805 lines
20 KiB
NASM
805 lines
20 KiB
NASM
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;*****************************************************************
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;
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; Copyrigth (C) 1984 Logitech. All Rights Reserved.
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;
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; Permission is hereby granted to registered users to use or
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; abstract the following program in the implementation of
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; customized versions. This permission does not include the
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; right to redistribute the source code of this program.
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;
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; LOGITECH SA. CH-1143 Apples, Switzerland
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;
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; Modula-2/86 Run Time Support package
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;
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; Module: LOADER.ASM
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; Loads Modula-2/86 '.LOD' files in memory
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; Version: 8086, RAM-based, MS-DOS 2.0 compatible
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; Release: 1.1 - Dec 84
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;
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;*****************************************************************
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CGROUP group code
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DGROUP group data
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assume CS: CGROUP
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assume DS: DGROUP
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assume ES: NOTHING
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assume SS: NOTHING
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include RTS.INC
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;*****************************************************************************
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; EXPORT QUALIFIED
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public LoadProg
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;*****************************************************************************
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data segment public 'data'
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; FROM RTS IMPORT
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extrn base_page:byte
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extrn START_MEM: word
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extrn MEM_SIZE: word
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data ends
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;*****************************************************************************
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;*****************************************************************************
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code segment public 'code'
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; FROM RTS IMPORT
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extrn WRITE_MSG: near
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code ends
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;*****************************************************************************
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;*****************************************************************************
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data segment public 'data'
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LD_FILE_HANDLE DW ? ; Load file handle
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LD_FILE_SPEC DB 64 DUP(?) ; Holds complete filename
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DEFAULT_NAME db 'MODULA ' ; default file to load
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; must be 8 characters long
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DEFAULT_TYPE db 'LOD' ; default filetype for loading
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; must be 3 characters long
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DEFAULT_PATH db '\M2LOD\' ; default directory for load-files
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DEF_PATH_LENGTH equ 7H
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FILE_MSG1 db ' '
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FILE_MSG2 db ' not found in current directory or in \M2LOD$'
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NO_FILE db 'File not found: $'
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NO_MEMORY db 'Insufficient Memory: $'
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;; - load error table and messages -
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badstr db '** Bad Structure - $'
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badver db '** Bad Version or Target system - $'
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badeof db '** Unexpected EOF - $'
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badmem db '** Insufficient Memory - $'
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badchk db '** Bad Checksum - $'
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baderr db '** LOAD error table fu - $'
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even
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LdErr dw badstr,badver,badeof,badmem,badchk,baderr
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data ends
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;*****************************************************************************
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;*****************************************************************************
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code segment public 'code'
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;-----------------------------------------------------------------
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LoadProg proc near
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; Finds the filename of the program to run and loads it in memory
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; It also builds the module-table.
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; in: AX prog id to use
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; CX:DX most recent entry in module-table
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;
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; out: BX status (0=ok)
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; ES:DI start address of Modula-2 program
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; CX:DX last module entry added to modula-table
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;
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PUSH CX
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PUSH DX
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PUSH AX
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CALL FIND_FILE
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POP AX
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POP DX
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POP CX
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CMP BX, 0FFFFH ; FIle found ?
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JNE LOAD_IT ; yes
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RET ; no
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LOAD_IT:
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CALL LOAD_FILE
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push bx
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call CLOSE_LOAD_FILE
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pop bx
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test bx,bx ; load ok?
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jz LOADED ; yes
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dec bx
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shl bx,1
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mov dx,LdErr[bx]
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CALL WRITE_MSG
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CALL WRITE_FILE_NAME
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MOV BX, 0FFFFH ; error return
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LOADED:
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RET
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LoadProg endp
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;---------------------------------------------------------------
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WRITE_FILE_NAME:
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mov di,offset LD_FILE_SPEC
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WFN1:
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cmp byte ptr[di],0
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je WFN3
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inc di
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jmp WFN1
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WFN3:
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mov byte ptr[di],'$'
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mov dx,offset LD_FILE_SPEC
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call WRITE_MSG
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ret
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;---------------------------------------------------------------
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FIND_FILE proc near
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; Finds the filename according to a search strategy and opens
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; the file. The file handle is stored in LD_FILE_HANDLE.
