Computer Select (Limited Edition)

home *** CD-ROM | disk | FTP | other *** search

/ Computer Select (Limited Edition) / Computer Select.iso / dobbs / v17n03 / ucrasm.exe / SOURCE.EXE / FILEIO.ASM < prev next >

Wrap

Assembly Source File | 1991-10-12 | 17.3 KB | 639 lines

;****************************************************************************** ; ; New routines and functions ; for the Stdlib package ; ; Featuring: ; - Opening and closing files ; - Creating new files ; - Blocked I/O: ; -Reading from files using getc ; -Writing to files using putc and puts ; - File-Buffer Flushing ; - File Seeking ; - File Deleting ; - File Renaming ; ;****************************************************************************** ; ; Written by: ; ; Mark Radleigh ; & ; Brian Harvey ; ; (CS 13) ; ;****************************************************************************** ; ; ;****************************************************************************** ; These externs are needed for this demonstration program. ;****************************************************************************** ; ; StdGrp group StdLib, StdData ; StdData segment para public 'sldata' ; ; Some useful constants: ; cr equ 13 lf equ 10 eos equ 0 EOF equ 04h ; true equ 1 false equ 0 NIL equ 0 ; ;****************************************************************************** ; The following is a Struct that contains all necessary information to ; handle multiple files opened or closed. ;****************************************************************************** ; ftype struc fbuffptr dd ? ;Buffer pointer that holds the Data fhandle dw ? ;DOS FileHandle findex dw ? ;Index into Buffer fcounter dw ? fflush_flag db ? ;Says if you can flush the buffer or not ftype ends ; ;****************************************************************************** ; The Folowing declares neccessary variables for the library. ; FILES is the base struct for the alloted number of files opened. ;****************************************************************************** ; FILES ftype 10 dup (<NIL,NIL,NIL,NIL,NIL>) Old_out_addrss dd 0 ;Keep the old address of output Old_in_addrss dd 0 ;Keep the old address of input current_fwrite dw ? ;Keep the current index of writing current_fread dw ? ;Keep the current index of reading ; ;****************************************************************************** ; The following are variables used by the demonstration program. ;****************************************************************************** ; fileptr dw ? fileptr2 dw ? fileptr3 dw ? ; StdData ends ; stdlib segment para public 'slcode' assume cs:StdGrp, ds:nothing ; extrn sl_SetOutAdrs:far, sl_GetOutAdrs:far extrn sl_SetInAdrs:far, sl_GetInAdrs:far extrn sl_malloc:far, sl_free:far ; ; ;---------------------------------------------------------------------------- ; Fcreate -> A procedure that creates a file for writing (Deletes any previous ; file of the same name.) ; INPUT-> ES:DI Contains the address of the filename for the new file. ; OUTPUT-> CARRY Flag is set if error occurs. ; OUTPUT-> AX contains the error code if carry flag is set, else AX ; contains the STDLIB FileHandle. ; public sl_fcreate sl_fcreate proc far push ds push dx push cx push si ; fcreate_read: xor si, si fcreate_test: cmp word ptr StdGrp:FILES[si].fbuffptr + 2, NIL jne fcreate_test2 cmp word ptr StdGrp:FILES[si].fbuffptr, NIL je Fcreate_file fcreate_test2: add si, size ftype cmp si, length FILES * size ftype jbe fcreate_test stc mov ax, 10 ;No more file buffer ->error jmp fcreate_done Fcreate_file: mov dx, es mov ds, dx ;get the segment adrs ready ;for DOS mov dx, di ;get the offset adrs ready ;for DOS mov ah, 3ch ;command for CREATE mov cx, 0 ;Tells DOS file is ARCHIVED. int 21h jc fcreate_done mov StdGrp:FILES[si].fflush_flag, true ;So we can flush ;the buffer! mov