ProfitPress Mega CDROM2 Shareware Freeware (MSDOS)(1992)(Eng)

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Assembly Source File | 1989-08-14 | 32.1 KB | 987 lines

.MODEL SMALL ;-----------------------------------------------------------------------; ; This file contains the procedures to handle disk I/O, such as reading ; ; and writing a disk sector. It also contains procedures that handle ; ; reading and writing of sectors within a file. ; ; ; ; One word of caution. As with the version in the book, Dskpatch ; ; assumes that sectors are 512 bytes. If your machine uses longer ; ; sectors, you may want to modify Dskpatch so that it handles longer ; ; sectors. In any case, the procedures that read and write file ; ; "sectors" are not dependent on the actual sector size. ; ; ; ; Here is a list of procedure in this file: ; ; ; ; INIT_DISK Initializes variables, etc. ; ; TRAP_DISK_ERRORS Handles disk errors for file functions ; ; WRITE_IO_ERROR Writes or clears the error message ; ; WRITE_ERROR_MESSAGE Writes an error message on screen ; ; CLEAR_ERROR_MESSAGE Clears the last error message ; ; READ_SECTOR Read logical or file sector ; ; READ_LOGICAL_SECTOR Read a logical disk sector ; ; WRITE_SECTOR Write logical or file sector ; ; WRITE_LOGICAL_SECTOR Writes a logical sector to the disk ; ; PREVIOUS_SECTOR Read the previous sector from disk/file ; ; NEXT_SECTOR Read the next sector from disk/file ; ; CHANGE_DISK_DRIVE Change to a different disk drive ; ; READ_SECTOR_NUMBER Change to a sector, by number ; ; OPEN_NEW_FILE Open a file for reading and writing ; ; READ_FILE_NAME Read the name of the file to open ; ; OPEN_FILE Actually open the file ; ; QUIT_FILE_MODE Closes the open file ; ; READ_OFFSET_NUMBER Ask for the sector number within a file ; ; READ_FILE_SECTOR Actually read a sector from the file ; ; SET_FILE_POINTER Move to the start of a sector in file ; ; WRITE_FILE_SECTOR Writes a file's sector back to the disk ; ;-----------------------------------------------------------------------; .DATA EXTRN SECTOR:BYTE EXTRN DISK_DRIVE_NO:BYTE EXTRN CURRENT_SECTOR_NO:WORD EXTRN ERROR_MESSAGE_LINE_NO:BYTE ERROR_CODE_TABLE LABEL WORD DW OFFSET ERROR_0 DW OFFSET ERROR_1 DW OFFSET ERROR_2 DW OFFSET ERROR_3 DW OFFSET ERROR_4 DW OFFSET ERROR_5 DW OFFSET ERROR_6 DW OFFSET ERROR_7 DW OFFSET ERROR_8 DW OFFSET ERROR_9 DW OFFSET ERROR_A DW OFFSET ERROR_B DW OFFSET ERROR_C DW OFFSET ERROR_D ;Used by File I/O procedure DW OFFSET ERROR_E ;Used by File I/O procedure DW OFFSET ERROR_F ;Used by READ_FILE_SECTOR DW OFFSET ERROR_10 ;Used by FILE_WRITE_SECTOR ERROR_0 DB 'Write attempt on write-protected diskette',0 ERROR_1 DB 'Unknown unit',0 ERROR_2 DB 'Drive not ready',0 ERROR_3 DB 'Unknown command',0 ERROR_4 DB 'Data error (CRC)',0 ERROR_5 DB 'Bad request structure length',0 ERROR_6 DB 'Seek error',0 ERROR_7 DB 'Unknown media type',0 ERROR_8 DB 'Sector not found',0 ERROR_9 DB 'Printer out of paper',0 ERROR_A DB 'Write fault',0 ERROR_B DB 'Read fault',0 ERROR_C DB 'General failure',0 ERROR_D DB 'Error reading file',0 ;Used by File I/O procedures ERROR_E DB 'File not found',0 ;Used by File I/O procedures ERROR_F DB 'Read past end of file',0 ;Used by READ_FILE_S... ERROR_10 DB 'No room on disk',0 ;Used by WRITE_FILE_SECTOR READING_MESSAGE DB ' Reading...',0 WRITING_MESSAGE DB ' Writing...',0 PRESS_KEY DB 'Press any key to continue... ',0 BYTES_READ DW ? ;Bytes read by READ_FILE_SECTOR .CODE PUBLIC DISK_ERROR_FLAG, DISK_ERROR_CODE DISK_ERROR_FLAG DB 0 ;Used to keep track of errors DISK_ERROR_CODE DB 0 ;Error code from disk operation PUBLIC INIT_DISK ;-----------------------------------------------------------------------; ; This procedure initializes several things that Disk Patch needs to ; ; function properly: ; ; ; ; 1. It sets DISK_DRIVE_NO to the number of the current