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; SCCSID = @(#)util.asm 1.1 85/04/10
TITLE UTIL - Handle utilities
NAME UTIL
;
; Handle related utilities for MSDOS 2.X.
;
; pJFNFromHandle written
; SFFromHandle written
; SFFromSFN written
; JFNFree written
; SFNFree written
;
; Modification history:
;
; Created: MZ 1 April 1983
;
.xlist
;
; get the appropriate segment definitions
;
include dosseg.asm
CODE SEGMENT BYTE PUBLIC 'CODE'
ASSUME SS:DOSGROUP,CS:DOSGROUP
.xcref
INCLUDE DOSSYM.INC
INCLUDE DEVSYM.INC
.cref
.list
.sall
I_need CurrentPDB,WORD ; current process data block location
I_need SFT_Addr,DWORD ; pointer to beginning of table
I_Need PROC_ID,WORD ; current process ID
I_Need USER_ID,WORD ; current user ID
if debug
I_need BugLev,WORD
I_need BugTyp,WORD
include bugtyp.asm
endif
BREAK <pJFNFromHandle - return pointer to JFN table entry>
;
; pJFNFromHandle - Given a handle, return the pointer to the JFN location
; in the user's data space
; Inputs: BX - Handle
; Outputs: Carry Set
; AX has error code
; Carry reset
; ES:DI point to the handle spot
; Registers modified:
; If no error, ES:DI, else AX,ES
; NOTE:
; This routine is called from $CREATE_PROCESS_DATA_BLOCK which is called
; at DOSINIT time with SS NOT DOSGROUP
procedure pJFNFromHandle,NEAR
ASSUME CS:DOSGROUP,DS:NOTHING,ES:NOTHING,SS:NOTHING
MOV ES,[CurrentPDB] ; get user process data block
CMP BX,ES:[PDB_JFN_Length] ; is handle greater than allocated
JB JFNAdd ; no, get offset
fmt TypAccess,LevSFN,<"$p: Illegal JFN %x\n">,<BX>
MOV AL,error_invalid_handle ; appropriate error
ReturnCarry:
STC ; signal error
return ; go back
JFNAdd: LES DI,ES:[PDB_JFN_Pointer] ; get pointer to beginning of table
ADD DI,BX ; add in offset
ReturnNoCarry:
CLC ; no holes
return ; bye!
EndProc pJFNFromHandle
BREAK <SFFromHandle - return pointer (or error) to SF entry from handle>
;
; SFFromHandle - Given a handle, get JFN and then index into SF table
;
; Input: BX has handle
; Output: Carry Set
; AX has error code
; Carry Reset
; ES:DI has pointer to SF entry
; Registers modified: If error, AX,ES, else ES:DI
; NOTE:
; This routine is called from $CREATE_PROCESS_DATA_BLOCK which is called
; at DOSINIT time with SS NOT DOSGROUP
procedure SFFromHandle,NEAR
ASSUME CS:DOSGROUP,DS:NOTHING,ES:NOTHING,SS:NOTHING
CALL pJFNFromHandle ; get jfn pointer
retc ; return if error
CMP BYTE PTR ES:[DI],-1 ; unused handle
JNZ GetSF ; nope, suck out SF
fmt TypAccess,LevSFN,<"$p: Illegal SFN $x:$x\n">,<ES,DI>
MOV AL,error_invalid_handle ; appropriate error
jump ReturnCarry ; signal it
GetSF:
SaveReg <BX> ; save handle
MOV BL,BYTE PTR ES:[DI] ; get SFN
XOR BH,BH ; ignore upper half
CALL SFFromSFN ; get real sf spot
RestoreReg <BX> ; restore
return ; say goodbye
EndProc SFFromHandle
BREAK <SFFromSFN - index into SF table for SFN>
;
; SFFromSFN - index into SF tables for SFN.
;
; Input: BX has SF index
; Output: ES:DI points to SF entry
; Registers modified: ES:DI, BX only
; NOTE:
; This routine is called from SFFromHandle which is called
; at DOSINIT time with SS NOT DOSGROUP
procedure SFFromSFN,NEAR
ASSUME CS:DOSGROUP,DS:NOTHING,ES:NOTHING,SS:NOTHING
LES DI,[SFT_Addr] ; get pointer to beginning of table
ScanLoop:
CMP BX,ES:[DI].SFCount ; is handle in this table?
