luau/VM/src/lobject.h

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
// This code is based on Lua 5.x implementation licensed under MIT License; see lua_LICENSE.txt for details
#pragma once

#include "lua.h"
#include "lcommon.h"

/*
** Union of all collectible objects
*/
typedef union GCObject GCObject;

/*
** Common Header for all collectible objects (in macro form, to be
** included in other objects)
*/
// clang-format off
#define CommonHeader \
    GCObject* next; \
     uint8_t tt; uint8_t marked; uint8_t memcat
// clang-format on

/*
** Common header in struct form
*/
typedef struct GCheader
{
    CommonHeader;
} GCheader;

/*
** Union of all Lua values
*/
typedef union
{
    GCObject* gc;
    void* p;
    double n;
    int b;
    float v[2]; // v[0], v[1] live here; v[2] lives in TValue::extra
} Value;

/*
** Tagged Values
*/

typedef struct lua_TValue
{
    Value value;
    int extra;
    int tt;
} TValue;

/* Macros to test type */
#define ttisnil(o) (ttype(o) == LUA_TNIL)
#define ttisnumber(o) (ttype(o) == LUA_TNUMBER)
#define ttisstring(o) (ttype(o) == LUA_TSTRING)
#define ttistable(o) (ttype(o) == LUA_TTABLE)
#define ttisfunction(o) (ttype(o) == LUA_TFUNCTION)
#define ttisboolean(o) (ttype(o) == LUA_TBOOLEAN)
#define ttisuserdata(o) (ttype(o) == LUA_TUSERDATA)
#define ttisthread(o) (ttype(o) == LUA_TTHREAD)
#define ttislightuserdata(o) (ttype(o) == LUA_TLIGHTUSERDATA)
#define ttisvector(o) (ttype(o) == LUA_TVECTOR)
#define ttisupval(o) (ttype(o) == LUA_TUPVAL)

/* Macros to access values */
#define ttype(o) ((o)->tt)
#define gcvalue(o) check_exp(iscollectable(o), (o)->value.gc)
#define pvalue(o) check_exp(ttislightuserdata(o), (o)->value.p)
#define nvalue(o) check_exp(ttisnumber(o), (o)->value.n)
#define vvalue(o) check_exp(ttisvector(o), (o)->value.v)
#define tsvalue(o) check_exp(ttisstring(o), &(o)->value.gc->ts)
#define uvalue(o) check_exp(ttisuserdata(o), &(o)->value.gc->u)
#define clvalue(o) check_exp(ttisfunction(o), &(o)->value.gc->cl)
#define hvalue(o) check_exp(ttistable(o), &(o)->value.gc->h)
#define bvalue(o) check_exp(ttisboolean(o), (o)->value.b)
#define thvalue(o) check_exp(ttisthread(o), &(o)->value.gc->th)
#define upvalue(o) check_exp(ttisupval(o), &(o)->value.gc->uv)

// beware bit magic: a value is false if it's nil or boolean false
// baseline implementation: (ttisnil(o) || (ttisboolean(o) && bvalue(o) == 0))
// we'd like a branchless version of this which helps with performance, and a very fast version
// so our strategy is to always read the boolean value (not using bvalue(o) because that asserts when type isn't boolean)
// we then combine it with type to produce 0/1 as follows:
// - when type is nil (0), & makes the result 0
// - when type is boolean (1), we effectively only look at the bottom bit, so result is 0 iff boolean value is 0
// - when type is different, it must have some of the top bits set - we keep all top bits of boolean value so the result is non-0
#define l_isfalse(o) (!(((o)->value.b | ~1) & ttype(o)))

/*
** for internal debug only
*/
#define checkconsistency(obj) LUAU_ASSERT(!iscollectable(obj) || (ttype(obj) == (obj)->value.gc->gch.tt))

#define checkliveness(g, obj) LUAU_ASSERT(!iscollectable(obj) || ((ttype(obj) == (obj)->value.gc->gch.tt) && !isdead(g, (obj)->value.gc)))

/* Macros to set values */
#define setnilvalue(obj) ((obj)->tt = LUA_TNIL)

#define setnvalue(obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.n = (x); \
        i_o->tt = LUA_TNUMBER; \
    }

