/***********************************************************************/
/*                                                                     */
/*                           Objective Caml                            */
/*                                                                     */
/*         Xavier Leroy and Damien Doligez, INRIA Rocquencourt         */
/*                                                                     */
/*  Copyright 1996 Institut National de Recherche en Informatique et   */
/*  en Automatique.  All rights reserved.  This file is distributed    */
/*  under the terms of the GNU Library General Public License.         */
/*                                                                     */
/***********************************************************************/

/* $Id: mlvalues.h,v 1.32 2001/01/05 13:55:13 doligez Exp $ */

#ifndef _mlvalues_
#define _mlvalues_


#include "config.h"
#include "misc.h"

/* Definitions

  word: Four bytes on 32 and 16 bit architectures,
        eight bytes on 64 bit architectures.
  long: A C long integer.
  val: The ML representation of something.  A long or a block or a pointer
       outside the heap.  If it is a block, it is the (encoded) address
       of an object.  If it is a long, it is encoded as well.
  block: Something allocated.  It always has a header and some
          fields or some number of bytes (a multiple of the word size).
  field: A word-sized val which is part of a block.
  bp: Pointer to the first byte of a block.  (a char *)
  op: Pointer to the first field of a block.  (a value *)
  hp: Pointer to the header of a block.  (a char *)
  int32: Four bytes on all architectures.
  int64: Eight bytes on all architectures.

  Remark: A block size is always a multiple of the word size, and at least
          one word plus the header.

  bosize: Size (in bytes) of the "bytes" part.
  wosize: Size (in words) of the "fields" part.
  bhsize: Size (in bytes) of the block with its header.
  whsize: Size (in words) of the block with its header.

  hd: A header.
  tag: The value of the tag field of the header.
  color: The value of the color field of the header.
         This is for use only by the GC.
*/

typedef long value;
typedef unsigned long header_t;
typedef unsigned long mlsize_t;
typedef unsigned int tag_t;             /* Actually, an unsigned char */
typedef unsigned long color_t;
typedef unsigned long mark_t;

/* Longs vs blocks. */
#define Is_long(x)   (((x) & 1) != 0)
#define Is_block(x)  (((x) & 1) == 0)

/* Conversion macro names are always of the form  "to_from". */
/* Example: Val_long as in "Val from long" or "Val of long". */
#define Val_long(x)     (((long)(x) << 1) + 1)
#define Long_val(x)     ((x) >> 1)
#define Max_long ((1L << (8 * sizeof(value) - 2)) - 1)
#define Min_long (-(1L << (8 * sizeof(value) - 2)))
#define Val_int Val_long
#define Int_val(x) ((int) Long_val(x))

/* Structure of the header:

For 16-bit and 32-bit architectures:
     +--------+-------+-----+
     | wosize | color | tag |
     +--------+-------+-----+
bits  31    10 9     8 7   0

For 64-bit architectures:

     +--------+-------+-----+
     | wosize | color | tag |
     +--------+-------+-----+
bits  63    10 9     8 7   0

*/

#define Tag_hd(hd) ((tag_t) ((hd) & 0xFF))
#define Wosize_hd(hd) ((mlsize_t) ((hd) >> 10))

#define Hd_val(val) (((header_t *) (val)) [-1])        /* Also an l-value. */
#define Hd_op(op) (Hd_val (op))                        /* Also an l-value. */
#define Hd_bp(bp) (Hd_val (bp))                        /* Also an l-value. */
#define Hd_hp(hp) (* ((header_t *) (hp)))              /* Also an l-value. */
#define Hp_val(val) ((char *) (((header_t *) (val)) - 1))
#define Hp_op(op) (Hp_val (op))
#define Hp_bp(bp) (Hp_val (bp))
#define Val_op(op) ((value) (op))
#define Val_hp(hp) ((value) (((header_t *) (hp)) + 1))
#define Op_hp(hp) ((value *) Val_hp (hp))
#define Bp_hp(hp) ((char *) Val_hp (hp))

#define Num_tags (1 << 8)
#ifdef ARCH_SIXTYFOUR
#define Max_wosize ((1L << 54) - 1)
#else
#define Max_wosize ((1 << 22) - 1)
#endif

#define Wosize_val(val) (Wosize_hd (Hd_val (val)))
#define Wosize_op(op) (Wosize_val (op))
#define Wosize_bp(bp) (Wosize_val (bp))
#define Wosize_hp(hp) (Wosize_hd (Hd_hp (hp)))
#define Whsize_wosize(sz) ((sz) + 1)
#define Wosize_whsize(sz) ((sz) - 1)
#define Wosize_bhsize(sz) ((sz) / sizeof (value) - 1)
#define Bsize_wsize(sz) ((sz) * sizeof (value))
#define Wsize_bsize(sz) ((sz) / sizeof (value))
#define Bhsize_wosize(sz) (Bsize_wsize (Whsize_wosize (sz)))
#define Bhsize_bosize(sz) ((sz) + sizeof (header_t))
#define Bosize_val(val) (Bsize_wsize (Wosize_val (val)))
#define Bosize_op(op) (Bosize_val (Val_op (op)))
#define Bosize_bp(bp) (Bosize_val (Val_bp (bp)))
#define Bosize_hd(hd) (Bsize_wsize (Wosize_hd (hd)))
#define Whsize_hp(hp) (Whsize_wosize (Wosize_hp (hp)))
#define Whsize_val(val) (Whsize_hp (Hp_val (val)))
#define Whsize_bp(bp) (Whsize_val (Val_bp (bp)))
#define Whsize_hd(hd) (Whsize_wosize (Wosize_hd (hd)))
#define Bhsize_hp(hp) (Bsize_wsize (Whsize_hp (hp)))
#define Bhsize_hd(hd) (Bsize_wsize (Whsize_hd (hd)))

