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Nero 7 months ago
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5 changed files with 322 additions and 149 deletions
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  1. 2
      Makefile
  2. 350
      a86.asm
  3. 36
      error.asm
  4. 77
      print.asm
  5. 6
      symbols.asm

2
Makefile
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@ -8,7 +8,7 @@ na86.com: *.asm
$(METRIC) $@
a86.com: na86.com *.asm
$(EMU) na86.com a86.asm
$(EMU) na86.com test.asm
$(METRIC) $@
clean:

350
a86.asm
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@ -1,66 +1,270 @@
org 0x100
jmp main
%include "print.asm"
%include "error.asm"
;; string output
; print AX in base BX
; destroys DX
putnum xor dx, dx
div bx
test cx, cx
loopnz .pad
test ax, ax
je .nib
.pad push dx
call putnum
pop dx
; print lower DL as digit
.nib add dl, 0x30
cmp dl, 0x3a
jl putc
add dl, 7
; print DL as char
putc mov ah, 2
int 0x21
ret
b_err db "OOM", 0
; print str at SI
; NUL-terminated
puts lodsb
test al, al
jz .l01
mov dl, al
call putc
jmp puts
.l01 ret
; print str at return addr
; NUL-terminated
putsh pop si
call puts
jmp si
; print a newline
newlin mov dl, 0x0A
call putc
mov dl, 0x0D
jmp putc
; print register set
; order AX CX DX BX BP SI DI IP
; trashes flags
debug push di
push si
push bp
push bx
push dx
push cx
push ax
mov si, sp
call dump
pop ax
pop cx
pop dx
pop bx
pop bp
pop si
pop di
ret
; dump the 8 words at SI
dump lea di, [si+16]
mov bx, 0x10
.loop lodsw
mov cx, 4
call putnum
mov dl, ' '
call putc
cmp si, di
jc .loop
jmp newlin
%include "error.asm"
b_vrfy mov ax, output
add ax, 0
sub ax, [s_start]
jc .l01
mov bp, b_err
jmp error
call errmsg
db "OOM", 0
.l01: ret
%include "symbols.asm"
%include "file.asm"
%include "parse.asm"
;; input file reading
; label of current line
l_cur db " "
lfcnt dw 1 ; LF counter
chrptr dw 0xFFFF ; infile blk ptr
l_read mov di, l_cur
call rdwrd
fcb1 equ 0x5C
eof equ 0x1A
dta equ 0x80
chr db ' ' ; input file next char
; read next chr from inbuf
nextc mov bx, [chrptr]
cmp bx, 0x80
jc .getit
; load new sector into dta
mov ah, 0x14
mov dx, fcb1
int 0x21
cmp al, 1
je .eof
mov bx, 0
mov [chrptr], bx
; we still have chars in dta
.getit mov al, [dta+bx]
cmp al, eof
je .l03
cmp al, 0
jne .l03
.eof mov al, eof
.l03 cmp al, eof
je .ret
cmp al, 0x0A
jne .ok
inc word [lfcnt]
.ok inc word [chrptr]
.ret xchg al, [chr]
ret
;; word and whitespace parsing
inword db " ", 0
issep cmp al, ','
je .ret
cmp al, ';'
.ret ret
isws cmp al, 0x20
je .ret
cmp al, 0x09
.ret ret
iseol cmp al, 0x0A
je .ret
cmp al, 0x0D
.ret ret
; read inword from infile
readw mov di, inword
lea cx, [di+6]
.loop mov al, [chr]
call issep
je .fill
call isws
je .fill
call iseol
je .fill
call nextc
cmp di, cx
jnc .loop
stosb
jmp .loop
.fill cmp di, cx
jnc .end
mov al, 0x20
stosb
jmp .fill
.end jmp eatws
; IN al ascii char
; OUT al number
; carry flag set if not digit
prsdgt sub al, 0x30
jc .ret
cmp al, 0x09
cmc
.ret ret
; parse integer from inword into DX
prsint mov si, inword
xor dx, dx
mov bx, 0xA
mov cx, 6
.loop lodsb
cmp al, ' '
je .ret
cmp al, 'x'
jne .nox
mov bx, 0x10
mov dx, 0
jmp .cont
.nox call prsdgt
jc .err
xor ah, ah
xchg ax, dx
push dx
mul bx
test dx, dx
jnz .err
pop dx
add dx, ax
.cont loop .loop
.ret ret
.err call errmsg
db "BADINT", 0
; eat space and tabs from inbuf
eatws mov al, [chr]
call isws
jne .ret
call nextc
jmp eatws
.ret ret
%include "symbols.asm"
i_cur dw 0 ; ptr to generator function
i_offs dw 0 ; offset of current instr in binary
; lookup in_str in opcode table
i_lkup mov dx, [in_str]
mov si, [in_str+2]
mov di, [in_str+4]
; lookup inword in opcode table
i_lkup mov dx, [inword]
mov si, [inword+2]
mov di, [inword+4]
mov bx, i_tab
.loop call s_comp
jz .found
add bx, 8
cmp byte [bx], 0
jne .loop
mov bp, i_err
jmp error
call errmsg
db "BAD OPCODE", 0
.found mov ax, [bx+6]
mov [i_cur], ax
ret
i_err db "BAD OPCODE", 0
i_tab db "equ "
dw i_equ
db "org "
dw i_org
db "jmp "
dw i_jmp
db "dw "
dw i_dw
db 0
i_equ ret
i_org call rdint
mov [o_org], dx
i_org call readw
call prsint
mov [b_org], dx
ret
i_dw xor ax, ax
mov [di], ax
mov bx, di
call wval
add word [wptr], 2
mov al, [chr]
cmp al, ','
jne .ret
call nextc
call eatws
jmp i_dw
.ret ret
i_jmp mov bx, [i_offs]
mov byte [output+bx], 0xE9
lea ax, [bx+3]
@ -73,19 +277,18 @@ i_jmp mov bx, [i_offs]
; read word value (literal or symbol)
; add it to [bx] now or when filling backrefs
wval push bx
mov di, in_str
call rdwrd
mov al, [in_str]
call pdigit
call readw
mov al, [inword]
call prsdgt
jc .sym
call psint
call prsint
pop bx
add [bx], dx
ret
; try to find defined symbol
.sym mov dx, [in_str]
mov si, [in_str+2]
mov di, [in_str+4]
.sym mov dx, [inword]
mov si, [inword+2]
mov di, [inword+4]
call s_get
jc .bref
pop bx
@ -97,39 +300,88 @@ wval push bx
pop word [bx+6]
ret
lineno dw 0
main mov dx, fcb1
mov ah, 0xf
int 0x21
; fail if al != 0
test al, al
mov bp, e_open
call errnz
mloop call l_read
mov di, in_str
call rdwrd
cmp byte [in_str], ' '
call ztoc
cmc
call errifc
db "INFILE", 0
; read first char
call nextc
; handle eof specially
mloop mov al, [chr]
cmp al, 0x1A
je final
; snapshot current line number
mov ax, [lfcnt]
mov [lineno], ax
; read label string
call readw
; push label string to stack
push word [inword]
push word [inword+2]
push word [inword+4]
; read op name
call readw
mov al, [inword]
cmp al, ' '
je .eol
cmp al, ';'
je .cmt
; loop up addr of instr generator
call i_lkup
mov bx, [i_cur]
; restore label string from stack
pop word [inword+4]
pop word [inword+2]
pop word [inword]
; handle instruction generator
mov di, [wptr]
call bx
; eat leftovers at end of line
; look what leftovers we got
call eatws
.eol call fpeek
mov bp, e_extr
.eol mov al, [chr]
cmp al, ';'
je .cmt ; a comment
cmp al, eof
je final ; end of file
call iseol
call errnz
call fgetc
jne .err ; characters! bad!
call nextc
; eat CR and LF until next line
.eatnl call fpeek
.eatnl mov al, [chr]
call iseol
jne mloop
call fgetc
call nextc
jmp .eatnl
ret
e_extr db "EXTRA DATA", 0
; eat comment txt until eol
.cmt mov al, [chr]
call iseol
je .eatnl
call nextc
jmp .cmt
; complain about extra shit on line
.err call errmsg
db "EXTRA DATA", 0
e_open db "INFILE", 0
final nop
; close
call putsh
db "BYTES: ", 0
mov bx, 0x0A
mov cx, 1
mov ax, [wptr]
sub ax, output
call putnum
call newlin
call errmsg
db "EOF", 0
o_org dw 0 ; offset of whole file
wptr dw output ; how far we've written
b_org dw 0 ; offset of binary start
output db 0

