http://jesusnjim.com/code/windows-dos/df.html
in looking at working code and wondering why mine wasing working for over a
month now, I came to realize 2 things:
1. I had swapped DS:DX and ES:DI (ouch). this was causing the error flag to be
set.
2. I was getting garbage back from the function call because you have to use
dosmemput and dosmemget very close to _dpmi_int(0x21, ®s) calls in djgpp, or
that memory will get written over by something else in your program quickly
without your knowledge! it can get scrambled.
________________________________
From: Walt Nagel <wr...@yahoo.com>
To: Jim Michaels <jmich...@yahoo.com>
Sent: Fri, March 18, 2011 11:52:17 AM
Subject: Re: [Freedos-devel] problem with 7303h?
Hi Jim,
"Translating" from assembly to C is not quite as straightforward as one might
expect (or desire). A good place to start is section 18 of DJ's FAQs. I believe
the missing part of the puzzle is that buffers used by/for interrupts must be
located in low memory.
I translated my earlier program to C (see attached). It appears to compile
under
DJGPP V2 and work without using 7300h.
Regards,
Walt
--- On Tue, 3/15/11, Jim Michaels <jmich...@yahoo.com> wrote:
>From: Jim Michaels <jmich...@yahoo.com>
>Subject: Re: [Freedos-devel] problem with 7303h?
>To: "Jim Michaels" <jmich...@yahoo.com>, freedos-devel@lists.sourceforge.net
>Date: Tuesday, March 15, 2011, 4:09 PM
>
>
>here's my code fragment.
>I'm sure I'm doing something wrong. why else would the free32 program work
>and
>mine not?
>
>I am using the same 7300h and 7303h function calls. but no dice. only diff I
>think is that I am doing this in C rather than assembler. I didn't read the
>entire program because I figured those were the core 2 functions anyway. the
>dirty buffers check on a specific drive and then the disk free space check on
>that drive, both fat32 calls. 7303h doesn't work without 7300h being called
>first.
>
>I know it's not your obligation to help me, but I am at my wits end with this
>program. nothing I try works in freedos except that assembler program free32.
>
>I know I can't do this on my own. I need help.
>
>
>#define STR_OFS 0x30
>#define STRUCT_OFS 0x0
>
>#if defined(__DJGPP__)
>//#define HANDLE_PRAGMA_PACK_PUSH_POP 1
>//#pragma pack(push,1)
>
>typedef struct extFAT32FreeSpaceStructure {
>/* 00h WORD*/uint16_t ret_size_of_returned_structure;
>/* 02h WORD*/uint16_t
>call_structure_version_ret_actual_structure_version;// (0000h)
>/* 04h DWORD*/uint32_t
>number_of_sectors_per_cluster_with_adjustment_for_compression;
>/* 08h DWORD*/uint32_t number_of_bytes_per_sector;
>/* 0Ch DWORD*/uint32_t number_of_available_clusters;
>/* 10h DWORD*/uint32_t total_number_of_clusters_on_the_drive;
>/* 14h DWORD*/uint32_t
>number_of_physical_sectors_available_on_the_drive_without_adjustment_for_compression;
>
>/* 18h DWORD*/uint32_t
>total_number_of_physical_sectors_on_the_drive_without_adjustment_for_compression;
>
>/* 1Ch DWORD*/uint32_t
>number_of_available_allocation_units_without_adjustment_for_compression;
>/* 20h DWORD*/uint32_t
>total_allocation_units_without_adjustment_for_compression;
>/* 24h 8 BYTEs*/uint64_t reserved;
>uint32_t wastedspace;
>} __attribute__((packed)) extFAT32FreeSpaceStructure;
>//typedef struct extFAT32FreeSpaceStructure extFAT32FreeSpaceStructure;
>
>//#pragma pack(pop)
>
>#endif
>
>char * dirpath[26] = {
> "A:\\", "B:\\", "C:\\", "D:\\", "E:\\",
> "F:\\", "G:\\", "H:\\", "I:\\", "J:\\",
> "K:\\", "L:\\", "M:\\", "N:\\", "O:\\",
> "P:\\", "Q:\\", "R:\\", "S:\\", "T:\\",
> "U:\\", "V:\\", "W:\\", "X:\\", "Y:\\",
> "Z:\\"
>};
>
>
> int64_t iDAvail, iTotal;
> struct diskfree_t df;
> extFAT32FreeSpaceStructure *pds = (extFAT32FreeSpaceStructure
>*)calloc(sizeof(extFAT32FreeSpaceStructure), 1);
>/*BUG: int21h 7303h returns a maximum of 2GB free space even on an FAT32
> partition larger than 2GB under some versions of Win95 and Win98,
> apparently by limiting the number of reported free clusters to no
> more than 64K -- but only in a DOS window if a TSR has hooked INT 21h
> */
> __dpmi_regs r;
> r.h.dl=drive;//curent drive
> r.h.cl=0x01;//dirty buffers flag
> r.x.ax=0x7300;
> pds->ret_size_of_returned_structure=0x30;
> __dpmi_int(0x21, &r);
> if (0x7300!=r.x.ax) {
> //supports fat32. 7303h doesn't work without this.