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; Upon return BX indicates if file successfully opened (0FFFFH = not ok)
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; First we look for the filename, which the operator
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; has entered:
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CALL GET_SPECIFIED_NAME
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CALL OPEN_LOAD_FILE
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JNB FOUND
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; Not found. Let's look in the Load-File default directory.
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; This second search is not done, if pathname was specified:
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MOV SI, OFFSET LD_FILE_SPEC
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SEARCH_SLASH:
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CMP BYTE PTR [SI],"\"
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JE NOT_FOUND ; path speficied, so don't retry
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CMP BYTE PTR [SI],0
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JE SECOND_LOOKUP
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INC SI
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JMP SEARCH_SLASH
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NOT_FOUND:
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MOV DX, OFFSET NO_FILE
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CALL WRITE_MSG
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CALL WRITE_FILE_NAME
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MOV BX, 0FFFFH ; some invalid handle
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RET
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SECOND_LOOKUP:
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; There was no directory specified
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CALL GET_SECOND_NAME
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CALL OPEN_LOAD_FILE
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JNB FOUND
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; not in default directory neither:
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MOV DX, OFFSET FILE_MSG1
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CALL WRITE_MSG
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MOV BX, 0FFFFH ; some invalid handle
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RET
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FOUND:
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MOV BX, 0
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RET
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FIND_FILE endp
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;-----------------------------------------------------------
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GET_SPECIFIED_NAME:
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; Builds the program name out of what the operator typed plus
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; the default parts for name and extension. Default drive and
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; directory are the current-one. The so constructed filename
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; is stored in variable LD_FILE_SPEC
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; No parameters for this procedure.
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mov di,offset LD_FILE_SPEC
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mov si,DEFAULT_DMA + offset base_page
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cld
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mov cx,0
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; check if operator gave a program name:
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mov cl,byte ptr[si]
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inc si
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jcxz USE_DEF_NAME ; no command tail, use default name
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; there is a command tail, skip leading blancs:
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SKIP_BLANK:
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lodsb ; look for first non-blank
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cmp al,' '
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jne PUT_FN_CHAR ; that must be file name
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loop SKIP_BLANK
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jmp USE_DEF_NAME ; only blanks, use default name
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GET_FN_CHAR: ; read char from name in command tail
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lodsb
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cmp al,' '
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jbe END_PROG_NAME ; until 'wrong' char
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cmp al,'*'
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jbe put_fn_char
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cmp al,','
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jbe END_PROG_NAME ; until 'wrong' char
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cmp al,'.'
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je END_PROG_NAME ; until 'wrong' char
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cmp al,'/'
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je END_PROG_NAME ; until 'wrong' char
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cmp al,':'
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jbe put_fn_char
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cmp al,'>'
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jbe END_PROG_NAME ; until 'wrong' char
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cmp al,'Z'
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jbe put_fn_char
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cmp al,'['
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je END_PROG_NAME ; until 'wrong' char
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cmp al,']'
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je END_PROG_NAME ; until 'wrong' char
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cmp al,'^'
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je END_PROG_NAME ; until 'wrong' char
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cmp al,'~'
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ja END_PROG_NAME ; until 'wrong' char
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PUT_FN_CHAR:
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stosb
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loop GET_FN_CHAR ; or end of command line
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inc si ; pretend we saw a blank..
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END_PROG_NAME:
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dec si ; SI is adjusted to pos of terminating blanc
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cmp byte ptr[si-1],":" ; was only the device there?
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je USE_DEF_NAME ; yes, so set the default name.
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SEARCH_DOT:
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dec si
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cmp byte ptr[si],"."
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je EXT_END ; extension already here.
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cmp si,DEFAULT_DMA ; at start of command tail?
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ja SEARCH_DOT ; no: keep looking for '.'