drive, ; ; rather than simply drive A:. This is useful if you start ; ; Dskpatch from a hard disk with no floppy disk in the drive. ; ; ; ; 2. It tells DOS to call TRAP_DISK_ERRORS whenever there is a ; ; disk error and we're reading a file. We use this so that ; ; we can report disk errors. ; ; ; ; Writes: DISK_DRIVE_NO ; ;-----------------------------------------------------------------------; INIT_DISK PROC MOV AH,19h ;Ask DOS for the disk drive number INT 21h MOV DISK_DRIVE_NO,AL ;Save this drive number MOV AL,24h ;Set INT 24H (ERROR) vector MOV AH,25h ;Set vector function LEA DX,TRAP_DISK_ERRORS INT 21h RET INIT_DISK ENDP PUBLIC TRAP_DISK_ERRORS ;-----------------------------------------------------------------------; ; DOS calls this procedure in case of INT 21h errors using an INT 24h ; ; call. ; ; ; ; This procedure saves the error code in DISK_ERROR_CODE, then returns ; ; to DOS with AL set to 0. This tells DOS to "ignore" the error. ; ; Dskpatch checks the error flag for errors after making INT 21h calls. ; ; ; ; Writes: DISK_ERROR_FLAG, DISK_ERROR_CODE ; ;-----------------------------------------------------------------------; TRAP_DISK_ERRORS PROC PUSH AX MOV AX,DI ;Get error code into AL MOV CS:DISK_ERROR_FLAG,1 ;Set the error flag MOV CS:DISK_ERROR_CODE,AL ;Save this disk error code POP AX MOV AL,0 ;Tell DOS to ignore this error IRET ;Let DOS return to Dskpatch TRAP_DISK_ERRORS ENDP PUBLIC WRITE_IO_ERROR ;-----------------------------------------------------------------------; ; This procedure writes an error message to the error message line. ; ; ; ; Uses: WRITE_ERROR_MESSAGE, CLEAR_ERROR_MESSAGE ; ; Reads: DISK_ERROR_FLAG, DISK_ERROR_CODE, ERROR_CODE_TABLE ; ;-----------------------------------------------------------------------; WRITE_IO_ERROR PROC PUSH BX PUSH DX CMP DISK_ERROR_FLAG,1 ;Was there an error? JE WRITE_MESSAGE ;Yes, then write the message CALL CLEAR_ERROR_MESSAGE ;No, then clear the message JMP DONE_WRITE_IO_ERROR ;We're all done here WRITE_MESSAGE: MOV BL,DISK_ERROR_CODE ;Get the error code XOR BH,BH ;Convert to a word SHL BX,1 ;Multiply by 2 for word look-up MOV DX,ERROR_CODE_TABLE[BX] ;Get address of error message CALL WRITE_ERROR_MESSAGE ;Display the error message DONE_WRITE_IO_ERROR: POP DX POP BX RET WRITE_IO_ERROR ENDP PUBLIC WRITE_ERROR_MESSAGE EXTRN GOTO_XY:PROC EXTRN WRITE_STRING:PROC EXTRN CLEAR_TO_END_OF_LINE:PROC EXTRN WRITE_ATTRIBUTE_N_TIMES:PROC ;-----------------------------------------------------------------------; ; This procedure writes an error message in the message area near the ; ; bottom of the screen. ; ; ; ; DS:DX Address of the error message ; ; ; ; Uses: GOTO_XY, WRITE_STRING, CLEAR_TO_END_OF_LINE ; ; WRITE_ATTRIBUTE_N_TIMES ; ; Reads: ERROR_MESSAGE_LINE_NO ; ;-----------------------------------------------------------------------; WRITE_ERROR_MESSAGE PROC PUSH CX PUSH DX MOV CX,DX ;Put the string address into CX MOV DH,ERROR_MESSAGE_LINE_NO ;Get the line number MOV DL,30 ;Indent message 30 spaces CALL GOTO_XY ;Move cursor to start of the message XCHG CX,DX ;Put the string address back into DX CALL WRITE_STRING ;Write the string here CALL CLEAR_TO_END_OF_LINE ;Then clear the rest of the line XCHG CX,DX ;Put the coordinates back into DX CALL GOTO_XY ;Move to the start of the message MOV DL,0Fh ;High-intensity attribute MOV CX,49 ;Set the entire line to bright CALL WRITE_ATTRIBUTE_N_TIMES POP DX POP CX RET WRITE_ERROR_MESSAGE ENDP PUBLIC CLEAR_ERROR_MESSAGE EXTRN GOTO_XY:PROC EXTRN CLEAR_TO_END_OF_LINE:PROC ;-----------------------------------------------------------------------; ; This procedure clears the error message which appears after a disk ; ; error. ; ; ; ; Uses: GOTO_XY, CLEAR_TO_END_OF_LINE ; ; Reads: ERROR_MESSAGE_LINE_NO ; ;-----------------------------------------------------------------------; CLEAR_ERROR_MESSAGE