;; ERRMSG.ASM--two procedures for checking for errors on DOS commands.
;;
;;	CCheck	checks for CFlag set and if so, prints error whose
;;		number is is in ax.  Not all messages available
;;		(Should contain those for I/O, EXEC, and Mem Alloc)
;;		_Exits with code 1 if error
;;	WCheck	Used for _Write command.  First does CCheck and if
;;		that returns, compares ax = number of bytes written
;;		to cx = number of bytes requested to write and
;;		prints message and _Exits with code 2
;;
;;  Library source text from "Assembly Language for the IBM PC Family" by
;;   William B. Jones, (c) Copyright 1992, 1997, Scott/Jones Inc.
;;
	.MODEL	SMALL
INCLUDE	PCMAC.INC

	.DATA
;*** first, as list of messages:
Inval	DB	'Invalid function number$'
NotFnd	DB	'File not found$'
Path	DB	'Path not found$'
TooMany	DB	'Too many open files$'
Access	DB	'Access denied$'
Handle	DB	'Invalid handle$'
Corrupt	DB	'Memory control blocks destroyed$'
NoMem	DB	'Insufficient memory$'
Block	DB	'Invalid memory block address$'
Envir	DB	'Invalid environment$'
Format	DB	'Invalid format$'
ACode	DB	'Invalid access code$'
Drive	DB	'Invalid drive specified$'
Device	DB	'Not same device$'
Files	DB	'No more files$'
Unk	DB	'Unknown error number$'
;*** Then, an array Msg of pointers such that Msg[n] = offset of 
;***  message for error n
Msg	DW	?, Inval, NotFnd, Path, TooMany, Access, Handle, Corrupt
	DW	NoMem, Block, Envir, Format, ACode, Unk, Unk, Drive, Unk
	DW	Device, Files
MSGLIM	EQU	($ - Msg - 2) /2
;*** Message for write count error
WrtCnt	DB	'Different number of bytes written than requested$'
Err1	DB	'*** DOS call ERROR at $'
Err2	DB	'h *** $'
CRLF	DB	13, 10, '$'

	.CODE
	PUBLIC	CCheck, WCheck
	EXTRN	PutHex : NEAR
CCheck	PROC
	jc	DoMessage
	ret
DoMessage:
	mov	bx, @data
	mov	ds, bx ;	Just in case
	mov	bx, ax
	_PutStr	Err1
	pop	ax ;	Return address is location of error
	call	PutHex ;	(Don't need it any more)
	_PutStr	Err2
	cmp	bx, 1
	jl	DispUnk ;	Just in case
	cmp	bx, MSGLIM
	jg	DispUnk
	shl	bx, 1
	add	bx, OFFSET Msg ;	bx --> appropriate error message
	mov	dx, [bx]
	mov	ah, 09h
	int	21h
Finish:
	_PutStr	CRLF
	_Exit	1
DispUnk:
	_PutStr	Unk
	jmp	Finish
CCheck	ENDP

WCheck	PROC
	jnc	NoDOSErr
	jmp	CCheck ;	Don't destroy original return address!
NoDOSErr:
	cmp	ax, cx
	jne	WErr
	ret
WErr:
	_PutStr	Err1, @data
	pop	ax
	call	PutHex
	_PutStr	Err2
	_PutStr	WrtCnt
	_PutStr	CRLF
	_Exit	2
WCheck	ENDP
	END