v4.0/src/DOS/OPEN.ASM

   1 ;       SCCSID = @(#)open.asm   1.1 85/04/10
   2 TITLE   DOS_OPEN - Internal OPEN call for MS-DOS
   3 NAME    DOS_OPEN
   4 ; Low level routines for openning a file from a file spec.
   5 ;   Also misc routines for sharing errors
   6 ;
   7 ;   DOS_Open
   8 ;   Check_Access_AX
   9 ;   SHARE_ERROR
  10 ;   SET_SFT_MODE
  11 ;   Code_Page_Mismatched_Error             ; DOS 4.00
  12 ;
  13 ;   Revision history:
  14 ;
  15 ;       Created: ARR 30 March 1983
  16 ;       A000    version 4.00   Jan. 1988
  17 ;
  18
  19 ;
  20 ; get the appropriate segment definitions
  21 ;
  22 .xlist
  23 include dosseg.asm
  24
  25 CODE    SEGMENT BYTE PUBLIC  'CODE'
  26         ASSUME  SS:DOSGROUP,CS:DOSGROUP
  27
  28 .xcref
  29 include dossym.inc
  30 include devsym.inc
  31 include fastopen.inc
  32 include fastxxxx.inc                   ;AN000;
  33 include ifssym.inc                     ;AN000;
  34 .cref
  35 .list
  36
  37 Installed = TRUE
  38
  39         i_need  NoSetDir,BYTE
  40         i_need  THISSFT,DWORD
  41         i_need  THISCDS,DWORD
  42         i_need  CURBUF,DWORD
  43         i_need  CurrentPDB,WORD
  44         i_need  CURR_DIR_END,WORD
  45         I_need  RetryCount,WORD
  46         I_need  Open_Access,BYTE
  47         I_need  fSharing,BYTE
  48         i_need  JShare,DWORD
  49         I_need  FastOpenFlg,byte
  50         I_need  EXTOPEN_ON,BYTE                   ;AN000;; DOS 4.00
  51         I_need  ALLOWED,BYTE                      ;AN000;; DOS 4.00
  52         I_need  EXTERR,WORD                       ;AN000;; DOS 4.00
  53         I_need  EXTERR_LOCUS,BYTE                 ;AN000;; DOS 4.00
  54         I_need  EXTERR_ACTION,BYTE                ;AN000;; DOS 4.00
  55         I_need  EXTERR_CLASS,BYTE                 ;AN000;; DOS 4.00
  56         I_need  CPSWFLAG,BYTE                     ;AN000;; DOS 4.00
  57         I_need  EXITHOLD,DWORD                    ;AN000;; DOS 4.00
  58         I_need  THISDPB,DWORD                     ;AN000;; DOS 4.00
  59         I_need  SAVE_CX,WORD                      ;AN000;; DOS 4.00
  60
  61 Break   <DOS_Open - internal file access>
  62
  63 ; Inputs:
  64 ;       [WFP_START] Points to WFP string ("d:/" must be first 3 chars, NUL
  65 ;               terminated)
  66 ;       [CURR_DIR_END] Points to end of Current dir part of string
  67 ;               ( = -1 if current dir not involved, else
  68 ;                Points to first char after last "/" of current dir part)
  69 ;       [THISCDS] Points to CDS being used
  70 ;               (Low word = -1 if NUL CDS (Net direct request))
  71 ;       [THISSFT] Points to SFT to fill in if file found
  72 ;               (sf_mode field set so that FCB may be detected)
  73 ;       [SATTRIB] Is attribute of search, determines what files can be found
  74 ;       AX is Access and Sharing mode
  75 ;         High NIBBLE of AL (Sharing Mode)
  76 ;               sharing_compat     file is opened in compatibility mode
  77 ;               sharing_deny_none  file is opened Multi reader, Multi writer
  78 ;               sharing_deny_read  file is opened Only reader, Multi writer
  79 ;               sharing_deny_write file is opened Multi reader, Only writer
  80 ;               sharing_deny_both  file is opened Only reader, Only writer
  81 ;         Low NIBBLE of AL (Access Mode)
  82 ;               open_for_read   file is opened for reading
  83 ;               open_for_write  file is opened for writing
  84 ;               open_for_both   file is opened for both reading and writing.
