1 files changed, 193 insertions, 0 deletions

diff --git a/lib/find_bit.c b/lib/find_bit.c
new file mode 100644
index 000000000000..18072ea9c20e
--- /dev/null
+++ b/lib/find_bit.c
@@ -0,0 +1,193 @@
+/* bit search implementation
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * Copyright (C) 2008 IBM Corporation
+ * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
+ * (Inspired by David Howell's find_next_bit implementation)
+ *
+ * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
+ * size and improve performance, 2015.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/bitops.h>
+#include <linux/bitmap.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+
+#if !defined(find_next_bit) || !defined(find_next_zero_bit)
+
+/*
+ * This is a common helper function for find_next_bit and
+ * find_next_zero_bit.  The difference is the "invert" argument, which
+ * is XORed with each fetched word before searching it for one bits.
+ */
+static unsigned long _find_next_bit(const unsigned long *addr,
+                unsigned long nbits, unsigned long start, unsigned long invert)
+{
+        unsigned long tmp;
+
+        if (!nbits || start >= nbits)
+                return nbits;
+
+        tmp = addr[start / BITS_PER_LONG] ^ invert;
+
+        /* Handle 1st word. */
+        tmp &= BITMAP_FIRST_WORD_MASK(start);
+        start = round_down(start, BITS_PER_LONG);
+
+        while (!tmp) {
+                start += BITS_PER_LONG;
+                if (start >= nbits)
+                        return nbits;
+
+                tmp = addr[start / BITS_PER_LONG] ^ invert;
+        }
+
+        return min(start + __ffs(tmp), nbits);
+}
+#endif
+
+#ifndef find_next_bit
+/*
+ * Find the next set bit in a memory region.
+ */
+unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
+                            unsigned long offset)
+{
+        return _find_next_bit(addr, size, offset, 0UL);
+}
+EXPORT_SYMBOL(find_next_bit);
+#endif
+
+#ifndef find_next_zero_bit
+unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
+                                 unsigned long offset)
+{
+        return _find_next_bit(addr, size, offset, ~0UL);
+}
+EXPORT_SYMBOL(find_next_zero_bit);
+#endif
+
+#ifndef find_first_bit
+/*
+ * Find the first set bit in a memory region.
+ */
+unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
+{
+        unsigned long idx;
+
+        for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
+                if (addr[idx])
+                        return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
+        }
+
+        return size;
+}
+EXPORT_SYMBOL(find_first_bit);
+#endif
+
+#ifndef find_first_zero_bit
+/*
+ * Find the first cleared bit in a memory region.
+ */
+unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
+{
+        unsigned long idx;
+
+        for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
+                if (addr[idx] != ~0UL)
+                        return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
+        }
+
+        return size;
+}
+EXPORT_SYMBOL(find_first_zero_bit);
+#endif
+
+#ifndef find_last_bit
+unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
+{
+        if (size) {
+                unsigned long val = BITMAP_LAST_WORD_MASK(size);
+                unsigned long idx = (size-1) / BITS_PER_LONG;
+
+                do {
+                        val &= addr[idx];
+                        if (val)
+                                return idx * BITS_PER_LONG + __fls(val);
+
+                        val = ~0ul;
+                } while (idx--);
+        }
+        return size;
+}
+EXPORT_SYMBOL(find_last_bit);
+#endif
+
+#ifdef __BIG_ENDIAN
+
+/* include/linux/byteorder does not support "unsigned long" type */
+static inline unsigned long ext2_swab(const unsigned long y)
+{
+#if BITS_PER_LONG == 64
+        return (unsigned long) __swab64((u64) y);
+#elif BITS_PER_LONG == 32
+        return (unsigned long) __swab32((u32) y);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
+static unsigned long _find_next_bit_le(const unsigned long *addr,
+                unsigned long nbits, unsigned long start, unsigned long invert)
+{
+        unsigned long tmp;
+
+        if (!nbits || start >= nbits)
+                return nbits;
+
+        tmp = addr[start / BITS_PER_LONG] ^ invert;
+
+        /* Handle 1st word. */
+        tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
+        start = round_down(start, BITS_PER_LONG);
+
+        while (!tmp) {
+                start += BITS_PER_LONG;
+                if (start >= nbits)
+                        return nbits;
+
+                tmp = addr[start / BITS_PER_LONG] ^ invert;
+        }
+
+        return min(start + __ffs(ext2_swab(tmp)), nbits);
+}
+#endif
+
+#ifndef find_next_zero_bit_le
+unsigned long find_next_zero_bit_le(const void *addr, unsigned
+                long size, unsigned long offset)
+{
+        return _find_next_bit_le(addr, size, offset, ~0UL);
+}
+EXPORT_SYMBOL(find_next_zero_bit_le);
+#endif
+
+#ifndef find_next_bit_le
+unsigned long find_next_bit_le(const void *addr, unsigned
+                long size, unsigned long offset)
+{
+        return _find_next_bit_le(addr, size, offset, 0UL);
+}
+EXPORT_SYMBOL(find_next_bit_le);
+#endif
+
+#endif /* __BIG_ENDIAN */