#define setvvalue(obj, x, y, z) \
    { \
        TValue* i_o = (obj); \
        float* i_v = i_o->value.v; \
        i_v[0] = (x); \
        i_v[1] = (y); \
        i_v[2] = (z); \
        i_o->tt = LUA_TVECTOR; \
    }

#define setpvalue(obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.p = (x); \
        i_o->tt = LUA_TLIGHTUSERDATA; \
    }

#define setbvalue(obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.b = (x); \
        i_o->tt = LUA_TBOOLEAN; \
    }

#define setsvalue(L, obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.gc = cast_to(GCObject*, (x)); \
        i_o->tt = LUA_TSTRING; \
        checkliveness(L->global, i_o); \
    }

#define setuvalue(L, obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.gc = cast_to(GCObject*, (x)); \
        i_o->tt = LUA_TUSERDATA; \
        checkliveness(L->global, i_o); \
    }

#define setthvalue(L, obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.gc = cast_to(GCObject*, (x)); \
        i_o->tt = LUA_TTHREAD; \
        checkliveness(L->global, i_o); \
    }

#define setclvalue(L, obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.gc = cast_to(GCObject*, (x)); \
        i_o->tt = LUA_TFUNCTION; \
        checkliveness(L->global, i_o); \
    }

#define sethvalue(L, obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.gc = cast_to(GCObject*, (x)); \
        i_o->tt = LUA_TTABLE; \
        checkliveness(L->global, i_o); \
    }

#define setptvalue(L, obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.gc = cast_to(GCObject*, (x)); \
        i_o->tt = LUA_TPROTO; \
        checkliveness(L->global, i_o); \
    }

#define setupvalue(L, obj, x) \
    { \
        TValue* i_o = (obj); \
        i_o->value.gc = cast_to(GCObject*, (x)); \
        i_o->tt = LUA_TUPVAL; \
        checkliveness(L->global, i_o); \
    }

#define setobj(L, obj1, obj2) \
    { \
        const TValue* o2 = (obj2); \
        TValue* o1 = (obj1); \
        *o1 = *o2; \
        checkliveness(L->global, o1); \
    }

/*
** different types of sets, according to destination
*/

/* from stack to (same) stack */
#define setobjs2s setobj
/* to stack (not from same stack) */
#define setobj2s setobj
#define setsvalue2s setsvalue
#define sethvalue2s sethvalue
#define setptvalue2s setptvalue
/* from table to same table */
#define setobjt2t setobj
/* to table */
#define setobj2t setobj
/* to new object */
#define setobj2n setobj
#define setsvalue2n setsvalue

#define setttype(obj, tt) (ttype(obj) = (tt))

#define iscollectable(o) (ttype(o) >= LUA_TSTRING)

typedef TValue* StkId; /* index to stack elements */

/*
** String headers for string table
*/
typedef struct TString
{
    CommonHeader;

    int16_t atom;

    unsigned int hash;
    unsigned int len;

    char data[1]; // string data is allocated right after the header
} TString;

#define getstr(ts) (ts)->data
#define svalue(o) getstr(tsvalue(o))

typedef struct Udata
{
    CommonHeader;

    uint8_t tag;

    int len;

    struct Table* metatable;

    union
    {
        char data[1];      // userdata is allocated right after the header
        L_Umaxalign dummy; // ensures maximum alignment for data
    };
} Udata;

/*
** Function Prototypes
*/
// clang-format off
typedef struct Proto
{
    CommonHeader;


    TValue* k;              /* constants used by the function */
    Instruction* code;      /* function bytecode */
    struct Proto** p;       /* functions defined inside the function */
    uint8_t* lineinfo;      /* for each instruction, line number as a delta from baseline */
    int* abslineinfo;       /* baseline line info, one entry for each 1<<linegaplog2 instructions; allocated after lineinfo */
    struct LocVar* locvars; /* information about local variables */
    TString** upvalues;     /* upvalue names */
    TString* source;

    TString* debugname;
    uint8_t* debuginsn; // a copy of code[] array with just opcodes