  85 ;
  86 ;         For FCB SFTs AL should = sharing_compat + open_for_both
  87 ;               (not checked)
  88 ; Function:
  89 ;       Try to open the specified file
  90 ; Outputs:
  91 ;       sf_ref_count is NOT altered
  92 ;       CARRY CLEAR
  93 ;           THISSFT filled in.
  94 ;       CARRY SET
  95 ;           AX is error code
  96 ;               error_file_not_found
  97 ;                       Last element of path not found
  98 ;               error_path_not_found
  99 ;                       Bad path (not in curr dir part if present)
 100 ;               error_bad_curr_dir
 101 ;                       Bad path in current directory part of path
 102 ;               error_invalid_access
 103 ;                       Bad sharing mode or bad access mode or bad combination
 104 ;               error_access_denied
 105 ;                       Attempt to open read only file for writting, or
 106 ;                       open a directory
 107 ;               error_sharing_violation
 108 ;                       The sharing mode was correct but not allowed
 109 ;                       generates an INT 24 on compatibility mode SFTs
 110 ; DS preserved, others destroyed
 111
 112         procedure   DOS_Open,NEAR
 113         DOSAssume   CS,<DS>,"DOS_Open"
 114         ASSUME  ES:NOTHING
 115
 116         MOV     [NoSetDir],0
 117         CALL    Check_Access_AX
 118         retc
 119         LES     DI,[THISSFT]
 120         XOR     AH,AH
 121 ; sleaze! move only access/sharing mode in.  Leave sf_isFCB unchanged
 122         MOV     BYTE PTR ES:[DI.sf_mode],AL ; For moment do this on FCBs too
 123         PUSH    ES
 124         LES     SI,[THISCDS]
 125         CMP     SI,-1
 126         JNZ     TEST_RE_NET
 127         POP     ES
 128 ;Extended open hooks
 129
 130         TEST    [EXTOPEN_ON],ext_open_on    ;FT. from extnded open              ;AN000;
 131         JZ      NOEXTOP                     ;FT. no, do normal                  ;AN000;
 132 IFS_extopen:                                                                    ;AN000;
 133         MOV     AL,byte ptr [SAVE_CX]       ;FT. al= create attribute           ;AN000;
 134         PUSH    AX                          ;FT. pass create attr to IFS        ;AN000;
 135         MOV     AX,(multNET SHL 8) OR 46    ;FT. issue extended open verb       ;AN000;
 136         INT     2FH                         ;FT.                                ;AN000;
 137         POP     BX                          ;FT. trash bx                       ;AN000;
 138         MOV     [EXTOPEN_ON],0              ;FT.                                ;AN000;
 139         JNC     update_size                 ;IFS. file may be opened            ;AN000;
 140         return                              ;FT.                                ;AN000;
 141 NOEXTOP:
 142 ;Extended open hooks
 143
 144
 145 IF NOT Installed
 146         transfer NET_SEQ_OPEN
 147 ELSE
 148         PUSH    AX
 149         MOV     AX,(multNET SHL 8) OR 22
 150         INT     2FH
 151         POP     BX                      ; clean stack
 152         return
 153 ENDIF
 154
 155 TEST_RE_NET:
 156         TEST    ES:[SI.curdir_flags],curdir_isnet
 157         POP     ES
 158         JZ      LOCAL_OPEN
 159 ;       CALL    IFS_SHARE_CHECK         ;IFS. check IFS share,may create share  ;AN000;
 160 ;       JC      nomore                  ;IFS. share violation                   ;AN000;
 161 ;Extended open hooks
 162
 163         TEST    [EXTOPEN_ON],ext_open_on    ;FT. from extnded open              ;AN000;
 164         JNZ     IFS_extopen                 ;FT. isuue extended open            ;AN000;
 165 ;Extended open hooks
 166
 167 IF NOT Installed
 168         transfer NET_OPEN