#ifdef ARCH_BIG_ENDIAN
#define Tag_val(val) (((unsigned char *) (val)) [-1])
                                                 /* Also an l-value. */
#define Tag_hp(hp) (((unsigned char *) (hp)) [sizeof(value)-1])
                                                 /* Also an l-value. */
#else
#define Tag_val(val) (((unsigned char *) (val)) [-sizeof(value)])
                                                 /* Also an l-value. */
#define Tag_hp(hp) (((unsigned char *) (hp)) [0])
                                                 /* Also an l-value. */
#endif

/* The lowest tag for blocks containing no value. */
#define No_scan_tag 251


/* 1- If tag < No_scan_tag : a tuple of fields.  */

/* Pointer to the first field. */
#define Op_val(x) ((value *) (x))
/* Fields are numbered from 0. */
#define Field(x, i) (((value *)(x)) [i])           /* Also an l-value. */

typedef int32 opcode_t;
typedef opcode_t * code_t;

/* Special case of tuples of fields: closures */

#define Closure_tag 250
#define Code_val(val) (((code_t *) (val)) [0])     /* Also an l-value. */

/* If tag == Infix_tag : an infix header inside a closure */
/* Infix_tag must be odd so that the infix header is scanned as an integer */
/* Infix_tag must be 1 modulo 4 and infix headers can only occur in blocks
   with tag Closure_tag (see compact.c). */

#define Infix_tag 249
#define Infix_offset_hd(hd) (Bosize_hd(hd))
#define Infix_offset_val(v) Infix_offset_hd(Hd_val(v))

/* Another special case: objects */
#define Object_tag 248
#define Class_val(val) Field(val, 0)
#define Oid_val(val) Long_val(Field(val, 1))

/* Another special case: variants */
extern value hash_variant(char * tag);

/* 2- If tag >= No_scan_tag : a sequence of bytes. */

/* Pointer to the first byte */
#define Bp_val(v) ((char *) (v))
#define Val_bp(p) ((value) (p))
/* Bytes are numbered from 0. */
#define Byte(x, i) (((char *) (x)) [i])            /* Also an l-value. */
#define Byte_u(x, i) (((unsigned char *) (x)) [i]) /* Also an l-value. */

/* Abstract things.  Their contents is not traced by the GC; therefore they
   must not contain any [value].
*/
#define Abstract_tag 251

/* Strings. */
#define String_tag 252
#define String_val(x) ((char *) Bp_val(x))
mlsize_t string_length (value);

/* Floating-point numbers. */
#define Double_tag 253
#define Double_wosize ((sizeof(double) / sizeof(value)))
#ifndef ARCH_ALIGN_DOUBLE
#define Double_val(v) (* (double *)(v))
#define Store_double_val(v,d) (* (double *)(v) = (d))
#else
double Double_val (value);
void Store_double_val (value,double);
#endif

/* Arrays of floating-point numbers. */
#define Double_array_tag 254
#define Double_field(v,i) Double_val((value)((double *)(v) + (i)))
#define Store_double_field(v,i,d) \
  Store_double_val((value)((double *)(v) + (i)),d)

/* Custom blocks.  They contain a pointer to a "method suite"
   of functions (for finalization, comparison, hashing, etc)
   followed by raw data.  The contents of custom blocks is not traced by
   the GC; therefore, they must not contain any [value].
   See [custom.h] for operations on method suites. */
#define Custom_tag 255
#define Data_custom_val(v) ((void *) &Field(v, 1))
struct custom_operations;       /* defined in [custom.h] */

/* Int32.t, Int64.t and Nativeint.t are represented as custom blocks. */

#define Int32_val(v) (*((int32 *) Data_custom_val(v)))
#define Nativeint_val(v) (*((long *) Data_custom_val(v)))
#ifndef ARCH_ALIGN_INT64
#define Int64_val(v) (*((int64 *) Data_custom_val(v)))
#else
extern int64 Int64_val(value v);
#endif

/* 3- Atoms are 0-tuples.  They are statically allocated once and for all. */

extern header_t atom_table[];
#define Atom(tag) (Val_hp (&(atom_table [tag])))

/* Is_atom tests whether a well-formed block is statically allocated
   outside the heap. For the bytecode system, only zero-sized block (Atoms)
   fall in this class. For the native-code generator, data
   emitted by the code generator (as described in the table
   caml_data_segments) are also atoms. */

#ifndef NATIVE_CODE
#define Is_atom(v) ((v) >= Atom(0) && (v) <= Atom(255))
#else
extern char * static_data_start, * static_data_end;
#define Is_atom(v) \
  ((((char *)(v) >= static_data_start && (char *)(v) < static_data_end) || \
   ((v) >= Atom(0) && (v) <= Atom(255))))
#endif

/* Booleans are integers 0 or 1 */

#define Val_bool(x) Val_int((x) != 0)
#define Bool_val(x) Int_val(x)
#define Val_false Val_int(0)
#define Val_true Val_int(1)
#define Val_not(x) (Val_false + Val_true - (x))

/* The unit value is 0 (tagged) */

#define Val_unit Val_int(0)

/* List constructors */
#define Val_emptylist Val_int(0)
#define Tag_cons 0

/* The table of global identifiers */

extern value global_data;


#endif /* _mlvalues_ */