PROC PUSH DX MOV DH,ERROR_MESSAGE_LINE_NO ;Get the line number for the error XOR DL,DL ;Start of the message line CALL GOTO_XY ;Move to start of error message line CALL CLEAR_TO_END_OF_LINE ;Clear the entire line POP DX RET CLEAR_ERROR_MESSAGE ENDP PUBLIC READ_SECTOR .DATA EXTRN DISK_DRIVE_NO:BYTE EXTRN CURRENT_SECTOR_NO:WORD EXTRN FILE_FLAG:BYTE .CODE ;-----------------------------------------------------------------------; ; This procedure reads one sector (512 bytes) into SECTOR. ; ; ; ; Uses: CLEAR_SECTOR, READ_LOGICAL_SECTOR, READ_FILE_SECTOR ; ; WRITE_IO_ERROR ; ; Reads: DISK_ERROR_FLAG, FILE_FLAG ; ; Writes: DISK_ERROR_FLAG ; ;-----------------------------------------------------------------------; READ_SECTOR PROC MOV DISK_ERROR_FLAG,0 ;Clear the disk error flag before read CALL CLEAR_SECTOR ;Clear the sector before we start CMP FILE_FLAG,1 ;Are we in file mode? JE FILE_READ ;Yes, then read sector from file CALL READ_LOGICAL_SECTOR ;No, read a logical disk sector JMP JUST_READ_SECTOR ;Now check for errors FILE_READ: CALL READ_FILE_SECTOR ;Read a sector from the file JUST_READ_SECTOR: CMP DISK_ERROR_FLAG,1 ;Was there a disk error? JNE DONE_READ_SECTOR ;No, then we're all done CALL CLEAR_SECTOR ;Yes, then clear SECTOR DONE_READ_SECTOR: CALL WRITE_IO_ERROR ;Write or clear error message RET READ_SECTOR ENDP PUBLIC CLEAR_SECTOR .DATA EXTRN SECTOR:BYTE .CODE ;-----------------------------------------------------------------------; ; This procedure sets SECTOR to all 0s. Call this procedure before ; ; you try a read a sector so that the sector will be all 0s if there ; ; is an error. ; ; ; ; Writes: SECTOR ; ;-----------------------------------------------------------------------; CLEAR_SECTOR PROC PUSH AX ;Clear SECTOR to all 0s PUSH CX PUSH DI LEA DI,SECTOR ;Point to the sector buffer MOV CX,512 ;Number of bytes in one sector CLD ;Set direction for increment MOV AL,0 ;Store zeros in SECTOR REP STOSB ;Clear SECTOR POP DI POP CX POP AX RET CLEAR_SECTOR ENDP PUBLIC READ_LOGICAL_SECTOR .DATA EXTRN DISK_DRIVE_NO:BYTE EXTRN CURRENT_SECTOR_NO:WORD EXTRN SECTOR:BYTE LONG_SECTOR_NO DD 0 ;A 4-byte sector number SECTORS_TO_READ DW 1 ;Number of sectors to read BUFFER_OFFSET DW 0 ;Where to save the segment BUFFER_SEGMENT DW 0 .CODE ;-----------------------------------------------------------------------; ; This procedure reads a logical sector from the disk, using the DOS ; ; function 25h. ; ; ; ; Reads: DISK_DRIVE_NO, CURRENT_SECTOR_NO ; ; Writes: SECTOR, DISK_ERROR_FLAG, DISK_ERROR_CODE ; ;-----------------------------------------------------------------------; READ_LOGICAL_SECTOR PROC PUSH AX PUSH BX PUSH CX PUSH DX MOV AL,DISK_DRIVE_NO ;Drive number MOV CX,1 ;Read only 1 sector MOV DX,CURRENT_SECTOR_NO ;Logical sector number LEA BX,SECTOR ;Where to store this sector INT 25h ;Read the sector JNC READ_LOGICAL_NO_ERROR ;There wasn't an error, continue ;---------------------------------------------------------------; ; If we're using DOS 4.0 (or COMPAQ DOS 3.31) with a hard disk ; ; partition larger than 32MB, we'll get the error 0207 in AX. ; ; In this case we need to set up the register differently. ; ;---------------------------------------------------------------; CMP AX,207h ;Could this be an extended partition? JNE READ_LOGICAL_ERROR ;No, report the error POPF ;Pop old flags off the stack MOV AL,DISK_DRIVE_NO ;Set up for DOS 4.0 extended read MOV CX,-1 ;Tell DOS we're making special read MOV BX,CURRENT_SECTOR_NO ;Which sector to read MOV Word Ptr LONG_SECTOR_NO,BX LEA BX,SECTOR ;Where to save the sector MOV BUFFER_OFFSET,BX MOV BUFFER_SEGMENT,DS ;Which segment buffer is in LEA BX,LONG_SECTOR_NO ;DS:BX points to extended info INT 25h JNC READ_LOGICAL_NO_ERROR ;There wasn't an error READ_LOGICAL_ERROR: MOV DISK_ERROR_FLAG,1 ;Set the