; Program segment prefix headers and constants

section .bss

curpsp:	resw 1

absolute 0

	resb 2 ; ret 0 exit
	resb 2 ; next unusable segment
PSPDD:	resb 1 ; BYTE default drive
	; CP/M entry point
	resb 1 ; instruction byte
	resw 1 ; usable length of segment (needs to be here for compata)
	resb 4 ; opcodes to call us

	; saved userdata
PSPAX:	resw 1
PSPCX:	resw 1
	; SS:SP
PSPSP:	resw 1
PSPSS:	resw 1
	; DS:DX
PSPDX:  resw 1
PSPDS:	resw 1
	; ES:BX
PSPBX:	resw 1
PSPES:	resw 1

PSPDTA:	resd 1 ; DWORD ptr to disk transfer area

section .text

	; set default drive for current process
	; IN	dl	drive number
setdd:	push es
	mov es, [curpsp]
	mov [es:PSPDD], dl
	pop es
	ret

	; get default drive for current process
	; OUT	al	drive number
getdd:	push es
	mov es, [curpsp]
	mov al, [es:PSPDD]
	pop es
	ret

	; set DTA ptr
	; IN	es:bx	far ptr
setdta:	push ds
	mov ds, [curpsp]
	mov [PSPDTA], bx
	mov [PSPDTA+2], es
	pop ds

	; get DTA ptr
	; OUT	es:bx	far ptr
getdta:	mov es, [curpsp]
	les bx, [es:PSPDTA]
	ret