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jmp USE_DEF_EXT ; yes: no extension, supply one.
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USE_DEF_NAME:
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mov si,offset DEFAULT_NAME
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mov cx,8
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COPY_FN_CHAR:
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movsb
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dec cx
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jz USE_DEF_EXT
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cmp byte ptr[si]," "
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jne COPY_FN_CHAR
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USE_DEF_EXT: ; end of all the 'write filename' loops
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mov byte ptr[di],"."
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inc di
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mov si,offset DEFAULT_TYPE
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mov cx,3
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COPY_EXT_CHAR:
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cmp byte ptr[si]," "
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je EXT_END
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movsb
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dec cx
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jnz COPY_EXT_CHAR
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EXT_END: ; name is complete
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mov byte ptr[di],0
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RET
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;------------------------------------------------------------
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GET_SECOND_NAME:
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mov cx,15
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mov di,offset FILE_MSG1
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mov si,offset LD_FILE_SPEC
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cld
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rep movsb
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mov cx,64-DEF_PATH_LENGTH
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mov di,offset LD_FILE_SPEC+63
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mov si,offset LD_FILE_SPEC+63-DEF_PATH_LENGTH
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std ; move filename towards the end,
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rep movsb ; so path can be inserted.
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mov di,offset LD_FILE_SPEC+2
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cmp byte ptr[di]-1,":"
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je INS_PATH
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mov di,offset LD_FILE_SPEC
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INS_PATH:
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mov si,offset DEFAULT_PATH
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cld
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mov cx,DEF_PATH_LENGTH
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rep movsb ; insert path
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ret
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;------------------------------------------------------------
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OPEN_LOAD_FILE:
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MOV AX, 3D00H ; open file for READ only
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MOV DX, offset LD_FILE_SPEC
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INT OS
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MOV LD_FILE_HANDLE, AX
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RET
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;------------------------------------------------------------
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READ_LD_FILE:
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mov bx,LD_FILE_HANDLE
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mov cx,LdBufSize
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mov dx,offset LdBuf
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mov ah,3FH
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int OS ; sequential read
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RET
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;------------------------------------------------------------
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CLOSE_LOAD_FILE:
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MOV AH, 3EH
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MOV BX, LD_FILE_HANDLE
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INT OS
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RET
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;------------------------------------------------------------
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; Alloc_Mem - called by LoadProg to allocate memory for the 'IPL'
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;
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; in: AX memory request size, in paragraphs
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; out: AX first paragraph of allocated chunk
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; BX =0 if ok, <>0 if memory not available
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;
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Alloc_Mem:
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mov bx,1
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cmp ax, MEM_SIZE ; can request be satisfied?
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ja AllFU ; no
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sub MEM_SIZE,ax ; yes
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add ax, START_MEM ; compute next free paragraph..
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xchg ax, START_MEM ; update start_mem, return old value
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xor bx,bx
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AllFU: ret
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;*****************************************************************************
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data segment public 'data'
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currentVersion equ 1
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targetSystem equ 0
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NameLength equ 24 ; bytes of module name
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KeyLength equ 6 ; bytes of module key
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MDescr struc
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MDname db NameLength dup (?) ; module name
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MDkey db KeyLength dup (?) ; key
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MDproc dw ? ; offset of procedure table
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MDcode dw ? ; base of code
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MDdata dw ? ; base of data
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MDprogid dw ? ; 'owner' program id
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MDnext dd ? ; forward link
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MDprev dd ? ; backward link
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MDescr ends
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MDSize equ size MDescr
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badStructure equ 1
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badVersion equ 2
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readEOF equ 3
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TooBig equ 4 ; not enough memory
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|||
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badCheck equ 5
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; Object Record Tags:
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FormatVersion equ 0
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ProgramHeader equ 1
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SCModHeader equ 2
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ImportElement equ 3
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FilledData equ 4
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ProcedureCode equ 5
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SCModInitCode equ 6
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ModuleCode equ 7
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SCModuleCall equ 8
|
|||
|
|
RefExtData equ 9
|
|||
|
|
RefExtCode equ 10
|
|||
|
|
RefExtProc equ 11
|
|||
|
|
RefOwnData equ 12
|
|||
|
|
RefOwnCode equ 13
|
|||
|
|
RefOwnProc equ 14
|
|||
|
|
SCModuleEnd equ 15
|
|||
|
|
ProgramEnd equ 16
|
|||
|
|
|
|||
|
|
|
|||
|
|
LoadSP dw ? ; sp inside LoadProg
|
|||
|
|
LdBufSize equ 512
|
|||
|
|
LdBuf db LdBufSize dup (?) ; read buffer
|
|||
|
|
LdCnt dw ? ; bytes left in buffer
|
|||
|
|
LowSum db ? ; low byte of checksum
|
|||
|
|
HiSum db ? ; high byte of checksum
|
|||
|
|
Checksum equ word ptr LowSum
|
|||
|
|
CodeSize dw ? ; code size in paragraphs
|
|||
|
|
DataSize dw ? ; data size in paragraphs
|
|||
|
|
LdProgId dw ? ; id of loading program?
