usbloadergx/source/libntfs/bitmap.c

/**
 * bitmap.c - Bitmap handling code. Originated from the Linux-NTFS project.
 *
 * Copyright (c) 2002-2006 Anton Altaparmakov
 * Copyright (c) 2004-2005 Richard Russon
 * Copyright (c) 2004-2008 Szabolcs Szakacsits
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (in the main directory of the NTFS-3G
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STDIO_H
#include <stdio.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif

#include "types.h"
#include "attrib.h"
#include "bitmap.h"
#include "debug.h"
#include "logging.h"
#include "misc.h"

/**
 * ntfs_bit_set - set a bit in a field of bits
 * @bitmap: field of bits
 * @bit:    bit to set
 * @new_value:  value to set bit to (0 or 1)
 *
 * Set the bit @bit in the @bitmap to @new_value. Ignore all errors.
 */
void ntfs_bit_set( u8 *bitmap, const u64 bit, const u8 new_value )
{
    if ( !bitmap || new_value > 1 )
        return;
    if ( !new_value )
        bitmap[bit >> 3] &= ~( 1 << ( bit & 7 ) );
    else
        bitmap[bit >> 3] |= ( 1 << ( bit & 7 ) );
}

/**
 * ntfs_bit_get - get value of a bit in a field of bits
 * @bitmap: field of bits
 * @bit:    bit to get
 *
 * Get and return the value of the bit @bit in @bitmap (0 or 1).
 * Return -1 on error.
 */
char ntfs_bit_get( const u8 *bitmap, const u64 bit )
{
    if ( !bitmap )
        return -1;
    return ( bitmap[bit >> 3] >> ( bit & 7 ) ) & 1;
}

/**
 * ntfs_bit_get_and_set - get value of a bit in a field of bits and set it
 * @bitmap: field of bits
 * @bit:    bit to get/set
 * @new_value:  value to set bit to (0 or 1)
 *
 * Return the value of the bit @bit and set it to @new_value (0 or 1).
 * Return -1 on error.
 */
char ntfs_bit_get_and_set( u8 *bitmap, const u64 bit, const u8 new_value )
{
    register u8 old_bit, shift;

    if ( !bitmap || new_value > 1 )
        return -1;
    shift = bit & 7;
    old_bit = ( bitmap[bit >> 3] >> shift ) & 1;
    if ( new_value != old_bit )
        bitmap[bit >> 3] ^= 1 << shift;
    return old_bit;
}

/**
 * ntfs_bitmap_set_bits_in_run - set a run of bits in a bitmap to a value
 * @na:     attribute containing the bitmap
 * @start_bit:  first bit to set
 * @count:  number of bits to set
 * @value:  value to set the bits to (i.e. 0 or 1)
 *
 * Set @count bits starting at bit @start_bit in the bitmap described by the
 * attribute @na to @value, where @value is either 0 or 1.
 *
 * On success return 0 and on error return -1 with errno set to the error code.
 */
static int ntfs_bitmap_set_bits_in_run( ntfs_attr *na, s64 start_bit,
                                        s64 count, int value )
{
    s64 bufsize, br;
    u8 *buf, *lastbyte_buf;
    int bit, firstbyte, lastbyte, lastbyte_pos, tmp, ret = -1;

    if ( !na || start_bit < 0 || count < 0 )
    {
        errno = EINVAL;
        ntfs_log_perror( "%s: Invalid argument (%p, %lld, %lld)",
                         __FUNCTION__, na, ( long long )start_bit, ( long long )count );
        return -1;
    }

    bit = start_bit & 7;
    if ( bit )
        firstbyte = 1;
    else
        firstbyte = 0;

    /* Calculate the required buffer size in bytes, capping it at 8kiB. */
    bufsize = ( ( count - ( bit ? 8 - bit : 0 ) + 7 ) >> 3 ) + firstbyte;
    if ( bufsize > 8192 )
        bufsize = 8192;

    buf = ntfs_malloc( bufsize );
    if ( !buf )
        return -1;

    /* Depending on @value, zero or set all bits in the allocated buffer. */
    memset( buf, value ? 0xff : 0, bufsize );

    /* If there is a first partial byte... */
    if ( bit )
    {
        /* read it in... */
        br = ntfs_attr_pread( na, start_bit >> 3, 1, buf );
        if ( br != 1 )
        {
            if ( br >= 0 )
                errno = EIO;
            goto free_err_out;
        }
        /* and set or clear the appropriate bits in it. */
        while ( ( bit & 7 ) && count-- )
        {
            if ( value )
                *buf |= 1 << bit++;
            else
                *buf &= ~( 1 << bit++ );
        }
        /* Update @start_bit to the new position. */
        start_bit = ( start_bit + 7 ) & ~7;
    }

