games/devtest/mods/basenodes/textures/default_sand.png

/*
Minetest
Copyright (C) 2022 sfan5 <sfan5@live.de>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include <cstdio>
#include <cstring>
#include <cmath>
#include <cassert>
#include <unordered_set>
#include <unordered_map>
#include "c_packer.h"
#include "c_internal.h"
#include "log.h"
#include "debug.h"
#include "threading/mutex_auto_lock.h"

extern "C" {
#include <lauxlib.h>
}

//
// Helpers
//

// convert negative index to absolute position on Lua stack
static inline int absidx(lua_State *L, int idx)
{
	assert(idx < 0);
	return lua_gettop(L) + idx + 1;
}

// does the type put anything into PackedInstr::sdata?
static inline bool uses_sdata(int type)
{
	switch (type) {
		case LUA_TSTRING:
		case LUA_TFUNCTION:
		case LUA_TUSERDATA:
			return true;
		default:
			return false;
	}
}

// does the type put anything into PackedInstr::<union>?
static inline bool uses_union(int type)
{
	switch (type) {
		case LUA_TNIL:
		case LUA_TSTRING:
		case LUA_TFUNCTION:
			return false;
		default:
			return true;
	}
}

static inline bool can_set_into(int ktype, int vtype)
{
	switch (ktype) {
		case LUA_TNUMBER:
			return !uses_union(vtype);
		case LUA_TSTRING:
			return !uses_sdata(vtype);
		default:
			return false;
	}
}

// is the key suitable for use with set_into?
static inline bool suitable_key(lua_State *L, int idx)
{
	if (lua_type(L, idx) == LUA_TSTRING) {
		// strings may not have a NULL byte (-> lua_setfield)
		size_t len;
		const char *str = lua_tolstring(L, idx, &len);
		return strlen(str) == len;
	} else {
		assert(lua_type(L, idx) == LUA_TNUMBER);
		// numbers must fit into an s32 and be integers (-> lua_rawseti)
		lua_Number n = lua_tonumber(L, idx);
		return std::floor(n) == n && n >= S32_MIN && n <= S32_MAX;
	}
}

namespace {
	// checks if you left any values on the stack, for debugging
	class StackChecker {
		lua_State *L;
		int top;
	public:
		StackChecker(lua_State *L) : L(L), top(lua_gettop(L)) {}
		~StackChecker() {
			assert(lua_gettop(L) >= top);
			if (lua_gettop(L) > top) {
				rawstream << "Lua stack not cleaned up: "
					<< lua_gettop(L) << " != " << top
					<< " (false-positive if exception thrown)" << std::endl;
			}
		}
	};

	// Since an std::vector may reallocate, this is the only safe way to keep
	// a reference to a particular element.
	template <typename T>
	class VectorRef {
		std::vector<T> *vec;
		size_t idx;
		VectorRef(std::vector<T> *vec, size_t idx) : vec(vec), idx(idx) {}
	public:
		constexpr VectorRef() : vec(nullptr), idx(0) {}
		static VectorRef<T> front(std::vector<T> &vec) {
			return VectorRef(&vec, 0);
		}
		static VectorRef<T> back(std::vector<T> &vec) {
			return VectorRef(&vec, vec.size() - 1);
		}
		T &operator*() { return (*vec)[idx]; }
		T *operator->() { return &(*vec)[idx]; }
		operator bool() const { return vec != nullptr; }
	};

	struct Packer {
		PackInFunc fin;
		PackOutFunc fout;
	};

	typedef std::pair<std::string, Packer> PackerTuple;
}

static inline auto emplace(PackedValue &pv, s16 type)
{
	pv.i.emplace_back();
	auto ref = VectorRef<PackedInstr>::back(pv.i);
	ref->type = type;
	// Initialize fields that may be left untouched
ofs	hex dump	ascii
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01c0	bc 20 16 63 3c a5 05 22 80 a4 14 98 fb cd c0 d8 b5 3e 15 9e fb 67 04 00 c2 2a 86 5e af 93 4b bc	...c<..".........>...g...*.^..K.
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0220	00 00 49 45 4e 44 ae 42 60 82	..IEND.B`.