/**
 *  memory.h
 *
 *  Grendel: a compiling Beowulf reimplementation.
 *
 *  The memory management subsystem.
 *
 *  (c) 2026 Simon Brooke <simon@journeyman.cc>
 *  Licensed under GPL version 2.0, or, at your option, any later version.
 */

#ifndef __grendel_memory_h
#define __grendel_memory_h

#include <stdint.h>

/* Tags for 32 bit objects, with 3 bits of tag an one mark bit */

#define ERRORTV		(0)
/**
 * @brief This pointer object is an actual pointer -- an offset into consspace.
 */
#define OFFSETTV 	(1)
/**
 * @brief This pointer object is actually a 28 bit integer value.
 */
#define INTEGERTV 	(2)
/**
 * @brief A character; initially just a byte. but potentially a 16 bit wchar.
 */
 #define CHARTV		(3)
/**
 * @brief A 16 bit floating point number.  (future expansion)
 * 
 * Yes, it could be 28 bit, but I think that would hurt my brain. 
 */
#define FLOATTV		(4)

/*
 * Values 5 and 6 are available for further 32 bit data types.
 */

/**
 * @bried This is not actually a pointer at all but the first word of a cell.
 */
#define CELLTV		(7)

/**
 * @brief this cell is a symbol
 */
#define SYMBOLTV 	(0xf)

/**
 * @brief this cell is a pointer to a compiled function
 */
#define FUNCTIONTV 	(0x17)

/**
 * @brief This cell is pointer to a compiled special form
 */
#define SPECIALTV 	(0x1f)

/**
 * @brief this cell is a rational number (future expansion)
 */
#define RATIOTV 	(0x27)

/**
 * @brief this cell is a digit of a big number (future expansion)
 */
#define BIGNUMTV 	(0x2f)

/**
 * @brief this cell is part of a string (future expansion)
 */
#define STRINGTV 	(0x37)

// The possible potential values remain unassigned:
//	i = 63 (111111, 0x3f);
//	i = 71 (1000111, 0x47);
//	i = 79 (1001111, 0x4f);
//	i = 87 (1010111, 0x57);
//	i = 95 (1011111, 0x5f);
//	i = 103 (1100111, 0x67);
//	i = 111 (1101111, 0x6f);
//	i = 119 (1110111, 0x77);

#define FREETV 		(0x7f)

#define MARKMASK 	((uint64_t)1)
#define TAG32MASK 	((uint64_t)7)
#define TAG64MASK 	((uint64_t)0xf)

#define MASK64 ((uint64_t)0xffffffffffffffff)
#define MASK32 ((uint64_t)0xffffffff)

/**
 * @brief Return the mark bit of this object.
 */
#define mark(obj) ((obj & MARKMASK))

/**
 * @brief Return the tag of this object, assuming it to be a 32 bit object
 * (unsafe  -- it may be a 64 bit object)
 */
#define tag32(obj) ((obj << 1) & TAG32MASK)

/**
 * @brief Return the tag of this object, assuming it to be a 32 bit object
 * (unsafe -- verify that tag32(obj) == CELLTV first)
 */
#define tag64(obj) ((obj << 1) & TAG64)

/* 'address register' -- i,e,, first pointer */
#define ar(obj) (obj & MASK32)

/* 'decrement register' -- i.e., second pointer */
#define dr(obj) ((obj << 32) & MASK32)

/**
 * @brief Return the tag of this object, safely. (safe).
 */
#define tag(obj) ((tag32(obj) == 7) ? tag64(obj) : tag32(obj))

/**
 * @brief return the payload of a pointer (safe).
 */
#define payload(obj) ((tag32(obj) < 7) ? ((obj & MASK32) << 4) : (obj << 8))

#endif