vfdfat.c

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/*
    vfdfat.c

    Virtual Floppy Drive for Windows
    Driver control library
    Formats the image with FAT12

    Copyright (C) 2003-2005 Ken Kato
*/

#ifdef __cplusplus
#pragma message(__FILE__": Compiled as C++ for testing purpose.")
#endif  // __cplusplus

#define WIN32_LEAN_AND_MEAN
#include <windows.h>

#include "vfdtypes.h"
#include "vfdio.h"
#include "vfdlib.h"
#include "vfdver.h"

#pragma pack(1)
//
//  BIOS parameter block
//
typedef struct _DOS_BPB
{
    USHORT  BytesPerSector;
    UCHAR   SectorsPerCluster;
    USHORT  ReservedSectors;
    UCHAR   NumberOfFATs;
    USHORT  RootEntries;
    USHORT  SmallSectors;
    UCHAR   MediaDescriptor;
    USHORT  SectorsPerFAT;
    USHORT  SectorsPerTrack;
    USHORT  NumberOfHeads;
    ULONG   HiddenSectors;
    ULONG   LargeSectors;
}
DOS_BPB, *PDOS_BPB;

//
//  Extended BIOS parameter block for FAT12/16/HUGE
//
typedef struct _EXBPB
{
    UCHAR   PhysicalDriveNumber;
    UCHAR   Reserved;
    UCHAR   BootSignature;
    ULONG   VolumeSerialNumber;
    CHAR    VolumeLabel[11];
    CHAR    FileSystemType[8];
}
EXBPB, *PEXBPB;

//
//  Partition Boot Record
//
typedef struct _DOS_PBR {           //  Partition Boot Record
    UCHAR   jump[3];                //  Jump Instruction (E9 or EB, xx, 90)
    CHAR    oemid[8];               //  OEM ID (OS type)
    DOS_BPB bpb;                    //  BIOS parameter block
    EXBPB   exbpb;                  //  Extended BIOS parameter block
}
DOS_PBR, *PDOS_PBR;

#pragma pack()

#define FAT_DIR_ENTRY_SIZE  32

// We need to have the 0xeb and 0x90 in the jump code
// because the file system recognizer checks these values
#define VFD_JUMP_CODE       "\xeb\x3c\x90"
#define VFD_OEM_NAME        "VFD" VFD_DRIVER_VERSION_STR "     "
#define VFD_VOLUME_LABEL    "NO NAME    "
#define VFD_FILESYSTEM      "FAT12   "

//
//  Select DOS BPB parameters from media size
//
static const DOS_BPB *SelectDosBpb(
    USHORT  nSectors)
{
    static const DOS_BPB bpb_tbl[] = {
        // b/s                s/c r fat root  sec  desc s/f s/t  h
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 112,  320, 0xFE,  1,  8, 1, 0, 0},  // 160KB 5.25"
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 112,  360, 0xFC,  1,  9, 1, 0, 0},  // 180KB 5.25"
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 112,  640, 0xFF,  1,  8, 2, 0, 0},  // 320KB 5.25"
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 112,  720, 0xFD,  2,  9, 2, 0, 0},  // 360KB 5.25"
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 112, 1280, 0xFB,  2,  8, 2, 0, 0},  // 640KB 5.25" / 3.5"
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 112, 1440, 0xF9,  3,  9, 2, 0, 0},  // 720KB 5.25" / 3.5"
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 112, 1640, 0xF9,  3, 10, 2, 0, 0},  // 820KB 3.5"
        {VFD_BYTES_PER_SECTOR, 1, 1, 2, 224, 2400, 0xF9,  7, 15, 2, 0, 0},  // 1.20MB 5.25" / 3.5"
        {VFD_BYTES_PER_SECTOR, 1, 1, 2, 224, 2880, 0xF0,  9, 18, 2, 0, 0},  // 1.44MB 3.5"
        {VFD_BYTES_PER_SECTOR, 1, 1, 2, 224, 3360, 0xF0, 10, 21, 2, 0, 0},  // 1.68MB 3.5"
        {VFD_BYTES_PER_SECTOR, 1, 1, 2, 224, 3444, 0xF0, 10, 21, 2, 0, 0},  // 1.72MB 3.5"
        {VFD_BYTES_PER_SECTOR, 2, 1, 2, 240, 5760, 0xF0,  9, 36, 2, 0, 0},  // 2.88MB 3.5"
    };