|
|||
|
|
SCMcnt dw ? ; number of SCM's to load
|
|||
|
|
ProgCodeBase dw ? ; base of program code segment
|
|||
|
|
ProgDataBase dw ? ; base of program data segment
|
|||
|
|
ModCodeBase dw ? ; base of module code segment
|
|||
|
|
ModDataBase dw ? ; base of module data segment
|
|||
|
|
StartOff dw ? ; start address of program, ..
|
|||
|
|
StartBase dw ? ; .. offset and segment.
|
|||
|
|
StartPtr equ dword ptr StartOff
|
|||
|
|
MDoff dw ?
|
|||
|
|
MDbase dw ?
|
|||
|
|
MDptr equ dword ptr MDoff
|
|||
|
|
PrevOff dw ?
|
|||
|
|
PrevBase dw ? ; previous module descrip. (init NIL)
|
|||
|
|
PrevPtr equ dword ptr PrevOff
|
|||
|
|
|
|||
|
|
ModCodeSize dw ?
|
|||
|
|
ModDataSize dw ?
|
|||
|
|
|
|||
|
|
LdMCB dw 3 dup (?) ; Memory Control Block
|
|||
|
|
even
|
|||
|
|
data ends
|
|||
|
|
|
|||
|
|
;*****************************************************************************
|
|||
|
|
|
|||
|
|
|
|||
|
|
; LOAD_FILE - load from file
|
|||
|
|
; in: AX prog id to use
|
|||
|
|
; CX:DX most recent entry in module 'tree'
|
|||
|
|
;
|
|||
|
|
; out: BX status
|
|||
|
|
; ES:DI start address
|
|||
|
|
; CX:DX last module entry added
|
|||
|
|
;
|
|||
|
|
|
|||
|
|
LOAD_FILE proc near
|
|||
|
|
|
|||
|
|
mov LdProgId,ax ; save prog id for module descriptors
|
|||
|
|
mov LoadSP,sp ; save stack pointer
|
|||
|
|
mov PrevBase,cx ; current 'top' of module table
|
|||
|
|
mov PrevOff,dx
|
|||
|
|
call ReadSeq ; initialize for subsequent reading
|
|||
|
|
mov Checksum,0 ; reset checksum
|
|||
|
|
call ReadFormatVersion
|
|||
|
|
call ReadProgHdr
|
|||
|
|
call AllocateProgMem ; allocate code, data, module table
|
|||
|
|
call LoadSCM ; load first module
|
|||
|
|
les bx,MDptr ; point to its descriptor
|
|||
|
|
mov bx,ES:MDproc[bx] ; get offset to procedure table
|
|||
|
|
mov ES,StartBase
|
|||
|
|
mov ax,ES:word ptr 2[bx] ; get offset to procedure 0
|
|||
|
|
mov StartOff,ax ; which is offset of start address
|
|||
|
|
dec SCMcnt ; more modules to load?
|
|||
|
|
jz SCMend ; guess not.