 169 ELSE
 170         PUSH    AX
 171         MOV     AX,(multNET SHL 8) OR 22
 172         INT     2FH
 173         POP     BX                      ; clean stack
 174 ;       JC      nomore                  ;IFS. error                             ;AN000;
 175 update_size:                                                                    ;AN000;
 176 ;       CALL    OWN_SHARE               ;IFS. IFS owns share ?                  ;AN000;
 177 ;       JZ      nomore2                 ;IFS. yes                               ;AN000;
 178 ;       MOV     AX,3                    ;IFS. update file size for all SFT      ;AN000;
 179 ;       LES     DI,ThisSFT              ;IFS.                                   ;AN000;
 180 ;       call    JShare + 14 * 4         ;IFS. call ShSu                         ;AN000;
 181 nomore2:
 182 ;       CLC
 183 nomore:
 184         return
 185 ENDIF
 186
 187 LOCAL_OPEN:
 188         EnterCrit   critDisk
 189
 190 ; DOS 3.3 FastOPen 6/16/86
 191
 192         OR      [FastOpenFlg],FastOpen_Set+Special_Fill_Set   ;  only open can
 193         invoke  GetPath
 194
 195
 196 ; DOS 3.3 FastOPen 6/16/86
 197
 198         JNC     Open_found
 199         JNZ     bad_path
 200         OR      CL,CL
 201         JZ      bad_path
 202 OpenFNF:
 203         MOV     AX,error_file_not_found
 204 OpenBadRet:
 205         AND     BYTE PTR CS:[FastOpenFlg],Fast_yes    ;; DOS 3.3
 206         STC
 207         LeaveCrit   critDisk
 208         JMP     Clear_FastOpen
 209
 210 bad_path:
 211         MOV     AX,error_path_not_found
 212         JMP     OpenBadRet
 213
 214 open_bad_access:
 215         MOV     AX,error_access_denied
 216         JMP     OpenBadRet
 217
 218 Open_found:
 219         JZ      Open_Bad_Access         ; test for directories
 220         OR      AH,AH
 221         JS      open_ok                 ; Devices don't have attributes
 222         MOV     ES,WORD PTR [CURBUF+2]  ; get buffer location
 223         MOV     AL,ES:[BX].dir_attr
 224         TEST    AL,attr_volume_id       ; can't open volume ids
 225         JNZ     open_bad_access
 226         TEST    AL,attr_read_only       ; check write on read only
 227         JZ      open_ok
 228 ;
 229 ; The file is marked READ-ONLY.  We verify that the open mode allows access to
 230 ; the read-only file.  Unfortunately, with FCB's and net-FCB's we cannot
 231 ; determine at the OPEN time if such access is allowed.  Thus, we defer such
 232 ; processing until the actual write operation:
 233 ;
 234 ; If FCB, then we change the mode to be read_only.
 235 ; If net_FCB, then we change the mode to be read_only.
 236 ; If not open for read then error.
 237 ;
 238         SaveReg <DS,SI>
 239         LDS     SI,[THISSFT]
 240         MOV     CX,[SI].sf_mode
 241         TEST    CX,sf_isFCB             ; is it FCB?
 242         JNZ     ResetAccess             ; yes, reset the access
 243         MOV     DL,CL
 244         AND     DL,sharing_mask
 245         CMP     DL,sharing_net_FCB      ; is it net FCB?
 246         JNZ     NormalOpen              ; no
 247 ResetAccess:
 248         AND     CX,NOT access_mask      ; clear access
 249         errnz   open_for_read
 250 ;       OR      CX,open_for_read        ; stick in open_for_read
 251         MOV     [SI].sf_mode,CX
 252         JMP     SHORT FillSFT
 253 ;
 254 ; The SFT is normal.  See if the requested access is open_for_read
 255 ;
 256 NormalOpen:
 257         AND     CL,access_mask          ; remove extras
 258         CMP     CL,open_for_read        ; is it open for read?
 259         JZ      FillSFT
 260         RestoreReg  <SI,DS>
 261         JMP     short open_bad_access
 262 ;
 263 ; All done, restore registers and fill the SFT.
