/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1999 by Sun Microsystems, Inc.
 * All rights reserved.
 */

/*
 * fsck_pcfs -- routines for manipulating the FAT.
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <libintl.h>
#include <sys/dktp/fdisk.h>
#include <sys/fs/pc_fs.h>
#include <sys/fs/pc_dir.h>
#include <sys/fs/pc_label.h>
#include "pcfs_common.h"
#include "fsck_pcfs.h"

extern  int32_t BytesPerCluster;
extern  int32_t TotalClusters;
extern  int32_t LastCluster;
extern  off64_t FirstClusterOffset;
extern  off64_t PartitionOffset;
extern  bpb_t   TheBIOSParameterBlock;
extern  int     ReadOnly;
extern  int     IsFAT32;
extern  int     Verbose;

static  uchar_t *TheFAT;
static  int     FATRewriteNeeded = 0;

int32_t         FATSize;
short           FATEntrySize;

static off64_t
seekFAT(int fd)
{
        off64_t seekto;
        /*
         *  The FAT(s) immediately follows the reserved sectors.
         */
        seekto = TheBIOSParameterBlock.bpb.resv_sectors *
                TheBIOSParameterBlock.bpb.bytes_per_sector + PartitionOffset;
        return (lseek64(fd, seekto, SEEK_SET));
}

void
getFAT(int fd)
{
        ssize_t bytesRead;

        if (TheFAT != NULL) {
                return;
        } else if ((TheFAT = (uchar_t *)malloc(FATSize)) == NULL) {
                mountSanityCheckFails();
                perror(gettext("No memory for a copy of the FAT"));
                (void) close(fd);
                exit(7);
        }
        if (seekFAT(fd) < 0) {
                mountSanityCheckFails();
                perror(gettext("Cannot seek to FAT"));
                (void) close(fd);
                exit(7);
        }
        if (Verbose)
                (void) fprintf(stderr,
                    gettext("Reading FAT\n"));
        if ((bytesRead = read(fd, TheFAT, FATSize)) != FATSize) {
                mountSanityCheckFails();
                if (bytesRead < 0) {
                        perror(gettext("Cannot read a FAT"));
                } else {
                        (void) fprintf(stderr,
                            gettext("Short read of FAT."));
                }
                (void) close(fd);
                exit(7);
        }
        /*
         * XXX - might want to read the other copies of the FAT
         * for comparison and/or to use if the first one seems hosed.
         */
        if (Verbose) {
                (void) fprintf(stderr,
                    gettext("Dump of FAT's first 32 bytes.\n"));
                header_for_dump();
                dump_bytes(TheFAT, 32);
        }
}

void
writeFATMods(int fd)
{
        ssize_t bytesWritten;

        if (TheFAT == NULL) {
                (void) fprintf(stderr,
                    gettext("Internal error: No FAT to write\n"));
                (void) close(fd);
                exit(11);
        }
        if (!FATRewriteNeeded) {
                if (Verbose) {
                        (void) fprintf(stderr,
                            gettext("No FAT changes need to be written.\n"));
                }
                return;
        }
        if (ReadOnly)
                return;
        if (Verbose)
                (void) fprintf(stderr, gettext("Writing FAT\n"));
        if (seekFAT(fd) < 0) {
                perror(gettext("Cannot seek to FAT"));
                (void) close(fd);
                exit(11);
        }
        if ((bytesWritten = write(fd, TheFAT, FATSize)) != FATSize) {
                if (bytesWritten < 0) {
                        perror(gettext("Cannot write FAT"));
                } else {
                        (void) fprintf(stderr,
                            gettext("Short write of FAT."));
                }
                (void) close(fd);
                exit(11);
        }
        FATRewriteNeeded = 0;
}

/*
 *  checkFAT32CleanBit()
 *      Return non-zero if the bit indicating proper Windows shutdown has
 *      been set.
 */
int
checkFAT32CleanBit(int fd)
{
        getFAT(fd);
        return (TheFAT[WIN_SHUTDOWN_STATUS_BYTE] & WIN_SHUTDOWN_BIT_MASK);
}

static uchar_t *
findClusterEntryInFAT(int32_t currentCluster)
{
        int32_t idx;
        if (FATEntrySize == 32) {
                idx = currentCluster * 4;
        } else if (FATEntrySize == 16) {
                idx = currentCluster * 2;
        } else {
                idx = currentCluster + currentCluster/2;
        }
        return (TheFAT + idx);
}

