129 строки
2.5 KiB
C
129 строки
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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*
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* Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved.
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*
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*/
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#include <linux/types.h>
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#include "ntfs_fs.h"
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#define BITS_IN_SIZE_T (sizeof(size_t) * 8)
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/*
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* fill_mask[i] - first i bits are '1' , i = 0,1,2,3,4,5,6,7,8
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* fill_mask[i] = 0xFF >> (8-i)
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*/
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static const u8 fill_mask[] = { 0x00, 0x01, 0x03, 0x07, 0x0F,
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0x1F, 0x3F, 0x7F, 0xFF };
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/*
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* zero_mask[i] - first i bits are '0' , i = 0,1,2,3,4,5,6,7,8
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* zero_mask[i] = 0xFF << i
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*/
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static const u8 zero_mask[] = { 0xFF, 0xFE, 0xFC, 0xF8, 0xF0,
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0xE0, 0xC0, 0x80, 0x00 };
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/*
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* are_bits_clear
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*
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* Return: True if all bits [bit, bit+nbits) are zeros "0".
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*/
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bool are_bits_clear(const ulong *lmap, size_t bit, size_t nbits)
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{
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size_t pos = bit & 7;
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const u8 *map = (u8 *)lmap + (bit >> 3);
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if (pos) {
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if (8 - pos >= nbits)
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return !nbits || !(*map & fill_mask[pos + nbits] &
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zero_mask[pos]);
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if (*map++ & zero_mask[pos])
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return false;
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nbits -= 8 - pos;
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}
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pos = ((size_t)map) & (sizeof(size_t) - 1);
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if (pos) {
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pos = sizeof(size_t) - pos;
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if (nbits >= pos * 8) {
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for (nbits -= pos * 8; pos; pos--, map++) {
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if (*map)
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return false;
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}
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}
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}
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for (pos = nbits / BITS_IN_SIZE_T; pos; pos--, map += sizeof(size_t)) {
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if (*((size_t *)map))
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return false;
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}
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for (pos = (nbits % BITS_IN_SIZE_T) >> 3; pos; pos--, map++) {
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if (*map)
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return false;
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}
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pos = nbits & 7;
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if (pos && (*map & fill_mask[pos]))
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return false;
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return true;
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}
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/*
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* are_bits_set
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*
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* Return: True if all bits [bit, bit+nbits) are ones "1".
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*/
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bool are_bits_set(const ulong *lmap, size_t bit, size_t nbits)
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{
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u8 mask;
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size_t pos = bit & 7;
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const u8 *map = (u8 *)lmap + (bit >> 3);
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if (pos) {
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if (8 - pos >= nbits) {
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mask = fill_mask[pos + nbits] & zero_mask[pos];
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return !nbits || (*map & mask) == mask;
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}
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mask = zero_mask[pos];
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if ((*map++ & mask) != mask)
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return false;
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nbits -= 8 - pos;
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}
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pos = ((size_t)map) & (sizeof(size_t) - 1);
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if (pos) {
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pos = sizeof(size_t) - pos;
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if (nbits >= pos * 8) {
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for (nbits -= pos * 8; pos; pos--, map++) {
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if (*map != 0xFF)
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return false;
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}
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}
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}
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for (pos = nbits / BITS_IN_SIZE_T; pos; pos--, map += sizeof(size_t)) {
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if (*((size_t *)map) != MINUS_ONE_T)
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return false;
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}
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for (pos = (nbits % BITS_IN_SIZE_T) >> 3; pos; pos--, map++) {
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if (*map != 0xFF)
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return false;
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}
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pos = nbits & 7;
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if (pos) {
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mask = fill_mask[pos];
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if ((*map & mask) != mask)
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return false;
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}
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return true;
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}
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