StdGrp:FILES[si].fhandle, ax mov ax, si call fmalloc_this ;Malloc space for the buffer ; fcreate_done: pop si pop cx pop dx pop ds ret sl_fcreate endp ; ;----------------------------------------------------------------------------- ; Fopen -> A procedure that opens a file for reading/writing. ; INPUT-> ES:DI Contains the address of the filename for the new file. ; OUTPUT-> CARRY Flag is set if error occurs. ; OUTPUT-> AX contains the error code if carry flag is set, else AX ; contains the STDLIB FileHandle. ; ; public sl_fopen sl_fopen proc far push cx push dx push si push di push ds push es cmp al, 1 ;Want to open for writing? je fopen_write cmp al, 0 ;Want to open for reading? je fopen_read stc mov ax, 5 ;Incorrect sub function passed in al jmp fopen_done ; ;-------------------------------------------------- ; Here we open the file for reading.. ; We first test to see if there is an open buffer, then we open the file, ; and if everything is ok, we Malloc space for the buffer. ; fopen_read: xor si, si fread_test: cmp word ptr StdGrp:FILES[si].fbuffptr + 2, NIL jne fread_test2 cmp word ptr StdGrp:FILES[si].fbuffptr, NIL je Open_file_r fread_test2: add si, size ftype cmp si, length FILES * size ftype jbe fread_test stc mov ax, 10 ;No more file buffers ->error jmp fopen_done ; Open_file_r: mov dx, es mov ds, dx mov dx, di mov ah, 3dh ; Code for opening for reading int 21h jc fopen_done mov StdGrp:FILES[si].fflush_flag, false ;so we don't flush the ;buffer mov StdGrp:FILES[si].fhandle, ax mov ax, si call fmalloc_this ;Get some buffer space jmp fopen_done ; ;-------------------------------------------------- ; Here we open the file for writing.. ; We first test to see if there is an open buffer, then we open the file, ; and if everything is ok, we Malloc space for the buffer. ; fopen_write: mov si, 0 fwrite_test: cmp word ptr StdGrp:FILES[si].fbuffptr + 2, NIL jne fwrite_test2 cmp word ptr StdGrp:FILES[si].fbuffptr, NIL je Open_file_w ; fwrite_test2: add si, size ftype cmp si, length FILES * size ftype jbe fwrite_test stc mov ax, 10 jmp fopen_done ; Open_file_w: mov dx, es mov ds, dx mov dx, di mov ah, 3dh ;Code for open for writing int 21h jc fopen_done mov StdGrp:FILES[si].fflush_flag, true ;So we do flush ;File buffer mov StdGrp:FILES[si].fhandle, ax mov ax, si call fmalloc_this ;Get some buffer space! ; fopen_done: pop es pop ds pop di pop si pop dx pop cx ret sl_fopen endp ; ;***************************************************************************** ; This small procedure Mallocs some space for our FILES buffer pointers, ; so we can read in and write out blocks at a time. ;***************************************************************************** ; fmalloc_this proc near mov cx, 256 call sl_malloc jnc FMalloc_it mov ax, 10 FMalloc_it: mov bx, es mov word ptr StdGrp:FILES[si].fbuffptr + 2, bx mov word ptr StdGrp:FILES[si].fbuffptr, di mov StdGrp:FILES[si].findex, 0 ret fmalloc_this endp ; ; ;--------------------------------------------------------------------------- ; Readon -> A procedure that changes the stdlib fuctions of character ; and string input to a specified file. ; -INPUT -> AX contains the FileHandle variable. ; public sl_freadon sl_freadon proc far push es push di push bx ;The following cmp instructions ;See if we have already set ;READON mov bx, word ptr StdGrp:Old_in_addrss + 2 cmp bx, 0 jne freadon_done mov di, word ptr StdGrp:Old_in_addrss cmp di, 0 jne freadon_done ; mov current_fread, ax call sl_GetInAdrs ;Get the origonal input adrs mov bx, es mov word ptr StdGrp:Old_in_addrss + 2, bx mov word ptr StdGrp:Old_in_addrss, di mov bx, cs ;Now we load in our fgetc mov es, bx lea di, sl_fgetc call sl_SetInAdrs ;Set to the new input adrs freadon_done: pop bx pop di pop es ret sl_freadon endp ; ;--------------------------------------------------------------------------- ; Readoff -> A