collapseos/apps/zasm/main.asm
2019-05-11 22:11:05 -04:00

173 lines
3.9 KiB
NASM

; zasm
;
; Reads input from specified blkdev ID, assemble the binary in two passes and
; spit the result in another specified blkdev ID.
;
; We don't buffer the whole source in memory, so we need our input blkdev to
; support Seek so we can read the file a second time. So, for input, we need
; GetC and Seek.
;
; For output, we only need PutC. Output doesn't start until the second pass.
;
; The goal of the second pass is to assign values to all symbols so that we
; can have forward references (instructions referencing a label that happens
; later).
;
; Labels and constants are both treated the same way, that is, they can be
; forward-referenced in instructions. ".equ" directives, however, are evaluated
; during the first pass so forward references are not allowed.
;
; *** Requirements ***
; blockdev
; JUMP_STRNCMP
; JUMP_ADDDE
; JUMP_ADDHL
; JUMP_UPCASE
; JUMP_UNSETZ
; JUMP_INTODE
; JUMP_FINDCHAR
; JUMP_BLKSEL
; RAMSTART (where we put our variables in RAM)
; *** Variables ***
; A bool flag indicating that we're on first pass. When we are, we don't care
; about actual output, but only about the length of each upcode. This means
; that when we parse instructions and directive that error out because of a
; missing symbol, we don't error out and just write down a dummy value.
.equ ZASM_FIRST_PASS RAMSTART
.equ ZASM_RAMEND ZASM_FIRST_PASS+1
; *** Code ***
jp zasmMain
#include "util.asm"
.equ IO_RAMSTART ZASM_RAMEND
#include "io.asm"
#include "tok.asm"
#include "parse.asm"
#include "instr.asm"
.equ DIREC_RAMSTART IO_RAMEND
#include "directive.asm"
.equ SYM_RAMSTART DIREC_RAMEND
#include "symbol.asm"
; Read file through blockdev ID in H and outputs its upcodes through blockdev
; ID in L.
zasmMain:
ld a, h
ld de, IO_IN_GETC
call JUMP_BLKSEL
ld a, l
ld de, IO_OUT_GETC
call JUMP_BLKSEL
; First pass
ld a, 1
ld (ZASM_FIRST_PASS), a
call zasmParseFile
; Second pass
call ioRewind
xor a
ld (ZASM_FIRST_PASS), a
call zasmParseFile
ret
; Sets Z according to whether we're in first pass.
zasmIsFirstPass:
ld a, (ZASM_FIRST_PASS)
cp 1
ret
; Increase (curOutputOffset) by A
incOutputOffset:
push de
ld de, (curOutputOffset)
call JUMP_ADDDE
ld (curOutputOffset), de
pop de
ret
zasmParseFile:
ld hl, 0
ld (curOutputOffset), hl
.loop:
call ioReadLine
or a ; is A 0?
ret z ; We have EOF
call parseLine
ret nz
jr .loop
; Parse line in (HL), write the resulting opcode(s) in (DE) and increases
; (curOutputOffset) by the number of bytes written. Advances HL where
; tokenization stopped and DE to where we should write the next upcode.
; Sets Z if parse was successful, unset if there was an error or EOF.
parseLine:
push bc
call tokenize
ld a, b ; TOK_*
cp TOK_INSTR
jr z, .instr
cp TOK_DIRECTIVE
jr z, .direc
cp TOK_LABEL
jr z, .label
cp TOK_EMPTY
jr z, .success ; empty line? do nothing but don't error out.
jr .error ; token not supported
.instr:
ld a, c ; I_*
call parseInstruction
or a ; is zero?
jr z, .error
ld b, a ; save output byte count
call incOutputOffset
call zasmIsFirstPass
jr z, .success ; first pass, nothing to write
ld hl, instrUpcode
.loopInstr:
ld a, (hl)
call ioPutC
inc hl
djnz .loopInstr
jr .success
.direc:
ld a, c ; D_*
call parseDirective
or a ; cp 0
jr z, .success ; if zero, shortcut through
ld b, a ; save output byte count
call incOutputOffset
call zasmIsFirstPass
jr z, .success ; first pass, nothing to write
ld hl, direcData
.loopDirec:
ld a, (hl)
call ioPutC
inc hl
djnz .loopDirec
jr .success
.label:
call zasmIsFirstPass
jr nz, .success ; not in first pass? nothing to do
; The string in (scratchpad) is a label with its trailing ':' removed.
ld hl, scratchpad
ld de, (curOutputOffset)
call symRegister
jr .success
.success:
xor a ; ensure Z
jr .end
.error:
call JUMP_UNSETZ
.end:
pop bc
ret
; *** Variables ***
; The offset where we currently are with regards to outputting opcodes
curOutputOffset:
.fill 2