 264 ;
 265 FillSFT:
 266         RestoreReg  <SI,DS>
 267 open_ok:
 268 ;;; File Tagging DOS 4.00
 269 ;       OR      AH,AH                  ;FT. device ?                            ;AN000;
 270 ;       JS      NORM0                  ;FT. yes, don't do code page matching    ;AN000;
 271 ;       CMP     [CPSWFLAG],0           ;FT. code page matching on               ;AN000;
 272 ;       JZ      NORM0                  ;FT. no                                  ;AN000;
 273 ;       CMP     ES:[BX].dir_CODEPG,0   ;FT. code page 0                         ;AN000;
 274 ;       JZ      NORM0                  ;FT. yes do nothing                      ;AN000;
 275 ;       PUSH    AX                     ;FT.                                     ;AN000;
 276 ;       invoke  Get_Global_CdPg        ;FT. get global code page                ;AN000;
 277 ;       CMP     ES:[BX].dir_CODEPG,AX  ;FT. equal to global code page           ;AN000;
 278 ;       JZ      NORM1                  ;FT. yes                                 ;AN000;
 279 ;       call    Code_Page_Mismatched_Error ;FT.                                 ;AN000;
 280 ;       CMP     AL,0                   ;FT. ignore ?                            ;AN000;
 281 ;       JZ      NORM1                  ;FT.                                     ;AN000;
 282 ;       POP     AX                     ;FT.                                     ;AN000;
 283 ;       JMP     open_bad_access        ;FT. set carry and return                ;AN000;
 284 NORM1:                                                                          ;AN000;
 285 ;       POP     AX                     ;FT.                                     ;AN000;
 286 NORM0:
 287
 288 ;;; File Tagging DOS 4.00
 289         invoke  DOOPEN                  ; Fill in SFT
 290         AND     BYTE PTR CS:[FastOpenFlg],Fast_yes    ;; DOS 3.3
 291         CALL    DO_SHARE_CHECK          ;
 292         JNC     Share_Ok
 293         LeaveCrit   critDisk
 294         JMP     Clear_FastOPen
 295
 296 SHARE_OK:
 297         MOV     AX,3
 298         LES     DI,ThisSFT
 299 if installed
 300         call    JShare + 14 * 4
 301 else
 302         Call    ShSU
 303 endif
 304 ;; DOS 4.00 10/27/86
 305         LES     DI,ThisSFT                         ; if this is a newly         ;AN000;
 306         CMP     ES:[DI.sf_firclus],0               ; created file then          ;AN000;
 307         JZ      no_fastseek                        ; do nothing                 ;AN000;
 308         MOV     CX,ES:[DI.sf_firclus]              ; first cluster #            ;AN000;
 309         LES     DI,ES:[DI.sf_devptr]               ; pointer to DPB             ;AN000;
 310         MOV     DL,ES:[DI.dpb_drive]               ; drive #                    ;AN000;
 311         invoke  FastSeek_Open                      ; call fastseek              ;AN000;
 312 no_fastseek:
 313
 314 ;; DOS 4.00 10/27/86
 315
 316         LeaveCrit   critDisk
 317
 318 ;
 319 ; Finish SFT initialization for new reference.  Set the correct mode.
 320 ;
 321 ;   Inputs:
 322 ;       ThisSFT points to SFT
 323 ;
 324 ;   Outputs:
 325 ;       Carry clear
 326 ;   Registers modified: AX.
