collapseos/apps/zasm/main.asm

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NASM
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; 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.
;
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; *** Requirements ***
; blockdev
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; JUMP_STRNCMP
; JUMP_ADDDE
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; JUMP_ADDHL
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; JUMP_UPCASE
; JUMP_UNSETZ
; JUMP_INTODE
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; JUMP_INTOHL
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; JUMP_FINDCHAR
; JUMP_BLKSEL
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; RAMSTART (where we put our variables in RAM)
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; *** 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"
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.equ IO_RAMSTART ZASM_RAMEND
#include "io.asm"
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#include "tok.asm"
#include "parse.asm"
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#include "expr.asm"
#include "instr.asm"
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.equ DIREC_RAMSTART IO_RAMEND
#include "directive.asm"
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.equ SYM_RAMSTART DIREC_RAMEND
#include "symbol.asm"
; Read file through blockdev ID in H and outputs its upcodes through blockdev
; ID in L.
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zasmMain:
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; Init I/O
ld a, h
ld de, IO_IN_GETC
call JUMP_BLKSEL
ld a, l
ld de, IO_OUT_GETC
call JUMP_BLKSEL
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; Init modules
call symInit
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; First pass
ld a, 1
ld (ZASM_FIRST_PASS), a
call zasmParseFile
ret nz
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; 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
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ret
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; Increase (curOutputOffset) by A
incOutputOffset:
push de
ld de, (curOutputOffset)
call JUMP_ADDDE
ld (curOutputOffset), de
pop de
ret
; Repeatedly reads lines from IO, assemble them and spit the binary code in
; IO. Z is set on success, unset on error. DE contains the last line number to
; be read (first line is 1).
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zasmParseFile:
ld de, 0
ld (curOutputOffset), de
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.loop:
inc de
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call ioReadLine
or a ; is A 0?
ret z ; We have EOF
call parseLine
ret nz ; error
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jr .loop
; Parse line in (HL), write the resulting opcode(s) through ioPutC and increases
; (curOutputOffset) by the number of bytes written.
; Sets Z if parse was successful, unset if there was an error or EOF.
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parseLine:
push bc
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call tokenize
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ld a, b ; TOK_*
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cp TOK_INSTR
jr z, .instr
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cp TOK_DIRECTIVE
jr z, .direc
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cp TOK_LABEL
jr z, .label
cp TOK_EMPTY
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jr .end ; Z is correct. If empty, Z is set and not an
; error, otherwise, it means bad token and
; errors out.
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.instr:
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call _parseInstr
jr .end ; Z is correct
.direc:
call _parseDirec
jr .end ; Z is correct
.label:
push hl
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call _parseLabel
pop hl
jr nz, .end ; error out
; We're finished here. However, because it's a label, it's possible that
; another logical line follows directly after the label. Let's parse
; this and propagate error.
call parseLine
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; Continue to .end, Z has proper value
.end:
pop bc
ret
_parseInstr:
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ld a, c ; I_*
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call parseInstruction
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or a ; is zero?
jr z, .error
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ld b, a ; save output byte count
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call incOutputOffset
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call zasmIsFirstPass
jr z, .success ; first pass, nothing to write
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ld hl, instrUpcode
.loopInstr:
ld a, (hl)
call ioPutC
inc hl
djnz .loopInstr
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; continue to success
.success:
xor a ; ensure Z
ret
.error:
call JUMP_UNSETZ
ret
_parseDirec:
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ld a, c ; D_*
call parseDirective
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or a ; cp 0
jr z, .success ; if zero, shortcut through
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ld b, a ; save output byte count
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call incOutputOffset
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call zasmIsFirstPass
jr z, .success ; first pass, nothing to write
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ld hl, direcData
.loopDirec:
ld a, (hl)
call ioPutC
inc hl
djnz .loopDirec
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; continue to success
.success:
xor a ; ensure Z
ret
_parseLabel:
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; The string in (scratchpad) is a label with its trailing ':' removed.
ex hl, de ; save current HL (end of label) in DE,
; we will need it later
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ld hl, scratchpad
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call zasmIsFirstPass
jr z, .registerLabel ; When we encounter a label in the first
; pass, we register it in the symbol
; list
; When we're not in the first pass, we set the context (if label is not
; local) to that label.
call symIsLabelLocal
jr z, .success ; local? don't set context
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call symSetContext
jr z, .success
; NZ? this means that (HL) couldn't be found in symbol list. Weird
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jr .error
.registerLabel:
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ld de, (curOutputOffset)
call symRegister
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jr nz, .error
; continue to .success
.success:
xor a ; ensure Z
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ret
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.error:
call JUMP_UNSETZ
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ret
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; *** Variables ***
; The offset where we currently are with regards to outputting opcodes
curOutputOffset:
.fill 2