1 files changed, 123 insertions, 0 deletions
diff --git a/src/script/common/c_packer.h b/src/script/common/c_packer.h
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+++ b/src/script/common/c_packer.h
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+/*
+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.
+*/
+
+#pragma once
+
+#include <string>
+#include <vector>
+#include "irrlichttypes.h"
+#include "util/basic_macros.h"
+
+extern "C" {
+#include <lua.h>
+}
+
+/*
+	This file defines an in-memory representation of Lua objects including
+	support for functions and userdata. It it used to move data between Lua
+	states and cannot be used for persistence or network transfer.
+*/
+
+#define INSTR_SETTABLE (-10)
+#define INSTR_POP      (-11)
+
+/**
+ * Represents a single instruction that pushes a new value or works with existing ones.
+ */
+struct PackedInstr
+{
+	s16 type; // LUA_T* or INSTR_*
+	u16 set_into; // set into table on stack
+	bool pop; // remove from stack?
+	union {
+		bool bdata; // boolean: value
+		lua_Number ndata; // number: value
+		struct {
+			u16 uidata1, uidata2; // table: narr, nrec
+		};
+		struct {
+			/*
+				SETTABLE: key index, value index
+				POP: indices to remove
+				otherwise w/ set_into: numeric key, -
+			*/
+			s32 sidata1, sidata2;
+		};
+		void *ptrdata; // userdata: implementation defined
+	};
+	/*
+		- string: value
+		- function: buffer
+		- w/ set_into: string key (no null bytes!)
+		- userdata: name in registry
+	*/
+	std::string sdata;
+
+	PackedInstr() : type(0), set_into(0), pop(false) {}
+};
+
+/**
+ * A packed value can be a primitive like a string or number but also a table
+ * including all of its contents. It is made up of a linear stream of
+ * 'instructions' that build the final value when executed.
+ */
+struct PackedValue
+{
+	std::vector<PackedInstr> i;
+	// Indicates whether there are any userdata pointers that need to be deallocated
+	bool contains_userdata = false;
+
+	PackedValue() = default;
+	~PackedValue();
+
+	DISABLE_CLASS_COPY(PackedValue)
+
+	ALLOW_CLASS_MOVE(PackedValue)
+};
+
+/*
+ * Packing callback: Turns a Lua value at given index into a void*
+ */
+typedef void *(*PackInFunc)(lua_State *L, int idx);
+/*
+ * Unpacking callback: Turns a void* back into the Lua value (left on top of stack)
+ *
+ * Note that this function must take ownership of the pointer, so make sure
+ * to free or keep the memory.
+ * `L` can be nullptr to indicate that data should just be discarded.
+ */
+typedef void (*PackOutFunc)(lua_State *L, void *ptr);
+/*
+ * Register a packable type with the name of its metatable.
+ *
+ * Even though the callbacks are global this must be called for every Lua state
+ * that supports objects of this type.
+ * This function is thread-safe.
+ */
+void script_register_packer(lua_State *L, const char *regname,
+		PackInFunc fin, PackOutFunc fout);
+
+// Pack a Lua value
+PackedValue *script_pack(lua_State *L, int idx);
+// Unpack a Lua value (left on top of stack)
+// Note that this may modify the PackedValue, you can't reuse it!
+void script_unpack(lua_State *L, PackedValue *val);
+
+// Dump contents of PackedValue to stdout for debugging
+void script_dump_packed(const PackedValue *val);