 327
 328         entry   SET_SFT_MODE
 329         DOSAssume   CS,<DS>,"Set_SFT_Mode"
 330         ASSUME  ES:NOTHING
 331
 332         LES     DI,ThisSFT
 333         invoke  DEV_OPEN_SFT
 334         TEST    ES:[DI.sf_mode],sf_isfcb; Clears carry
 335         retz                            ; sf_mode correct
 336         MOV     AX,[CurrentPDB]
 337         MOV     ES:[DI.sf_PID],AX       ; For FCB sf_PID=PID
 338
 339 Clear_FastOpen:
 340         return                         ;;;;; DOS 3.3
 341
 342 EndProc DOS_Open
 343
 344 ; Called on sharing violations. ES:DI points to SFT. AX has error code
 345 ; If SFT is FCB or compatibility mode gens INT 24 error.
 346 ; Returns carry set AX=error_sharing_violation if user says ignore (can't
 347 ; really ignore).  Carry clear
 348 ; if user wants a retry. ES, DI, DS preserved
 349
 350 procedure SHARE_ERROR,NEAR
 351         DOSAssume   CS,<DS>,"Share_Error"
 352         ASSUME  ES:NOTHING
 353         TEST    ES:[DI.sf_mode],sf_isfcb
 354         JNZ     HARD_ERR
 355         MOV     CL,BYTE PTR ES:[DI.sf_mode]
 356         AND     CL,sharing_mask
 357         CMP     CL,sharing_compat
 358         JNE     NO_HARD_ERR
 359 HARD_ERR:
 360         invoke  SHARE_VIOLATION
 361         retnc                           ; User wants retry
 362 NO_HARD_ERR:
 363         MOV     AX,error_sharing_violation
 364         STC
 365         return
 366
 367 EndProc SHARE_ERROR
 368
 369
 370 ; Input: THISDPB, WFP_Start, THISSFT set
 371 ; Functions: check file sharing mode is valid
 372 ; Output: carry set, error
 373 ;         carry clear, share ok
 374
 375 procedure DO_SHARE_CHECK,NEAR
 376         DOSAssume   CS,<DS>,"DO_SHARE__CHECK"
 377         ASSUME  ES:NOTHING
 378         EnterCrit   critDisk            ; enter critical section
 379
 380 OPN_RETRY:
 381         MOV     CX,RetryCount           ; Get # tries to do
 382 OpenShareRetry:
 383         SaveReg <CX>                    ; Save number left to do
 384         invoke  SHARE_CHECK             ; Final Check
 385         RestoreReg  <CX>                ; CX = # left
 386         JNC     Share_Ok2               ; No problem with access
 387         Invoke  Idle
 388         LOOP    OpenShareRetry          ; One more retry used up
 389 OpenShareFail:
 390         LES     DI,[ThisSft]
 391         invoke  SHARE_ERROR
 392         JNC     OPN_RETRY               ; User wants more retry
 393 Share_Ok2:
 394         LeaveCrit   critDisk            ; leave critical section
 395         return
 396
 397 EndProc DO_SHARE_CHECK
 398
 399
 400 ; Input: ES:DI -> SFT
 401 ; Functions: check if IFS owns SHARE
 402 ; Output: Zero set, use IFS SHARE
 403 ;         otherwise, use DOS SHARE
 404
 405 procedure OWN_SHARE,NEAR                ;AN000;
 406         DOSAssume   CS,<DS>,"OWN_SHARE" ;AN000;
 407         ASSUME  ES:NOTHING              ;AN000;
 408
 409 ;       PUSH    DS                      ;IFS. save reg                          ;AN000;
 410 ;       PUSH    SI                      ;IFS. save reg                          ;AN000;
 411 ;       LDS     SI,ES:[DI.sf_IFS_HDR]   ;IFS. ds:si-> IFS header                ;AN000;
 412 ;       TEST    [SI.IFS_ATTRIBUTE],IFSUSESHARE  ;IFS. save reg                  ;AN000;
 413 ;       POP     SI                      ;IFS. retore reg                        ;AN000;
 414 ;       POP     DS                      ;IFS. restore reg                       ;AN000;
 415         return                          ;IFS. return                            ;AN000;
 416
 417 EndProc OWN_SHARE                       ;AN000;
 418
 419
 420 ; Input: THISCDS -> CDS
 421 ; Functions: check if IFS owns SHARE
 422 ; Output: Zero set, use IFS SHARE
 423 ;         otherwise, use DOS SHARE
 424
 425 procedure OWN_SHARE2,NEAR                 ;AN000;
 426         DOSAssume   CS,<DS>,"OWN_SHARE2"  ;AN000;
 427         ASSUME  ES:NOTHING                ;AN000;
 428