|
|||
|
|
SCMloop:
|
|||
|
|
add MDoff,MDSize ; allocate a new module descriptor
|
|||
|
|
call LoadSCM ; load one SCM
|
|||
|
|
dec SCMcnt ; more?
|
|||
|
|
jnz SCMloop ; yes, load them too (why not)
|
|||
|
|
SCMend: call ReadProgEnd ; process ProgramEnd
|
|||
|
|
les di,StartPtr
|
|||
|
|
mov cx,MDbase
|
|||
|
|
mov dx,MDoff ; pointer to last module entry
|
|||
|
|
xor bx,bx ; if no error, return BX=0
|
|||
|
|
LoadFU: mov sp,LoadSP ; reset stack pointer
|
|||
|
|
ret
|
|||
|
|
LOAD_FILE endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
ReadFormatVersion proc near
|
|||
|
|
call GetByte ; record tag
|
|||
|
|
cmp al,FormatVersion
|
|||
|
|
je RFV2
|
|||
|
|
mov bx,badStructure
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
RFV2: call GetByte ; object file format
|
|||
|
|
cmp al,currentVersion
|
|||
|
|
je RFV4 ; right version
|
|||
|
|
mov bx,badVersion
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
RFV4: call GetByte ; read target system
|
|||
|
|
cmp al,targetSystem
|
|||
|
|
je RFV6
|
|||
|
|
mov bx,badVersion
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
RFV6: jmp CheckChecksum
|
|||
|
|
ReadFormatVersion endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
ReadProgHdr proc near
|
|||
|
|
call GetByte
|
|||
|
|
cmp al,ProgramHeader
|
|||
|
|
je RPH2
|
|||
|
|
mov bx,badStructure
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
RPH2: call GetWord
|
|||
|
|
mov CodeSize,ax
|
|||
|
|
call GetWord
|
|||
|
|
mov DataSize,ax
|
|||
|
|
call GetWord
|
|||
|
|
mov SCMcnt,ax
|
|||
|
|
jmp CheckChecksum
|
|||
|
|
ReadProgHdr endp
|
|||
|
|
|
|||
|
|
AllocateProgMem proc near
|
|||
|
|
mov ax,MDSize ; size of a module descriptor
|
|||
|
|
mul SCMcnt ; times number of modules..
|
|||
|
|
add ax,15
|
|||
|
|
mov cl,4
|
|||
|
|
shr ax,cl ; convert to paragraphs
|
|||
|
|
add ax,CodeSize ; add paragraphs of code..
|
|||
|
|
add ax,DataSize ; and paragraphs of data
|
|||
|
|
call Alloc_Mem ; allocate memory, base => AX
|
|||
|
|
test bx,bx ; got it?
|
|||
|
|
jz GotMem ; yes
|
|||
|
|
mov bx,TooBig ; nope.
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
GotMem: mov ProgCodeBase,ax ; start of code segment
|
|||
|
|
mov ModCodeBase,ax ; start of first module
|
|||
|
|
mov StartBase,ax ; save base of start address
|
|||
|
|
add ax,CodeSize
|
|||
|
|
mov ProgDataBase,ax ; start of data segment
|
|||
|
|
mov ModDataBase,ax ; data of first module
|
|||
|
|
add ax,DataSize
|
|||
|
|
mov MDbase,ax ; base of module descriptor table
|
|||
|
|
mov MDoff,0 ; initial offset
|
|||
|
|
ret
|
|||
|
|
AllocateProgMem endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
; LoadSCM - load one module
|
|||
|
|
;
|
|||
|
|
LoadSCM proc near
|
|||
|
|
call ReadSCMHdr
|
|||
|
|
call GetByte ; next field tag..
|
|||
|
|
cmp al,ModuleCode ; ModuleCode record?
