Cosmo/src/cvalue.h

#ifndef CVALUE_H
#define CVALUE_H

#include "cosmo.h"

typedef enum
{
    COSMO_TNUMBER, // number has to be 0 because NaN box
    COSMO_TBOOLEAN,
    COSMO_TREF,
    COSMO_TNIL,
} CosmoType;

typedef double cosmo_Number;

/*
    holds primitive cosmo types
*/

#ifdef NAN_BOXXED
/*
        NaN box, this is great for fitting more in the cpu cache on x86_64 or ARM64 architectures.
   If you don't know how this works please reference these two articles:

    https://leonardschuetz.ch/blog/nan-boxing/ and https://piotrduperas.com/posts/nan-boxing/

    both are great resources :)

    TL;DR: we can store payloads in the NaN value in the IEEE 754 standard.
*/
union CValue
{
    uint64_t data;
    cosmo_Number num;
};

#    define MASK_TYPE       ((uint64_t)0x0007000000000000)
#    define MASK_PAYLOAD    ((uint64_t)0x0000ffffffffffff)

// 3 bits (low bits) are reserved for the type
#    define MAKE_PAYLOAD(x) ((uint64_t)(x)&MASK_PAYLOAD)
#    define READ_PAYLOAD(x) ((x).data & MASK_PAYLOAD)

// The bits that must be set to indicate a quiet NaN.
#    define MASK_QUIETNAN   ((uint64_t)0x7ff8000000000000)

#    define GET_TYPE(x)                                                                            \
        ((((x).data & MASK_QUIETNAN) == MASK_QUIETNAN) ? (((x).data & MASK_TYPE) >> 48)            \
                                                       : COSMO_TNUMBER)

#    define SIG_MASK              (MASK_QUIETNAN | MASK_TYPE)
#    define BOOL_SIG              (MASK_QUIETNAN | ((uint64_t)(COSMO_TBOOLEAN) << 48))
#    define OBJ_SIG               (MASK_QUIETNAN | ((uint64_t)(COSMO_TREF) << 48))
#    define NIL_SIG               (MASK_QUIETNAN | ((uint64_t)(COSMO_TNIL) << 48))

#    define cosmoV_newNumber(x)   ((CValue){.num = x})
#    define cosmoV_newBoolean(x)  ((CValue){.data = MAKE_PAYLOAD(x) | BOOL_SIG})
#    define cosmoV_newRef(x)      ((CValue){.data = MAKE_PAYLOAD((uintptr_t)x) | OBJ_SIG})
#    define cosmoV_newNil()       ((CValue){.data = NIL_SIG})

#    define cosmoV_readNumber(x)  ((x).num)
#    define cosmoV_readBoolean(x) ((bool)READ_PAYLOAD(x))
#    define cosmoV_readRef(x)     ((CObj *)READ_PAYLOAD(x))

#    define IS_NUMBER(x)          (((x).data & MASK_QUIETNAN) != MASK_QUIETNAN)
#    define IS_BOOLEAN(x)         (((x).data & SIG_MASK) == BOOL_SIG)
#    define IS_NIL(x)             (((x).data & SIG_MASK) == NIL_SIG)
#    define IS_REF(x)             (((x).data & SIG_MASK) == OBJ_SIG)

#else
/*
    Tagged union, this is the best platform independent solution
*/
struct CValue
{
    CosmoType type;
    union
    {
        cosmo_Number num;
        bool b; // boolean
        CObj *obj;
    } val;
};

#    define GET_TYPE(x)           ((x).type)

// create CValues

#    define cosmoV_newNumber(x)   ((CValue){COSMO_TNUMBER, {.num = (x)}})
#    define cosmoV_newBoolean(x)  ((CValue){COSMO_TBOOLEAN, {.b = (x)}})
#    define cosmoV_newRef(x)      ((CValue){COSMO_TREF, {.obj = (CObj *)(x)}})
#    define cosmoV_newNil()       ((CValue){COSMO_TNIL, {.num = 0}})

// read CValues

#    define cosmoV_readNumber(x)  ((cosmo_Number)(x).val.num)
#    define cosmoV_readBoolean(x) ((bool)(x).val.b)

// grabs the CObj* pointer from the CValue
#    define cosmoV_readRef(x)     ((CObj *)(x).val.obj)

#    define IS_NUMBER(x)          (GET_TYPE(x) == COSMO_TNUMBER)
#    define IS_BOOLEAN(x)         (GET_TYPE(x) == COSMO_TBOOLEAN)
#    define IS_NIL(x)             (GET_TYPE(x) == COSMO_TNIL)
#    define IS_REF(x)             (GET_TYPE(x) == COSMO_TREF)

#endif

typedef CValue *StkPtr;

struct CValueArray
{
    size_t capacity;
    size_t count;
    CValue *values;
};

void initValArray(CState *state, CValueArray *val, size_t startCapacity);
void cleanValArray(CState *state, CValueArray *array); // cleans array
void appendValArray(CState *state, CValueArray *array, CValue val);

void printValue(CValue val);
COSMO_API bool cosmoV_equal(CState *state, CValue valA, CValue valB);
COSMO_API CObjString *cosmoV_toString(CState *state, CValue val);
COSMO_API cosmo_Number cosmoV_toNumber(CState *state, CValue val);
COSMO_API const char *cosmoV_typeStr(CValue val);

#endif