write");
}

void enum_identity::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    base_type->lua_read(state, fname_idx, ptr);
}

void enum_identity::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    base_type->lua_write(state, fname_idx, ptr, val_index);
}

void df::number_identity_base::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    lua_pushnumber(state, read(ptr));
}

void df::number_identity_base::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    if (!lua_isnumber(state, val_index))
        field_error(state, fname_idx, "number expected", "write");

    write(ptr, lua_tonumber(state, val_index));
}

void df::bool_identity::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    lua_pushboolean(state, *(bool*)ptr);
}

void df::bool_identity::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    char *pb = (char*)ptr;

    if (lua_isboolean(state, val_index) || lua_isnil(state, val_index))
        *pb = lua_toboolean(state, val_index);
    else if (lua_isnumber(state, val_index))
        *pb = lua_tointeger(state, val_index);
    else
        field_error(state, fname_idx, "boolean or number expected", "write");
}

void df::ptr_string_identity::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    auto pstr = (char**)ptr;
    if (*pstr)
        lua_pushstring(state, *pstr);
    else
        lua_pushnil(state);
}

void df::ptr_string_identity::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    field_error(state, fname_idx, "raw pointer string", "write");
}

void df::stl_string_identity::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    auto pstr = (std::string*)ptr;
    lua_pushlstring(state, pstr->data(), pstr->size());
}

void df::stl_string_identity::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    size_t size;
    const char *bytes = lua_tolstring(state, val_index, &size);
    if (!bytes)
        field_error(state, fname_idx, "string expected", "write");

    *(std::string*)ptr = std::string(bytes, size);
}

void df::pointer_identity::lua_read(lua_State *state, int fname_idx, void *ptr, type_identity *target)
{
    push_object_internal(state, target, *(void**)ptr);
}

void df::pointer_identity::lua_read(lua_State *state, int fname_idx, void *ptr)
{
    lua_read(state, fname_idx, ptr, target);
}

void df::pointer_identity::lua_write(lua_State *state, int fname_idx, void *ptr,
                                     type_identity *target, int val_index)
{
    auto pptr = (void**)ptr;

    if (lua_isnil(state, val_index))
        *pptr = NULL;
    else
    {
        void *nval = get_object_internal(state, target, val_index, false);
        if (nval)
            *pptr = nval;
        else
            field_error(state, fname_idx, "incompatible pointer type", "write");
    }
}

void df::pointer_identity::lua_write(lua_State *state, int fname_idx, void *ptr, int val_index)
{
    lua_write(state, fname_idx, ptr, target, val_index);
}

int container_identity::lua_item_count(lua_State *state, void *ptr, CountMode mode)
{
    if (lua_isnumber(state, UPVAL_ITEM_COUNT))
        return lua_tointeger(state, UPVAL_ITEM_COUNT);
    else
        return item_count(ptr, mode);
}

void container_identity::lua_item_reference(lua_State *state, int fname_idx, void *ptr, int idx)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);
    void *pitem = item_pointer(id, ptr, idx);
    push_object_internal(state, id, pitem);
}

void container_identity::lua_item_read(lua_State *state, int fname_idx, void *ptr, int idx)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);
    void *pitem = item_pointer(id, ptr, idx);
    id->lua_read(state, fname_idx, pitem);
}

void container_identity::lua_item_write(lua_State *state, int fname_idx, void *ptr, int idx, int val_index)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);
    void *pitem = item_pointer(id, ptr, idx);
    id->lua_write(state, fname_idx, pitem, val_index);
}

bool container_identity::lua_insert(lua_State *state, int fname_idx, void *ptr, int idx, int val_index)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);

    char tmp[32];
    void *pitem = &tmp;

    if (id->isPrimitive())
    {
        if (id->isConstructed())
            luaL_error(state, "Temporaries of type %s not supported", id->getFullName().c_str());

        assert(id->byte_size() <= sizeof(tmp));
        id->lua_write(state, fname_idx, pitem, val_index);
    }
    else
    {
        pitem = get_object_internal(state, id, val_index, false);
        if (!pitem)
            field_error(state, fname_idx, "incompatible object type", "insert");
    }

    return insert(ptr, idx, pitem);
}

void ptr_container_identity::lua_item_reference(lua_State *state, int fname_idx, void *ptr, int idx)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);
    void *pitem = item_pointer(id, ptr, idx);
    push_adhoc_pointer(state, pitem, id);
}

