(Logical change 1.59)
cantab.net!aia21
parent
26a99e4db3
commit
54cde7ab8e
167
libntfs/bitmap.c
167
libntfs/bitmap.c
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/*
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* bitmap.c - Bitmap handling code. Part of the Linux-NTFS project.
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*
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* Copyright (c) 2002 Anton Altaparmakov
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*
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* This program/include file is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program/include file is distributed in the hope that it will be
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* useful, but WITHOUT ANY WARRANTY; without even the implied warranty
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* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (in the main directory of the Linux-NTFS
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* distribution in the file COPYING); if not, write to the Free Software
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* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <stdlib.h>
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#include <errno.h>
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#include "types.h"
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#include "attrib.h"
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#include "bitmap.h"
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/**
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* ntfs_bitmap_clear_run - clear a run of bits in a bitmap
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* @na: attribute containing the bitmap
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* @start_bit: first bit to clear
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* @count: number of bits to clear
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*
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* Clear @count bits starting at bit @start_bit in the bitmap described by the
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* attribute @na.
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*
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* On success return 0 and on error return -1 with errno set to the error code.
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*/
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int ntfs_bitmap_clear_run(ntfs_attr *na, s64 start_bit, s64 count)
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{
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u8 *buf, *lastbyte_buf;
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s64 bufsize, br;
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int bit, firstbyte, lastbyte, lastbyte_pos, tmp, err;
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if (!na || start_bit < 0 || count < 0) {
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errno = EINVAL;
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return -1;
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}
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bit = start_bit & 7;
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if (bit)
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firstbyte = 1;
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else
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firstbyte = 0;
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/* Calculate the required buffer size in bytes, capping it at 8kiB. */
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bufsize = ((count - (bit ? 8 - bit : 0) + 7) >> 3) + firstbyte;
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if (bufsize > 8192)
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bufsize = 8192;
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/* Allocate already zeroed memory. */
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buf = (u8*)calloc(1, bufsize);
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if (!buf)
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return -1;
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/* If there is a first partial byte... */
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if (bit) {
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/* read it in... */
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br = ntfs_attr_pread(na, start_bit >> 3, 1, buf);
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if (br != 1) {
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free(buf);
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errno = EIO;
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return -1;
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}
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/* and clear the appropriate bits in it. */
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while ((bit & 7) && count--)
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*buf &= ~(1 << bit++);
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/* Update @start_bit to the new position. */
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start_bit = (start_bit + 7) & ~7;
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}
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/* Loop until @count reaches zero. */
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lastbyte = 0;
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lastbyte_buf = NULL;
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bit = count & 7;
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do {
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/* If there is a last partial byte... */
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if (bit) {
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lastbyte_pos = ((count + 7) >> 3) + firstbyte;
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if (!lastbyte_pos) {
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// FIXME: Eeek! BUG!
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fprintf(stderr, "%s(): Eeek! lastbyte is zero. "
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"Leaving inconsistent "
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"metadata.\n", __FUNCTION__);
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err = EIO;
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goto free_err_out;
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}
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/* and it is in the currently loaded bitmap window... */
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if (lastbyte_pos <= bufsize) {
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lastbyte_buf = buf + lastbyte_pos - 1;
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/* read the byte in... */
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br = ntfs_attr_pread(na, (start_bit + count) >>
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3, 1, lastbyte_buf);
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if (br != 1) {
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// FIXME: Eeek! We need rollback! (AIA)
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fprintf(stderr, "%s(): Eeek! Read of "
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"last byte failed. "
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"Leaving inconsistent "
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"metadata.\n",
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__FUNCTION__);
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err = EIO;
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goto free_err_out;
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}
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/* and clear the appropriate bits in it. */
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while (bit && count--)
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*lastbyte_buf &= ~(1 << --bit);
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/* We don't want to come back here... */
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bit = 0;
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/* We have a last byte that we have handled. */
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lastbyte = 1;
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}
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}
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/* Write the prepared buffer to disk. */
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tmp = (start_bit >> 3) - firstbyte;
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br = ntfs_attr_pwrite(na, tmp, bufsize, buf);
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if (br != tmp) {
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// FIXME: Eeek! We need rollback! (AIA)
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fprintf(stderr, "%s(): Eeek! Failed to write buffer "
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"to bitmap. Leaving inconsistent "
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"metadata.\n", __FUNCTION__);
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err = EIO;
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goto free_err_out;
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}
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/* Update counters. */
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tmp = (bufsize - firstbyte - lastbyte) << 3;
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firstbyte = 0;
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start_bit += tmp;
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count -= tmp;
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if (bufsize > (count + 7) >> 3)
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bufsize = (count + 7) >> 3;
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if (lastbyte && count != 0) {
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// FIXME: Eeek! BUG!
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fprintf(stderr, "%s(): Eeek! Last buffer but count is "
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"not zero (= %Li). Leaving "
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"inconsistent metadata.\n",
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__FUNCTION__, count);
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err = EIO;
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goto free_err_out;
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}
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} while (count > 0);
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/* Done! */
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free(buf);
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return 0;
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free_err_out:
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free(buf);
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errno = err;
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return -1;
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}
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