getc.inc

Windows上的精简Linux系统

;; $Id: getc.inc,v 1.3 2002/10/24 22:11:46 hpa Exp $
;; -----------------------------------------------------------------------
;;   
;;   Copyright 1994-2002 H. Peter Anvin - All Rights Reserved
;;
;;   This program is free software; you can redistribute it and/or modify
;;   it under the terms of the GNU General Public License as published by
;;   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
;;   Bostom MA 02111-1307, USA; either version 2 of the License, or
;;   (at your option) any later version; incorporated herein by reference.
;;
;; -----------------------------------------------------------------------

;;
;; getc.inc
;;
;; Simple file handling library (open, getc, ungetc)
;;

;
; open,getc:	Load a file a character at a time for parsing in a manner
;		similar to the C library getc routine.	Only one simultaneous
;		use is supported.  Note: "open" trashes the trackbuf.
;
;		open:	Input:	mangled filename in DS:DI
;			Output: ZF set on file not found or zero length
;
;		openfd:	Input:	file handle in SI
;			Output:	none
;
;		getc:	Output: CF set on end of file
;				Character loaded in AL
;
open:
		call searchdir
		jz open_return
openfd:
		pushf
		mov [FBytes1],ax
		mov [FBytes2],dx
		add ax,[ClustSize]
		adc dx,byte 0
		sub ax,byte 1
		sbb dx,byte 0
		div word [ClustSize]
		mov [FClust],ax		; Number of clusters
		mov [FNextClust],si	; Cluster pointer
		mov ax,[EndOfGetCBuf]	; Pointer at end of buffer ->
		mov [FPtr],ax		;  nothing loaded yet
		popf			; Restore no ZF
open_return:	ret

getc:
		stc			; If we exit here -> EOF
		mov ecx,[FBytes]
		jecxz getc_ret
		mov si,[FPtr]
		cmp si,[EndOfGetCBuf]
		jb getc_loaded
		; Buffer empty -- load another set
		mov cx,[FClust]
		cmp cx,[BufSafe]
		jna getc_oksize
		mov cx,[BufSafe]
getc_oksize:	sub [FClust],cx		; Reduce remaining clusters
		mov si,[FNextClust]
		push es			; ES may be != DS, save old ES
		push ds
		pop es
		mov bx,getcbuf
		push bx
		call getfssec		; Load a trackbuf full of data
		mov [FNextClust],si	; Store new next pointer
		pop si			; SI -> newly loaded data
		pop es			; Restore ES
getc_loaded:	lodsb			; Load a byte, increment SI
		mov [FPtr],si		; Update next byte pointer
		dec dword [FBytes]	; Update bytes left counter
		clc			; Not EOF
getc_ret:	ret

;
; ungetc:	Push a character (in AL) back into the getc buffer
;		Note: if more than one byte is pushed back, this may cause
;		bytes to be written below the getc buffer boundary.  If there
;		is a risk for this to occur, the getcbuf base address should
;		be moved up.
;
ungetc:
		mov si,[FPtr]
		dec si
		mov [si],al
		mov [FPtr],si
		inc dword [FBytes]
		ret

;
; skipspace:	Skip leading whitespace using "getc".  If we hit end-of-line
;		or end-of-file, return with carry set; ZF = true of EOF
;		ZF = false for EOLN; otherwise CF = ZF = 0.
;
;		Otherwise AL = first character after whitespace
;
skipspace:
skipspace_loop: call getc
		jc skipspace_eof
		cmp al,1Ah			; DOS EOF
		je skipspace_eof
		cmp al,0Ah
		je skipspace_eoln
		cmp al,' '
		jbe skipspace_loop
		ret				; CF = ZF = 0
skipspace_eof:	cmp al,al			; Set ZF
		stc				; Set CF
		ret
skipspace_eoln: add al,0FFh			; Set CF, clear ZF
		ret

;
; getint:	Load an integer from the getc file.
;		Return CF if error; otherwise return integer in EBX
;
getint:
		mov di,NumBuf
gi_getnum:	cmp di,NumBufEnd	; Last byte in NumBuf
		jae gi_loaded
		push di
		call getc
		pop di
		jc gi_loaded
		stosb
		cmp al,'-'
		jnb gi_getnum
		call ungetc		; Unget non-numeric
gi_loaded:	mov byte [di],0
		mov si,NumBuf
		; Fall through to parseint

