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-rw-r--r--fs/ntfs3/bitfunc.c128
1 files changed, 128 insertions, 0 deletions
diff --git a/fs/ntfs3/bitfunc.c b/fs/ntfs3/bitfunc.c
new file mode 100644
index 000000000..50d838093
--- /dev/null
+++ b/fs/ntfs3/bitfunc.c
@@ -0,0 +1,128 @@
+// 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 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;
+
+ return true;
+}
+
+/*
+ * are_bits_set
+ *
+ * Return: 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) {
+ mask = fill_mask[pos];
+ if ((*map & mask) != mask)
+ return false;
+ }
+
+ return true;
+}