Internet Info 1994 March

home *** CD-ROM | disk | FTP | other *** search

/ Internet Info 1994 March / Internet Info CD-ROM (Walnut Creek) (March 1994).iso / networking / ip / ka9q / aztecnos.arc / PCGEN.ASM < prev next >

Wrap

Assembly Source File | 1989-03-19 | 8.6 KB | 438 lines

include lmacros.h assume ds:dataseg public Sssave,Spsave,Intstk_,doret,Isat_,dbase_,cbase_ extrn _Dorg_:byte,_Corg_:byte ifdef FARPROC extrn ctick_:far else extrn ctick_:near endif dbase dw seg _Dorg_ ; save loc for ds (must be in code segment) ; common routine for interrupt return ifdef FARPROC doret proc far else doret proc near endif cmp Isat_,1 jnz notat ; Only one 8259, so skip this stuff mov al,0bh ; read in-service register from out 0a0h,al ; secondary 8259 nop ; settling delay nop nop in al,0a0h ; get it or al,al ; Any bits set? jz notat ; nope, not a secondary interrupt mov al,20h ; Get EOI instruction out 0a0h,al ; Secondary 8259 (PC/AT only) notat: mov al,20h ; 8259 end-of-interrupt command out 20h,al ; Primary 8259 pop es pop di pop si pop bp pop dx pop cx pop bx pop ax mov ss,Sssave mov sp,Spsave ; restore original stack context pop ds iret doret endp ; Null interrupt handler procdef nullvec iret pend nullvec ; setvect - set interrupt vector ; called from C as follows ; setvect(vec,vecval) ; char vec; /* Interrupt number */ ; void (*vecval)(); /* offset (and segment in large code model) */ procdef setvect,<<vec,byte>,<ipval,fptr>> mov dx,word ptr ipval push ds ; save ifdef FARPROC mov ds,word ptr ipval+2 else mov ax,cs mov ds,ax endif mov ah,25h mov al,vec int 21h pop ds ; restore pret pend setvect ; getvect - return current interrupt vector ; called from C as ; long /* Returns CS in high word, IP in low word */ ; getvect(vecnum) ; char vecnum; /* Interrupt number */ procdef getvect,<<vecnum,byte>> mov ah,35h mov al,vecnum push es ; save, since DOS uses it for a return value int 21h mov dx,es ; CS value into DX (C high word) mov ax,bx ; IP value into AX (C low word) pop es ; restore es pret pend getvect ; kbraw - raw, nonblocking read from console ; If character is ready, return it; if not, return -1 procdef kbraw mov ah,06h ; Direct Console I/O mov dl,0ffh ; Read from keyboard int 21h ; Call DOS jz nochar ; zero flag set -> no character ready mov ah,0 ; valid char is 0-255 pret nochar: mov ax,-1 ; no char, return -1 pret pend kbraw ; Return nonzero if a key is ready, without reading it procdef kbhit mov ah,0bh ; Check Standard Input Status int 21h ; Call DOS mov ah,0 ; clear upper half of return value pret pend kbhit ; istate - return current interrupt state procdef istate pushf pop ax and ax,200h jnz ion1 pret ion1: mov ax,1 pret pend istate ; dirps - disable interrupts and return previous state: 0 = disabled, ; 1 = enabled procdef dirps pushf ; save state on stack cli ; interrupts off pop ax ; original flags -> ax and ax,200h ; 1<<9 is IF bit jnz ion ; nonzero -> interrupts were on pret ion: mov ax,1 pret pend dirps ; restore - restore interrupt state: 0 = off, nonzero = on procdef restore,<<istate,byte>> test istate,0ffh jz ioff sti pret ioff: cli pret pend restore ; enable - enable interrupts unconditionally procdef enable sti pret pend enable ; Halt until an interrupt occurs, then return procdef eihalt sti ; make sure interrupts are enabled hlt pret pend eihalt ; multitasker types NONE equ 0 DOUBLEDOS equ 1 DESQVIEW equ 2 ; Relinquish processor so other task can run procdef giveup pushf ;save caller's interrupt state sti ;re-enable interrupts cmp mtasker,DOUBLEDOS jnz givedesqview mov al,2 ; 110 ms mov ah,0eeh int 21h popf ; restore interrupts pret givedesqview: cmp mtasker,DESQVIEW jnz notask mov ax, 1000h int 15h popf ; restore interrupts pret notask: hlt ; wait for an interrupt popf ; restore interrupts pret pend giveup ; check for a multitasker running procdef chktasker mov mtasker, NONE ; do the doubledos test mov ah, 0e4h int 21h cmp al, 1 jz isdos cmp al, 2 jnz test_desq isdos: mov mtasker, DOUBLEDOS pret ; test for desqview test_desq: mov ax, 2b01h mov cx, 4445h mov dx, 5351h int 21h cmp al, 0ffh jnz isdesq pret