mirror of https://github.com/hsoft/collapseos.git
52 lines
920 B
NASM
52 lines
920 B
NASM
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; Glue code for the emulated environment
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.equ USER_CODE 0x4000
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.equ RAMEND 0xffff
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.equ ZASM_INPUT 0xa000
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.equ ZASM_OUTPUT 0xd000
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.equ STDIO_PORT 0x00
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jr init ; 2 bytes
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; *** JUMP TABLE ***
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jp strncmp
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jp addDE
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jp upcase
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jp unsetZ
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jp intoDE
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init:
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di
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ld hl, RAMEND
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ld sp, hl
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ld hl, ZASM_INPUT
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; yes, this means that input can't have null bytes
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.inloop:
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in a, (STDIO_PORT)
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ld (hl), a ; before cond jr so we write a final \0
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or a
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jr z, .inloopend
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inc hl
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jr .inloop
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.inloopend:
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ld hl, ZASM_INPUT
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ld de, ZASM_OUTPUT
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call USER_CODE
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; BC contains the number of written bytes
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xor a
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cp b
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jr nz, .spit
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cp c
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jr z, .end ; no output
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.spit:
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ld hl, ZASM_OUTPUT
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.outloop:
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ld a, (hl)
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out (STDIO_PORT), a
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cpi ; a trick to inc HL and dec BC at the same time.
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; P/V indicates whether BC reached 0
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jp pe, .outloop ; BC is not zero, loop
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.end:
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; signal the emulator we're done
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halt
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#include "core.asm"
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