[HELP] Reading FAT12/16 file size and allocating far memory

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bitshifter

Joined: 04 Dec 2007
Posts: 796
Location: Massachusetts, USA

bitshifter 07 Dec 2014, 22:40

Im working on new boot code to load files > 64kib
The FAT directory structure stores file size at [28,30] as dword
I need to allocate memory for the file
Note: must be 16bit code

Code:

;es:di -> root directory entity

 mov ax,[es:di+28]      ;file size loword
 mov dx,[es:di+30]      ;file size hiword

;HELP: what to do here?

;ax = size in paragraphs
 call FarAlloc
;out: es = segment base

_________________
Coding a 3D game engine with fasm is like trying to eat an elephant,
you just have to keep focused and take it one 'byte' at a time.

07 Dec 2014, 22:40

SeproMan

Joined: 11 Oct 2009
Posts: 70
Location: Belgium

SeproMan 14 Dec 2014, 18:58

To convert double word into paragraphs first add 15 and then divide by 16.

Code:

add ax,15
adc dx,0
mov cx,16
div cx

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Real Address Mode.

14 Dec 2014, 18:58

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