524 lines
14 KiB
C++
524 lines
14 KiB
C++
/*
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* CiderPress
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* Copyright (C) 2007 by faddenSoft, LLC. All Rights Reserved.
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* See the file LICENSE for distribution terms.
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*/
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/*
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* Implementation of the Windows FAT filesystem.
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*
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* Right now we just try to identify that a disk is in a PC format rather
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* than Apple II. The trick here is to figure out whether block 0 is a
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* Master Boot Record or merely a Boot Sector.
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*/
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#include "StdAfx.h"
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#include "DiskImgPriv.h"
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/*
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* ===========================================================================
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* DiskFSFAT
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* ===========================================================================
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*/
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const int kBlkSize = 512;
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const long kBootBlock = 0;
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const unsigned short kSignature = 0xaa55; // MBR or boot sector
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const int kSignatureOffset = 0x1fe;
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const unsigned char kOpcodeMumble = 0x33; // seen on 2nd drive
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const unsigned char kOpcodeBranch = 0xeb;
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const unsigned char kOpcodeSetInt = 0xfa;
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typedef struct PartitionTableEntry {
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unsigned char driveNum; // dl (0x80 or 0x00)
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unsigned char startHead; // dh
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unsigned char startSector; // cl (&0x3f=sector, +two hi bits cyl)
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unsigned char startCylinder; // ch (low 8 bits of 10-bit cylinder)
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unsigned char type; // partition type
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unsigned char endHead; // dh
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unsigned char endSector; // cl
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unsigned char endCylinder; // ch
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unsigned long startLBA; // in blocks
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unsigned long size; // in blocks
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} PartitionTableEntry;
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/*
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* Definition of a Master Boot Record, which is block 0 of a physical volume.
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*/
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typedef struct DiskFSFAT::MasterBootRecord {
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/*
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* Begins immediately with code, usually 0xfa (set interrupt flag) or
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* 0xeb (relative branch).
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*/
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unsigned char firstByte;
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/*
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* Partition table starts at 0x1be. Four entries, each 16 bytes.
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*/
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PartitionTableEntry parTab[4];
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} MasterBootRecord;
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/*
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* Definition of a boot sector, which is block 0 of a logical volume.
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*/
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typedef struct DiskFSFAT::BootSector {
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/*
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* The first few bytes of the boot sector is called the BIOS Parameter
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* Block, or BPB.
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*/
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unsigned char jump[3]; // usually EB XX 90
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unsigned char oemName[8]; // e.g. "MSWIN4.1" or "MSDOS5.0"
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unsigned short bytesPerSector; // usually (always?) 512
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unsigned char sectPerCluster;
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unsigned short reservedSectors;
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unsigned char numFAT;
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unsigned short numRootDirEntries;
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unsigned short numSectors; // if set, ignore numSectorsHuge
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unsigned char mediaType;
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unsigned short numFATSectors;
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unsigned short sectorsPerTrack;
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unsigned short numHeads;
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unsigned long numHiddenSectors;
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unsigned long numSectorsHuge; // only if numSectors==0
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/*
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* This next part can start immediately after the above (at 0x24) for
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* FAT12/FAT16, or somewhat later (0x42) for FAT32. It doesn't seem
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* to exist for NTFS. Probably safest to assume it doesn't exist.
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*
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* The only way to be sure of what we're dealing with is to know the
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* partition type, but if this is our block 0 then we can't know what
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* that is.
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*/
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unsigned char driveNum;
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unsigned char reserved;
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unsigned char signature; // 0x29
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unsigned long volumeID;
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unsigned char volumeLabel[11]; // e.g. "FUBAR "
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unsigned char fileSysType[8]; // e.g. "FAT12 "
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/*
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* Code follows. Signature 0xaa55 in the last two bytes.
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*/
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} BootSector;
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// some values for MediaType
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enum MediaType {
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kMediaTypeLarge = 0xf0, // 1440KB or 2800KB 3.5" disk
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kMediaTypeHardDrive = 0xf8,
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kMediaTypeMedium = 0xf9, // 720KB 3.5" disk or 1.2MB 5.25" disk
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kMediaTypeSmall = 0xfd, // 360KB 5.25" disk
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};
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/*
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* Unpack the MBR.
