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431 lines
11 KiB
431 lines
11 KiB
PAGE ,132
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TITLE DXFIND.ASM -- Dos Extender Find File Routine
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; Copyright (c) Microsoft Corporation 1988-1991. All Rights Reserved.
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;***********************************************************************
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;
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; DXFIND.ASM -- Dos Extender Find File Routine
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;
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;-----------------------------------------------------------------------
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;
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; This module provides the locate file logic for the 286 DOS Extender.
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;
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;-----------------------------------------------------------------------
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;
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; 09/27/89 jimmat Original version -- considerable code taken from
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; old GetChildName routine in dxinit.asm.
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;
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;***********************************************************************
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.286p
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; -------------------------------------------------------
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; INCLUDE FILE DEFINITIONS
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; -------------------------------------------------------
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.xlist
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.sall
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include segdefs.inc
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include gendefs.inc
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.list
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; -------------------------------------------------------
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; GENERAL SYMBOL DEFINITIONS
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; -------------------------------------------------------
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; -------------------------------------------------------
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; EXTERNAL SYMBOL DEFINITIONS
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; -------------------------------------------------------
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extrn strcpy:NEAR
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extrn toupper:NEAR
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; -------------------------------------------------------
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; DATA SEGMENT DEFINITIONS
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; -------------------------------------------------------
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DXDATA segment
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extrn segPSP:WORD
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extrn rgbXfrBuf1:BYTE
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DXDATA ends
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; -------------------------------------------------------
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; CODE SEGMENT VARIABLES
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; -------------------------------------------------------
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DXCODE segment
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szPath db 'PATH',0
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szWindir db 'WINDIR',0
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DXCODE ends
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; -------------------------------------------------------
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subttl Find File Routine
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page
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; -------------------------------------------------------
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; FIND FILE ROUTINE
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; -------------------------------------------------------
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DXCODE segment
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assume cs:DXCODE
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; -------------------------------------------------------
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; FindFile -- This routine is used to locate a particular file.
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; If successful, this routine will setup the buffer in rgbXfrBuf1
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; at offset EXEC_PROGNAME with the string for the file name that
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; can be used in a DOS open call.
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;
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; This routine searches for the file in the following sequence:
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;
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; 1) If the file name contains a relative or complete path
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; component, only look for that particular file,
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;
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; otherwise:
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;
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; 1) Look int the environment for a WINDIR= variable, and if
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; found, check that directory first.
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; 2) Look in the directory the dos extender was loaded from
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; 3) Look in the current directory
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; 4) Look in all directories in the PATH environment variable
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;
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; NOTE: This routine must be called in real mode!
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;
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; Input: RELOC_BUFFER has the file name to search for.
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; EXEC_DXNAME has the complete path the dos extender
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; Output: EXEC_PROGNAME has complete path to child program.
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; Errors: returns CY set if unable to find child
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; Uses: All registers preserved
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assume ds:DGROUP,es:NOTHING,ss:NOTHING
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public FindFile
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FindFile proc near
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pusha
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push ds
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push es
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push ds
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pop es
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assume es:DGROUP
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; If the base file name contains a ':' '\' or '/', then we'll see if the
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; file can be found with that name. This isn't exactly the way Windows wants
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; us to search for kernel, but allows a user to specify a relative or complete
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; path on the command line. If we get run for Windows/286 pMode, the base
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; child name will not include any of these characters, so we will not make
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; this check.
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mov si,offset RELOC_BUFFER
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@@: lodsb
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or al,al
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jz fndf20 ;no path characters, go do other search
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cmp al,':'
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jz fndf10
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cmp al,'\'
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jz fndf10
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cmp al,'/'
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jnz @b
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; The name seems to include a path component. We just want to look for that
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; file, and only that file.
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fndf10: mov si,offset RELOC_BUFFER
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mov di,offset EXEC_PROGNAME
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mov dx,di
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call strcpy
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mov ax,4300h ;use get file attributes to check
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int 21h
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jmp fndf90 ;found it or not, either way we're done
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; The file name doesn't include a path component. If we were run for pMode
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; Windows, the environment should include a WINDIR= entry that points to
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; the Windows directory. Look for this env variable, and check that directory
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; first.
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fndf20:
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push es ;look for the
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push cs ;WINDIR= env variable
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pop es
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assume es:NOTHING
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mov di,offset DXCODE:szWindir
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call GetEnv
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pop es
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assume ds:NOTHING,es:DGROUP
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jnz fndf_dosx_dir
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; Found WINDIR, copy over the path name, add child name and search
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mov di,offset EXEC_PROGNAME ;copy WINDIR path
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mov dx,di
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call strcpy
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cmp byte ptr es:[di-1],'\' ;add trailing \ if necessary
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jz @f
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mov byte ptr es:[di],'\'
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inc di
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@@:
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push es ;ds back to DGROUP
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pop ds
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assume ds:DGROUP
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mov si,offset RELOC_BUFFER ;add child name
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call strcpy
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mov ax,4300h ;use get file attributes to check
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int 21h
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jc fndf_dosx_dir ;no there, go do next check
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jmp fndf90 ;found it!
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; Next, we try looking in the directory that the Dos Extender was loaded
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; from. Start with the complete path to the Dos Extender program file.
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fndf_dosx_dir:
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push es
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pop ds
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assume ds:DGROUP
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mov si,offset EXEC_DXNAME
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mov di,offset EXEC_PROGNAME
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mov dx,di
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call strcpy
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; Now, search backward from the end of the string until we find the
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; first backslash or colon. This will take us back past the file name
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; and leave us with the raw path.
