--- gforth/struct.fs	1997/03/21 12:21:13	1.10
+++ gforth/struct.fs	1998/04/14 16:43:07	1.13
@@ -1,6 +1,6 @@
 \ data structures (like C structs)
 
-\ Copyright (C) 1995 Free Software Foundation, Inc.
+\ Copyright (C) 1995, 1997 Free Software Foundation, Inc.
 
 \ This file is part of Gforth.
 
@@ -18,67 +18,86 @@
 \ along with this program; if not, write to the Free Software
 \ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-
-\ Usage example:
-\
-\ struct
-\     1 cells: field search-method
-\     1 cells: field reveal-method
-\ end-struct wordlist-map
-\
-\ The structure can then be extended in the following way
-\ wordlist-map
-\     1 cells: field enum-method
-\ end-struct ext-wordlist-map \ with the fields search-method,...,enum-method
-
-: nalign ( addr1 n -- addr2 )
-\ addr2 is the aligned version of addr1 wrt the alignment size n
+: nalign ( addr1 n -- addr2 ) \ gforth
+\g @code{addr2} is the aligned version of @code{addr1} wrt the
+\g alignment @code{n}.
  1- tuck +  swap invert and ;
 
-: field ( offset1 align1 size align -- offset2 align2 )
-\ note: this version uses local variables
-    [IFDEF]  (Field) (Field)  [ELSE]  Header reveal dofield: cfa,  [THEN]
-	>r rot r@ nalign  dup ,  ( align1 size offset )
-	+ swap r> nalign ;
-
-: end-struct ( size align -- )
- 2constant ;
-
-0 1 chars end-struct struct
-
-\ : field  ( offset1 align1 size align -- offset2 align2 )
-\    create-field
-\    does> ( addr1 -- addr2 )
-\	@ + ;
-
-\ I don't really like the "type:" syntax. Any other ideas? - anton
-\ Also, this seems to be somewhat general. It probably belongs to some
-\ other place
-: cells: ( n -- size align )
-    cells cell ;
-
-: doubles: ( n -- size align )
-    2* cells cell ;
-
-: chars: ( n -- size align )
-    chars 1 chars ;
-
-: floats: ( n -- size align )
-    floats 1 floats ;
-
-: dfloats: ( n -- size align )
-    dfloats 1 dfloats ;
-
-: sfloats: ( n -- size align )
-    sfloats 1 sfloats ;
-
-: struct-align ( size align -- )
-    dp @ swap nalign dp !
+: dozerofield ( -- )
+    \ a field that makes no change
+    \ to enable accessing the offset with "['] <field> >body @" this
+    \ is not implemented with "['] noop alias"
+    last @
+    if
+	immediate
+    then
+does> ( name execution: -- )
     drop ;
 
-: struct-allot ( size align -- addr )
-    over swap struct-align
+: field, ( align1 offset1 align size --  align2 offset2 )
+    swap rot over nalign dup , ( align1 size align offset )
+    rot + >r nalign r> ;
+
+: create-field ( align1 offset1 align size --  align2 offset2 )
+    create field, ;
+
+: field ( align1 offset1 align size "name" --  align2 offset2 ) \ gforth
+    \G name execution: ( addr1 -- addr2 )
+    2 pick 
+    if \ field offset <> 0
+	[IFDEF]  (Field)
+	    (Field)
+	[ELSE]
+	    Header reveal dofield: cfa,
+	[THEN]
+    else
+	create dozerofield
+    then
+    field, ;
+
+: end-struct ( align size "name" -- ) \ gforth
+\g @code{name} execution: @code{addr1 -- addr1+offset1}@*
+\g create a field @code{name} with offset @code{offset1}, and the type
+\g given by @code{size align}. @code{offset2} is the offset of the
+\g next field, and @code{align2} is the alignment of all fields.
+    over nalign \ pad size to full alignment
+    2constant ;
+
+1 chars 0 end-struct struct ( -- align size ) \ gforth
+\g an empty structure, used to start a structure definition.
+
+\ type descriptors
+1 aligned   1 cells   2constant cell% ( -- align size ) \ gforth
+1 chars     1 chars   2constant char% ( -- align size ) \ gforth
+1 faligned  1 floats  2constant float% ( -- align size ) \ gforth
+1 dfaligned 1 dfloats 2constant dfloat% ( -- align size ) \ gforth
+1 sfaligned 1 sfloats 2constant sfloat% ( -- align size ) \ gforth
+cell% 2*              2constant double% ( -- align size ) \ gforth
+
+\ memory allocation words
+' drop alias %alignment ( align size -- align ) \ gforth
+\g the alignment of the structure
+' nip alias %size ( align size -- size ) \ gforth
+\g the size of the structure
+
+: %align ( align size -- ) \ gforth
+    \G align the data space pointer to the alignment @code{align}. 
+    drop here swap nalign here - allot ;
+
+: %allot ( align size -- addr ) \ gforth
+    \g allot @code{size} address units of data space with alignment
+    \g @code{align}; the resulting block of data is found at
+    \g @code{addr}.
+    tuck %align
     here swap allot ;
 
-: struct-allocate ( size align -- addr ior )
-    drop allocate ;
+: %allocate ( align size -- addr ior ) \ gforth
+    \g allocate @code{size} address units with alignment @code{align},
+    \g similar to @code{allocate}.
+    nip allocate ;
+
+: %alloc ( size align -- addr ) \ gforth
+    \g allocate @code{size} address units with alignment @code{align},
+    \g giving a data block at @code{addr}; @code{throw}s an ior code
+    \g if not successful.
+    %allocate throw ;