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From: Jim Michaels <jmichae3 AT yahoo DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: help on using dosmemput, dosmemget, anything like it
Date: Fri, 20 Feb 2009 00:23:53 -0800 (PST)
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To: djgpp AT delorie DOT com
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Background:
I have no revision control (my fault), and I did something to make my
bios disk routines not work.  it has gone through several fixes and
revisions.
problem may be that I am using a different compiler (djgpp current
instead of 2.03 or 2.04), or it may be the code change.

The code seemed (?) to work on an IDE based computer, but not with my
SATA drive.  SATA drives used to work with this program (I wrote to
the SATA drive

with this program once).

question:
what are the steps for doing BIOS disk I/O, for a write and a read?

what I currently have is the following:
write:
//constructor
setup structure
allocate buffer in memory (malloc)
point structure to __tb{seg,ofs}
bufallocated=true
//member function
set starting absolute block number
//put buffer x to class member function
if buffersize >
_go32_info_block.size_of_transfer_buffer-2*BYTES_PER_SECTOR then
reject
realloc buffer based on buffersize
if not successful then reject
memcpy(buffer, x, buffersize)
    //putToDosMem member function
    dosmemput(buffer, numdiskblocks*BYTESPERSECTOR, __tb
+BYTES_PER_SECTOR)
    dosmemput(&structure, sizeof(structure), __tb)
    structure.addressoftransferbuffer=__tb
//ExtendedWrite function
    //putdostomem function
    dosmemput(buffer, numdiskblocks*BYTESPERSECTOR, __tb
+BYTES_PER_SECTOR)
    dosmemput(&structure, sizeof(structure), __tb)
    structure.addressoftransferbuffer=__tb
    //get segment and offset calls (member functions)
    setup registers for int 13h call
    dpmi_int(0x13, &registers)
    //updateafterdiskio member function
       //getfromdosmem member function
       dosmemget(__tb+BYTES_PER_SECTOR, numdiskblocks*BYTESPERSECTOR,
buffer)
       dosmemget(__tb, sizeof(structure), &structure)
    set number of blocks read or written
    if registers' carry flag set,
        return error code in ah
    else
	return true
delete buffer

read (pretty much same except for setting up registers is different
for read than write):
//constructor
setup structure
allocate buffer in memory (malloc)
point structure to __tb{seg,ofs}
bufallocated=true
//member function
set starting absolute block number
//put buffer x to class member function
if buffersize >
_go32_info_block.size_of_transfer_buffer-2*BYTES_PER_SECTOR then
reject
realloc buffer based on buffersize
if not successful then reject
memcpy(buffer, x, buffersize)
    //putToDosMem member function
    dosmemput(buffer, numdiskblocks*BYTESPERSECTOR, __tb
+BYTES_PER_SECTOR)
    dosmemput(&structure, sizeof(structure), __tb)
    structure.addressoftransferbuffer=__tb
//ExtendedRead function
    //putdostomem function
    dosmemput(buffer, numdiskblocks*BYTESPERSECTOR, __tb
+BYTES_PER_SECTOR)
    dosmemput(&structure, sizeof(structure), __tb)
    structure.addressoftransferbuffer=__tb
    //get segment and offset calls (member functions)
    setup registers for int 13h call
    dpmi_int(0x13, &registers)
    //updateafterdiskio member function
       //getfromdosmem member function
       dosmemget(__tb+BYTES_PER_SECTOR, numdiskblocks*BYTESPERSECTOR,
buffer)
       dosmemget(__tb, sizeof(structure), &structure)
    set number of blocks read or written
    if registers' carry flag set,
        return error code in ah
    else
	return true
delete buffer