|
|||
|
|
je LdSCM2 ; yes
|
|||
|
|
mov bx,badStructure
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
LdSCM2: call RestModCode ; yes, process rest of record
|
|||
|
|
call ReadFixups ; process rest of module (fixups & end)
|
|||
|
|
ret
|
|||
|
|
LoadSCM endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
; ReadSCMhdr - process an SCModHeader record
|
|||
|
|
; out: ModName module name
|
|||
|
|
; ModKey module key
|
|||
|
|
ReadSCMhdr proc near
|
|||
|
|
call GetByte
|
|||
|
|
cmp al,SCModHeader
|
|||
|
|
je RSCMH2
|
|||
|
|
mov bx,badStructure
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
RSCMH2: les di,MDptr
|
|||
|
|
mov ax,ModCodeBase
|
|||
|
|
mov ES:MDcode[di],ax ; code-base for this module
|
|||
|
|
mov ax,ModDataBase
|
|||
|
|
mov ES:MDdata[di],ax ; data base for this module
|
|||
|
|
mov ax,LdProgId
|
|||
|
|
mov ES:MDprogid[di],ax ; owner-program id for this module
|
|||
|
|
;;;;;;;;add di,offset MDname ; DOESN'T WORK!!!
|
|||
|
|
MOV AX, OFFSET MDname
|
|||
|
|
ADD DI, AX
|
|||
|
|
mov ax,NameLength
|
|||
|
|
call GetNBytes ; read module name
|
|||
|
|
les di,MDptr
|
|||
|
|
;;;;;;;;add di,offset MDkey ; DOESN'T WORK
|
|||
|
|
MOV AX, OFFSET MDkey
|
|||
|
|
ADD DI, AX
|
|||
|
|
mov ax,KeyLength
|
|||
|
|
call GetNBytes ; read module key
|
|||
|
|
call GetWord
|
|||
|
|
les di,MDptr
|
|||
|
|
mov ES:MDproc[di],ax ; offset of procedure table
|
|||
|
|
call GetWord
|
|||
|
|
mov ModCodeSize,ax ; bytes of code
|
|||
|
|
call GetWord
|
|||
|
|
mov ModDataSize,ax ; bytes of data
|
|||
|
|
call GetWord ; (internal use by compiler)
|
|||
|
|
jmp CheckChecksum
|
|||
|
|
ReadSCMhdr endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
; RestModCode - read the rest of a ModuleCode record
|
|||
|
|
; (called after the tag has been read)
|
|||
|
|
RestModCode proc near
|
|||
|
|
call GetWord ; length of code (bytes)
|
|||
|
|
mov ES,ModCodeBase ; base
|
|||
|
|
mov di,0 ; offset
|
|||
|
|
call GetNBytes ; read AX bytes at ES:0000
|
|||
|
|
jmp CheckChecksum
|
|||
|
|
RestModCode endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
; ReadFixups - process fixup records until SCModuleEnd record is processed
|
|||
|
|
;
|
|||
|
|
ReadFixups proc near
|
|||
|
|
call GetByte
|
|||
|
|
cmp al,RefOwnCode
|
|||
|
|
jne RFIX2
|
|||
|
|
call GetWord ; offset of fixup (current module)
|
|||
|
|
push ax
|
|||
|
|
call GetWord ; 'bias' (paragraphs from codebase)
|
|||
|
|
add ax,ProgCodeBase ; compute fixup value
|
|||
|
|
pop bx ; fixup offset..
|
|||
|
|
mov ES,ModCodeBase ; fixup base: current module
|
|||
|
|
mov ES:[bx],ax
|
|||
|
|
call CheckChecksum
|
|||
|
|
jmp short ReadFixups
|
|||
|
|
;
|
|||
|
|
RFIX2: cmp al,SCModuleEnd
|
|||
|
|
je RFIX4
|
|||
|
|
mov bx,badStructure
|
|||
|
|
jmp LoadFU
|
|||
|
|
; end of module:
|
|||
|
|
RFIX4: mov ax,ModCodeSize ; adjust base-of-module-code
|
|||
|
|
add ax,15 ; paragraph pointer by size
|
|||
|
|
mov cl,4 ; of module code, rounded up
|
|||
|
|
shr ax,cl ; and converted to paragraphs.
