_gptrget.c

很少见的源码公开的msc51和z80的c编译器。

/*-------------------------------------------------------------------------

  _gptrget.c :- get value for a generic pointer               

             Written By -  Sandeep Dutta . [e-mail] (1999)

   This library is free software; you can redistribute it and/or modify it
   under the terms of the GNU Library General Public License as published by the
   Free Software Foundation; either version 2, or (at your option) any
   later version.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Library General Public License for more details.
   
   You should have received a copy of the GNU Library General Public License
   along with this program; if not, write to the Free Software
   Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
   
   In other words, you are welcome to use, share and improve this program.
   You are forbidden to forbid anyone else to use, share and improve
   what you give them.   Help stamp out software-hoarding!  
-------------------------------------------------------------------------*/

unsigned char _gptrget ()
{
    _asm
    ;   save values passed
	xch    a,r0
	push   acc
    ;
    ;   depending on the pointer type
    ;
        mov     a,b
        jz      00001$
	dec     a
	jz      00002$
        dec     a
        jz      00003$
	dec     a
	jz      00004$
    ;
    ;   any other value for type 
    ;   return xFF
	mov     a,#0xff
	sjmp    00005$
    ;
    ;   Pointer to data space
    ;   
 00001$:
	mov     r0,dpl     ; use only low order address
	mov     a,@r0
        sjmp    00005$
    ;
    ;   pointer to xternal data
    ;
 00002$:
        movx    a,@dptr
        sjmp    00005$
;
;   pointer to code area
;   
 00003$:
	clr     a
        movc    a,@a+dptr
        sjmp    00005$
;
;   pointer to xternal stack
;
 00004$:
	mov     r0,dpl
        movx    a,@r0
;
;   restore and return
;
 00005$:	       
        mov     r0,a	
        pop     acc
	xch     a,r0
     _endasm ;
	
}