libxfs: add xfs_bit.c

The header side of xfs_bit.c is already in libxfs, and the sparse
inode code requires the xfs_next_bit() function so pull in the
xfs_bit.c file so that a sparse inode enabled libxfs compiles
cleanly in userspace.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_bit.c

@@ -0,0 +1,118 @@
+/*
+ * Copyright (c) 2000-2005 Silicon Graphics, Inc.
+ * All Rights Reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include "xfs.h"
+#include "xfs_log_format.h"
+#include "xfs_bit.h"
+
+/*
+ * XFS bit manipulation routines, used in non-realtime code.
+ */
+
+/*
+ * Return whether bitmap is empty.
+ * Size is number of words in the bitmap, which is padded to word boundary
+ * Returns 1 for empty, 0 for non-empty.
+ */
+int
+xfs_bitmap_empty(uint *map, uint size)
+{
+	uint i;
+	uint ret = 0;
+
+	for (i = 0; i < size; i++) {
+		ret |= map[i];
+	}
+
+	return (ret == 0);
+}
+
+/*
+ * Count the number of contiguous bits set in the bitmap starting with bit
+ * start_bit.  Size is the size of the bitmap in words.
+ */
+int
+xfs_contig_bits(uint *map, uint	size, uint start_bit)
+{
+	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
+	uint result = 0;
+	uint tmp;
+
+	size <<= BIT_TO_WORD_SHIFT;
+
+	ASSERT(start_bit < size);
+	size -= start_bit & ~(NBWORD - 1);
+	start_bit &= (NBWORD - 1);
+	if (start_bit) {
+		tmp = *p++;
+		/* set to one first offset bits prior to start */
+		tmp |= (~0U >> (NBWORD-start_bit));
+		if (tmp != ~0U)
+			goto found;
+		result += NBWORD;
+		size -= NBWORD;
+	}
+	while (size) {
+		if ((tmp = *p++) != ~0U)
+			goto found;
+		result += NBWORD;
+		size -= NBWORD;
+	}
+	return result - start_bit;
+found:
+	return result + ffz(tmp) - start_bit;
+}
+
+/*
+ * This takes the bit number to start looking from and
+ * returns the next set bit from there.  It returns -1
+ * if there are no more bits set or the start bit is
+ * beyond the end of the bitmap.
+ *
+ * Size is the number of words, not bytes, in the bitmap.
+ */
+int xfs_next_bit(uint *map, uint size, uint start_bit)
+{
+	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
+	uint result = start_bit & ~(NBWORD - 1);
+	uint tmp;
+
+	size <<= BIT_TO_WORD_SHIFT;
+
+	if (start_bit >= size)
+		return -1;
+	size -= result;
+	start_bit &= (NBWORD - 1);
+	if (start_bit) {
+		tmp = *p++;
+		/* set to zero first offset bits prior to start */
+		tmp &= (~0U << start_bit);
+		if (tmp != 0U)
+			goto found;
+		result += NBWORD;
+		size -= NBWORD;
+	}
+	while (size) {
+		if ((tmp = *p++) != 0U)
+			goto found;
+		result += NBWORD;
+		size -= NBWORD;
+	}
+	return -1;
+found:
+	return result + ffs(tmp) - 1;
+}