 429 ;       CMP     WORD PTR [THISCDS],-1   ;IFS. UNC ?                             ;AN000;
 430 ;       JZ      ifs_hasit               ;IFS. yes                               ;AN000;
 431 ;       PUSH    DS                      ;IFS. save reg                          ;AN000;
 432 ;       PUSH    SI                      ;IFS. save reg                          ;AN000;
 433 ;       LDS     SI,[THISCDS]            ;IFS. DS:SI -> ThisCDS                  ;AN000;
 434 ;       LDS     SI,[SI.curdir_IFS_HDR]  ;IFS. ds:si-> IFS header                ;AN000;
 435 ;       TEST    [SI.IFS_ATTRIBUTE],IFSUSESHARE  ;IFS.                           ;AN000;
 436 ;       POP     SI                      ;IFS. retore reg                        ;AN000;
 437 ;       POP     DS                      ;IFS. restore reg                       ;AN000;
 438 ifs_hasit:                              ;AN000;
 439         return                          ;IFS. return                            ;AN000;
 440
 441 EndProc OWN_SHARE2                      ;AN000;
 442
 443
 444 ; Input: ES:DI -> SFT
 445 ; Functions: set THISDPB
 446 ; Output: none
 447
 448 procedure SET_THISDPB,NEAR                     ;AN000;
 449         DOSAssume   CS,<DS>,"SET_THISDPB"      ;AN000;
 450         ASSUME  ES:NOTHING                     ;AN000;
 451
 452 ;       PUSH    DS                      ;IFS. save reg                          ;AN000;
 453 ;       PUSH    SI                      ;IFS. save reg                          ;AN000;
 454 ;       LDS     SI,[THISCDS]            ;IFS. ds:si-> CDS                       ;AN000;
 455 ;       LDS     SI,[SI.CURDIR_DEVPTR]   ;IFS. ds:si-> DPB                       ;AN000;
 456 ;       MOV     WORD PTR [THISDPB],SI   ;IFS. set THISDPB                       ;AN000;
 457 ;       MOV     WORD PTR [THISDPB+2],DS ;IFS.                                   ;AN000;
 458 ;       POP     SI                      ;IFS. retore reg                        ;AN000;
 459 ;       POP     DS                      ;IFS. restore reg                       ;AN000;
 460         return                          ;IFS. return                            ;AN000;
 461
 462 EndProc SET_THISDPB                     ;AN000;
 463
 464
 465 ; Input: ES:DI -> SFT
 466 ; Functions: check IFS share
 467 ; Output: none
 468
 469 procedure IFS_SHARE_CHECK,NEAR                     ;AN000;
 470         DOSAssume   CS,<DS>,"IFS_SHARE_CHECK"      ;AN000;
 471         ASSUME  ES:NOTHING                         ;AN000;
 472
 473
 474 ;       CALL    OWN_SHARE               ;IFS. IFS owns share                    ;AN000;
 475 ;       JZ      IFSSHARE                ;IFS. yes                               ;AN000;
 476 ;       PUSH    AX                      ;IFS. save mode                         ;AN000;
 477 ;       CALL    SET_THISDPB             ;IFS. set THISDPB for SHARE_VIOLATION   ;AN000;
 478 ;       CALL    DO_SHARE_CHECK          ;IFS. check share                       ;AN000;
 479 ;       POP     AX                      ;IFS. restore mode and share ok         ;AN000;
 480 IFSSHARE:                               ;AN000;
 481         return                          ;IFS. return                            ;AN000;
 482
 483 EndProc IFS_SHARE_CHECK                 ;AN000;
 484
 485 ; Inputs:
 486 ;       AX is mode
 487 ;         High NIBBLE of AL (Sharing Mode)
 488 ;               sharing_compat     file is opened in compatibility mode
 489 ;               sharing_deny_none  file is opened Multi reader, Multi writer
 490 ;               sharing_deny_read  file is opened Only reader, Multi writer
 491 ;               sharing_deny_write file is opened Multi reader, Only writer
 492 ;               sharing_deny_both  file is opened Only reader, Only writer
 493 ;         Low NIBBLE of AL (Access Mode)
 494 ;               open_for_read   file is opened for reading
 495 ;               open_for_write  file is opened for writing
 496 ;               open_for_both   file is opened for both reading and writing.
