80 lines
2.5 KiB
NASM
80 lines
2.5 KiB
NASM
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; File:
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; memdisk.asm
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; Description:
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; Query for memdisk provided config.sys parameters
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;
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; DOS-C
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; Copyright (c) 2011
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; FreeDOS
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; All Rights Reserved
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;
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; This file is part of DOS-C.
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;
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; DOS-C is free software; you can redistribute it and/or
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; modify it under the terms of the GNU General Public License
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; as published by the Free Software Foundation; either version
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; 2, or (at your option) any later version.
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;
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; DOS-C is distributed in the hope that it will be useful, but
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; WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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; the GNU General Public License for more details.
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;
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;
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; requires 386+ registers, check LoL->CPU >=3 prior to calling (or use 386 build)
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%include "segs.inc"
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segment INIT_TEXT
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CPU 386
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;*********************************************************************
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;
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; query_memdisk() based on similar subroutine in Eric Auer's public domain getargs.asm which is based on IFMEMDSK
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; input: drive (in AL) to query if memdisk provided disk
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; output: a far * to a memdiskinfo structure as defined by memdisk (see config.c)
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; struct memdiskinfo FAR * query_memdisk(UBYTE drive);
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global _query_memdisk
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_query_memdisk:
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; save registers, assumes enough space on stack & valid stack frame setup, ax & dx return values
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push es
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push di
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push ebx
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push ecx
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push edx ; we only care about high word
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push eax ; we only care about high word
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mov edx,53490000h ; magic3 +
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mov dl, al ; drive number (only argument, assumed to be in AL)
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mov eax,454d0800h ; magic1 + AH=8 (get geometry)
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mov ecx,444d0000h ; magic2
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mov ebx,3f4b0000h ; magic4
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int 13h ; BIOS DISK API
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shr eax,16 ; ignore AX
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shr ebx,16 ; ignore BX
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shr ecx,16 ; ignore CX (geometry C/S)
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shr edx,16 ; ignore DX (geometry H in DH)
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cmp ax,4d21h ; magic5
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jnz nomemdisk
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cmp cx,4d45h ; magic6
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jnz nomemdisk
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cmp dx,4944h ; magic7
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jnz nomemdisk
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cmp bx,4b53h ; magic8
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jnz nomemdisk
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jmp cleanup
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nomemdisk:
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xor di, di ; return NULL;
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mov es, di
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cleanup:
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pop eax
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pop edx
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mov ax, di ; return MK_FP(es, di);
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mov dx, es
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pop ecx
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pop ebx
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pop di
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pop es
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retn
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