;NXOS shell
;----------
;Written by: Alberto Venturini (Alb‚) - 2001
;Email address: -albe-@libero.it

	org 0h

	cld
Main1:
	mov si,offset Prompt	;shows the prompt
	mov ah,01h
	mov bl,07h
	int 24h

	mov di,offset Command
	xor cx,cx

GetCommand:		;Get a string from the keyboard
	mov si,offset Command
	mov ah,07h
	int 25h
	dec si

ToUpCase:		;Turns everything upcase
	inc si
	mov al,ds:[si]
	cmp al,13
	je EndCommand
	cmp al,90
	jbe ToUpCase
	sub al,32
	mov ds:[si],al
	jmp ToUpCase

EndCommand:
	test cx,cx	;If only CR was pressed, just re-write the prompt
	jz ClearCommandBuffer

	push cx
	mov di,offset Command

Test4Extension:			;tests if file extension is available
	mov al,es:[di]
	cmp al,'.'
	je ExtensionOk
	inc di
	dec cx
	jnz Test4Extension

NoExtension:			;there's no extension...assume it's an internal
				;shell command

	pop cx

	mov di,offset Command

	mov cx,3
	mov si,offset ClsCmd
	rep cmpsb
	je ShellCommand_Cls

	mov ah,01h
	mov si,offset Error3
	mov bl,7
	int 24h

	jmp ClearCommandBuffer

ShellCommand_Cls:		;executes the "CLS" command
	mov ah,04h
	int 24h
	jmp ClearCommandBuffer

;[...]

ExtensionOk:	;there's the extension
	pop cx

StoreExtension:	;store the extension in a buffer ("Extension")
	push di
	inc di
	mov si,di
	mov di,offset Extension

	movsb
	movsb
	movsb

	pop di

	push di
	sub di,offset Command

	cmp di,8
	jb StoreExtension2

	pop di		;file name must be <= 8
	mov di,offset Command
	add di,8
	jmp StoreExtension3

StoreExtension2:
	mov cx,8
	sub cx,di
	mov al,' '

	pop di

	rep stosb

StoreExtension3:
	mov si,offset Extension
	movsb
	movsb
	movsb

ExecuteProgram:
	mov di,offset Extension
	mov si,offset BinExtension

	mov cx,3

	rep cmpsb	;tests if the extension is "BIN"
	je ExecuteBinProgram

	mov ah,01h
	mov si,offset Error2
	mov bl,7
	int 24h

	jmp Main1

ExecuteBinProgram:
	push es

	mov si,offset Command
	mov ah,00h
	int 20h
	test dx,dx
	jz FileNotFound
	mov bl,0
	mov ah,01h
	int 20h

	pop es

	jmp ClearCommandBuffer

FileNotFound:
	pop es
	mov si,offset Error1
	mov ah,01h
	mov bl,7
	int 24h

ClearCommandBuffer:
	mov di,offset Command
	mov al,' '
	mov cx,95

ClearCommandBuffer2:
	mov byte ptr cs:[di],al
	inc di
	loop ClearCommandBuffer2

	jmp Main1


;------------------------------------------------------------------------------

Command db 100 dup (32)
Prompt	db 13,10,'Ready:',0
Error1	db 13,10,'File not found',13,10,0
Error2	db 13,10,'Invalid file name',13,10,0
Error3	db 13,10,'Invalid command',13,10,0
NextLine db 13,10,0
Extension db 3 dup (?)
BinExtension db 'BIN',0

ClsCmd	db 'CLS'

;------------------------------------------------------------------------------