rdos/bdos/8086.asm

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NASM
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ORG BDOS
%include "bios/header.asm"
DISKBUF: EQU (BDOS-0x200) ; deblocking
STACK: EQU (DISKBUF) ; grows down
DEFDRV: EQU 4
FCB_DRV: EQU 0 ; BYTE 0=A: 1=B: 2=C: ...
FCB_NAM: EQU 1 ; 8 BYTES, space padded
FCB_EXT: EQU 9 ; 3 BYTES, space padded
FCB_TYP: EQU 12 ; 1 for regular file
FCB_BLK: EQU 13 ; current 128b block in sector
FCB_CLU: EQU 14 ; current sector
FCB_LFT: EQU 16 ; bytes left to read in current file
SYSCALL:
TEST CL, CL
JE SETUP
CMP CL, 1
JE GETC
CMP CL, 2
JE PUTC
CMP CL, 9
JE PUTS
CMP CL, 10
JE GETS
STC
RET
SETUP:
MOV SP, STACK
MOV BYTE [DEFDRV], 0x01
MOV CX, DISKBUF
CALL SETDMA
MOV DL, BYTE [DEFDRV]
ADD DL, '@'
CALL PUTC
MOV DL, '>'
CALL PUTC
MOV DX, 0x7F
MOV BYTE [0x7F], 0x2F
MOV BYTE [0x80], 2
CALL GETS
INT3
CLI
HALT:
HLT
JMP HALT
GETC:
CALL CONIN
TEST AL, AL
JZ GETC
PUSH DX
MOV DL, AL
CALL CONOUT
POP DX
ret
PUTC:
CALL CONOUT
RET
PUTS:
PUSH SI
MOV SI, DX
PUTS_L:
MOV DL, BYTE [SI]
CMP DL, '$'
JZ PUTS_E
CALL CONOUT
INC SI
JMP PUTS_L
PUTS_E:
POP SI
RET
; BX base ptr to buffer
; CH maximum BL
; CL minimum BL
GETS:
PUSH AX
PUSH CX
PUSH DX
PUSH BX
; BX is base pointer
MOV BX, DX
; CL is maximum, CH is current position
MOV CX, [BX]
XOR CH, CH
; BX starts at actual character area
ADD BX, 2
GETS_L:
; Read and maybe handle control chars
CALL GETC
CMP AL, 0x0D
JE GETS_E
CMP AL, 8
JE GETS_BS
; Store character
PUSH BX
ADD BL, CH
ADC BH, 0
MOV [BX], AL
POP BX
; Loop if we arent full yet
INC CH
CMP CH, CL
JC GETS_L
GETS_E:
; Append LF to CR
MOV DL, 0x0A
CALL PUTC
; Write back length data
SUB BX, 2
MOV [BX], CX
; Restore registers
POP BX
POP DX
POP CX
POP AX
ret
GETS_BS:
TEST CH, CH
JZ GETS_L
MOV DL, 0x20
CALL PUTC
MOV DL, 8
CALL PUTC
DEC CL
JMP GETS_L