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*
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* Returns "true" if this looks like an MBR, "false" otherwise.
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*/
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/*static*/ bool
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DiskFSFAT::UnpackMBR(const unsigned char* buf, MasterBootRecord* pOut)
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{
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const unsigned char* ptr;
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int i;
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pOut->firstByte = buf[0x00];
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ptr = &buf[0x1be];
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for (i = 0; i < 4; i++) {
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pOut->parTab[i].driveNum = ptr[0x00];
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pOut->parTab[i].startHead = ptr[0x01];
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pOut->parTab[i].startSector = ptr[0x02];
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pOut->parTab[i].startCylinder = ptr[0x03];
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pOut->parTab[i].type = ptr[0x04];
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pOut->parTab[i].endHead = ptr[0x05];
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pOut->parTab[i].endSector = ptr[0x06];
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pOut->parTab[i].endCylinder = ptr[0x07];
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pOut->parTab[i].startLBA = GetLongLE(&ptr[0x08]);
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pOut->parTab[i].size = GetLongLE(&ptr[0x0c]);
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ptr += 16;
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}
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if (pOut->firstByte != kOpcodeBranch &&
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pOut->firstByte != kOpcodeSetInt &&
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pOut->firstByte != kOpcodeMumble)
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return false;
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bool foundActive = false;
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for (i = 0; i < 4; i++) {
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if (pOut->parTab[i].driveNum == 0x80)
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foundActive = true;
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else if (pOut->parTab[i].driveNum != 0x00)
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return false; // must be 0x00 or 0x80
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}
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// CFFA cards don't seem to set the "active" flag
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//if (!foundActive)
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// return false;
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return true;
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}
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/*
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* Unpack the boot sector.
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*
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* Returns "true" if this looks like a boot sector, "false" otherwise.
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*/
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/*static*/ bool
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DiskFSFAT::UnpackBootSector(const unsigned char* buf, BootSector* pOut)
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{
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memcpy(pOut->jump, &buf[0x00], sizeof(pOut->jump));
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memcpy(pOut->oemName, &buf[0x03], sizeof(pOut->oemName));
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pOut->bytesPerSector = GetShortLE(&buf[0x0b]);
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pOut->sectPerCluster = buf[0x0d];
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pOut->reservedSectors = GetShortLE(&buf[0x0e]);
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pOut->numFAT = buf[0x10];
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pOut->numRootDirEntries = GetShortLE(&buf[0x11]);
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pOut->numSectors = GetShortLE(&buf[0x13]);
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pOut->mediaType = buf[0x15];
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pOut->numFATSectors = GetShortLE(&buf[0x16]);
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pOut->sectorsPerTrack = GetShortLE(&buf[0x18]);
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pOut->numHeads = GetShortLE(&buf[0x1a]);
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pOut->numHiddenSectors = GetLongLE(&buf[0x1c]);
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pOut->numSectorsHuge = GetLongLE(&buf[0x20]);
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if (pOut->jump[0] != kOpcodeBranch && pOut->jump[0] != kOpcodeSetInt)
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return false;
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if (pOut->bytesPerSector != 512)
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return false;
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return true;
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}
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/*
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* See if this looks like a FAT volume.
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*/
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/*static*/ DIError
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DiskFSFAT::TestImage(DiskImg* pImg, DiskImg::SectorOrder imageOrder)
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{
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DIError dierr = kDIErrNone;
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unsigned char blkBuf[kBlkSize];
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MasterBootRecord mbr;
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BootSector bs;
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dierr = pImg->ReadBlockSwapped(kBootBlock, blkBuf, imageOrder,
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DiskImg::kSectorOrderProDOS);
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if (dierr != kDIErrNone)
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goto bail;
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/*
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* Both MBR and boot sectors have the same signature in block 0.
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*/
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if (GetShortLE(&blkBuf[kSignatureOffset]) != kSignature) {
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dierr = kDIErrFilesystemNotFound;
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goto bail;
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}
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/*
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* Decode it as an MBR and as a partition table. Figure out which
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* one makes sense. If neither make sense, fail.