    int i;

    for (i = 0; i < sizeof(bpb_tbl) / sizeof(bpb_tbl[0]); i++) {
        if (nSectors == bpb_tbl[i].SmallSectors) {
            return &bpb_tbl[i];
        }
    }

    return NULL;
}

//
//  Format the buffer with FAT12
//
DWORD FormatBufferFat(
    PUCHAR          pBuffer,
    ULONG           nSectors)
{
    const DOS_BPB   *bpb;   // BIOS Parameter Block
    PDOS_PBR        pbr;    // Partition Boot Record
    PUCHAR          fat;    // File Allocation Table
    USHORT          idx;

    VFDTRACE(0,
        ("[VFD] VfdFormatImage - IN\n"));

    //
    //  Select DOS BPB parameters from media size
    //
    bpb = SelectDosBpb((USHORT)nSectors);

    if (!bpb) {
        VFDTRACE(0,
            ("[VFD] Unsupported media size %lu\n",
            nSectors));
        return ERROR_INVALID_PARAMETER;
    }

    //
    //  Initialize the whole area with the fill data
    //
    FillMemory(pBuffer,
        VFD_SECTOR_TO_BYTE(nSectors),
        VFD_FORMAT_FILL_DATA);

    //
    //  Make up the FAT boot record
    //
    ZeroMemory(pBuffer, VFD_BYTES_PER_SECTOR);

    pbr = (PDOS_PBR)pBuffer;

    CopyMemory(pbr->jump,   VFD_JUMP_CODE,  sizeof(pbr->jump));
    CopyMemory(pbr->oemid,  VFD_OEM_NAME,   sizeof(pbr->oemid));
    CopyMemory(&pbr->bpb,   bpb,            sizeof(pbr->bpb));

    //  Make up the extended BPB

    pbr->exbpb.BootSignature        = 0x29;

    //  use the tick count as the volume serial number
    pbr->exbpb.VolumeSerialNumber   = GetTickCount();

    CopyMemory(pbr->exbpb.VolumeLabel,
        VFD_VOLUME_LABEL, sizeof(pbr->exbpb.VolumeLabel));

    CopyMemory(pbr->exbpb.FileSystemType,
        VFD_FILESYSTEM, sizeof(pbr->exbpb.FileSystemType));

    //  Set the boot record signature

    *(pBuffer + VFD_BYTES_PER_SECTOR - 2) = 0x55;
    *(pBuffer + VFD_BYTES_PER_SECTOR - 1) = 0xaa;

    //
    //  Clear FAT areas
    //
    fat = pBuffer + VFD_SECTOR_TO_BYTE(bpb->ReservedSectors);

    ZeroMemory(
        fat,
        VFD_SECTOR_TO_BYTE(bpb->SectorsPerFAT * bpb->NumberOfFATs));

    //
    //  Make up FAT entries for the root directory
    //
    for (idx = 0; idx < bpb->NumberOfFATs; idx++) {
        *fat = bpb->MediaDescriptor;
        *(fat + 1) = 0xff;
        *(fat + 2) = 0xff;

        fat += VFD_SECTOR_TO_BYTE(bpb->SectorsPerFAT);
    }

    //
    //  Clear root directory entries
    //
    ZeroMemory(fat, bpb->RootEntries * FAT_DIR_ENTRY_SIZE);

    VFDTRACE(0,
        ("[VFD] VfdFormatImage - OUT\n"));

    return ERROR_SUCCESS;
}