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