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