void ptr_container_identity::lua_item_read(lua_State *state, int fname_idx, void *ptr, int idx)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);
    void *pitem = item_pointer(&df::identity_traits<void*>::identity, ptr, idx);
    df::pointer_identity::lua_read(state, fname_idx, pitem, id);
}

void ptr_container_identity::lua_item_write(lua_State *state, int fname_idx, void *ptr, int idx, int val_index)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);
    void *pitem = item_pointer(&df::identity_traits<void*>::identity, ptr, idx);
    df::pointer_identity::lua_write(state, fname_idx, pitem, id, val_index);
}

bool ptr_container_identity::lua_insert(lua_State *state, int fname_idx, void *ptr, int idx, int val_index)
{
    auto id = (type_identity*)lua_touserdata(state, UPVAL_ITEM_ID);

    void *pitem = NULL;
    df::pointer_identity::lua_write(state, fname_idx, &pitem, id, val_index);

    return insert(ptr, idx, pitem);
}

void bit_container_identity::lua_item_reference(lua_State *state, int, void *, int)
{
    lua_pushnil(state);
}

void bit_container_identity::lua_item_read(lua_State *state, int fname_idx, void *ptr, int idx)
{
    lua_pushboolean(state, get_item(ptr, idx));
}

void bit_container_identity::lua_item_write(lua_State *state, int fname_idx, void *ptr, int idx, int val_index)
{
    if (lua_isboolean(state, val_index) || lua_isnil(state, val_index))
        set_item(ptr, idx, lua_toboolean(state, val_index));
    else if (lua_isnumber(state, val_index))
        set_item(ptr, idx, lua_tointeger(state, val_index) != 0);
    else
        field_error(state, fname_idx, "boolean or number expected", "write");
}

/**
 * Resolve the field name in UPVAL_FIELDTABLE, die if not found.
 */
static void lookup_field(lua_State *state, int index, const char *mode)
{
    lua_pushvalue(state, index);
    lua_gettable(state, UPVAL_FIELDTABLE); // uses metatable with enum keys

    if (lua_isnil(state, -1))
        field_error(state, index, "not found", mode);
}

// Resolve the field in the metatable and return
static int get_metafield(lua_State *state)
{
    lua_rawget(state, UPVAL_METATABLE);
    return 1;
}

static void *find_field(lua_State *state, int index, const char *mode)
{
    lookup_field(state, index, mode);

    // Methods
    if (lua_isfunction(state, -1))
        return NULL;

    // Otherwise must be a pointer
    if (!lua_isuserdata(state, -1))
        field_error(state, index, "corrupted field table", mode);

    void *p = lua_touserdata(state, -1);
    lua_pop(state, 1);

    // NULL => metafield
    if (!p)
        get_metafield(state);
    return p;
}

static uint8_t *check_method_call(lua_State *state, int min_args, int max_args)
{
    int argc = lua_gettop(state)-1;
    if (argc < min_args || argc > max_args)
        field_error(state, UPVAL_METHOD_NAME, "wrong argument count", "call");

    return get_object_addr(state, 1, UPVAL_METHOD_NAME, "call");
}

static void GetAdHocMetatable(lua_State *state, const struct_field_info *field);

static void read_field(lua_State *state, const struct_field_info *field, void *ptr)
{
    switch (field->mode)
    {
        case struct_field_info::STATIC_STRING:
        {
            int len = strnlen((char*)ptr, field->count);
            lua_pushlstring(state, (char*)ptr, len);
            return;
        }

        case struct_field_info::OBJ_METHOD:
        case struct_field_info::CLASS_METHOD:
            // error

        case struct_field_info::PRIMITIVE:
        case struct_field_info::SUBSTRUCT:
            field->type->lua_read(state, 2, ptr);
            return;

        case struct_field_info::POINTER:
            df::pointer_identity::lua_read(state, 2, ptr, field->type);
            return;

        case struct_field_info::CONTAINER:
            if (!field->eid || !field->type->isContainer() ||
                field->eid == ((container_identity*)field->type)->getIndexEnumType())
            {
                field->type->lua_read(state, 2, ptr);
                return;
            }
            // fallthrough