 497 ; Function:
 498 ;       Check this access mode for correctness
 499 ; Outputs:
 500 ;       [open_access] = AL input
 501 ;       Carry Clear
 502 ;               Mode is correct
 503 ;               AX unchanged
 504 ;       Carry Set
 505 ;               Mode is bad
 506 ;               AX = error_invalid_access
 507 ; No other registers effected
 508
 509         procedure Check_Access_AX
 510         DOSAssume   CS,<DS>,"Check_Access"
 511         ASSUME  ES:NOTHING
 512
 513         MOV     Open_Access,AL
 514         PUSH    BX
 515 ;
 516 ; If sharing, then test for special sharing mode for FCBs
 517 ;
 518         MOV     BL,AL
 519         AND     BL,sharing_mask
 520         CMP     fSharing,-1
 521         JNZ     CheckShareMode          ; not through server call, must be ok
 522         CMP     BL,sharing_NET_FCB
 523         JZ      CheckAccessMode         ; yes, we have an FCB
 524 CheckShareMode:
 525         CMP     BL,40h                  ; is this a good sharing mode?
 526         JA      Make_Bad_Access
 527 CheckAccessMode:
 528         MOV     BL,AL
 529         AND     BL,access_mask
 530         CMP     BL,2
 531         JA      Make_Bad_Access
 532         POP     BX
 533         CLC
 534         return
 535
 536 make_bad_access:
 537         MOV     AX,error_invalid_access
 538         POP     BX
 539         STC
 540         return
 541
 542 EndProc Check_Access_AX
 543
 544 ; Input: none
 545 ; Function: Issue Code Page Mismatched INT 24 Critical Error
 546 ; OutPut: AL =0    ignore
 547 ;            =3    fail
 548
 549 procedure Code_Page_Mismatched_Error,NEAR                ;AN000;
 550         DOSAssume   CS,<DS>,"Code_Page_Mismatched_Error" ;AN000;
 551         ASSUME  ES:NOTHING                               ;AN000;
 552
 553 ;       PUSH    DS                     ;FT.                                     ;AN000;
 554 ;       Context DS                     ;FT. ds=cs                               ;AN000;
 555 ;       MOV     AH,0A9H                ;FT. fail,ignore,device,write            ;AN000;
 556 ;       MOV     DI,error_I24_gen_failure                 ;FT. set error         ;AN000;
 557 ;       MOV     [EXTERR],error_Code_Page_Mismatched      ;FT.                   ;AN000;
 558 ;       MOV     [EXTERR_CLASS],errCLASS_NotFnd           ;FT.                   ;AN000;
 559 ;       MOV     [EXTERR_ACTION],errACT_Abort             ;FT.                   ;AN000;
 560 ;       MOV     [EXTERR_LOCUS],errLOC_Unk                ;FT.                   ;AN000;
 561 ;       MOV     word ptr [EXITHOLD + 2],ES               ;FT. save es:bp        ;AN000;
 562 ;       MOV     word ptr [EXITHOLD],BP                   ;FT.                   ;AN000;
 563 ;       invoke  NET_I24_ENTRY                            ;FT. issue int 24H     ;AN000;
 564 ;       POP     DS                                       ;FT.                   ;AN000;
 565 ;       return                                           ;FT.                   ;AN000;
 566
 567 EndProc Code_Page_Mismatched_Error                       ;AN000;
 568 CODE    ENDS
 569     END