|
|||
|
|
add ModCodeBase,ax
|
|||
|
|
mov ax,ModDataSize
|
|||
|
|
add ax,15
|
|||
|
|
mov cl,4
|
|||
|
|
shr ax,cl
|
|||
|
|
add ModDataBase,ax
|
|||
|
|
call LinkModuleDescriptor
|
|||
|
|
jmp CheckChecksum
|
|||
|
|
ReadFixups endp
|
|||
|
|
|
|||
|
|
LinkModuleDescriptor proc near
|
|||
|
|
les di,PrevPtr
|
|||
|
|
cmp di,NIL_OFF
|
|||
|
|
jne LMD2
|
|||
|
|
mov ax,ES
|
|||
|
|
cmp ax,NIL_SEG
|
|||
|
|
je LMD4 ; IF PrevPtr <> NIL THEN..
|
|||
|
|
LMD2: mov ax,MDoff
|
|||
|
|
mov ES:word ptr MDnext[di],ax
|
|||
|
|
mov ax,MDbase
|
|||
|
|
mov ES:word ptr MDnext+2[di],ax ; PrevPtr^.next := MDptr
|
|||
|
|
LMD4: les di,MDptr ; END
|
|||
|
|
mov ES:word ptr MDnext[di],NIL_OFF
|
|||
|
|
mov ES:word ptr MDnext+2[di],NIL_SEG ; MDptr^.next := NIL
|
|||
|
|
mov ax,PrevOff
|
|||
|
|
mov ES:word ptr MDprev[di],ax
|
|||
|
|
mov ax,PrevBase
|
|||
|
|
mov ES:word ptr MDprev+2[di],ax ; MDptr^.prev := PrevPtr
|
|||
|
|
mov PrevOff,di
|
|||
|
|
mov PrevBase,ES ; PrevPtr := MDptr
|
|||
|
|
ret
|
|||
|
|
LinkModuleDescriptor endp
|
|||
|
|
|
|||
|
|
ReadProgEnd proc near
|
|||
|
|
call GetByte
|
|||
|
|
cmp al,ProgramEnd
|
|||
|
|
je RPE2
|
|||
|
|
mov bx,badStructure
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
RPE2: jmp CheckChecksum
|
|||
|
|
ReadProgEnd endp
|
|||
|
|
|
|||
|
|
; GetWord - get next word from object record (update checksum)
|
|||
|
|
; out: AX data word
|
|||
|
|
; BX status/error code
|
|||
|
|
; <CC> set for BX
|
|||
|
|
GetWord proc near
|
|||
|
|
call GetByte ; read lo byte
|
|||
|
|
mov ah,al
|
|||
|
|
call GetByte ; read hi byte
|
|||
|
|
xchg ah,al ; shuffle into position
|
|||
|
|
ret
|
|||
|
|
GetWord endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
; GetNBytes - get multiple bytes into memory (with Checksum)
|
|||
|
|
; in: AX byte count (must be > 0!)
|
|||
|
|
; ES:DI where to put the bytes
|
|||
|
|
; out: CX =0
|
|||
|
|
; ES:DI points past last byte read
|
|||
|
|
GetNBytes proc near
|
|||
|
|
mov cx,ax
|
|||
|
|
mov dx,Checksum ; move checksum into reg for speed
|
|||
|
|
NBcont: mov bx,LdCnt ; ditto for bytes-left-in-buffer
|
|||
|
|
cld ; make sure direction flag is forward
|
|||
|
|
xor ah,ah ; extend each byte to cardinal
|
|||
|
|
NBytes: lodsb ; fetch next byte from buffer
|
|||
|
|
sub bx,1
|
|||
|
|
jc NBfill ; refill buffer
|
|||
|
|
add dx,ax ; update checksum
|
|||
|
|
stosb ; place byte into memory
|
|||
|
|
loop NBytes ; and repeat N times
|
|||
|
|
mov LdCnt,bx ; bring memory variables up to date
|
|||
|
|
mov Checksum,dx
|
|||
|
|
ret
|
|||
|
|
;
|
|||
|
|
NBfill: call ReadSeq ; read next buffer sequentially
|
|||
|
|
jmp short NBcont
|
|||
|
|
GetNBytes endp
|
|||
|
|
|
|||
|
|
; GetByte - get next byte from object record (updates checksum)
|
|||
|
|
; out: AL data byte
|
|||
|
|
; BX status/error code
|
|||
|
|
; note: CX, DX, DI, ES preserved
|
|||
|
|
GetByte proc near
|
|||
|
|
call ReadByte ; read one raw
|
|||
|
|
add LowSum,al ; update checksum
|
|||
|
|
adc HiSum,0
|
|||
|
|
ret
|
|||
|
|
GetByte endp
|
|||
|
|
|
|||
|
|
CheckChecksum proc near
|
|||
|
|
call ReadWord ; read record checksum field
|
|||
|
|
cmp ax,Checksum ; checksum checks?