        case struct_field_info::STATIC_ARRAY:
        case struct_field_info::STL_VECTOR_PTR:
            GetAdHocMetatable(state, field);
            push_object_ref(state, ptr);
            return;

        case struct_field_info::END:
            break;
    }

    lua_pushnil(state);
}

static void field_reference(lua_State *state, const struct_field_info *field, void *ptr)
{
    switch (field->mode)
    {
        case struct_field_info::PRIMITIVE:
        case struct_field_info::SUBSTRUCT:
            push_object_internal(state, field->type, ptr);
            return;

        case struct_field_info::POINTER:
            push_adhoc_pointer(state, ptr, field->type);
            return;

        case struct_field_info::OBJ_METHOD:
        case struct_field_info::CLASS_METHOD:
            // error

        case struct_field_info::CONTAINER:
            read_field(state, field, ptr);
            return;

        case struct_field_info::STATIC_STRING:
        case struct_field_info::STATIC_ARRAY:
        case struct_field_info::STL_VECTOR_PTR:
            GetAdHocMetatable(state, field);
            push_object_ref(state, ptr);
            return;

        case struct_field_info::END:
            break;
    }

    lua_pushnil(state);
}

static void write_field(lua_State *state, const struct_field_info *field, void *ptr, int value_idx)
{
    switch (field->mode)
    {
        case struct_field_info::STATIC_STRING:
        {
            size_t size;
            const char *str = lua_tolstring(state, value_idx, &size);
            if (!str)
                field_error(state, 2, "string expected", "write");
            memcpy(ptr, str, std::min(size+1, size_t(field->count)));
            return;
        }

        case struct_field_info::OBJ_METHOD:
        case struct_field_info::CLASS_METHOD:
            // error

        case struct_field_info::PRIMITIVE:
        case struct_field_info::SUBSTRUCT:
        case struct_field_info::CONTAINER:
            field->type->lua_write(state, 2, ptr, value_idx);
            return;

        case struct_field_info::POINTER:
            df::pointer_identity::lua_write(state, 2, ptr, field->type, value_idx);

        case struct_field_info::STATIC_ARRAY:
        case struct_field_info::STL_VECTOR_PTR:
            field_error(state, 2, "complex object", "write");

        case struct_field_info::END:
            return;
    }
}

/**
 * Metamethod: represent a type node as string.
 */
static int meta_type_tostring(lua_State *state)
{
    if (!lua_getmetatable(state, 1))
        return 0;

    lua_getfield(state, -1, "__metatable");
    const char *cname = lua_tostring(state, -1);

    lua_pushstring(state, stl_sprintf("<type: %s>", cname).c_str());
    return 1;
}

/**
 * Metamethod: represent a DF object reference as string.
 */
static int meta_ptr_tostring(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 0, "access");

    lua_getfield(state, UPVAL_METATABLE, "__metatable");
    const char *cname = lua_tostring(state, -1);

    lua_pushstring(state, stl_sprintf("<%s: 0x%08x>", cname, (unsigned)ptr).c_str());
    return 1;
}

/**
 * Metamethod: __index for structures.
 */
static int meta_struct_index(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "read");
    auto field = (struct_field_info*)find_field(state, 2, "read");
    if (!field)
        return 1;
    read_field(state, field, ptr + field->offset);
    return 1;
}

/**
 * Method: _field for structures.
 */
static int meta_struct_field_reference(lua_State *state)
{
    if (lua_gettop(state) != 2)
        luaL_error(state, "Usage: object._field(name)");
    uint8_t *ptr = get_object_addr(state, 1, 2, "reference");
    auto field = (struct_field_info*)find_field(state, 2, "reference");
    if (!field)
        field_error(state, 2, "builtin property or method", "reference");
    field_reference(state, field, ptr + field->offset);
    return 1;
}

/**
 * Metamethod: __newindex for structures.
 */
static int meta_struct_newindex(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "write");
    auto field = (struct_field_info*)find_field(state, 2, "write");
    if (!field)
        field_error(state, 2, "builtin property or method", "write");
    write_field(state, field, ptr + field->offset, 3);
    return 0;
}

