| 1 | |
| 2 | |
| 3 | *
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| 4 | * Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved.
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| 5 | *
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| 6 |
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| 7 |
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| 8 | #include <linux/types.h>
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| 9 |
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| 10 | #include "ntfs_fs.h"
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| 11 |
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| 12 | #define BITS_IN_SIZE_T (sizeof(size_t) * 8)
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| 13 |
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| 14 | |
| 15 | * fill_mask[i] - first i bits are '1' , i = 0,1,2,3,4,5,6,7,8
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| 16 | * fill_mask[i] = 0xFF >> (8-i)
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| 17 |
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| 18 | static const u8 fill_mask[] = { 0x00, 0x01, 0x03, 0x07, 0x0F,
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| 19 | 0x1F, 0x3F, 0x7F, 0xFF };
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| 20 |
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| 21 | |
| 22 | * zero_mask[i] - first i bits are '0' , i = 0,1,2,3,4,5,6,7,8
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| 23 | * zero_mask[i] = 0xFF << i
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| 24 |
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| 25 | static const u8 zero_mask[] = { 0xFF, 0xFE, 0xFC, 0xF8, 0xF0,
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| 26 | 0xE0, 0xC0, 0x80, 0x00 };
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| 27 |
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| 28 | |
| 29 | * are_bits_clear
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| 30 | *
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| 31 | * Return: True if all bits [bit, bit+nbits) are zeros "0".
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| 32 |
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| 33 | bool are_bits_clear(const void *lmap, size_t bit, size_t nbits)
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| 34 | {
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| 35 | size_t pos = bit & 7;
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| 36 | const u8 *map = (u8 *)lmap + (bit >> 3);
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| 37 |
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| 38 | if (pos) {
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| 39 | if (8 - pos >= nbits)
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| 40 | return !nbits || !(*map & fill_mask[pos + nbits] &
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| 41 | zero_mask[pos]);
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| 42 |
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| 43 | if (*map++ & zero_mask[pos])
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| 44 | return false;
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| 45 | nbits -= 8 - pos;
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| 46 | }
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| 47 |
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| 48 | pos = ((size_t)map) & (sizeof(size_t) - 1);
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| 49 | if (pos) {
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| 50 | pos = sizeof(size_t) - pos;
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| 51 | if (nbits >= pos * 8) {
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| 52 | for (nbits -= pos * 8; pos; pos--, map++) {
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| 53 | if (*map)
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| 54 | return false;
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| 55 | }
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| 56 | }
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| 57 | }
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| 58 |
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| 59 | for (pos = nbits / BITS_IN_SIZE_T; pos; pos--, map += sizeof(size_t)) {
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| 60 | if (*((size_t *)map))
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| 61 | return false;
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| 62 | }
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| 63 |
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| 64 | for (pos = (nbits % BITS_IN_SIZE_T) >> 3; pos; pos--, map++) {
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| 65 | if (*map)
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| 66 | return false;
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| 67 | }
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| 68 |
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| 69 | pos = nbits & 7;
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| 70 | if (pos && (*map & fill_mask[pos]))
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| 71 | return false;
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| 72 |
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| 73 | return true;
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| 74 | }
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| 75 |
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| 76 | |
| 77 | * are_bits_set
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| 78 | *
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| 79 | * Return: True if all bits [bit, bit+nbits) are ones "1".
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| 80 |
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| 81 | bool are_bits_set(const void *lmap, size_t bit, size_t nbits)
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| 82 | {
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| 83 | u8 mask;
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| 84 | size_t pos = bit & 7;
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| 85 | const u8 *map = (u8 *)lmap + (bit >> 3);
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| 86 |
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| 87 | if (pos) {
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| 88 | if (8 - pos >= nbits) {
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| 89 | mask = fill_mask[pos + nbits] & zero_mask[pos];
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| 90 | return !nbits || (*map & mask) == mask;
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| 91 | }
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| 92 |
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| 93 | mask = zero_mask[pos];
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| 94 | if ((*map++ & mask) != mask)
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| 95 | return false;
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| 96 | nbits -= 8 - pos;
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| 97 | }
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| 98 |
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| 99 | pos = ((size_t)map) & (sizeof(size_t) - 1);
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| 100 | if (pos) {
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| 101 | pos = sizeof(size_t) - pos;
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| 102 | if (nbits >= pos * 8) {
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| 103 | for (nbits -= pos * 8; pos; pos--, map++) {
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| 104 | if (*map != 0xFF)
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| 105 | return false;
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| 106 | }
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| 107 | }
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| 108 | }
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| 109 |
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| 110 | for (pos = nbits / BITS_IN_SIZE_T; pos; pos--, map += sizeof(size_t)) {
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| 111 | if (*((size_t *)map) != MINUS_ONE_T)
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| 112 | return false;
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| 113 | }
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| 114 |
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| 115 | for (pos = (nbits % BITS_IN_SIZE_T) >> 3; pos; pos--, map++) {
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| 116 | if (*map != 0xFF)
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| 117 | return false;
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| 118 | }
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| 119 |
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| 120 | pos = nbits & 7;
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| 121 | if (pos) {
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| 122 | mask = fill_mask[pos];
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| 123 | if ((*map & mask) != mask)
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| 124 | return false;
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| 125 | }
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| 126 |
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| 127 | return true;
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| 128 | }
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