    /* Loop until @count reaches zero. */
    lastbyte = 0;
    lastbyte_buf = NULL;
    bit = count & 7;
    do
    {
        /* If there is a last partial byte... */
        if ( count > 0 && bit )
        {
            lastbyte_pos = ( ( count + 7 ) >> 3 ) + firstbyte;
            if ( !lastbyte_pos )
            {
                // FIXME: Eeek! BUG!
                ntfs_log_error( "Lastbyte is zero. Leaving "
                                "inconsistent metadata.\n" );
                errno = EIO;
                goto free_err_out;
            }
            /* and it is in the currently loaded bitmap window... */
            if ( lastbyte_pos <= bufsize )
            {
                lastbyte_buf = buf + lastbyte_pos - 1;

                /* read the byte in... */
                br = ntfs_attr_pread( na, ( start_bit + count ) >>
                                      3, 1, lastbyte_buf );
                if ( br != 1 )
                {
                    // FIXME: Eeek! We need rollback! (AIA)
                    if ( br >= 0 )
                        errno = EIO;
                    ntfs_log_perror( "Reading of last byte "
                                     "failed (%lld). Leaving inconsistent "
                                     "metadata", ( long long )br );
                    goto free_err_out;
                }
                /* and set/clear the appropriate bits in it. */
                while ( bit && count-- )
                {
                    if ( value )
                        *lastbyte_buf |= 1 << --bit;
                    else
                        *lastbyte_buf &= ~( 1 << --bit );
                }
                /* We don't want to come back here... */
                bit = 0;
                /* We have a last byte that we have handled. */
                lastbyte = 1;
            }
        }

        /* Write the prepared buffer to disk. */
        tmp = ( start_bit >> 3 ) - firstbyte;
        br = ntfs_attr_pwrite( na, tmp, bufsize, buf );
        if ( br != bufsize )
        {
            // FIXME: Eeek! We need rollback! (AIA)
            if ( br >= 0 )
                errno = EIO;
            ntfs_log_perror( "Failed to write buffer to bitmap "
                             "(%lld != %lld). Leaving inconsistent metadata",
                             ( long long )br, ( long long )bufsize );
            goto free_err_out;
        }

        /* Update counters. */
        tmp = ( bufsize - firstbyte - lastbyte ) << 3;
        if ( firstbyte )
        {
            firstbyte = 0;
            /*
             * Re-set the partial first byte so a subsequent write
             * of the buffer does not have stale, incorrect bits.
             */
            *buf = value ? 0xff : 0;
        }
        start_bit += tmp;
        count -= tmp;
        if ( bufsize > ( tmp = ( count + 7 ) >> 3 ) )
            bufsize = tmp;

        if ( lastbyte && count != 0 )
        {
            // FIXME: Eeek! BUG!
            ntfs_log_error( "Last buffer but count is not zero "
                            "(%lld). Leaving inconsistent metadata.\n",
                            ( long long )count );
            errno = EIO;
            goto free_err_out;
        }
    }
    while ( count > 0 );

    ret = 0;

free_err_out:
    free( buf );
    return ret;
}

/**
 * ntfs_bitmap_set_run - set a run of bits in a bitmap
 * @na:     attribute containing the bitmap
 * @start_bit:  first bit to set
 * @count:  number of bits to set
 *
 * Set @count bits starting at bit @start_bit in the bitmap described by the
 * attribute @na.
 *
 * On success return 0 and on error return -1 with errno set to the error code.
 */
int ntfs_bitmap_set_run( ntfs_attr *na, s64 start_bit, s64 count )
{
    int ret;

    ntfs_log_enter( "Set from bit %lld, count %lld\n",
                    ( long long )start_bit, ( long long )count );
    ret = ntfs_bitmap_set_bits_in_run( na, start_bit, count, 1 );
    ntfs_log_leave( "\n" );
    return ret;
}

/**
 * ntfs_bitmap_clear_run - clear a run of bits in a bitmap
 * @na:     attribute containing the bitmap
 * @start_bit:  first bit to clear
 * @count:  number of bits to clear
 *
 * Clear @count bits starting at bit @start_bit in the bitmap described by the
 * attribute @na.
 *
 * On success return 0 and on error return -1 with errno set to the error code.
 */
int ntfs_bitmap_clear_run( ntfs_attr *na, s64 start_bit, s64 count )
{
    int ret;

    ntfs_log_enter( "Clear from bit %lld, count %lld\n",
                    ( long long )start_bit, ( long long )count );
    ret = ntfs_bitmap_set_bits_in_run( na, start_bit, count, 0 );
    ntfs_log_leave( "\n" );
    return ret;
}