36
error.asm
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@ -1,28 +1,28 @@
errz jz error
ztoc lahf
ror ah, 1
sahf
ret
errnz jnz error
ret
errc jc error
ret
; use cmc; call errc instead of call errnc
errifc jc errmsg
pop di
mov al, 0
repne scasb
mov al, [di]
jmp di
error call putsh
db "LINE ", 0
errmsg mov dl, 'L'
call putc
mov bx, 0x0A
mov ax, [lineno]
mov cx, 1
call putnum
call putsh
db " COL ", 0
mov ax, [col]
mov cx, 1
mov cx, 3
call putnum
mov dl, ' '
call putc
mov si, inword
call puts
call putsh
db ": ", 0
mov si, bp
db " ", 0
pop si
call puts
call newlin
mov ah, 0

77
print.asm
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@ -1,77 +0,0 @@
;; string output
; print AX in base BX
; destroys DX
putnum xor dx, dx
div bx
test cx, cx
loopnz .pad
test ax, ax
je .nib
.pad push dx
call putnum
pop dx
; print lower DL as digit
.nib add dl, 0x30
cmp dl, 0x3a
jl putc
add dl, 7
; print DL as char
putc mov ah, 2
int 0x21
ret
; print str at SI
; NUL-terminated
puts lodsb
test al, al
jz .l01
mov dl, al
call putc
jmp puts
.l01 ret
; print str at return addr
; NUL-terminated
putsh pop si
call puts
jmp si
; print a newline
newlin mov dl, 0x0A
call putc
mov dl, 0x0D
jmp putc
; print register set
; order AX CX DX BX BP SI DI IP
; trashes flags
debug push di
push si
push bp
push bx
push dx
push cx
push ax
mov si, sp
call dump
pop ax
pop cx
pop dx
pop bx
pop bp
pop si
pop di
ret
; dump the 8 words at SI
dump lea di, [si+16]
mov bx, 0x10
mov cx, 4
.loop lodsw
call putnum
mov dl, ' '
call putc
cmp si, di
jc .loop
jmp newlin

6
symbols.asm
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@ -2,8 +2,6 @@ s_gaps db 0
s_start dw 0xC000
s_end dw 0xC000
s_dup dw "DUP", 0
; allocate a symbol table entry
; OUT bx ptr to entry
s_alloc mov bx, [s_start]
@ -73,8 +71,8 @@ s_set mov bx, [s_start]
test byte [bx], 0x80
jnz .bref
call s_prnt
mov bp, s_dup
jmp error
call errmsg
db "DUP", 0
.bref call s_bref
jmp .next
.l01 cmp dl, '.'

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