    GCObject* gclist;


    int sizecode;
    int sizep;
    int sizelocvars;
    int sizeupvalues;
    int sizek;
    int sizelineinfo;
    int linegaplog2;


    uint8_t nups; /* number of upvalues */
    uint8_t numparams;
    uint8_t is_vararg;
    uint8_t maxstacksize;
} Proto;
// clang-format on

typedef struct LocVar
{
    TString* varname;
    int startpc; /* first point where variable is active */
    int endpc;   /* first point where variable is dead */
    uint8_t reg; /* register slot, relative to base, where variable is stored */
} LocVar;

/*
** Upvalues
*/

typedef struct UpVal
{
    CommonHeader;
    TValue* v; /* points to stack or to its own value */
    union
    {
        TValue value; /* the value (when closed) */
        struct
        { /* double linked list (when open) */
            struct UpVal* prev;
            struct UpVal* next;
        } l;
    } u;
} UpVal;

/*
** Closures
*/

typedef struct Closure
{
    CommonHeader;

    uint8_t isC;
    uint8_t nupvalues;
    uint8_t stacksize;
    uint8_t preload;

    GCObject* gclist;
    struct Table* env;

    union
    {
        struct
        {
            lua_CFunction f;
            lua_Continuation cont;
            const char* debugname;
            TValue upvals[1];
        } c;

        struct
        {
            struct Proto* p;
            TValue uprefs[1];
        } l;
    };
} Closure;

#define iscfunction(o) (ttype(o) == LUA_TFUNCTION && clvalue(o)->isC)
#define isLfunction(o) (ttype(o) == LUA_TFUNCTION && !clvalue(o)->isC)

/*
** Tables
*/

typedef struct TKey
{
    ::Value value;
    int extra;
    unsigned tt : 4;
    int next : 28; /* for chaining */
} TKey;

typedef struct LuaNode
{
    TValue val;
    TKey key;
} LuaNode;

/* copy a value into a key */
#define setnodekey(L, node, obj) \
    { \
        LuaNode* n_ = (node); \
        const TValue* i_o = (obj); \
        n_->key.value = i_o->value; \
        n_->key.extra = i_o->extra; \
        n_->key.tt = i_o->tt; \
        checkliveness(L->global, i_o); \
    }

/* copy a value from a key */
#define getnodekey(L, obj, node) \
    { \
        TValue* i_o = (obj); \
        const LuaNode* n_ = (node); \
        i_o->value = n_->key.value; \
        i_o->extra = n_->key.extra; \
        i_o->tt = n_->key.tt; \
        checkliveness(L->global, i_o); \
    }

// clang-format off
typedef struct Table
{
    CommonHeader;


    uint8_t flags;      /* 1<<p means tagmethod(p) is not present */
    uint8_t readonly;   /* sandboxing feature to prohibit writes to table */
    uint8_t safeenv;    /* environment doesn't share globals with other scripts */
    uint8_t lsizenode;  /* log2 of size of `node' array */
    uint8_t nodemask8; /* (1<<lsizenode)-1, truncated to 8 bits */

    int sizearray; /* size of `array' array */
    union
    {
        int lastfree;  /* any free position is before this position */
        int aboundary; /* negated 'boundary' of `array' array; iff aboundary < 0 */
    };


    struct Table* metatable;
    TValue* array;  /* array part */
    LuaNode* node;
    GCObject* gclist;
} Table;
// clang-format on

/*
** `module' operation for hashing (size is always a power of 2)
*/
#define lmod(s, size) (check_exp((size & (size - 1)) == 0, (cast_to(int, (s) & ((size)-1)))))

#define twoto(x) ((int)(1 << (x)))
#define sizenode(t) (twoto((t)->lsizenode))

#define luaO_nilobject (&luaO_nilobject_)

LUAI_DATA const TValue luaO_nilobject_;

#define ceillog2(x) (luaO_log2((x)-1) + 1)

LUAI_FUNC int luaO_log2(unsigned int x);
LUAI_FUNC int luaO_rawequalObj(const TValue* t1, const TValue* t2);
LUAI_FUNC int luaO_rawequalKey(const TKey* t1, const TValue* t2);
LUAI_FUNC int luaO_str2d(const char* s, double* result);
LUAI_FUNC const char* luaO_pushvfstring(lua_State* L, const char* fmt, va_list argp);
LUAI_FUNC const char* luaO_pushfstring(lua_State* L, const char* fmt, ...);
LUAI_FUNC void luaO_chunkid(char* out, const char* source, size_t len);