error flag MOV DISK_ERROR_CODE,AL ;And save the error code READ_LOGICAL_NO_ERROR: POPF ;Discard flags put on stack by INT 25h POP DX POP CX POP BX POP AX RET READ_LOGICAL_SECTOR ENDP PUBLIC WRITE_SECTOR EXTRN WRITE_STRING:PROC, WRITE_PROMPT_LINE:PROC .DATA EXTRN FILE_FLAG:BYTE .CODE ;-----------------------------------------------------------------------; ; This procedure writes a sector back to the disk. Note, if the last ; ; read resulted in an error (in which case the error flag will still ; ; be set) this procedure does nothing. ; ; ; ; Uses: WRITE_IO_ERROR, WRITE_STRING, WRITE_EDITOR_PROMPT ; ; WRITE_LOGICAL_SECTOR, WRITE_FILE_SECTOR ; ; Reads: FILE_FLAG, WRITING_MESSAGE, DISK_ERROR_FLAG ; ;-----------------------------------------------------------------------; WRITE_SECTOR PROC PUSH AX CMP DISK_ERROR_FLAG,0 ;Was there a disk error? JNE DONT_WRITE_SECTOR ;Yes, then don't write a sector LEA DX,WRITING_MESSAGE ;Provide feedback while we write CALL WRITE_STRING CMP FILE_FLAG,1 ;Are we in file mode? JE FILE_WRITE ;Yes, then write sector to file CALL WRITE_LOGICAL_SECTOR ;No, write a logical disk sector JMP JUST_WROTE_SECTOR ;Now check for errors FILE_WRITE: CALL WRITE_FILE_SECTOR ;Write a sector to the file JUST_WROTE_SECTOR: CMP DISK_ERROR_FLAG,1 ;Was there a disk error? JE WRITE_SECTOR_ERROR ;Yes, then report it DONE_WRITE_SECTOR: CALL WRITE_IO_ERROR ;Write or clear error message CALL WRITE_EDITOR_PROMPT DONT_WRITE_SECTOR: POP AX RET WRITE_SECTOR_ERROR: CALL WRITE_IO_ERROR ;Display the error message LEA DX,PRESS_KEY ;Display "Press any key..." message CALL WRITE_PROMPT_LINE ;Display this prompt CALL READ_KEY ;And read a character MOV DISK_ERROR_FLAG,0 ;Clear the error flag JMP DONE_WRITE_SECTOR ;We're all done WRITE_SECTOR ENDP PUBLIC WRITE_LOGICAL_SECTOR EXTRN WRITE_EDITOR_PROMPT:PROC .DATA EXTRN SECTOR:BYTE EXTRN DISK_DRIVE_NO:BYTE EXTRN CURRENT_SECTOR_NO:WORD .CODE ;-----------------------------------------------------------------------; ; This procedure writes a logical sector to the disk drive. Not, if ; ; the last read resulted in an error, this procedure won't write a ; ; sector to the disk. ; ; ; ; Reads: DISK_DRIVE_NO, CURRENT_SECTOR_NO ; ; Writes: SECTOR, DISK_ERROR_FLAG, DISK_ERROR_CODE ; ;-----------------------------------------------------------------------; WRITE_LOGICAL_SECTOR PROC PUSH AX PUSH BX PUSH CX PUSH DX MOV AL,DISK_DRIVE_NO ;Drive number MOV CX,1 ;Write 1 sector MOV DX,CURRENT_SECTOR_NO ;Logical sector LEA BX,SECTOR ;Get address of our sector INT 26h ;Write the sector to disk JNC WRITE_LOGICAL_NO_ERROR ;There wasn't an error, continue ;---------------------------------------------------------------; ; If we're using DOS 4.0 (or COMPAQ DOS 3.31) with a hard disk ; ; partition larger than 32MB, we'll get the error 0207 in AX. ; ; In this case we need to set up the registers differently. ; ;---------------------------------------------------------------; CMP AX,207h ;Could this be an extended partition? JNE WRITE_LOGICAL_ERROR ;No, report the error POPF ;Pop old flags off the stack MOV AL,DISK_DRIVE_NO ;Set up for DOS 4.0 extended read MOV CX,-1 ;Tell DOS we're making special read MOV BX,CURRENT_SECTOR_NO ;Which sector to read MOV Word Ptr LONG_SECTOR_NO,BX LEA BX,SECTOR ;Where to save the sector MOV BUFFER_OFFSET,BX MOV BUFFER_SEGMENT,DS ;Which segment buffer is in LEA BX,LONG_SECTOR_NO ;DS:BX points to extended info INT 26h JNC WRITE_LOGICAL_NO_ERROR ;There wasn't an error WRITE_LOGICAL_ERROR: MOV DISK_ERROR_FLAG,1 ;Set the error flag MOV DISK_ERROR_CODE,AL ;Save the error code WRITE_LOGICAL_NO_ERROR: POPF ;Discard the flag information POP DX POP CX POP BX POP AX RET WRITE_LOGICAL_SECTOR ENDP PUBLIC PREVIOUS_SECTOR EXTRN INIT_SEC_DISP:PROC EXTRN WRITE_STRING:PROC EXTRN WRITE_EDITOR_PROMPT:PROC .DATA EXTRN CURRENT_SECTOR_NO:WORD .CODE ;-----------------------------------------------------------------------; ; This procedure reads the previous sector, if possible ; ; ; ; Uses: WRITE_STRING, WRITE_EDITOR_PROMPT, INIT_SEC_DISP ; ; Reads: CURRENT_SECTOR_NO, READING_MESSAGE ; ; Writes: CURRENT_SECTOR_NO ; ;-----------------------------------------------------------------------; PREVIOUS_SECTOR PROC PUSH AX PUSH DX MOV AX,CURRENT_SECTOR_NO ;Get current sector number OR AX,AX ;Is sector number zero? JZ DONT_DECREMENT_SECTOR ;Yes, then we're all done DEC AX ;No, then subtract one MOV CURRENT_SECTOR_NO,AX ;Save new sector number LEA DX,READING_MESSAGE ;Provide feedback while we're reading CALL WRITE_STRING CALL INIT_SEC_DISP ;Display the new screen CALL WRITE_EDITOR_PROMPT ;Display the editor prompt DONT_DECREMENT_SECTOR: POP DX POP AX RET PREVIOUS_SECTOR ENDP PUBLIC NEXT_SECTOR EXTRN INIT_SEC_DISP:PROC EXTRN WRITE_STRING:PROC EXTRN WRITE_EDITOR_PROMPT:PROC .DATA EXTRN CURRENT_SECTOR_NO:WORD .CODE ;-----------------------------------------------------------------------; ; Read the next sector. ; ; ; ; Uses: WRITE_EDITOR_PROMPT, INIT_SEC_DISP, WRITE_STRING ; ; Reads: CURRENT_SECTOR_NO, READING_MESSAGE ; ; Writes: CURRENT_SECTOR_NO ; ;-----------------------------------------------------------------------; NEXT_SECTOR PROC PUSH AX PUSH DX MOV AX,CURRENT_SECTOR_NO ;Get the current sector number INC AX ;Move to next sector MOV CURRENT_SECTOR_NO,AX ;Save this new number LEA DX,READING_MESSAGE ;Provide feedback while we read CALL WRITE_STRING CALL INIT_SEC_DISP ;Display the new screen CALL WRITE_EDITOR_PROMPT POP DX POP AX RET NEXT_SECTOR ENDP PUBLIC CHANGE_DISK_DRIVE EXTRN READ_BYTE:PROC EXTRN WRITE_STRING:PROC EXTRN CHAR_TO_UPPER:PROC EXTRN WRITE_PROMPT_LINE:PROC EXTRN WRITE_EDITOR_PROMPT:PROC EXTRN INIT_SEC_DISP:PROC .DATA EXTRN DISK_DRIVE_NO:BYTE, DISK_PROMPT:BYTE EXTRN FILE_FLAG:BYTE, CURRENT_SECTOR_NO:WORD .CODE ;-----------------------------------------------------------------------; ; This procedure prompts for a new disk drive letter, like A, B, .... ; ; ; ; Uses: WRITE_PROMPT_LINE, WRITE_EDITOR_PROMPT, INIT_SEC_DISP ; ; WRITE_STRING, CHAR_TO_UPPER, READ_BYTE, QUIT_FILE_MODE ; ; Reads: DISK_PROMPT, FILE_FLAG, READING_MESSAGE ; ; Writes: DISK_DRIVE_NO, CURRENT_SECTOR_NO ; ;-----------------------------------------------------------------------; CHANGE_DISK_DRIVE PROC PUSH AX PUSH DX READ_DRIVE_LOOP: LEA DX,DISK_PROMPT ;Display prompt for drive letter CALL WRITE_PROMPT_LINE CALL READ_BYTE ;Get new disk-drive number CMP AH,0 ;Did it read one character? JNZ DONT_CHANGE_DRIVE ;No, don't change the drive number CMP AL,25 ;Yes, was it hex number <=25 decimal JBE CHANGE_DRIVE ;Yes, change drive number CMP AL,'0' ;No, is it a single digit number JB READ_DRIVE_LOOP ;Yes, convert to drive number CMP AL,'9' ;Is it a digit? JBE IS_SINGLE_DIGIT ;Yes, convert to drive number CALL CHAR_TO_UPPER ;Convert letter to upper-case CMP AL,'A' ;Is this a legal drive letter? JB READ_DRIVE_LOOP ;No, try again CMP AL,'Z' ;Is this a legal drive letter? JA READ_DRIVE_LOOP ;No, then try again IS_DRIVE_LETTER: ;Yes, then convert to drive number SUB AL,'A' ;Convert Upper letter to drive number JMP CHANGE_DRIVE ;Change the drive number IS_SINGLE_DIGIT: SUB AL,'0' ;Convert to drive number CHANGE_DRIVE: CALL QUIT_FILE_MODE ;Turn off file mode, if on MOV CURRENT_SECTOR_NO,0 ;And view sector 0 of new drive CHANGE_DRIVE_NOT_FILE: MOV DISK_DRIVE_NO,AL ;Save the new drive number LEA DX,READING_MESSAGE ;Provide some feedback while reading CALL WRITE_STRING ;Display this string CALL INIT_SEC_DISP ;And display the new sector DONT_CHANGE_DRIVE: CALL WRITE_EDITOR_PROMPT ;Display the Edit prompt POP DX POP AX RET CHANGE_DISK_DRIVE ENDP PUBLIC READ_SECTOR_NUMBER EXTRN WRITE_PROMPT_LINE:PROC, READ_DECIMAL:PROC EXTRN WRITE_STRING:PROC, INIT_SEC_DISP:PROC