glblinit.asm

DOS 源代码 系列之 command 源码

Exit_Alloc_Fat_Buf:
	ret

Alloc_Fat_Buf	endp

;==========================================================================
;
;  Alloc_Fat_Sec_Buf : This procedure allocates a memory block for the fat 
;		       sector buffer which is used when copying chains from
;		       the old FAT to the new FAT.
;
;  Inputs   	  :  DeviceParameters.DP_BPB.BPB_BytesPerSector
;  Outputs	  :  CY CLEAR - FatSector pointer to buffer
;		     CY SET   - failure
;  Modifies	  :  AX, BX, FatSector
;
;==========================================================================

Alloc_Fat_Sec_Buf	proc	near
					; FatSector =
				 	; malloc( Bytes Per Sector )
	mov	BX, DeviceParameters.DP_BPB.BPB_BytesPerSector
	add	BX, 0fH
	shr	BX, 1			; Divide by 16 to get #paragraphs
	shr	BX, 1
	shr	BX, 1
	shr	BX, 1
	mov	AH, Alloc
	int	21h
	jc      Exit_Alloc_Fat_Sec_Buf
					; Base address of newly allocated
					; block is AX:0000
	mov	WORD PTR FatSector+2,AX
	xor	AX,AX
	mov	WORD PTR FatSector,AX

Exit_Alloc_Fat_Sec_Buf:
	ret

Alloc_Fat_Sec_Buf	endp

;===========================================================================
; Routine name:	Alloc_Header_Buf
;===========================================================================
;
; Description: Allocate the work buffers that will be needed by SAFE to
;	       build the restore file.
;
; Arguments:		None
; ---------------------------
; Returns:   		Carry set if error
; ----------------------------------------
; Registers destroyed:	AX BX DX
; ----------------------------------------
; Strategy:
; ---------
;	Allocate Buffer for file header	+ first root DIR sector
;===========================================================================

;Alloc_Header_Buf	 proc	 near
;
;	mov	BX,deviceParameters.DP_BPB.BPB_BytesPerSector ; Sector size
;	add	BX,(HEADER_SIZE + 15)		; Add header size and round
;						; for para conversion
;ConvertToParas:
;	shr	BX,1				; Convert to paragrphs by
;	shr	BX,1				; dividing by 16
;	shr	BX,1
;	shr	BX,1
;
;	mov	AH,48h				; DOS allocate memory function
;	int	21h
;	jc	Exit_Alloc_Header_Buf		; Check for error
;
;SaveAddresses:
;	mov	WORD PTR HeaderBuf[2],AX	; Save header buffer segment
;	mov	WORD PTR HeaderBuf,0		; Set offset to 0
;
;	add	AX,(Header_Size SHR 4)		; Find header buffer segment
;	mov	WORD PTR DirBuf[2],AX		; Save DIR buf segment address
;	mov	WORD PTR DirBuf,0		; Set offset to 0
;
;Exit_Alloc_Header_Buf:
;	ret
;
;Alloc_Header_Buf	endp



;==========================================================================
;
;  Alloc_DirBuf2  :  This procedure allocates a memory block for a 1-sector
;		     buffer.  This buffer is used when reading in the boot
;		     sector in Phase1.
;
;  Inputs   	  :  DeviceParameters.DP_BPB.BPB_BytesPerSector
;  Outputs	  :  CY CLEAR - DirBuf pointer to buffer
;		     CY SET   - failure
;  Modifies	  :  AX, BX, DirBuf
;
;==========================================================================

Alloc_DirBuf2	proc	near
					; DirBuf =
				 	; malloc( Bytes Per Sector )
	mov	BX, DeviceParameters.DP_BPB.BPB_BytesPerSector
	add	BX, 0fH
	shr	BX, 1			; Divide by 16 to get #paragraphs
	shr	BX, 1
	shr	BX, 1
	shr	BX, 1
	mov	AH, Alloc
	int	21h
	jc      Exit_Alloc_DirBuf2
					; Base address of newly allocated
					; block is AX:0000
	mov	WORD PTR DirBuf+2,AX
	xor	AX,AX
	mov	WORD PTR DirBuf,AX