/**
 * Metamethod: __index for primitives, i.e. simple object references.
 *   Fields point to identity, or NULL for metafields.
 */
static int meta_primitive_index(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "read");
    auto type = (type_identity*)find_field(state, 2, "read");
    if (!type)
        return 1;
    type->lua_read(state, 2, ptr);
    return 1;
}

/**
 * Metamethod: __newindex for primitives.
 */
static int meta_primitive_newindex(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "write");
    auto type = (type_identity*)find_field(state, 2, "write");
    if (!type)
        field_error(state, 2, "builtin property or method", "write");
    type->lua_write(state, 2, ptr, 3);
    return 0;
}

/**
 * Metamethod: __len for containers.
 */
static int meta_container_len(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 0, "get length");
    auto id = (container_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    int len = id->lua_item_count(state, ptr, container_identity::COUNT_LEN);
    lua_pushinteger(state, len);
    return 1;
}

/**
 * Field lookup for containers:
 *
 *   - Numbers are indices and handled directly.
 *   - NULL userdata are metafields; push and exit;
 */
static int lookup_container_field(lua_State *state, int field, const char *mode = NULL)
{
    if (lua_type(state, field) == LUA_TNUMBER)
        return field;

    lookup_field(state, field, mode ? mode : "read");

    if (lua_isuserdata(state, -1) && !lua_touserdata(state, -1))
    {
        if (mode)
            field_error(state, field, "builtin property or method", mode);

        lua_pop(state, 1);
        get_metafield(state);
        return 0;
    }

    return -1;
}

/**
 * Index verification: number and in range.
 */
static int check_container_index(lua_State *state, int len,
                                 int fidx, int iidx, const char *mode)
{
    if (!lua_isnumber(state, iidx))
        field_error(state, fidx, "invalid index", mode);

    int idx = lua_tointeger(state, iidx);
    if (idx < 0 || (idx >= len && len >= 0))
        field_error(state, fidx, "index out of bounds", mode);

    return idx;
}

/**
 * Metamethod: __index for containers.
 */
static int meta_container_index(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "read");
    int iidx = lookup_container_field(state, 2);
    if (!iidx)
        return 1;

    auto id = (container_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    int len = id->lua_item_count(state, ptr, container_identity::COUNT_READ);
    int idx = check_container_index(state, len, 2, iidx, "read");
    id->lua_item_read(state, 2, ptr, idx);
    return 1;
}

/**
 * Method: _field for containers.
 */
static int meta_container_field_reference(lua_State *state)
{
    if (lua_gettop(state) != 2)
        luaL_error(state, "Usage: object._field(index)");
    uint8_t *ptr = get_object_addr(state, 1, 2, "reference");
    int iidx = lookup_container_field(state, 2, "reference");

    auto id = (container_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    int len = id->lua_item_count(state, ptr, container_identity::COUNT_WRITE);
    int idx = check_container_index(state, len, 2, iidx, "reference");
    id->lua_item_reference(state, 2, ptr, idx);
    return 1;
}

/**
 * Metamethod: __index for containers.
 */
static int meta_container_newindex(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "write");
    int iidx = lookup_container_field(state, 2, "write");

    auto id = (container_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    int len = id->lua_item_count(state, ptr, container_identity::COUNT_WRITE);
    int idx = check_container_index(state, len, 2, iidx, "write");
    id->lua_item_write(state, 2, ptr, idx, 3);
    return 0;
}

/**
 * Method: resize container
 */
static int method_container_resize(lua_State *state)
{
    uint8_t *ptr = check_method_call(state, 1, 1);

    auto id = (container_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    int idx = check_container_index(state, -1, UPVAL_METHOD_NAME, 2, "call");

    if (!id->resize(ptr, idx))
        field_error(state, UPVAL_METHOD_NAME, "not supported", "call");
    return 0;
}

/**
 * Method: erase item from container
 */
static int method_container_erase(lua_State *state)
{
    uint8_t *ptr = check_method_call(state, 1, 1);

    auto id = (container_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    int len = id->lua_item_count(state, ptr, container_identity::COUNT_LEN);
    int idx = check_container_index(state, len, UPVAL_METHOD_NAME, 2, "call");

    if (!id->erase(ptr, idx))
        field_error(state, UPVAL_METHOD_NAME, "not supported", "call");
    return 0;
}