EXTRN WRITE_EDITOR_PROMPT:PROC .DATA EXTRN SECTOR_PROMPT:BYTE EXTRN CURRENT_SECTOR_NO:WORD, FILE_FLAG:BYTE .CODE ;-----------------------------------------------------------------------; ; This procedure prompts for the number of a new sector to read. ; ; ; ; Uses: WRITE_PROMPT_LINE, READ_DECIMAL, WRITE_STRING ; ; INIT_SEC_DISP, QUIT_FILE_MODE, WRITE_EDITOR_PROMPT ; ; Reads: SECTOR_PROMPT, READING_MESSAGE ; ; Writes: CURRENT_SECTOR_NO ; ;-----------------------------------------------------------------------; READ_SECTOR_NUMBER PROC PUSH AX PUSH DX LEA DX,SECTOR_PROMPT ;Prompt for the sector number CALL WRITE_PROMPT_LINE CALL READ_DECIMAL ;Read the new sector number into AX JC DONT_CHANGE_SECTOR ;Error, so exit without changing CALL QUIT_FILE_MODE ;Turn off file mode, if on MOV CURRENT_SECTOR_NO,AX ;Save the new sector number LEA DX,READING_MESSAGE ;Provide feedback while we read CALL WRITE_STRING CALL INIT_SEC_DISP ;Display the new sector DONT_CHANGE_SECTOR: CALL WRITE_EDITOR_PROMPT ;Display the Edit prompt POP DX POP AX RET READ_SECTOR_NUMBER ENDP PUBLIC OPEN_NEW_FILE EXTRN WRITE_STRING:PROC, INIT_SEC_DISP:PROC EXTRN WRITE_PROMPT_LINE:PROC, READ_KEY:PROC EXTRN WRITE_EDITOR_PROMPT:PROC .DATA EXTRN CURRENT_SECTOR_NO:WORD, FILE_FLAG:BYTE .CODE ;-----------------------------------------------------------------------; ; This procedure reads a file name, opens that file, and displays the ; ; first sector. ; ; ; ; If the open failed, puts you back to editing whatever you were ; ; editing before. ; ; ; ; NOTE: This procedure needs a lot of work. If you were in file mode ; ; when you ask to open a new file, this procedure closes the old ; ; file, then tries to open the new file. If there was an error ; ; reading the new file, or you just hit <Enter>, this procedure ; ; doesn't return to the file you were previously editing. ; ; instead, it returns to sector mode. See if you can change ; ; this procedure so that it returns to editing the last file you ; ; were on if you were in file mode. ; ; ; ; Uses: READ_FILE_NAME, OPEN_FILE, WRITE_STRING ; ; INIT_SEC_DISP, WRITE_IO_ERROR, WRITE_PROMPT_LINE ; ; READ_KEY, WRITE_EDITOR_PROMPT, QUIT_FILE_MODE ; ; Reads: READING_MESSAGE, DISK_ERROR_FLAG, PRESS_KEY ; ; Writes: CURRENT_SECTOR_NO, FILE_FLAG, DISK_ERROR_FLAG ; ;-----------------------------------------------------------------------; OPEN_NEW_FILE PROC PUSH AX PUSH DX CALL QUIT_FILE_MODE ;Turn off old file mode, if on CALL READ_FILE_NAME ;First, read in the file name OR AX,AX ;Did we read any characters? JLE DONE_OPEN_NEW_FILE ;No, then return without change LEA DX,READING_MESSAGE ;Yes, Provide feedback while we read CALL WRITE_STRING CALL OPEN_FILE ;Try to open this file CMP DISK_ERROR_FLAG,1 ;Was there an I/O error? JE OPEN_NEW_FILE_ERROR ;Yes, then report it. SET_FILE_MODE: MOV FILE_FLAG,1 ;No, signal now in file mode MOV CURRENT_SECTOR_NO,0 ;Start at beginning of file DONE_OPEN_NEW_FILE: CALL INIT_SEC_DISP ;Display this new sector CALL WRITE_IO_ERROR ;Display or clear error message CALL WRITE_EDITOR_PROMPT ;Display the Edit prompt POP DX POP AX RET ;-----------------------------------------------; ; Here we report the error, then pause until ; ; you press a key before returning to the ; ; previous mode and sector that you were ; ; viewing. ; ;-----------------------------------------------; OPEN_NEW_FILE_ERROR: CALL WRITE_IO_ERROR ;Display the error message LEA DX,PRESS_KEY ;Display prompt message CALL WRITE_PROMPT_LINE ;Display this prompt CALL READ_KEY ;Read one character JMP DONE_OPEN_NEW_FILE ;We're all done now OPEN_NEW_FILE ENDP PUBLIC READ_FILE_NAME EXTRN WRITE_PROMPT_LINE:PROC, READ_STRING:PROC .DATA EXTRN FILE_NAME_PROMPT:BYTE EXTRN FILE_NAME_STRING:BYTE EXTRN LENGTH_READ:BYTE EXTRN FILE_NAME:BYTE .CODE ;-----------------------------------------------------------------------; ; This procedure prompts for a file name, then reads in the file name. ; ; We've written this as a separate procedure only to make the code more ; ; readable. ; ; ; ; Returns: AX Number of characters read. ; ; -1 if you pressed a special key ; ; ; ; Uses: WRITE_PROMPT_LINE, READ_STRING ; ; Reads: FILE_NAME_PROMPT, FILE_NAME_STRING, LENGTH_READ ; ; Writes: FILE_NAME ; ;-----------------------------------------------------------------------; READ_FILE_NAME PROC PUSH BX PUSH DX LEA DX,FILE_NAME_PROMPT ;Display the "file name:" CALL WRITE_PROMPT_LINE ; prompt LEA DX,FILE_NAME_STRING ;Read in the file name READ_NAME_AGAIN: CALL READ_STRING MOV BL,LENGTH_READ ;Get number of OR BL,BL ;Was this a function key? JL DONE_READ_FILE_NAME ;Yes, then ignore it XOR BH,BH ;Clear the upper byte MOV FILE_NAME[BX],0 ;Convert string into ASCIIZ DONE_READ_FILE_NAME: MOV AL,BL ;Return the length of the string CBW ;Extend sign into the upper byte POP DX POP BX RET READ_FILE_NAME ENDP PUBLIC OPEN_FILE .DATA EXTRN FILE_HANDLE:WORD .CODE ;-----------------------------------------------------------------------; ; This procedure is used by OPEN_NEW_FILE to open a file for reading ; ; and writing. ; ; ; ; Reads: FILE_NAME ; ; Writes: DISK_ERROR_FLAG, DISK_ERROR_CODE, FILE_HANDLE ; ;-----------------------------------------------------------------------; OPEN_FILE PROC PUSH AX PUSH DX MOV DISK_ERROR_FLAG,0 ;Clear the error condition MOV AX,3D02h ;Open file for read/write LEA DX,FILE_NAME ;Get address of the file name INT 21h JC FILE_OPEN_ERROR ;There was an error, report it MOV FILE_HANDLE,AX ;Save this file handle DONE_OPEN_FILE: POP DX POP AX RET FILE_OPEN_ERROR: CMP AX,2 ;Is this a file-not-found message? JNE CHECK_ACCESS MOV AX,0Eh ;Error code for file-not-found JMP DONE_FILE_ERROR CHECK_ACCESS: MOV AX,0Dh ;General Error reading file message DONE_FILE_ERROR: MOV DISK_ERROR_FLAG,1 ;Set the error flag MOV DISK_ERROR_CODE,AL ;Save the new error code JMP DONE_OPEN_FILE ;We're all done, return. OPEN_FILE ENDP PUBLIC QUIT_FILE_MODE .DATA EXTRN FILE_HANDLE:WORD EXTRN CURRENT_SECTOR_NO:WORD .CODE ;-----------------------------------------------------------------------; ; This procedure checks to see if we're in file mode, and if so, it ; ; closes the file, then turns off file mode. ; ; ; ; Reads: FILE_HANDLE ; ; Writes: FILE_FLAG, CURRENT_SECTOR_NO, DISK_ERROR_FLAG ; ;-----------------------------------------------------------------------; QUIT_FILE_MODE PROC PUSH AX PUSH BX CMP FILE_FLAG,1 ;Are we in file mode? JNE DONE_QUIT_FILE ;No, then we're all done MOV AH,3Eh ;Ask to close this file MOV BX,FILE_HANDLE ;Get the file handle INT 21h ;Close this file MOV FILE_FLAG,0 ;Turn off file mode MOV CURRENT_SECTOR_NO,0 ;Move to start of disk MOV DISK_ERROR_FLAG,0 ;Ignore any error conditions DONE_QUIT_FILE: POP BX POP AX RET QUIT_FILE_MODE ENDP PUBLIC READ_OFFSET_NUMBER .DATA EXTRN OFFSET_PROMPT:BYTE EXTRN FILE_FLAG:BYTE, CURRENT_SECTOR_NO:WORD .CODE EXTRN WRITE_PROMPT_LINE:PROC, READ_DECIMAL:PROC EXTRN WRITE_STRING:PROC, INIT_SEC_DISP:PROC EXTRN WRITE_EDITOR_PROMPT:PROC ;-----------------------------------------------------------------------; ; This procedure reads in the sector offset within a file, then ; ; displays the new sector. ; ; ; ; Uses: WRITE_PROMPT_LINE, READ_DECIMAL, WRITE_STRING ; ; INIT_SEC_DISP, WRITE_EDITOR_PROMPT ; ; Reads: FILE_FLAG, OFFSET_PROMPT, READING_MESSAGE ; ; Writes: CURRENT_SECTOR_NO ; ;-----------------------------------------------------------------------; READ_OFFSET_NUMBER PROC PUSH AX PUSH DX CMP FILE_FLAG,1 ;In file mode? JNE READ_OFFSET_NOT_FILE_MODE ;No, then just ignore request LEA DX,OFFSET_PROMPT ;Yes, display the offset prompt CALL WRITE_PROMPT_LINE CALL READ_DECIMAL ;Read in the decimal number JC DONT_CHANGE_OFFSET ;Error, so exit without changing LEA DX,READING_MESSAGE ;Provide feedback while we read CALL WRITE_STRING MOV CURRENT_SECTOR_NO,AX ;Save the new number CALL INIT_SEC_DISP ;Draw the new display DONT_CHANGE_OFFSET: READ_OFFSET_NOT_FILE_MODE: CALL WRITE_EDITOR_PROMPT ;Display the Edit prompt POP DX POP AX RET READ_OFFSET_NUMBER ENDP PUBLIC READ_FILE_SECTOR .DATA EXTRN FILE_HANDLE:WORD EXTRN SECTOR:BYTE .CODE ;-----------------------------------------------------------------------; ; This procedure reads a random sector from a file. It also saves a ; ; count of the number of bytes actually read so that the write function ; ; won't increase the size of a file. ; ; ; ; Uses: SET_FILE_POINTER ; ; Reads: FILE_HANDLE, DISK_ERROR_FLAG ; ; Writes: SECTOR, DISK_ERROR_FLAG, DISK_ERROR_CODE, BYTES_READ ; ;-----------------------------------------------------------------------; READ_FILE_SECTOR PROC PUSH AX PUSH BX PUSH CX PUSH DX CALL SET_FILE_POINTER ;Set to start of current sector CMP DISK_ERROR_FLAG,1 ;Was there an error? JE DONE_READ_FILE_SECTOR ;Yes, then don't try to read sector MOV AH,3Fh ;Call for a read on this file MOV BX,FILE_HANDLE ;Get the file handle MOV CX,512 ;Read one sector of 512 bytes LEA DX,SECTOR ;Address of our sector buffer INT 21h ;Let DOS read this sector MOV BYTES_READ,AX ;Save number of bytes we read OR AX,AX ;Did we read anything from file? JZ READ_PAST_END ;No, we read past end of file, signal DONE_READ_FILE_SECTOR: POP DX POP CX POP BX POP AX RET READ_PAST_END: MOV DISK_ERROR_FLAG,1 ;Signal that there was an error MOV DISK_ERROR_CODE,0Fh ;Read-past-end error code JMP DONE_READ_FILE_SECTOR READ_FILE_SECTOR ENDP PUBLIC SET_FILE_POINTER .DATA EXTRN CURRENT_SECTOR_NO:WORD EXTRN FILE_HANDLE:WORD .CODE ;-----------------------------------------------------------------------; ; This procedure sets the file pointer to the sector number. ; ; ; ; Reads: CURRENT_SECTOR_NO, FILE_HANDLE ; ;-----------------------------------------------------------------------; SET_FILE_POINTER PROC PUSH AX PUSH BX PUSH CX PUSH DX MOV AX,CURRENT_SECTOR_NO ;Get sector number for sector to read MOV BX,512 ;Size of the sector MUL BX ;DX:AX = Offset from start of file MOV CX,AX ;DX:CX = Offset in bytes XCHG CX,DX ;CX:DX now contains the offset MOV AX,4200h ;Move to this position in the file MOV BX,FILE_HANDLE ;Get the file handle INT 21h ;Move the file pointer POP DX POP CX POP BX POP AX RET SET_FILE_POINTER ENDP PUBLIC WRITE_FILE_SECTOR .DATA EXTRN FILE_HANDLE:WORD .CODE ;-----------------------------------------------------------------------; ; This procedure writes a single sector back to the file that you were ; ; viewing. Note, this can change the length of the file if you write ; ; the last sector, and the file was not a multiple of 512 bytes. In ; ; such cases, this procedure will increase the file length to a ; ; multiple of 512 bytes. ; ; ; ; Uses: SET_FILE_POINTER ; Reads: DISK_ERROR_FLAG, FILE_HANDLE, BYTES_READ, SECTOR ;-----------------------------------------------------------------------; WRITE_FILE_SECTOR PROC PUSH AX PUSH BX PUSH CX PUSH DX CALL SET_FILE_POINTER ;Set to start of current sector CMP DISK_ERROR_FLAG,1 ;Was there an error? JE DONE_WRITE_FILE_SECTOR ;Yes, then don't try to write sector MOV AH,40h ;Call for a write to this file MOV BX,FILE_HANDLE ;Get the file handle MOV CX,BYTES_READ ;Don't write more than we read LEA DX,SECTOR ;Address of our sector buffer INT 21h ;Let DOS write this sector CMP DISK_ERROR_FLAG,1 ;Was there a disk error JE DONE_WRITE_FILE_SECTOR ;Yes, then return MOV AH,45h ;Duplicate the file handle INT 21h ;AX == the new file handle MOV BX,AX ;Put new file handle into AX MOV AH,3Eh ;Close duplicate handle to update INT 21h ;The changes we just made DONE_WRITE_FILE_SECTOR: POP DX POP CX POP BX POP AX RET WRITE_FILE_SECTOR ENDP END