Exit_Alloc_DirBuf2:
	ret

Alloc_DirBuf2	endp



;=========================================================================
; Alloc_Cluster_Buf	         : This	routine	will allocate a	buffer
;				   based on a cluster's	size.  If enough
;				   space does not exist, a cluster will
;				   be redefined	to a smaller size for
;				   purposes of sector retries.
;				   Note: This buffer is used only for bad
;				   tracks on hard disks.
;
;	 Inputs	 : DeviceParameters.DP_BPB.BPB_BytesPerSector
;		   DeviceParameters.DP_BPB.BPB_SectorsPerCluster
;
;	 Outputs : ClustBound_Flag	 - True	(space available)
;					   False(not enough space)
;		   ClustBound_Buffer_Seg - Pointer to buffer
;=========================================================================

Procedure Alloc_Cluster_Buf

	push	AX				; Save regs
	push	BX

	mov	AX,(Alloc shl 8)		; Allocate memory
	mov	BX,0ffffh			; Get available memory
	int	21h

	mov	AX, DeviceParameters.DP_BPB.BPB_BytesPerSector
	add	AX, 0fH
	shr	AX, 1
	shr	AX, 1
	shr	AX, 1
	shr	AX, 1
	mul	DeviceParameters.DP_BPB.BPB_SectorsPerCluster

	cmp	BX,AX				; Enough room
	jna	$$IF137 			; Yes

	mov	BX,AX				; Allocate needed memory
	mov	AX,(Alloc shl 8)
	int	21h
	mov	ClustBound_Buffer_Seg,AX	; Save pointer to buffer
	mov	ClustBound_Flag,True		; Signal space available
	jmp	SHORT $$EN137			; Not enough room

$$IF137:
	mov	ClustBound_Flag,False		; Signal not enough space

$$EN137:
	pop	BX				; Restore regs
	pop	AX

	ret

Alloc_Cluster_Buf ENDP

;=========================================================================
;
;  DO_SWITCH_S  :	This procedure will load the system files into
;			memory (if there's space) if the /s switch is
;			specified.
;
;  CALLS  :		ReadDos
;			SysPrm
;  CALLED BY :		Global_Init
;  STRATEGY :		The largest block of memory available is first
;			determined.  The program is aborted if this is zero.
;			This block is then allocated, and the system files
;			are read into it.  A prompt for the system disk
;			will be given if the system files are not found.
;
;=========================================================================

Do_Switch_S	proc	near

	test	SwitchMap,SWITCH_S
	jz	End_Do_Switch_S			; System files not required
						; allocate memory for system files
	mov	BX,0ffffh			; This call will actually fail
	mov	AH,Alloc			; so that BX returns max block avlbl
	int	21h

	or	BX,BX
	jz	MemErr  			; No memory
	mov	[mSize],BX			; Now allocate the largest block
	mov	AH,alloc
	int	21h
	jnc	Mem_OK

MemErr:
	mov	AX, seg data			; Check for memory allocation error
	mov	DS, AX
	Message msgOutOfMemory			; call PrintString
;	jmp	FatalExit
	stc 				; Let the jump to FatalExit be made
	jmp	SHORT End_Do_Switch_S	;  in the main routine, upon returning

Mem_OK:
	mov	[mStart],AX			; Save the starting paragraph

; =========================================================================
; This call to ReadDos may not be able to read in all of the DOS files if
; there is insufficient memory available. In that case the files will
; be read in after the disk is formatted. If the Drive being formatted is
; also the boot Drive this function will read the files from that
; Drive if there is enough memory. If there is insufficent memory it will
; force the files to be read from Drive A: if the Drive being formatted
; is also the boot Drive
; M011; Wrong: Try Boot, Then Default, Then sysprm (usually "A").
;       If not enough memory at boot time, we fail.
; =========================================================================