JB GetOffset ; yes, go grab it
SUB BX,ES:[DI].SFCount
LES DI,ES:[DI].SFLink ; get next table segment
CMP DI,-1 ; end of tables?
JNZ ScanLoop ; no, try again
STC ; error...
JMP SHORT Restore ; go restore
GetOffset:
SaveReg <AX> ; save AX
MOV AX,SIZE SF_Entry ; put it in a nice place
MUL BL ; times size
ADD DI,AX ; offset by size
RestoreReg <AX> ; get world back
ADD DI,SFTable ; offset into structure
CLC ; no holes
Restore:
return ; bye!
EndProc SFFromSFN
BREAK <JFNFree - return a jfn pointer if one is free>
;
; JFNFree - scan through the JFN table and return a pointer to a free slot
;
; Input: None.
; Output: Carry Set
; AX has error code, BX,ES,DI garbage
; Carry Reset
; BX has new handle, ES:DI is pointer to JFN slot
; Registers modified: As above only.
procedure JFNFree,NEAR
ASSUME CS:DOSGROUP,DS:NOTHING,ES:NOTHING,SS:DOSGROUP
XOR BX,BX ; try starting low
JFNScan:
CALL pJFNFromHandle ; get the appropriate handle
JC JFNNone ; no more handles
CMP BYTE PTR ES:[DI],-1 ; free?
JZ JFNFound ; yes, carry is clear
INC BX ; no, next handle
JMP JFNScan ; and try again
JFNNone:
MOV AL,error_too_many_open_files
JFNFound:
return ; bye
EndProc JFNFree
BREAK <SFNFree - find a free SFN>
;
; SFNFree - scan through the sf table looking for free entries
; Inputs: none
; Outputs: Carry Set - AX has error code, BX destroyed
; Carry Clear - BX has SFN
; ES:DI - pointer to SFT
; SFT_ref_count is set to 1
; Registers modified: none
Procedure SFNFree,NEAR
ASSUME CS:DOSGROUP,DS:NOTHING,ES:NOTHING,SS:DOSGROUP
XOR BX,BX ; start at beginning
SFNFreeLoop:
SaveReg <BX> ; Next call zaps BX
CALL SFFromSFN ; get the potential handle
RestoreReg <BX>
JNC SFNCheck ; no carry, check to see if its free
MOV AL,error_too_many_open_files ; appropriate error
JMP SFNDone
SFNCheck:
CMP ES:[DI.sf_Ref_Count],0 ; free?
IF NOT DEBUG
JZ SFNGot ; yep, got return him
ELSE
JNZ NoGot
JMP SFNGot
NoGot:
ENDIF
CMP ES:[DI.sf_ref_count],sf_busy
JNZ SFNNext ; not marked busy...
fmt TypAccess,LevSFN,<"$p: SFT $x:$x($x)is busy, owner $x:$x\n">,<ES,DI,BX,ES:[DI].sf_UID,ES:[DI].sf_pid>
SaveReg <BX>
MOV BX,User_ID
CMP ES:[DI.sf_UID],BX
JNZ SFNNextP
MOV BX,Proc_ID
CMP ES:[DI.sf_PID],BX
JZ SFNGotP
SFNNextP:
fmt TypAccess,LevSFN,<"$p: SFT unusable\n">
RestoreReg <BX>
SFNNext:
INC BX ; no, try next sf number
JMP SFNFreeLoop ; and go until it fails
SFNGot:
SaveReg <BX>
SFNGotP:
CLC ; no error
fmt TypAccess,LevSFN,<"$p: SFT $x:$x($x) marked busy\n">,<ES,DI,BX>
MOV ES:[DI.sf_ref_count],sf_busy ; make sure that this is allocated
MOV BX,User_ID
MOV ES:[DI.sf_UID],BX
MOV BX,Proc_ID
MOV ES:[DI.sf_PID],BX
RestoreReg <BX>
SFNDone:
return ; bye
EndProc SFNFree
CODE ENDS
END
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