;
; parseint:	Convert an integer to a number in EBX
;		Get characters from string in DS:SI
;		Return CF on error
;		DS:SI points to first character after number
;
;               Syntaxes accepted: [-]dec, [-]0+oct, [-]0x+hex, val+K, val+M
;
parseint:
                push eax
                push ecx
		push bp
		xor eax,eax		; Current digit (keep eax == al)
		mov ebx,eax		; Accumulator
		mov ecx,ebx		; Base
                xor bp,bp               ; Used for negative flag
pi_begin:	lodsb
		cmp al,'-'
		jne pi_not_minus
		xor bp,1		; Set unary minus flag
		jmp short pi_begin
pi_not_minus:
		cmp al,'0'
		jb pi_err
		je pi_octhex
		cmp al,'9'
		ja pi_err
		mov cl,10		; Base = decimal
		jmp short pi_foundbase
pi_octhex:
		lodsb
		cmp al,'0'
		jb pi_km		; Value is zero
		or al,20h		; Downcase
		cmp al,'x'
		je pi_ishex
		cmp al,'7'
		ja pi_err
		mov cl,8		; Base = octal
		jmp short pi_foundbase
pi_ishex:
		mov al,'0'		; No numeric value accrued yet
		mov cl,16		; Base = hex
pi_foundbase:
                call unhexchar
                jc pi_km                ; Not a (hex) digit
                cmp al,cl
		jae pi_km		; Invalid for base
		imul ebx,ecx		; Multiply accumulated by base
                add ebx,eax             ; Add current digit
		lodsb
		jmp short pi_foundbase
pi_km:
		dec si			; Back up to last non-numeric
		lodsb
		or al,20h
		cmp al,'k'
		je pi_isk
		cmp al,'m'
		je pi_ism
		dec si			; Back up
pi_fini:	and bp,bp
		jz pi_ret		; CF=0!
		neg ebx			; Value was negative
pi_done:	clc
pi_ret:		pop bp
                pop ecx
                pop eax
		ret
pi_err:		stc
		jmp short pi_ret
pi_isk:		shl ebx,10		; x 2^10
		jmp short pi_done
pi_ism:		shl ebx,20		; x 2^20
		jmp short pi_done

;
; unhexchar:    Convert a hexadecimal digit in AL to the equivalent number;
;               return CF=1 if not a hex digit
;
unhexchar:
                cmp al,'0'
		jb uxc_ret		; If failure, CF == 1 already
                cmp al,'9'
                ja uxc_1
		sub al,'0'		; CF <- 0
		ret
uxc_1:          or al,20h		; upper case -> lower case
		cmp al,'a'
                jb uxc_ret		; If failure, CF == 1 already
                cmp al,'f'
                ja uxc_err
                sub al,'a'-10           ; CF <- 0
                ret
uxc_err:        stc
uxc_ret:	ret

;
;
; getline:	Get a command line, converting control characters to spaces
;               and collapsing streches to one; a space is appended to the
;               end of the string, unless the line is empty.
;		The line is terminated by ^J, ^Z or EOF and is written
;		to ES:DI.  On return, DI points to first char after string.
;		CF is set if we hit EOF.
;
getline:
		call skipspace
                mov dl,1                ; Empty line -> empty string.
                jz gl_eof               ; eof
                jc gl_eoln              ; eoln
		call ungetc
gl_fillloop:	push dx
		push di
		call getc
		pop di
		pop dx
		jc gl_ret		; CF set!
		cmp al,' '
		jna gl_ctrl
		xor dx,dx
gl_store:	stosb
		jmp short gl_fillloop
gl_ctrl:	cmp al,10
		je gl_ret		; CF clear!
		cmp al,26
		je gl_eof
		and dl,dl
		jnz gl_fillloop		; Ignore multiple spaces
		mov al,' '		; Ctrl -> space
		inc dx
		jmp short gl_store
gl_eoln:        clc                     ; End of line is not end of file
                jmp short gl_ret
gl_eof:         stc
gl_ret:		pushf			; We want the last char to be space!
		and dl,dl
		jnz gl_xret
		mov al,' '
		stosb
gl_xret:	popf
		ret