RdFrst:

;M011 - begin

	mov	AH,GET_DEFAULT_Drive		; Find out default Drive
	int	21h
	push	AX				; save default Drive
	mov	AH,Get_In_Vars			; Find out boot	Drive
	int	21h
						; get 1 based Drive ID
	mov	AL,BYTE PTR ES:[BX].SysI_Boot_Drive
	add	AL,40h				; Make it ASCII
	pop	BX				; restore default Drive
	cmp	AL,41h				; Q: Booted from Drive A?
	jnz	go_get_Bios			;  N: Not a special case
	cmp	bl,1				; Q: is	B: current Drive
	jnz	go_get_Bios			;  N: Not a special case
	jmp	short check_default		; check	default	Drive

go_get_Bios:					; Here to check booted
	call	Get_Host_Drive			; Translate to DblSpace host
	mov	SystemDriveLetter,AL		;   (if necessary)

	call	ReadDos
	jnc	CheckAllFilesIn

check_default:					; Here to check default
	mov	AH,GET_DEFAULT_Drive		; Find out default Drive
	int	21h
	add	AL,41h				; Make it ASCII, 1 based
	call	Get_Host_Drive			; Translate to DblSpace host
	mov	SystemDriveLetter,AL

TryThisOne:
	call	ReadDos				; Read BIOS and	DOS
	jnc	CheckAllFilesIn			; Files read in OK
NeedSys:
	call	SysPrm				; Prompt for system disk
	jmp	TryThisOne			; Try again

;M011 - end


CheckAllFilesIn:
				; abort program here if all system files
				; have not been read into memory, since
				; program fails when trying to read them
				; in after formatting is complete
	and	FileStat,3fh			; zero out 2 msb
	cmp	FileStat,2ah			; are all 3 sys files in memory?
	jne	MemErr				; no - abort program

	clc					; yes
End_Do_Switch_S:
	ret

Do_Switch_S	ENDP

;******************* START OF SPECIFICATIONS ***********************************
;Routine name: Get_Host_Drive
;*******************************************************************************
;
;Description: Given a drive letter in AL, check to see if it is a dblspace
;	      drive, and if so, translate the drive letter to the host
;	      drive letter.
;
;Called Procedures: None
;
;Input: ASCII drive letter in AL
;
;Output: drive letter in AL
;
;Change History: Created			11/21/92	 MD
;		 Cut and paste from SYS command 12/07/92	 JEM
;
;******************* END OF SPECIFICATIONS *************************************

public Get_Host_Drive

Get_Host_Drive PROC NEAR

        push    ax
   	mov	ax,4a11h	; DBLSPACE multiplex number
	xor	bx,bx		; inquire version number
	int	2fh
	or	ax,ax		; error?
	jnz	not_dblspace
	cmp	bx,'DM'		; stamp returned correctly?
	jnz	not_dblspace

;	DBLSPACE.BIN is loaded.  At this time:
;
;	(dx & 0x7fff) == driver internal version number
;	high bit of DH set of driver has not yet been permanently placed
;	cl == first disk letter reserved for DBLSPACE
;	ch == number of disk letters reserved for DBLSPACE

	mov	ax,4a11h	; DBLSPACE multiplex number
	mov	bx,1		; inquire drive map
        pop     dx
	push	dx
	sub	dl, 'A' 	; convert drv letter to 0 based drv number
	int	2fh
	test	bl,80h		; COMPRESSED bit true?
	jz	not_dblspace

;	Drive is compressed.  At this time:
;
;	(bl & 0x7f) == host drive's CURRENT drive number
;	bh          == CVF extension number
;
        mov     al,bl
	and	al,7Fh
	add	al, 'A' 	; convert drv number to drv letter
        cbw
        pop     dx
        push    ax

not_dblspace:
        pop     ax
        ret

Get_Host_Drive	ENDP

CODE	ENDS

	END