forth: a little housekeeping
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Virgil Dupras
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cf95bbcace
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5458a1f7ff
125
forth/forth.asm
125
forth/forth.asm
@ -210,7 +210,7 @@ printcrlf:
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; This routine also takes care of echoing received characters back to the TTY.
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; It also manages backspaces properly.
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readline:
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push bc
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call printcrlf
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ld hl, INPTBUF
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ld b, INPT_BUFSIZE-1
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.loop:
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@ -240,7 +240,7 @@ readline:
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xor a
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ld (hl), a
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ld hl, INPTBUF
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pop bc
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ld (INPUTPOS), hl
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ret
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.delchr:
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@ -423,22 +423,6 @@ divide:
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ld h, a
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ret
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; DE * BC -> DE (high) and HL (low)
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multDEBC:
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ld hl, 0
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ld a, 0x10
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.loop:
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add hl, hl
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rl e
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rl d
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jr nc, .noinc
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add hl, bc
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jr nc, .noinc
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inc de
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.noinc:
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dec a
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jr nz, .loop
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ret
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; Parse string at (HL) as a decimal value and return value in DE.
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; Reads as many digits as it can and stop when:
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@ -508,7 +492,7 @@ parseDecimal:
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; *** Support routines ***
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; Advance (INPUTPOS) until a non-whitespace is met. If needed,
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; call fetchline.
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; call readline.
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; Set HL to newly set (INPUTPOS)
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toword:
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ld hl, (INPUTPOS)
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@ -524,13 +508,13 @@ toword:
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jr c, .loop
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ret
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.empty:
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call fetchline
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call readline
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jr toword
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; Read word from (INPUTPOS) and return, in HL, a null-terminated word.
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; Advance (INPUTPOS) to the character following the whitespace ending the
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; word.
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; When we're at EOL, we call fetchline directly, so this call always returns
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; When we're at EOL, we call readline directly, so this call always returns
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; a word.
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readword:
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call toword
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@ -565,40 +549,6 @@ HLPointsDE:
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cp d ; Z has our answer
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ret
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; Skip the compword where HL is currently pointing. If it's a regular word,
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; it's easy: we inc by 2. If it's a NUMBER, we inc by 4. If it's a LIT, we skip
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; to after null-termination.
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compSkip:
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ld de, NUMBER
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call HLPointsDE
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jr z, .isNum
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ld de, FBR
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call HLPointsDE
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jr z, .isBranch
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ld de, BBR
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call HLPointsDE
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jr z, .isBranch
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ld de, LIT
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call HLPointsDE
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jr nz, .isWord
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; We have a literal
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inc hl \ inc hl
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call strskip
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inc hl ; byte after word termination
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ret
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.isNum:
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; skip by 4
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inc hl
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; continue to isBranch
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.isBranch:
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; skip by 3
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inc hl
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; continue to isWord
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.isWord:
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; skip by 2
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inc hl \ inc hl
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ret
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; Find the entry corresponding to word where (HL) points to and sets DE to
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; point to that entry.
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; Z if found, NZ if not.
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@ -685,12 +635,6 @@ DEinHL:
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inc hl
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ret
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fetchline:
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call printcrlf
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call readline
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ld (INPUTPOS), hl
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ret
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; *** Stack management ***
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; The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
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; maintained by IX. This allows us to generally use push and pop freely because
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@ -724,17 +668,6 @@ popRSIP:
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ld (IP), hl
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ret
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; Skip the next two bytes in RS' TOS
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skipRS:
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push hl
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ld l, (ix)
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ld h, (ix+1)
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inc hl \ inc hl
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ld (ix), l
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ld (ix+1), h
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pop hl
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ret
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; Verifies that SP and RS are within bounds. If it's not, call ABORT
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chkRS:
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push ix \ pop hl
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@ -1652,7 +1585,20 @@ MULT:
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pop de
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pop bc
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call chkPS
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call multDEBC
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; DE * BC -> DE (high) and HL (low)
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ld hl, 0
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ld a, 0x10
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.loop:
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add hl, hl
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rl e
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rl d
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jr nc, .noinc
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add hl, bc
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jr nc, .noinc
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inc de
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.noinc:
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dec a
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jr nz, .loop
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push hl
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jp next
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@ -1702,6 +1648,9 @@ CMP:
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push bc
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jp next
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; Skip the compword where HL is currently pointing. If it's a regular word,
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; it's easy: we inc by 2. If it's a NUMBER, we inc by 4. If it's a LIT, we skip
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; to after null-termination.
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.db "SKIP?"
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.fill 2
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.dw CMP
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@ -1714,7 +1663,35 @@ CSKIP:
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or l
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jp z, next ; False, do nothing.
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ld hl, (IP)
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call compSkip
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ld de, NUMBER
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call HLPointsDE
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jr z, .isNum
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ld de, FBR
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call HLPointsDE
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jr z, .isBranch
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ld de, BBR
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call HLPointsDE
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jr z, .isBranch
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ld de, LIT
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call HLPointsDE
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jr nz, .isWord
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; We have a literal
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inc hl \ inc hl
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call strskip
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inc hl ; byte after word termination
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jr .end
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.isNum:
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; skip by 4
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inc hl
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; continue to isBranch
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.isBranch:
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; skip by 3
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inc hl
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; continue to isWord
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.isWord:
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; skip by 2
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inc hl \ inc hl
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.end:
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ld (IP), hl
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jp next
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