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*/
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bool hasMBR, hasBS;
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hasMBR = UnpackMBR(blkBuf, &mbr);
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hasBS = UnpackBootSector(blkBuf, &bs);
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LOGI(" FAT hasMBR=%d hasBS=%d", hasMBR, hasBS);
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if (!hasMBR && !hasBS) {
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dierr = kDIErrFilesystemNotFound;
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goto bail;
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}
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if (hasMBR) {
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LOGI(" FAT partition table found:");
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for (int i = 0; i < 4; i++) {
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LOGI(" %d: type=0x%02x start LBA=%-9lu size=%lu",
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i, mbr.parTab[i].type,
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mbr.parTab[i].startLBA, mbr.parTab[i].size);
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}
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}
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if (hasBS) {
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LOGI(" FAT boot sector found:");
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LOGI(" OEMName is '%.8s'", bs.oemName);
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}
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// looks good!
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bail:
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return dierr;
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}
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/*
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* Test to see if the image is a FAT disk.
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*/
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/*static*/ DIError
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DiskFSFAT::TestFS(DiskImg* pImg, DiskImg::SectorOrder* pOrder,
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DiskImg::FSFormat* pFormat, FSLeniency leniency)
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{
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/* must be block format, should be at least 360K */
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if (!pImg->GetHasBlocks() || pImg->GetNumBlocks() < kExpectedMinBlocks)
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return kDIErrFilesystemNotFound;
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if (pImg->GetIsEmbedded()) // don't look for FAT inside CFFA!
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return kDIErrFilesystemNotFound;
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DiskImg::SectorOrder ordering[DiskImg::kSectorOrderMax];
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DiskImg::GetSectorOrderArray(ordering, *pOrder);
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for (int i = 0; i < DiskImg::kSectorOrderMax; i++) {
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if (ordering[i] == DiskImg::kSectorOrderUnknown)
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continue;
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if (TestImage(pImg, ordering[i]) == kDIErrNone) {
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*pOrder = ordering[i];
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*pFormat = DiskImg::kFormatMSDOS;
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return kDIErrNone;
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}
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}
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LOGI(" FAT didn't find valid FS");
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return kDIErrFilesystemNotFound;
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}
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/*
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* Get things rolling.
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*/
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DIError
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DiskFSFAT::Initialize(void)
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{
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DIError dierr = kDIErrNone;
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strcpy(fVolumeName, "[MS-DOS]"); // max 11 chars
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strcpy(fVolumeID, "FATxx [MS-DOS]");
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// take the easy way out
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fTotalBlocks = fpImg->GetNumBlocks();
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CreateFakeFile();
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SetVolumeUsageMap();
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return dierr;
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}
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/*
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* Blank out the volume usage map.
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*/
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void
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DiskFSFAT::SetVolumeUsageMap(void)
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{
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VolumeUsage::ChunkState cstate;
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long block;
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fVolumeUsage.Create(fpImg->GetNumBlocks());
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cstate.isUsed = true;
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cstate.isMarkedUsed = true;
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cstate.purpose = VolumeUsage::kChunkPurposeUnknown;
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for (block = fTotalBlocks-1; block >= 0; block--)
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fVolumeUsage.SetChunkState(block, &cstate);
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}
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/*
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* Fill a buffer with some interesting stuff, and add it to the file list.
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*/
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void
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DiskFSFAT::CreateFakeFile(void)
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{
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A2FileFAT* pFile;
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char buf[768]; // currently running about 430
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static const char* kFormatMsg =
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"The FAT12/16/32 and NTFS filesystems are not supported. CiderPress knows\r\n"
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"how to recognize MS-DOS and Windows volumes so that it can identify\r\n"
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"PC data on removable media, but it does not know how to view or extract\r\n"
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"files from them.\r\n"
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"\r\n"
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"Some information about this FAT volume:\r\n"
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"\r\n"
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" Volume name : '%s'\r\n"
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" Volume size : %ld blocks (%.2fMB)\r\n"
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"\r\n"
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"(CiderPress limits itself to 8GB, so larger volume sizes may not be shown.)\r\n"
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;
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long capacity;
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capacity = fTotalBlocks;
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memset(buf, 0, sizeof(buf));
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sprintf(buf, kFormatMsg,
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fVolumeName,
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capacity,
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(double) capacity / 2048.0);
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pFile = new A2FileFAT(this);
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pFile->SetFakeFile(buf, strlen(buf));
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strcpy(pFile->fFileName, "(not supported)");
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AddFileToList(pFile);
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}
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/*
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* ===========================================================================
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* A2FileFAT
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* ===========================================================================
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*/
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/*
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* Dump the contents of the A2File structure.