>
> pds->call_structure_version_ret_actual_structure_version=0;
> dosmemput(pds, sizeof(extFAT32FreeSpaceStructure), __tb +
>STRUCT_OFS);
> dosmemput(dirpath[drive-a_drive],
>strlen(dirpath[drive-a_drive])+1, __tb + STR_OFS);
> r.x.ax=0x7303;
> r.x.cx=sizeof(extFAT32FreeSpaceStructure);//0x30 whereas
> before
>it was 0x2c
> r.x.ds=(__tb+STRUCT_OFS)>>4;
> r.x.dx=(__tb+STRUCT_OFS)& 0x0f;
> r.x.es=(__tb+STR_OFS)>>4;
> r.x.di=(__tb+STR_OFS)&0x0f;
> r.x.flags = 1; //set carry bit to show error in case there is
> no
>change
> r.x.ss=0;
> r.x.sp=0;
> __dpmi_int(0x21, &r);
> if (1==r.x.flags & 1 //carry flag
> || (1==r.x.flags & 1 && 0==r.h.al)
> ) {
> //error, so try fallback method of using old dos int21h
>function 36h _dos_getdiskfree()
> //long long iTotal, iDAvail;
>
> //for this function, drive starting with 1 is correct.
> if (0==_dos_getdiskfree(drive, &df)) { // 0=default, 1=a,
>2=b...
> iDAvail =df.avail_clusters; iTotal
>=df.total_clusters;
> iDAvail*=df.bytes_per_sector;
>iTotal*=df.bytes_per_sector;
> iDAvail*=df.sectors_per_cluster;
>iTotal*=df.sectors_per_cluster;
> } else {
> printf("ERROR:_dos_getdiskfree() failed, int21h 7303h
>failed.");
> return false;
> }
> } else {
> printf("AX=0x%04x,FLAGS=0x%04x\n", r.x.ax,
>r.x.flags);//DEBUG
> //success on int 21h 7303h, so extract results.
> unsigned long adr=r.x.es;
> adr<<=4;
> adr += r.x.di;
> dosmemget(/*__tb+STRUCT_OFS+*/adr,
>sizeof(extFAT32FreeSpaceStructure), pds);
>
> if (pds->ret_size_of_returned_structure < 0x24
> || pds->ret_size_of_returned_structure >
>sizeof(extFAT32FreeSpaceStructure)) {
> printf("ERROR:structure size returned=0x%04x on drive
>%d\n",pds->ret_size_of_returned_structure, drive);
>
> if (0==_dos_getdiskfree(drive, &df)) { // 0=default,
>1=a, 2=b...
> printf("_dos_getdiskfree() SUCCESS, int21h 7303h
>failed. sizeof struct was
>%hd,flags=0x%04x,AX=0x%04x\n",pds->ret_size_of_returned_structure,r.x.flags,r.x.ax);
>
> iDAvail =df.avail_clusters; iTotal
>=df.total_clusters;
> iDAvail*=df.bytes_per_sector;
>iTotal*=df.bytes_per_sector;
> iDAvail*=df.sectors_per_cluster;
>iTotal*=df.sectors_per_cluster;
> } else {
> printf("ERROR:_dos_getdiskfree() failed on drive
>%d, int21h 7303h failed.\n", drive);
> return false;
> }
> } else {
> printf("SUCCESS on int21h 7303h\n");//DEBUG
> iDAvail =
>pds->number_of_sectors_per_cluster_with_adjustment_for_compression;
> iDAvail *= pds->number_of_bytes_per_sector;
> iDAvail *= pds->number_of_available_clusters;
>
> iTotal =
>pds->number_of_sectors_per_cluster_with_adjustment_for_compression;
> iTotal *= pds->number_of_bytes_per_sector;
> iTotal *= pds->total_number_of_clusters_on_the_drive;
> }
> }
> }
> free(pds);
>
>
>
>
>
>
>
________________________________
From: Jim Michaels <jmich...@yahoo.com>
>To: freedos development <freedos-devel@lists.sourceforge.net>
>Sent: Tue, March 15, 2011 11:33:25 AM
>Subject: [Freedos-devel] problem with 7303h?
>
>
>I am calling 7303H, but I am getting failure under freedos.
>upon return,
>int21h 7303h failed. sizeof struct was 14917=0x3a45,flags=0x3003,AX=0x000f
>
>function 36h succeeded.
>I am using djgpp, and while I haven't gotten the best of help on how to
>implement that return of ES:DI buffer pointer, I should think I would have
>gotten it by now with all the things I have tried.
>
> -------------
>Jim Michaels
>jmich...@yahoo.com
>j...@jimscomputerrepairandwebdesign.com
>http://JimsComputerRepairandWebDesign.com
>http://JesusnJim.com (my personal site, has software)
>http://DoLifeComputers.JesusnJim.com (group which I lead)
>---
>Computer memory/disk size measurements:
>[KB KiB] [MB MiB] [GB GiB] [TB TiB]
>[10^3B=1,000B=1KB][2^10B=1,024B=1KiB]
>[10^6B=1,000,000B=1MB][2^20B=1,048,576B=1MiB]
>[10^9B=1,000,000,000B=1GB][2^30B=1,073,741,824B=1GiB]
>[10^12B=1,000,000,000,000B=1TB][2^40B=1,099,511,627,776B=1TiB]
>Note: disk size is measured in MB, GB, or TB, not in MiB, GiB, or TiB.
>computer
>memory (RAM) is measured in MiB and GiB.
>
>
>
>
>
>
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>
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