* f_a.prg -- FORCE FAQ Sample code -- a_exmpl1.zip
*
* The following code shows how you can mix FORCE and ASSEMBLER.  This
* FORCE module calls a hash function written in assembler with some
* trivial data, and prints the results.
*-------------------------------------------------------------------------
* RCSid = "$Header:$"
*-------------------------------------------------------------------------
#include io.hdr
#include string.hdr
FUNCTION INT hash PROTOTYPE
   PARAMETERS char, value int
*-------------------------------------------------------------------------
procedure force_main

   vardef
      char              string
      int               hashval
   enddef

   scrn_dos()

   string = "Holmes, David W."

   hashval = hash( string, 100 )

   ? " hash( " + chr(34) + string + chr(34) + ", 100 ) = ",hashval
   ?

endpro




;-------------------------------------------------------------------------
; hash.asm -- FORCE FAQ Sample Code -- A_Exmpl1.zip
;-------------------------------------------------------------------------
                public  _hash

_code           segment word public 'CODE'
                assume cs:_code
;-------------------------------------------------------------------------
; Here's a hash function that takes a NULL terminated string and
; adds all the characters in the string together, and mods by the
; given word.
;-------------------------------------------------------------------------
_hash           proc    far
                push    bp              ; set up our stack ref
                mov     bp,sp
                push    ds              ; save the segment registers
                push    si

                mov     ax,word ptr ss:[ bp+8 ] ; grab the string's segment
                mov     ds,ax
                mov     ax,word ptr ss:[ bp+6 ] ; grab the string's offset
                mov     si,ax
                mov     dx,word ptr ss:[ bp+10] ; grab the hashvalue

                and     dx,dx
                jnz     _no_div_by_0
                mov     dx,1

        ; Instead of relying on faith that the string will be NULL
        ; terminated, we'll set CX to be 255, the longest FORCE string.

  _no_div_by_0: mov     cx,0ffh

        ; accumulate the hash value in bx for the moment
                xor     bx,bx
                xor     ax,ax   ; clear out AH

  _hash_loop:   lodsb
                and     al,al
                jz      _found_null
                add     bx,ax
                loop    _hash_loop

  _found_null:  mov     ax,bx   ; perform a modulus with an idiv: remainder
                mov     cx,dx
                cwd             ; is stored in DX
                idiv    cx

                mov     ax,dx

                pop     si
                pop     ds
                pop     bp
                ret
_hash           endp
;-------------------------------------------------------------------------
_code           ends

                end