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fndf24: dec di
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cmp di,dx ;check if we have gone back past the start
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; of the string. (DX still has the address
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; of the start of the buffer from above)
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jb fndf_cd ;and if so skip this part as the path is null.
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mov al,es:[di]
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cmp al,':'
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jz fndf26
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cmp al,'\'
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jnz fndf24
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; Add the file name string onto the raw path and see if the file exists.
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fndf26: inc di
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mov si,offset RELOC_BUFFER
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call strcpy
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mov ax,4300h ;use get file attributes to check
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int 21h
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jc fndf_cd
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jmp fndf90
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; We didn't find the file in the same directory as the Extender itself.
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; Now, try looking for the file in the current directory!
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fndf_cd:
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mov di,offset EXEC_PROGNAME ;build current directory path string
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dossvc 19h
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add al,'A'
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stosb ;drive letter
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mov ax,'\:'
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stosw
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xor dl,dl
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mov si,di
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dossvc 47h ;current directory
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mov al,es:[di] ;check if it's the root
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or al,al ;empty string?
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jz short fndf_cd_cpy ;yes, don't add another '\'
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@@: lodsb ;find end of string
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or al,al
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jnz @b
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mov byte ptr [si-1],'\' ;add ending \
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fndf_cd_cpy:
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mov di,si ;add base child name
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mov si,offset RELOC_BUFFER
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call strcpy
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mov dx,offset EXEC_PROGNAME ;use get file attributes to check
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mov ax,4300h
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int 21h
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jc fndf30
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jmp short fndf90
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; We didn't find it in the current directory, look at the PATH
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; environment variable and see if the file can be found in any of
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; its directories. First off, search for the PATH environment
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; string.
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fndf30:
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push es
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mov di,offset DXCODE:szPath ;point ES:DI to path str
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push cs
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pop es
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assume es:NOTHING
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call GetEnv ;find the path env var
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assume ds:NOTHING
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pop es
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assume es:DGROUP
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jnz fndf80 ;Z flag set if FOUND
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; We are pointing at the beginning of the path environment variable. We need
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; to loop for each directory specified to see if we can find the file in
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; that directory.
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mov bx,ds ;keep env segment in BX
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fndf40: mov ds,bx ;environment segment to DS
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assume ds:NOTHING
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mov al,ds:[si]
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or al,al ;check for end of path variable.
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jz fndf80 ;if so, we didn't find any directory with
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; the desired file in it.
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mov di,offset EXEC_PROGNAME
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fndf42: lods byte ptr [si]
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cmp al,';' ;is it the separator between strings in
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jz fndf52 ; the environment variable?
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or al,al ;is it the 0 at the end of the environment
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jz fndf50 ; string?
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stos byte ptr [di]
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jmp fndf42
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fndf50: dec si
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fndf52: push si ;save pointer to start of next string
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mov al,'\'
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cmp al,byte ptr es:[di-1] ;dir name already end with \ (root dir?)
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jnz fndf54
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dec di ; yes, don't make it two \'s
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fndf54: stos byte ptr [di]
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mov si,offset RELOC_BUFFER ;pointer to file base name
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mov ax,es ;put our data segment address in DS
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mov ds,ax
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assume ds:DGROUP
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call strcpy ;append file base name to path
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mov ax,4300h ;use get file attributes to check
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int 21h
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pop si ;restore pointer to start of next string
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jc fndf40
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jmp short fndf90
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; Unable to find the file
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fndf80: stc
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; Finished, successful or not
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fndf90:
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pop es
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pop ds
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popa
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ret
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FindFile endp
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; -------------------------------------------------------
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; GetEnv -- This routine searches the environment for a
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; specific variable.
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;
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; Input: ES:DI - far pointer to wanted variable name
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; Output: DS:SI - far pointer to variable value string
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; Errors: return Z true if variable located
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; Uses: DS:SI modified, all else preserved
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assume ds:DGROUP,es:NOTHING,ss:NOTHING
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public GetEnv
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GetEnv proc near
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push ax
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push dx
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push di
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; Point DS:SI to our environment block
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mov ds,segPSP
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assume ds:PSPSEG
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mov ds,segEnviron
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xor si,si
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assume ds:NOTHING
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; See if DS:SI is pointing at desired environment variable
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mov dx,di ;keep var name offset in dx
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gete10:
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cmp byte ptr es:[di],0 ;at end of variable name?
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jz gete50 ; yes, go check '=' & optional blanks
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gete20:
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lodsb ;get variable char
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call toupper ;just in case...
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cmp al,es:[di] ;match desired name so far?
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jnz gete30 ; no, go find the next var name
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inc di ;bump var pointer
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jmp short gete10 ; and keep on checking
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gete30:
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mov di,dx ;reset source name pointer
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or al,al ;already at end of this env var?!
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jz gete35
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@@: lodsb
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or al,al ;find next environment var name
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jnz @b
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gete35:
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cmp byte ptr ds:[si],0 ;at end of environment?
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jz gete80 ; yes, go fail the call
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jmp short gete10 ; no, try try again
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; Found the env variable, now skip the '=' and any spaces
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gete50:
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cmp byte ptr ds:[si],'=' ;when we get here, better be pointing
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jnz gete30 ; at an '='
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inc si
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@@: cmp byte ptr ds:[si],' ' ;skip any optional blanks
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jnz @f
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inc si
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jmp short @b
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@@:
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xor ax,ax ;set the Z flag
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jmp short @f
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gete80:
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or ax,si ;pretty sure this clears Z
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@@:
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pop di
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pop dx
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pop ax
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ret
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GetEnv endp
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; -------------------------------------------------------
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DXCODE ends
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;****************************************************************
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end
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