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*/
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void
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A2FileFAT::Dump(void) const
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{
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LOGI("A2FileFAT '%s'", fFileName);
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}
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/*
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* Not a whole lot to do.
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*/
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DIError
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A2FileFAT::Open(A2FileDescr** ppOpenFile, bool readOnly,
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bool rsrcFork /*=false*/)
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{
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A2FDFAT* pOpenFile = NULL;
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if (fpOpenFile != NULL)
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return kDIErrAlreadyOpen;
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if (rsrcFork)
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return kDIErrForkNotFound;
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assert(readOnly == true);
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pOpenFile = new A2FDFAT(this);
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fpOpenFile = pOpenFile;
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*ppOpenFile = pOpenFile;
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return kDIErrNone;
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}
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/*
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* ===========================================================================
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* A2FDFAT
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* ===========================================================================
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*/
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/*
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* Read a chunk of data from the fake file.
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*/
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DIError
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A2FDFAT::Read(void* buf, size_t len, size_t* pActual)
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{
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LOGI(" FAT reading %d bytes from '%s' (offset=%ld)",
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len, fpFile->GetPathName(), (long) fOffset);
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A2FileFAT* pFile = (A2FileFAT*) fpFile;
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/* don't allow them to read past the end of the file */
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if (fOffset + (long)len > pFile->fLength) {
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if (pActual == NULL)
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return kDIErrDataUnderrun;
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len = (size_t) (pFile->fLength - fOffset);
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}
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if (pActual != NULL)
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*pActual = len;
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memcpy(buf, pFile->GetFakeFileBuf(), len);
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fOffset += len;
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return kDIErrNone;
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}
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/*
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* Write data at the current offset.
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*/
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DIError
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A2FDFAT::Write(const void* buf, size_t len, size_t* pActual)
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{
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return kDIErrNotSupported;
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}
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/*
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* Seek to a new offset.
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*/
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DIError
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A2FDFAT::Seek(di_off_t offset, DIWhence whence)
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{
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di_off_t fileLen = ((A2FileFAT*) fpFile)->fLength;
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switch (whence) {
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case kSeekSet:
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if (offset < 0 || offset > fileLen)
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return kDIErrInvalidArg;
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fOffset = offset;
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break;
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case kSeekEnd:
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if (offset > 0 || offset < -fileLen)
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return kDIErrInvalidArg;
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fOffset = fileLen + offset;
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break;
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case kSeekCur:
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if (offset < -fOffset ||
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offset >= (fileLen - fOffset))
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{
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return kDIErrInvalidArg;
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}
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fOffset += offset;
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break;
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default:
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assert(false);
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return kDIErrInvalidArg;
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}
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assert(fOffset >= 0 && fOffset <= fileLen);
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return kDIErrNone;
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}
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/*
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* Return current offset.
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*/
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di_off_t
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A2FDFAT::Tell(void)
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{
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return fOffset;
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}
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/*
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* Release file state, and tell our parent to destroy us.
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*/
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DIError
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A2FDFAT::Close(void)
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{
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fpFile->CloseDescr(this);
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return kDIErrNone;
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}
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/*
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* Return the #of sectors/blocks in the file.
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*/
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long
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A2FDFAT::GetSectorCount(void) const
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{
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A2FileFAT* pFile = (A2FileFAT*) fpFile;
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return (long) ((pFile->fLength+255) / 256);
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}
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long
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A2FDFAT::GetBlockCount(void) const
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{
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A2FileFAT* pFile = (A2FileFAT*) fpFile;
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return (long) ((pFile->fLength+511) / 512);
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}
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/*
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* Return the Nth track/sector in this file.
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*/
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DIError
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A2FDFAT::GetStorage(long sectorIdx, long* pTrack, long* pSector) const
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{
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return kDIErrNotSupported;
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}
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/*
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* Return the Nth 512-byte block in this file.
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*/
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DIError
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A2FDFAT::GetStorage(long blockIdx, long* pBlock) const
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{
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return kDIErrNotSupported;
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}
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