/*
 *  {read,write}FATentry
 *      For the 16 and 32 bit FATs these routines are relatively easy
 *      to follow.
 *
 *      12 bit FATs are kind of strange, though.  The magic index for
 *      12 bit FATS computed below, 1.5 * clusterNum, is a
 *      simplification that there are 8 bits in a byte, so you need
 *      1.5 bytes per entry.
 *
 *      It's easiest to think about FAT12 entries in pairs:
 *
 *      ---------------------------------------------
 *      | mid1 | low1 | low2 | high1 | high2 | mid2 |
 *      ---------------------------------------------
 *
 *      Each box in the diagram represents a nibble (4 bits) of a FAT
 *      entry.  A FAT entry is made up of three nibbles.  So if you
 *      look closely, you'll see that first byte of the pair of
 *      entries contains the low and middle nibbles of the first
 *      entry.  The second byte has the low nibble of the second entry
 *      and the high nibble of the first entry.  Those two bytes alone
 *      are enough to read the first entry.  The second FAT entry is
 *      finished out by the last nibble pair.
 */
int32_t
readFATEntry(int32_t currentCluster)
{
        int32_t value;
        uchar_t *ep;

        ep = findClusterEntryInFAT(currentCluster);
        if (FATEntrySize == 32) {
                read_32_bits(ep, (uint32_t *)&value);
        } else if (FATEntrySize == 16) {
                read_16_bits(ep, (uint32_t *)&value);
                /*
                 *  Convert 16 bit entry to 32 bit if we are
                 *  into the reserved or higher values.
                 */
                if (value >= PCF_RESCLUSTER)
                        value |= 0xFFF0000;
        } else {
                value = 0;
                if (currentCluster & 1) {
                        /*
                         * Odd numbered cluster
                         */
                        value = (((unsigned int)*ep++ & 0xf0) >> 4);
                        value += (*ep << 4);
                } else {
                        value = *ep++;
                        value += ((*ep & 0x0f) << 8);
                }
                /*
                 *  Convert 12 bit entry to 32 bit if we are
                 *  into the reserved or higher values.
                 */
                if (value >= PCF_12BCLUSTER)
                        value |= 0xFFFF000;
        }
        return (value);
}

void
writeFATEntry(int32_t currentCluster, int32_t value)
{
        uchar_t *ep;

        FATRewriteNeeded = 1;
        ep = findClusterEntryInFAT(currentCluster);
        if (FATEntrySize == 32) {
                store_32_bits(&ep, value);
        } else if (FATEntrySize == 16) {
                store_16_bits(&ep, value);
        } else {
                if (currentCluster & 1) {
                        /*
                         * Odd numbered cluster
                         */
                        *ep = (*ep & 0x0f) | ((value << 4) & 0xf0);
                        ep++;
                        *ep = (value >> 4) & 0xff;
                } else {
                        *ep++ = value & 0xff;
                        *ep = (*ep & 0xf0) | ((value >> 8) & 0x0f);
                }
        }
}

/*
 * reservedInFAT - Is this cluster marked in the reserved range?
 *      The range from PCF_RESCLUSTER32 to PCF_BADCLUSTER32 - 1,
 *      have been reserved by Microsoft.  No cluster should be
 *      marked with these; they are effectively invalid cluster values.
 */
int
reservedInFAT(int32_t clusterNum)
{
        int32_t e;

        e = readFATEntry(clusterNum);
        return (e >= PCF_RESCLUSTER32 && e < PCF_BADCLUSTER32);
}

/*
 *  badInFAT - Is this cluster marked as bad?  I.e., is it inaccessible?
 */
int
badInFAT(int32_t clusterNum)
{
        return (readFATEntry(clusterNum) == PCF_BADCLUSTER32);
}

/*
 *  lastInFAT - Is this cluster marked as free?  I.e., is it available
 *      for use?
 */
int
freeInFAT(int32_t clusterNum)
{
        return (readFATEntry(clusterNum) == PCF_FREECLUSTER);
}

/*
 *  lastInFAT - Is this cluster the last in its cluster chain?
 */
int
lastInFAT(int32_t clusterNum)
{
        return (readFATEntry(clusterNum) == PCF_LASTCLUSTER32);
}

/*
 *  markLastInFAT - Mark this cluster as the last in its cluster chain.
 */
void
markLastInFAT(int32_t clusterNum)
{
        writeFATEntry(clusterNum, PCF_LASTCLUSTER32);
}

void
markFreeInFAT(int32_t clusterNum)
{
        writeFATEntry(clusterNum, PCF_FREECLUSTER);
}

void
markBadInFAT(int32_t clusterNum)
{
        writeFATEntry(clusterNum, PCF_BADCLUSTER32);
}