237 lines
5.5 KiB
NASM
237 lines
5.5 KiB
NASM
; zasm
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;
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; Reads input from specified blkdev ID, assemble the binary in two passes and
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; spit the result in another specified blkdev ID.
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;
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; We don't buffer the whole source in memory, so we need our input blkdev to
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; support Seek so we can read the file a second time. So, for input, we need
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; GetC and Seek.
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;
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; For output, we only need PutC. Output doesn't start until the second pass.
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;
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; The goal of the second pass is to assign values to all symbols so that we
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; can have forward references (instructions referencing a label that happens
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; later).
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;
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; Labels and constants are both treated the same way, that is, they can be
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; forward-referenced in instructions. ".equ" directives, however, are evaluated
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; during the first pass so forward references are not allowed.
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;
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; *** Requirements ***
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; blockdev
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; strncmp
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; addDE
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; addHL
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; upcase
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; unsetZ
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; intoDE
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; intoHL
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; findchar
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; parseHex
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; parseHexPair
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; blkSel
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; fsFindFN
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; fsOpen
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; fsGetC
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; fsSeek
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; fsTell
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; RAMSTART (where we put our variables in RAM)
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; FS_HANDLE_SIZE
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; *** Variables ***
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; A bool flag indicating that we're on first pass. When we are, we don't care
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; about actual output, but only about the length of each upcode. This means
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; that when we parse instructions and directive that error out because of a
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; missing symbol, we don't error out and just write down a dummy value.
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.equ ZASM_FIRST_PASS RAMSTART
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; whether we're in "local pass", that is, in local label scanning mode. During
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; this special pass, ZASM_FIRST_PASS will also be set so that the rest of the
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; code behaves as is we were in the first pass.
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.equ ZASM_LOCAL_PASS ZASM_FIRST_PASS+1
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; What IO_PC was when we started our context
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.equ ZASM_CTX_PC ZASM_LOCAL_PASS+1
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.equ ZASM_RAMEND ZASM_CTX_PC+2
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; *** Code ***
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jp zasmMain
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#include "zasm/util.asm"
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.equ IO_RAMSTART ZASM_RAMEND
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#include "zasm/io.asm"
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.equ TOK_RAMSTART IO_RAMEND
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#include "zasm/tok.asm"
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#include "zasm/parse.asm"
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#include "zasm/expr.asm"
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#include "zasm/instr.asm"
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.equ DIREC_RAMSTART TOK_RAMEND
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#include "zasm/directive.asm"
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.equ SYM_RAMSTART DIREC_RAMEND
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#include "zasm/symbol.asm"
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; Read file through blockdev ID in H and outputs its upcodes through blockdev
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; ID in L.
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zasmMain:
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; Init I/O
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ld a, h
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ld de, IO_IN_GETC
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call blkSel
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ld a, l
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ld de, IO_OUT_GETC
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call blkSel
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; Init modules
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xor a
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ld (ZASM_LOCAL_PASS), a
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call ioInit
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call symInit
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; First pass
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ld a, 1
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ld (ZASM_FIRST_PASS), a
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call zasmParseFile
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ret nz
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; Second pass
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call ioRewind
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xor a
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ld (ZASM_FIRST_PASS), a
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call zasmParseFile
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ret
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; Sets Z according to whether we're in first pass.
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zasmIsFirstPass:
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ld a, (ZASM_FIRST_PASS)
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cp 1
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ret
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; Sets Z according to whether we're in local pass.
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zasmIsLocalPass:
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ld a, (ZASM_LOCAL_PASS)
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cp 1
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ret
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; Repeatedly reads lines from IO, assemble them and spit the binary code in
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; IO. Z is set on success, unset on error. DE contains the last line number to
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; be read (first line is 1).
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zasmParseFile:
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call ioResetPC
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.loop:
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call parseLine
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ret nz ; error
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ld a, b ; TOK_*
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cp TOK_EOF
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jr z, .eof
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jr .loop
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.eof:
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call zasmIsLocalPass
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jr nz, .end ; EOF and not local pass
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; we're in local pass and EOF. Unwind this
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call _endLocalPass
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jr .loop
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.end:
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cp a ; ensure Z
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ret
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; Parse next token and accompanying args (when relevant) in I/O, write the
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; resulting opcode(s) through ioPutC and increases (IO_PC) by the number of
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; bytes written. BC is set to the result of the call to tokenize.
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; Sets Z if parse was successful, unset if there was an error. EOF is not an
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; error.
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parseLine:
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call tokenize
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ld a, b ; TOK_*
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cp TOK_INSTR
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jp z, _parseInstr
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cp TOK_DIRECTIVE
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jp z, _parseDirec
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cp TOK_LABEL
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jr z, _parseLabel
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cp TOK_EOF
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ret ; Z is correct. If EOF, Z is set and not an
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; error, otherwise, it means bad token and
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; errors out.
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_parseInstr:
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ld a, c ; I_*
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jp parseInstruction
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_parseDirec:
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ld a, c ; D_*
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call parseDirective
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cp a ; ensure Z
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ret
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_parseLabel:
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; The string in (scratchpad) is a label with its trailing ':' removed.
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ld hl, scratchpad
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call zasmIsLocalPass
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jr z, .processLocalPass
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; Is this a local label? If yes, we don't process it in the context of
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; parseLine, whether it's first or second pass. Local labels are only
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; parsed during the Local Pass
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call symIsLabelLocal
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jr z, .success ; local? don't do anything.
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call zasmIsFirstPass
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jr z, .registerLabel ; When we encounter a label in the first
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; pass, we register it in the symbol
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; list
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; At this point, we're in second pass, we've encountered a global label
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; and we'll soon continue processing our file. However, before we do
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; that, we should process our local labels.
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call _beginLocalPass
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jr .success
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.processLocalPass:
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call symIsLabelLocal
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jr z, .registerLabel ; local label? all good, register it
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; normally
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; not a local label? Then we need to end local pass
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call _endLocalPass
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jr .success
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.registerLabel:
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ld de, (IO_PC)
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call symRegister
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jr nz, .error
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; continue to .success
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.success:
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xor a ; ensure Z
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ret
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.error:
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call unsetZ
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ret
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_beginLocalPass:
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; remember were I/O was
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call ioSavePos
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; Remember where PC was
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ld hl, (IO_PC)
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ld (ZASM_CTX_PC), hl
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; Fake first pass
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ld a, 1
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ld (ZASM_FIRST_PASS), a
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; Set local pass
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ld (ZASM_LOCAL_PASS), a
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; Empty local label registry
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xor a
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ld (SYM_LOC_NAMES), a
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call symSelectLocalRegistry
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ret
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_endLocalPass:
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call symSelectGlobalRegistry
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; recall I/O pos
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call ioRecallPos
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; recall PC
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ld hl, (ZASM_CTX_PC)
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ld (IO_PC), hl
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; unfake first pass
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xor a
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ld (ZASM_FIRST_PASS), a
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; Unset local pass
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ld (ZASM_LOCAL_PASS), a
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cp a ; ensure Z
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ret
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