procedure that resets the stdlib functions of character ; and string input. ; public sl_freadoff sl_freadoff proc far push es push di les di, StdGrp:Old_In_Addrss call sl_SetInAdrs mov word ptr StdGrp:Old_In_Addrss + 2, 0 mov word ptr StdGrp:Old_In_Addrss, 0 pop di pop es ret sl_freadoff endp ; ;---------------------------------------------------------------------------- ; Fgetc -> A procedure that is called whenever GETC is called and ; READON was called previously. ; NOTE: CARRY FLAG IS SET and AX contains 8 if it encounters EOF. ; public sl_fgetc sl_fgetc proc far push si push di push ds push dx push cx push bx ; mov si, StdGrp:current_fread ;Get the current ;Readfile index ;----------------- ;The following 4 instruc ;see if we have an ;available buffer... cmp word ptr StdGrp:FILES[si].fbuffptr + 2, NIL jne fgetc_getchar cmp word ptr StdGrp:FILES[si].fbuffptr, NIL je fgetc_nada fgetc_getchar: cmp StdGrp:FILES[si].fcounter, 0 je fget_new_block les di, StdGrp:FILES[si].fbuffptr add di, StdGrp:FILES[si].findex mov al, es:[di] inc StdGrp:FILES[si].findex dec StdGrp:FILES[si].fcounter jmp fgetc_done fget_new_block: lds dx, StdGrp:FILES[si].fbuffptr mov bx, StdGrp:FILES[si].fhandle mov cx, 256 mov ah, 3fh int 21h jc fgetc_done cmp ax, 0 ;How many bytes did it read in? je EOF_error mov StdGrp:FILES[si].fcounter, ax mov StdGrp:FILES[si].findex, 0 jmp fgetc_getchar fgetc_nada: stc mov ax, 6 ;Invalid FileHandle ;(Just a safeguard) EOF_error: stc mov ax, 8 ;End of file... ; fgetc_done: pop bx pop cx pop dx pop ds pop di pop si ret sl_fgetc endp ; ; ; ;------------------------------------------------------------------------------ ; ; Fclose - A procedure that closes an open file. ; - INPUT -> AX contains the FileHandle variable of the file to close. ; - OUTPUT -> Carry flag is set if error occurs. ; - OUTPUT -> Ax contains 6 which is invalid file handle error (if ; carry flag is set) or AX contains 7 if trouble with FREE. ; public sl_fclose sl_fclose proc far push bx push si mov si, ax mov bx, StdGrp:FILES[si].fhandle ;Move file handle into bx cmp StdGrp:FILES[si].fflush_flag, true jne fclose_it call far ptr sl_fflush ;Make sure the buffer is empty fclose_it: mov ah, 3eh int 21h les di, StdGrp:FILES[si].fbuffptr call sl_free ;Conserve space!!!!! jnc fclose_cont mov ax, 7 ;Trouble with FREE fclose_cont: mov word ptr StdGrp:FILES[si].fbuffptr + 2, 0 mov word ptr StdGrp:FILES[si].fbuffptr, 0 mov StdGrp:FILES[si].findex, 0 mov StdGrp:FILES[si].fcounter, 0 pop si pop bx ret sl_fclose endp ; ; ;------------------------------------------------------------------------------ ; Fflush -> A procedure that flushes the write buffer into the file. ; Usefull if user didn't read in 256 blocks ; INPUT -> AX contains the STDLIB FileHandle ; public sl_fflush sl_fflush proc far push di push si push ds push dx push cx push bx mov di, ax mov si, StdGrp:FILES[di].findex cmp si, 0 ;Is the buffer empty? je fwbuffempty mov cx, si ;The number of bytes to write lds dx, StdGrp:FILES[di].fbuffptr mov ah, 40h int 21h fwbuffempty: pop bx pop cx pop dx pop ds pop si pop di ret sl_fflush endp ;------------------------------------------------------------------------------ ; ; Writeon - A procedure that changes stdlib functions of character and string ; output to a specified file instead. ; -INPUT -> AX contains the FileHandle variable. ; public sl_fwriteon sl_fwriteon proc far push es push di push bx ;The following cmp instructions ;See if we have already set ;WRITEON ; mov bx, word ptr StdGrp:Old_out_addrss + 2 cmp bx, 0 jne fwriteon_done mov di, word ptr StdGrp:Old_out_addrss cmp di, 0 jne fwriteon_done ; mov StdGrp:current_fwrite, ax call sl_GetOutAdrs ;Get the original ouput address mov bx, es mov word ptr StdGrp:Old_out_addrss + 2, bx mov word ptr StdGrp:Old_out_addrss, di mov bx, cs ;Load in our fputc mov es, bx lea di, StdGrp:sl_fputc