/**
 * Method: insert item into container
 */
static int method_container_insert(lua_State *state)
{
    uint8_t *ptr = check_method_call(state, 2, 2);

    auto id = (container_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    int len = id->lua_item_count(state, ptr, container_identity::COUNT_LEN);
    if (len >= 0) len++;
    int idx = check_container_index(state, len, UPVAL_METHOD_NAME, 2, "call");

    if (!id->lua_insert(state, UPVAL_METHOD_NAME, ptr, idx, 3))
        field_error(state, UPVAL_METHOD_NAME, "not supported", "call");
    return 0;
}

/**
 * Metamethod: __len for bitfields.
 */
static int meta_bitfield_len(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 0, "get size");
    auto id = (bitfield_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    lua_pushinteger(state, id->getNumBits());
    return 1;
}

/**
 * Metamethod: __index for bitfields.
 */
static int meta_bitfield_index(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "read");
    int iidx = lookup_container_field(state, 2);
    if (!iidx)
        return 1;

    auto id = (bitfield_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);

    // whole
    if (lua_isuserdata(state, iidx) && lua_touserdata(state, iidx) == id)
    {
        size_t intv = 0;
        memcpy(&intv, ptr, std::min(sizeof(intv), size_t(id->byte_size())));
        lua_pushnumber(state, intv);
        return 1;
    }

    int idx = check_container_index(state, id->getNumBits(), 2, iidx, "read");
    int size = id->getBits()[idx].size;

    int value = getBitfieldField(ptr, idx, size);
    if (size <= 1)
        lua_pushboolean(state, value != 0);
    else
        lua_pushinteger(state, value);
    return 1;
}

/**
 * Metamethod: __newindex for bitfields.
 */
static int meta_bitfield_newindex(lua_State *state)
{
    uint8_t *ptr = get_object_addr(state, 1, 2, "write");
    int iidx = lookup_container_field(state, 2, "write");

    auto id = (bitfield_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);

    // whole
    if (lua_isuserdata(state, iidx) && lua_touserdata(state, iidx) == id)
    {
        if (!lua_isnumber(state, 3))
            field_error(state, 2, "number expected", "write");

        size_t intv = (size_t)lua_tonumber(state, 3);
        memcpy(ptr, &intv, std::min(sizeof(intv), size_t(id->byte_size())));
        return 0;
    }

    int idx = check_container_index(state, id->getNumBits(), 2, iidx, "write");
    int size = id->getBits()[idx].size;

    if (lua_isboolean(state, 3) || lua_isnil(state, 3))
        setBitfieldField(ptr, idx, size, lua_toboolean(state, 3));
    else if (lua_isnumber(state, 3))
        setBitfieldField(ptr, idx, size, lua_tointeger(state, 3));
    else
        field_error(state, 2, "number or boolean expected", "write");
    return 0;
}

/**
 * Metamethod: __index for df.global
 */
static int meta_global_index(lua_State *state)
{
    auto field = (struct_field_info*)find_field(state, 2, "read");
    if (!field)
        return 1;
    void *ptr = *(void**)field->offset;
    if (!ptr)
        field_error(state, 2, "global address not known", "read");
    read_field(state, field, ptr);
    return 1;
}

/**
 * Metamethod: __newindex for df.global
 */
static int meta_global_newindex(lua_State *state)
{
    auto field = (struct_field_info*)find_field(state, 2, "write");
    if (!field)
        field_error(state, 2, "builtin property or method", "write");
    void *ptr = *(void**)field->offset;
    if (!ptr)
        field_error(state, 2, "global address not known", "write");
    write_field(state, field, ptr, 3);
    return 0;
}

/**
 * Wrapper for c++ methods and functions.
 */
static int meta_call_function(lua_State *state)
{
    auto id = (function_identity_base*)lua_touserdata(state, UPVAL_CONTAINER_ID);
    if (lua_gettop(state) != id->getNumArgs())
        field_error(state, UPVAL_METHOD_NAME, "invalid argument count", "invoke");
    id->invoke(state, 1);
    return 1;
}

