/* texmfmem.h: the memory_word type, which is too hard to translate
   automatically from Pascal.  We have to make sure the byte-swapping
   that the (un)dumping routines do suffices to put things in the right
   place in memory.

   A memory_word can be broken up into a `twohalves' or a
   `fourquarters', and a `twohalves' can be further broken up.  Here is
   a picture.  ..._M = most significant byte, ..._L = least significant
   byte.
   
   The halfword fields are four bytes if we are building a big TeX or MF;
   this leads to further complications:
   
   BigEndian:
   twohalves.v:  RH_MM RH_ML RH_LM RH_LL LH_MM LH_ML LH_LM LH_LL
   twohalves.u:  ---------JUNK----------  B0         B1
   fourquarters:   B0    B1    B2    B3

   LittleEndian:
   twohalves.v:  LH_LL LH_LM LH_ML LH_MM RH_LL RH_LM RH_ML RH_MM
   twohalves.u:  B1          B0
   fourquarters: ---------JUNK----------  B3    B2    B1    B0

   I guess TeX and Metafont never refer to the B1 and B0 in the
   fourquarters structure as the B1 and B0 in the twohalves.u structure.
   
   The B0 and B1 fields are declared short instead of quarterword,
   because they are used in character nodes to store a font number and a
   character.  If left as a quarterword (which is a single byte), we
   couldn't support more than 256 fonts. (If shorts aren't two bytes,
   this will lose.)
   
   In the old four-byte memory structure (something more needs to be
   done to handle >256 fonts):
   
   If BigEndian:
   twohalves.v:  RH_M  RH_L  LH_M  LH_L
   twohalves.u:  JNK1  JNK2    B0    B1
   fourquarters:   B0    B1    B2    B3
   
   If LittleEndian:
   twohalves.v:  LH_L  LH_M  RH_L  RH_M
   twohalves.u:    B1    B0  JNK1  JNK2
   fourquarters:   B3    B2    B1    B0
   
   In Omega, quarterwords are two octets, so the picture becomes simpler:
   
   BigEndian:
   twohalves.v:  RH_MM RH_ML RH_LM RH_LL LH_MM LH_ML LH_LM LH_LL
   twohalves.u:  ---------JUNK---------- ----B0----- ----B1-----
   fourquarters: ----B0----- ----B1----- ----B2----- ----B3-----
   twoints:      ---------CINT0--------- ---------CINT1---------
   
   LittleEndian:
   twohalves.v:  LH_LL LH_LM LH_ML LH_MM RH_LL RH_LM RH_ML RH_MM
   twohalves.u:  ----B1----- ----B0-----
   fourquarters: ----B3----- ----B2----- ----B1----- ----B0-----
   twoints:      ---------CINT1--------- ---------CINT0---------
   
   This file can't be part of texmf.h, because texmf.h gets included by
   {tex,mf,mp}d.h before the `halfword' etc. types are defined.  So we
   include it from the change file instead.
*/

typedef union
{
  struct
  {
#ifdef WORDS_BIGENDIAN
    halfword RH, LH;
#else
    halfword LH, RH;
#endif
  } v;

  struct
  { /* Make B0,B1 overlap the most significant bytes of LH.  */
#ifdef WORDS_BIGENDIAN
    halfword junk;
    short B0, B1;
#else /* not WORDS_BIGENDIAN */
  /* If 32-bit memory words, have to do something.  */
#if defined (SMALLTeX) || defined (SMALLMF) || defined (SMALLMP)
    fixme
#else
    short B1, B0;
#endif /* big memory words */
#endif /* LittleEndian */
  } u;
} twohalves;

typedef struct
{
  struct
  {
#ifdef WORDS_BIGENDIAN
    quarterword B0, B1, B2, B3;
#else
    quarterword B3, B2, B1, B0;
#endif
  } u;
} fourquarters;


typedef union
{
#ifdef TeX
  glueratio gr;
  twohalves hh;
#else
  twohalves hhfield;
#endif
#ifdef WORDS_BIGENDIAN
  integer cint;
  fourquarters qqqq;
#else /* not WORDS_BIGENDIAN */
  struct
  {
#if defined (TeX) && !defined (Omega) && !defined (SMALLTeX) || defined (MF) && !defined (SMALLMF) || defined (MP) && !defined (SMALLMP)
    halfword junk;
#endif /* big {TeX,MF,MP} */
    integer CINT;
  } u;

  struct
  {
#if defined (TeX) && !defined (Omega) && !defined (SMALLTeX) || defined (MF) && !defined (SMALLMF) || defined (MP) && !defined (SMALLMP)
    halfword junk;
#endif /* big {TeX,MF,MP} */
    fourquarters QQQQ;
  } v;
#endif /* not WORDS_BIGENDIAN */
} memoryword;


/* fmemory_word for font_list; needs to be only four bytes.  This saves
   significant space in the .fmt files. */

typedef union
{
#ifdef WORDS_BIGENDIAN
  integer cint;
  fourquarters qqqq;
#else /* not WORDS_BIGENDIAN */
  struct
  {
    integer CINT;
  } u;

  struct
  {
    fourquarters QQQQ;
  } v;
#endif /* not WORDS_BIGENDIAN */
} fmemoryword;


/* To keep the original structure accesses working, we must go through
   the extra names C forced us to introduce.  */
#define	b0 u.B0
#define	b1 u.B1
#define	b2 u.B2
#define	b3 u.B3

#define rh v.RH
#define lhfield	v.LH

#ifndef WORDS_BIGENDIAN
#define cint u.CINT
#define qqqq v.QQQQ
#endif