isdesq: mov mtasker, DESQVIEW pret pend chktasker ; getss - Read SS for debugging purposes procdef getss mov ax,ss pret pend getss ; Internet checksum subroutine ; Compute 1's-complement sum of data buffer ; Uses an unwound loop inspired by "Duff's Device" for performance ; ; Called from C as ; unsigned short ; lcsum(buf,cnt) ; unsigned short *buf; ; unsigned short cnt; procdef lcsum,<<buf,ptr>,<cnt,word>> pushds ; save if using large model push si ldptr si,buf,ds ; ds:si = buf mov cx,cnt ; cx = cnt cld ; autoincrement si mov ax,cx shr cx,1 ; cx /= 16, number of loop iterations shr cx,1 shr cx,1 shr cx,1 inc cx ; make fencepost adjustment for 1st pass and ax,15 ; ax = number of words modulo 16 shl ax,1 ; *=2 for word table index lea bx,jtable ; bx -> branch table add bx,ax ; index into jump table clc ; initialize carry = 0 mov dx,0 ; clear accumulated sum jmp word ptr[bx] ; jump into loop ; Here the real work gets done. The numeric labels on the lodsw instructions ; are the targets for the indirect jump we just made. ; ; Each label corresponds to a possible remainder of (count / 16), while ; the number of times around the loop is determined by the quotient. ; ; The loop iteration count in cx has been incremented by one to adjust for ; the first pass. ; deloop: lodsw adc dx,ax l15: lodsw adc dx,ax l14: lodsw adc dx,ax l13: lodsw adc dx,ax l12: lodsw adc dx,ax l11: lodsw adc dx,ax l10: lodsw adc dx,ax l9: lodsw adc dx,ax l8: lodsw adc dx,ax l7: lodsw adc dx,ax l6: lodsw adc dx,ax l5: lodsw adc dx,ax l4: lodsw adc dx,ax l3: lodsw adc dx,ax l2: lodsw adc dx,ax l1: lodsw adc dx,ax l0: loop deloop ; :-) adc dx,0 ; get last carries adc dx,0 mov ax,dx ; result into ax xchg al,ah ; byte swap result (8088 is little-endian) pop si popds ; all done pret pend lcsum ; Clock tick interrupt handler public btick_ btick_ proc far ; Note that we don't save DS. It has already been saved by the BIOS, ; and if we saved and restored it the indirect jmp at the end would ; go off into the ozone. mov ds,cs:dbase ; establish interrupt data segment mov Sssave,ss ; stash user stack context mov Spsave,sp mov ss,cs:dbase lea sp,Intstk_+512 push ax ; save user regs on interrupt stack push bx push cx push dx push bp push si push di push es mov ax,ds mov es,ax call ctick_ pop es pop di pop si pop bp pop dx pop cx pop bx pop ax mov ss,Sssave mov sp,Spsave ; restore original stack context jmp dword ptr Tvec_ ; link to previous vector btick_ endp ; Convert 32-bit int in network order to host order (dh, dl, ah, al) procdef get32,<<cp32,ptr>> pushds cld push si ldptr si,cp32,ds lodsw mov dh,al ; high word to dx, a-swapping as we go mov dl,ah lodsw xchg al,ah ; low word stays in ax, just swap pop si popds pret pend get32 ; Convert 16-bit int in network order to host order (ah, al) procdef get16,<<cp16,ptr>> pushds cld push si ldptr si,cp16,ds lodsw xchg al,ah ; low word stays in ax, just swap pop si popds pret pend get16 ; Convert 32-bit int to network order, returning new pointer procdef put32,<<cpo32,ptr>,<pi32,dword>> pushds push es cld push di push si ldptr di,cpo32,es ; point di to network output buffer lea si,pi32 ; point si to input doubleword ifdef LONGPTR mov ax,ss mov ds,ax endif lodsw ; fetch low word of machine version mov dh,al ; swap bytes and save mov dl,ah lodsw ; fetch high word xchg ah,al ; byte swap stosw ; store in output mov ax,dx ; retrieve low word and store in output stosw mov ax,di ; return incremented output pointer pop si pop di pop es popds pret pend put32 ; Convert 16-bit int to network order, returning new pointer procdef put16,<<cpo16,ptr>,<pi16,word>> push es cld push di ldptr di,cpo16,es mov ax,pi16 ; fetch source word in machine order xchg ah,al ; swap bytes stosw ; save in network order mov ax,di ; return new output pointer to user pop di pop es pret pend put16 finish public Tvec_ dataseg segment para public 'data' jtable dw l0,l1,l2,l3,l4,l5,l6,l7,l8,l9,l10,l11,l12,l13,l14,l15 dbase_ dw seg _Dorg_ cbase_ dw seg _Corg_ bss Spsave:word,2 bss Sssave:word,2 bss Intstk_:byte,512 bss mtasker:byte,1 bss Tvec_:word,4 dataseg ends end