/**
 * Create a closure invoking the given function, and add it to the field table.
 */
static void AddMethodWrapper(lua_State *state, int meta_idx, int field_idx,
                             const char *name, function_identity_base *fun)
{
    lua_getfield(state, LUA_REGISTRYINDEX, DFHACK_TYPETABLE_NAME);
    lua_pushvalue(state, meta_idx);
    lua_pushfstring(state, "%s()", name);
    lua_pushlightuserdata(state, fun);
    lua_pushcclosure(state, meta_call_function, 4);

    lua_setfield(state, field_idx, name);
}

/**
 * Add fields in the array to the UPVAL_FIELDTABLE candidates on the stack.
 */
static void IndexFields(lua_State *state, struct_identity *pstruct)
{
    // stack: metatable fieldtable

    int base = lua_gettop(state) - 2;

    for (struct_identity *p = pstruct; p; p = p->getParent())
    {
        auto fields = p->getFields();
        if (!fields)
            continue;

        for (int i = 0; fields[i].mode != struct_field_info::END; ++i)
        {
            switch (fields[i].mode)
            {
            case struct_field_info::OBJ_METHOD:
                AddMethodWrapper(state, base+1, base+2, fields[i].name,
                                 (function_identity_base*)fields[i].type);
                break;

            case struct_field_info::CLASS_METHOD:
                break;

            default:
                lua_pushstring(state,fields[i].name);
                lua_pushlightuserdata(state,(void*)&fields[i]);
                lua_rawset(state,base+2);
                break;
            }
        }
    }
}

void LuaWrapper::IndexStatics(lua_State *state, int meta_idx, int ftable_idx, struct_identity *pstruct)
{
    // stack: metatable fieldtable

    for (struct_identity *p = pstruct; p; p = p->getParent())
    {
        auto fields = p->getFields();
        if (!fields)
            continue;

        for (int i = 0; fields[i].mode != struct_field_info::END; ++i)
        {
            switch (fields[i].mode)
            {
            case struct_field_info::CLASS_METHOD:
                AddMethodWrapper(state, meta_idx, ftable_idx, fields[i].name,
                                 (function_identity_base*)fields[i].type);
                break;

            default:
                break;
            }
        }
    }
}

/**
 * Make a struct-style object metatable.
 */
static void MakeFieldMetatable(lua_State *state, struct_identity *pstruct,
                               lua_CFunction reader, lua_CFunction writer)
{
    int base = lua_gettop(state);

    MakeMetatable(state, pstruct, "struct"); // meta, fields

    IndexFields(state, pstruct);

    SetStructMethod(state, base+1, base+2, reader, "__index");
    SetStructMethod(state, base+1, base+2, writer, "__newindex");

    // returns: [metatable readfields writefields];
}

/**
 * Make a primitive-style metatable
 */
static void MakePrimitiveMetatable(lua_State *state, type_identity *type)
{
    int base = lua_gettop(state);

    MakeMetatable(state, type, "primitive");

    SetPtrMethods(state, base+1, base+2);

    EnableMetaField(state, base+2, "value", type);

    SetStructMethod(state, base+1, base+2, meta_primitive_index, "__index");
    SetStructMethod(state, base+1, base+2, meta_primitive_newindex, "__newindex");
}

static void AddContainerMethodFun(lua_State *state, int meta_idx, int field_idx,
                                  lua_CFunction function, const char *name,
                                  type_identity *container, type_identity *item, int count)
{
    lua_pushfstring(state, "%s()", name);
    SetContainerMethod(state, meta_idx, lua_gettop(state), function, name, container, item, count);
    lua_pop(state, 1);

    EnableMetaField(state, field_idx, name);
}

/**
 * Make a container-style object metatable.
 */
static void MakeContainerMetatable(lua_State *state, container_identity *type,
                                   type_identity *item, int count, type_identity *ienum)
{
    int base = lua_gettop(state);

    MakeMetatable(state, type, "container");
    SetPtrMethods(state, base+1, base+2);

    // Update the type name using full info
    lua_pushstring(state, type->getFullName(item).c_str());
    lua_dup(state);
    lua_setfield(state, base+1, "__metatable");
    lua_setfield(state, base+1, "_type");

    lua_pushlightuserdata(state, item);
    lua_setfield(state, base+1, "_field_identity");

    if (count >= 0)
    {
        lua_pushinteger(state, count);
        lua_setfield(state, base+1, "_count");
    }

    SetContainerMethod(state, base+1, base+2, meta_container_len, "__len", type, item, count);
    SetContainerMethod(state, base+1, base+2, meta_container_index, "__index", type, item, count);
    SetContainerMethod(state, base+1, base+2, meta_container_newindex, "__newindex", type, item, count);

