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author | Konstantin Komarov <almaz.alexandrovich@paragon-software.com> | 2021-08-13 17:21:29 +0300 |
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committer | Konstantin Komarov <almaz.alexandrovich@paragon-software.com> | 2021-08-13 07:55:41 -0700 |
commit | 3f3b442b5ad2455507c9bfdacf39a3792eb3a6d0 (patch) | |
tree | 19d6f9d45bee5dd44d46149e9104ef4458445ab7 /fs/ntfs3/bitfunc.c | |
parent | 82cae269cfa953032fbb8980a7d554d60fb00b17 (diff) | |
download | linux-3f3b442b5ad2455507c9bfdacf39a3792eb3a6d0.tar.gz linux-3f3b442b5ad2455507c9bfdacf39a3792eb3a6d0.tar.bz2 linux-3f3b442b5ad2455507c9bfdacf39a3792eb3a6d0.zip |
fs/ntfs3: Add bitmap
This adds bitmap
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Diffstat (limited to 'fs/ntfs3/bitfunc.c')
-rw-r--r-- | fs/ntfs3/bitfunc.c | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/fs/ntfs3/bitfunc.c b/fs/ntfs3/bitfunc.c new file mode 100644 index 000000000000..2de5faef2721 --- /dev/null +++ b/fs/ntfs3/bitfunc.c @@ -0,0 +1,135 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * + * Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved. + * + */ +#include <linux/blkdev.h> +#include <linux/buffer_head.h> +#include <linux/fs.h> +#include <linux/nls.h> + +#include "debug.h" +#include "ntfs.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 + * + * Returns true if all bits [bit, bit+nbits) are zeros "0" + */ +bool are_bits_clear(const ulong *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; + + // All bits are zero + return true; +} + +/* + * are_bits_set + * + * Returns true if all bits [bit, bit+nbits) are ones "1" + */ +bool are_bits_set(const ulong *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) { + u8 mask = fill_mask[pos]; + + if ((*map & mask) != mask) + return false; + } + + // All bits are ones + return true; +} |