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/* supple/lib/supple/capi.c
*
* Sandbox (for) Untrusted Procedure Partitioning (in) Lua Engine - Supple
*
* Useful C methods for Supple including the userdata partitioning.
*
* Copyright 2012 Daniel Silverstone <dsilvers@digital-scurf.org>
*
* For licence terms, see COPYING
*
*/
#include <lua.h>
#include <lauxlib.h>
#include <string.h>
/* The API exposed, increment on backward-compatible changes */
#define CAPI_API 1
/* The ABI exposed, increment on backward-incompatible changes */
#define CAPI_ABI 1
static int
supple_capi_explain(lua_State *L)
{
int one_type;
if (lua_gettop(L) != 2) {
return luaL_error(L, "Expected 2 args got %d", lua_gettop(L));
}
one_type = lua_type(L, 1);
if ((one_type != LUA_TTABLE) &&
(one_type != LUA_TFUNCTION) &&
(one_type != LUA_TUSERDATA)) {
return luaL_error(L,
"Expected one of table, function or userdata. " \
"Got %s instead",
lua_typename(L, one_type));
}
if (lua_type(L, 2) != LUA_TSTRING) {
return luaL_error(L, "Expected string, got %s instead",
lua_typename(L, lua_type(L, 2)));
}
lua_newtable(L);
lua_pushvalue(L, 2);
lua_setfield(L, -2, "tag");
lua_pushstring(L, lua_typename(L, one_type));
lua_setfield(L, -2, "type");
if (one_type != LUA_TFUNCTION) {
/* Get the metatable */
if (lua_getmetatable(L, 1) != 0) {
int idx = 1;
/* Prepare a methods table */
lua_newtable(L);
lua_pushnil(L); /* For iterating */
while (lua_next(L, -3) != 0) { /* Iterate the metatable */
lua_pop(L, 1); /* Don't need the value */
if (lua_type(L, -1) != LUA_TSTRING) {
/* Not a string key */
} else if (strcmp(lua_tostring(L, -1),
"__mode") == 0) {
/* mode key is ignored */
} else {
/* dup */
lua_pushvalue(L, -1);
/* And copy into methods */
lua_rawseti(L, -3, idx++);
}
/* Key is left ready for lua_next() */
}
/* Stuff the methods table into the return */
lua_setfield(L, -3, "methods");
/* And pop the metatable */
lua_pop(L, 1);
}
}
/* And return the new table */
return 1;
}
static int
supple_capi_proxy_tostring(lua_State *L)
{
/* arg 1 is the object, upvalue 1 is the original type */
const char *orig_type = lua_tostring(L, lua_upvalueindex(1));
lua_pushfstring(L, "%s: %p", orig_type, lua_touserdata(L, 1));
return 1;
}
static int
supple_capi_proxy_type(lua_State *L)
{
/* arg 1 is the object, upvalue 1 is the original type */
lua_pushvalue(L, lua_upvalueindex(1));
return 1;
}
static int
supple_capi_new_proxy(lua_State *L)
{
void *proxy_ptr;
/* Input is a type string */
if (lua_type(L, 1) != LUA_TSTRING) {
return luaL_error(L, "Expected type string, got %s",
lua_typename(L, lua_type(L, 1)));
}
proxy_ptr = lua_newuserdata(L, 1);
if (proxy_ptr == NULL) {
return 0;
}
lua_newtable(L);
/* typestr, proxyobj, metatable */
/* First job is the tostring metamethod, we always add that */
lua_pushvalue(L, 1);
lua_pushcclosure(L, supple_capi_proxy_tostring, 1);
lua_setfield(L, -2, "__tostring");
/* next the __type metamethod for the lua level type call */
lua_pushvalue(L, 1);
lua_pushcclosure(L, supple_capi_proxy_type, 1);
lua_setfield(L, -2, "__type");
/* And now prevent anything poking in us later */
lua_pushboolean(L, 1);
lua_setfield(L, -2, "__metatable");
/* Finally set the metatable and return proxy, metatable */
lua_pushvalue(L, -1);
lua_setmetatable(L, -3);
return 2;
}
/* Replacement for lbaselib.c's type method, honouring __type */
static int
supple_capi_type(lua_State *L)
{
lua_settop(L, 1);
if (lua_getmetatable(L, 1) != 0) {
/* There is a metatable, try and find __type */
lua_getfield(L, 2, "__type");
if (lua_isfunction(L, 3)) {
lua_pushvalue(L, 1);
lua_call(L, 1, 1);
return 1;
}
}
lua_pushstring(L, lua_typename(L, lua_type(L, 1)));
return 1;
}
/* Reimplementation of base type in case it's not available */
static int
supple_capi_rawtype(lua_State *L)
{
lua_settop(L, 1);
lua_pushstring(L, lua_typename(L, lua_type(L, 1)));
return 1;
}
static const struct luaL_Reg
supple_capi_functions[] = {
{ "explain", supple_capi_explain },
{ "new_proxy", supple_capi_new_proxy },
{ "type", supple_capi_type },
{ "rawtype", supple_capi_rawtype },
{ NULL, NULL }
};
int
luaopen_supple_capi(lua_State *L)
{
luaL_register(L, "supple.capi", supple_capi_functions);
lua_pushnumber(L, CAPI_API);
lua_setfield(L, -2, "_API");
lua_pushnumber(L, CAPI_ABI);
lua_setfield(L, -2, "_ABI");
return 1;
}
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