    SetContainerMethod(state, base+1, base+2, meta_container_field_reference, "_field", type, item, count);

    AddContainerMethodFun(state, base+1, base+2, method_container_resize, "resize", type, item, count);
    AddContainerMethodFun(state, base+1, base+2, method_container_erase, "erase", type, item, count);
    AddContainerMethodFun(state, base+1, base+2, method_container_insert, "insert", type, item, count);

    AttachEnumKeys(state, base+1, base+2, ienum);
}

/*
 * Metatable construction identity methods.
 */
void type_identity::build_metatable(lua_State *state)
{
    MakePrimitiveMetatable(state, this);
}

void container_identity::build_metatable(lua_State *state)
{
    MakeContainerMetatable(state, this, getItemType(), -1, getIndexEnumType());
}

void bitfield_identity::build_metatable(lua_State *state)
{
    int base = lua_gettop(state);

    MakeMetatable(state, this, "bitfield");

    SetPtrMethods(state, base+1, base+2);

    SetContainerMethod(state, base+1, base+2, meta_bitfield_len, "__len", this, NULL, -1);
    SetContainerMethod(state, base+1, base+2, meta_bitfield_index, "__index", this, NULL, -1);
    SetContainerMethod(state, base+1, base+2, meta_bitfield_newindex, "__newindex", this, NULL, -1);

    AttachEnumKeys(state, base+1, base+2, this);

    EnableMetaField(state, base+2, "whole", this);
}

void struct_identity::build_metatable(lua_State *state)
{
    int base = lua_gettop(state);
    MakeFieldMetatable(state, this, meta_struct_index, meta_struct_newindex);
    SetStructMethod(state, base+1, base+2, meta_struct_field_reference, "_field");
    SetPtrMethods(state, base+1, base+2);
}

void global_identity::build_metatable(lua_State *state)
{
    MakeFieldMetatable(state, this, meta_global_index, meta_global_newindex);
}

/**
 * Construct a metatable for an object type folded into the field descriptor.
 * This is done to reduce compile-time symbol table bloat due to templates.
 */
static void GetAdHocMetatable(lua_State *state, const struct_field_info *field)
{
    lua_pushlightuserdata(state, (void*)field);

    if (!LookupTypeInfo(state, true))
    {
        switch (field->mode)
        {
        case struct_field_info::CONTAINER:
        {
            auto ctype = (container_identity*)field->type;
            MakeContainerMetatable(state, ctype, ctype->getItemType(), -1, field->eid);
            break;
        }

        case struct_field_info::STATIC_STRING:
            MakeContainerMetatable(state, &df::buffer_container_identity::base_instance,
                                   &df::identity_traits<char>::identity, field->count, NULL);
            break;

        case struct_field_info::STATIC_ARRAY:
            MakeContainerMetatable(state, &df::buffer_container_identity::base_instance,
                                   field->type, field->count, field->eid);
            break;

        case struct_field_info::STL_VECTOR_PTR:
            MakeContainerMetatable(state, &df::identity_traits<std::vector<void*> >::identity,
                                   field->type, -1, field->eid);
            break;

        default:
            luaL_error(state, "Invalid ad-hoc field: %d", field->mode);
        }

        lua_pop(state, 1);

        SaveTypeInfo(state, (void*)field);
    }
}

void LuaWrapper::push_adhoc_pointer(lua_State *state, void *ptr, type_identity *target)
{
    if (!target)
    {
        push_object_internal(state, &df::identity_traits<void*>::identity, ptr);
        return;
    }

    LookupInTable(state, target, DFHACK_PTR_IDTABLE_NAME);

    type_identity *id = (type_identity*)lua_touserdata(state, -1);
    lua_pop(state, 1);

    if (!id)
    {
        /*
         * HACK: relies on
         *   1) pointer_identity destructor being no-op
         *   2) lua gc never moving objects in memory
         */

        void *newobj = lua_newuserdata(state, sizeof(pointer_identity));
        id = new (newobj) pointer_identity(target);

        SaveInTable(state, target, DFHACK_PTR_IDTABLE_NAME);
        lua_pop(state, 1);
    }

    push_object_internal(state, id, ptr);
}