Return to vdiv.m CVS log

Up to [MW Coherent from dump] / coherent / b / lib / libc / crt / i8086

Annotation of coherent/b/lib/libc/crt/i8086/vdiv.m, revision 1.1.1.1

1.1       root        1: //////////
                      2: / i8086 C library runtime support.
                      3: / vdiv()
                      4: / Unsigned long division and remainder support.
                      5: //////////
                      6: 
                      7: #include "larges.h"
                      8: 
                      9: //////////
                     10: / Returns  (dx ax) / (bx cx) in (si di)
                     11: /     and  (dx ax) % (bx cx) in (dx ax).
                     12: / All are unsigned longs.
                     13: //////////
                     14: 
                     15:        .globl  vdiv
                     16: 
                     17: vdiv:  mov     si, bx
                     18:        or      si, cx
                     19:        mov     si, $-1         / does not affect flags
                     20:        mov     di, si
                     21:        jne     0f
                     22:        sub     si, si
                     23:        mov     di, si          / divisor = 0
                     24:        Gret
                     25: 
                     26: 1:     shr     si, $1          / "count" quotient bits
                     27:        rcr     di, $1
                     28: 0:     cmp     dx, bx
                     29:        jb      1f
                     30:        shl     cx, $1          / shift until big enough
                     31:        rcl     bx, $1
                     32:        jnc     1b
                     33:                                / oops!
                     34: 3:     rcr     bx, $1          / carry!=0  only if drop from above
                     35:        rcr     cx, $1
                     36: 1:     sub     ax, cx
                     37:        sbb     dx, bx
                     38:        jnc     2f
                     39:        add     ax, cx
                     40:        adc     dx, bx          / produces another carry
                     41: 2:     rcl     di, $1          / collect inverted quotient
                     42:        rcl     si, $1
                     43:        jnc     3b              / use above "count"
                     44: 
                     45:        not     si
                     46:        not     di
                     47:        Gret
                     48: 
                     49: / end of vdiv.m

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.