#include <stddef.h>
#include <stdint.h>

// common types
typedef uintptr_t U;
typedef intptr_t I;

typedef uint8_t U8;
typedef uint32_t U32;
typedef int32_t I32;
typedef size_t Z;

// objects
typedef uintptr_t O;

// cons pair
typedef struct C C;
struct C {
  O head, tail;
};

// symbol
typedef struct S S;
struct S {
  U8 *data;
  U32 hash;
  Z len;
};

// symbol table
typedef struct St St;
struct St {
  I count;
  Z capacity;
  S **data;
};

// gc header
enum { OBJ_CONS, OBJ_SYM, OBJ_FWD };

typedef struct H H;
struct H {
  I type;
  Z size;
};

// heap
typedef struct E E;
struct E {
  struct {
    U8 *start, *end;
    U8 *free;
  } from, to;

  I root_count;
  Z root_capacity;
  O **roots;
};

extern E heap;
extern St syms;

#define IMM(x) ((x) & 1)
#define NUM(x) (((O)((I)(x) << 1)) | (V)1)
#define ORD(x) ((I)(x) >> 1)
#define BOX(x) ((O)(x))
#define UNBOX(x) ((H *)(x))

#define NIL ((O)0)
#define GC_HEAP_BYTES (1024 * 1024)

// GC
void addroot(O *ptr);
I rootmark(void);
void rootreset(I mark);
void collect(void);
H *alloc(Z sz);
void gcinit(void);
void gcfinalize(void);

S *intern(const char *str, I len);
O mksym(const char *str);

O cons(O head, O tail);
C *uncons(O obj);