call sl_SetOutAdrs ;sets the ouput address to file fwriteon_done: pop bx pop di pop es ret sl_fwriteon endp ; ; ;------------------------------------------------------------------------------ ; Fputc -> A procedure that is called whenever PUTC is called and ; WRITEON was called previously. ; public sl_fputc sl_fputc proc far push si push di push ds push dx push cx push bx ; mov si, StdGrp:current_fwrite ;gets the current index of FILES ;The following comparisons see ;If we have a valid buffer.. cmp word ptr StdGrp:FILES[si].fbuffptr + 2, NIL jne fputc_do_this cmp word ptr StdGrp:FILES[si].fbuffptr, NIL je no_such_thing fputc_do_this: les di, StdGrp:FILES[si].fbuffptr add di, StdGrp:FILES[si].findex mov es:[di], al ;Stick that char in the buffer inc byte ptr StdGrp:FILES[si].findex jne fwrite_done ;If we hit 0, write the buffer! lds dx, StdGrp:FILES[si].fbuffptr mov bx, StdGrp:FILES[si].fhandle mov cx, 256 mov ah, 40h int 21h ; fwrite_done: pop bx pop cx pop dx pop ds pop di pop si ret no_such_thing: stc mov ax, 6 ;invalid filehandle ;(Safe guard - shouldn't happen) jmp fwrite_done sl_fputc endp ; ; ;--------------------------------------------------------------------------- ; Writeoff -> A procedure that resets the stdlib functions of character ; and string output. ; public sl_fwriteOff sl_fwriteOff proc far push es push di mov es, word ptr StdGrp:Old_out_addrss + 2 mov di, word ptr StdGrp:Old_out_addrss call sl_SetOutAdrs mov word ptr StdGrp:Old_out_addrss + 2, 0 mov word ptr StdGrp:Old_out_addrss, 0 pop di pop es ret sl_fwriteOff endp ; ; ; ; ;------------------------------------------------------------------------ ; Fseek -> Moves the File Pointer a specified # of Bytes.. ; INPUT-> AL contains the offset from where to start the file seeking. ; AL=0; Seek from the begining of the file. ; AL=1; Seek from the current pointer possition. ; AL=2; Seek backwards from the end of the file. ; INPUT-> SI contains the Unique FileHandle given by these procedures. ; INPUT-> CX:DX contains the number of bytes to seek (Unsigned number). ; OUTPUT -> Carry flag is set if error.. ; OUTPUT -> AX contains the error code. ; OUTPUT -> DX:AX contains the new file positoin if no error. ; public sl_fseek sl_fseek proc far push bx mov ah, 42h mov bx, StdGrp:FILES[si].fhandle ;Get the FileHandle int 21h pop bx sl_fseek endp ; ;----------------------------------------------------------------------- ; DOSHandle -> A procedure that returns the DOS given FileHandle. ; INPUT-> AX contains the stdlib given FileHandle. ; OUTPUT->Carry is set if error. ; OUTPUT->AX contains error code. ; AX=1; Invalid user input FileIndex. ; OUTPUT->AX contains the DOS FileHandle. ; public sl_DOSHandle sl_DOSHandle proc far push si mov si, ax cmp si, length FILES * size ftype ja Handle_error cmp si, 0 jb Handle_error clc mov ax, StdGrp:FILES[si].fhandle jmp DOS_Done Handle_error: stc mov ax, 1 DOS_Done: pop si ret sl_DOSHandle endp ; ;-------------------------------------------------------------------------- ; Fdel -> A procedure that deletes a file. ; INPUT->ES:DI contains the address of zero terminated pathname of file. ; OUTPUT -> CARRY Flag is set if error and ; AX=2 File not found ; AX=5 Access denied ; public sl_fdel sl_fdel proc far push ds push dx mov dx, es mov ds, dx mov dx, di mov ah, 41h int 21h pop dx pop ds ret sl_fdel endp ; ;-------------------------------------------------------------------------- ; Frename -> A procedure that renames one file to another. ; INPUT -> DX:SI contains the origonal pathname of the file. ; INPUT -> ES:DI contains the new pathname of the file. ; OUTPUT -> CARRY Flag is set if error and: ; AX=2 File not found ; AX=5 Access denied ; AX=17 Not the Same device ; public sl_frename sl_frename proc far push ds mov ds, dx mov dx, si mov ah, 56h int 21h pop ds ret sl_frename endp ; ; stdlib ends ; ; end