|
|||
|
|
jne Struct ; no
|
|||
|
|
ret
|
|||
|
|
;
|
|||
|
|
Struct: mov bx,badCheck ; no
|
|||
|
|
jmp LoadFU ; short-circuit exit
|
|||
|
|
CheckChecksum endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
ReadWord proc near
|
|||
|
|
call ReadByte ; read low byte
|
|||
|
|
mov ah,al ; save it
|
|||
|
|
call ReadByte ; read high byte
|
|||
|
|
xchg ah,al ; swap into position
|
|||
|
|
ret
|
|||
|
|
ReadWord endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
; ReadByte - get next raw byte from input file
|
|||
|
|
; out: AL next byte
|
|||
|
|
; BX status/error code
|
|||
|
|
; note: AH, CX, DX, DI, ES preserved
|
|||
|
|
;
|
|||
|
|
ReadByte proc near
|
|||
|
|
cld
|
|||
|
|
lodsb ; yes: pull next byte from buffer
|
|||
|
|
sub LdCnt,1 ; anything left in buffer?
|
|||
|
|
jc ReadB2 ; no, refill buffer
|
|||
|
|
ret
|
|||
|
|
;
|
|||
|
|
ReadB2: call ReadSeq
|
|||
|
|
jmp short ReadByte ; try again
|
|||
|
|
ReadByte endp
|
|||
|
|
|
|||
|
|
|
|||
|
|
; ReadSeq - read next sequential block into buffer
|
|||
|
|
;
|
|||
|
|
; out: BX status/error code
|
|||
|
|
; SI points to start of buffer
|
|||
|
|
; LdCnt number of bytes read
|
|||
|
|
; note: AX, CX, DX, DI, ES are preserved
|
|||
|
|
ReadSeq proc near
|
|||
|
|
push ax ; just to be polite
|
|||
|
|
push cx
|
|||
|
|
push dx
|
|||
|
|
push di
|
|||
|
|
push ES
|
|||
|
|
push DS
|
|||
|
|
call READ_LD_FILE
|
|||
|
|
pop DS
|
|||
|
|
cmp ax,LdBufSize ; full record?
|
|||
|
|
je RstBuf ; yes
|
|||
|
|
cmp ax,0 ; partial record?
|
|||
|
|
jne RstBuf ; yes
|
|||
|
|
mov bx,readEOF ; no, EOF, which should never happen!
|
|||
|
|
jmp LoadFU
|
|||
|
|
;
|
|||
|
|
RstBuf: mov si,offset LdBuf ; reset buffer scanner
|
|||
|
|
mov LdCnt,LdBufSize ; and buffer count
|
|||
|
|
pop ES
|
|||
|
|
pop di
|
|||
|
|
pop dx
|
|||
|
|
pop cx
|
|||
|
|
pop ax
|
|||
|
|
ret
|
|||
|
|
ReadSeq endp
|
|||
|
|
|
|||
|
|
code ends
|
|||
|
|
|
|||
|
|
;*****************************************************************************
|
|||
|
|
|
|||
|
|
end
|
|||
|
|
|