2ddca57f3f
The goal was to be able to implement "(" in forth, but I realised that my
INTERPRET approach was wrong. Compiling the line beforehand is, after all,
not good. I'll have to change it again.
46 lines
1.2 KiB
NASM
46 lines
1.2 KiB
NASM
; *** Const ***
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; Base of the Return Stack
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.equ RS_ADDR 0xf000
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; Number of bytes we keep as a padding between HERE and the scratchpad
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.equ PADDING 0x20
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; Max length of dict entry names
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.equ NAMELEN 7
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; Offset of the code link relative to the beginning of the word
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.equ CODELINK_OFFSET NAMELEN+3
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; *** Variables ***
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.equ INITIAL_SP FORTH_RAMSTART
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.equ CURRENT @+2
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.equ HERE @+2
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.equ INPUTPOS @+2
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; Buffer where we compile the current input line. Same size as STDIO_BUFSIZE.
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.equ COMPBUF @+2
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.equ FORTH_RAMEND @+0x40
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; *** Code ***
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forthMain:
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; STACK OVERFLOW PROTECTION:
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; To avoid having to check for stack underflow after each pop operation
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; (which can end up being prohibitive in terms of costs), we give
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; ourselves a nice 6 bytes buffer. 6 bytes because we seldom have words
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; requiring more than 3 items from the stack. Then, at each "exit" call
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; we check for stack underflow.
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push af \ push af \ push af
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ld (INITIAL_SP), sp
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ld hl, LATEST
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ld (CURRENT), hl
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ld hl, FORTH_RAMEND
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ld (HERE), hl
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forthRdLine:
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ld hl, msgOk
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call printstr
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call printcrlf
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call stdioReadLine
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ld (INPUTPOS), hl
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forthInterpret:
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ld ix, RS_ADDR-2 ; -2 because we inc-before-push
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ld iy, INTERPRET
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jp executeCodeLink
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msgOk:
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.db " ok", 0
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