[PATCH 1/3] erofs-utils: lib: add bitops header

[Hongzhen Luo]

Add bitops header for subsequent bloom filter implementation.
This is borrowed from a part of the previous patch. See:
https://lore.kernel.org/all/20230802091750.74181-3-jefflexu@linux.alibaba.com/.

Signed-off-by: Hongzhen Luo <hongzhen at linux.alibaba.com>
---
 include/erofs/bitops.h | 42 ++++++++++++++++++++++++++++++++++++++++++
 lib/Makefile.am        |  1 +
 2 files changed, 43 insertions(+)
 create mode 100644 include/erofs/bitops.h

diff --git a/include/erofs/bitops.h b/include/erofs/bitops.h
new file mode 100644
index 0000000..ef60d6e
--- /dev/null
+++ b/include/erofs/bitops.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0 */
+#ifndef __EROFS_BITOPS_H
+#define __EROFS_BITOPS_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+#include "defs.h"
+
+struct bitmap {
+	unsigned long size;	/* size of bitmap in bits */
+	unsigned long *map;
+};
+
+static inline void set_bit(int nr, volatile unsigned long *addr)
+{
+	unsigned long mask = BIT_MASK(nr);
+	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+
+	*p  |= mask;
+}
+
+static inline void clear_bit(int nr, volatile unsigned long *addr)
+{
+	unsigned long mask = BIT_MASK(nr);
+	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+
+	*p &= ~mask;
+}
+
+static inline int test_bit(int nr, const volatile unsigned long *addr)
+{
+	return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 2cb4cab..6b52470 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -20,6 +20,7 @@ noinst_HEADERS = $(top_srcdir)/include/erofs_fs.h \
       $(top_srcdir)/include/erofs/io.h \
       $(top_srcdir)/include/erofs/list.h \
       $(top_srcdir)/include/erofs/print.h \
+      $(top_srcdir)/include/erofs/bitops.h \
       $(top_srcdir)/include/erofs/tar.h \
       $(top_srcdir)/include/erofs/trace.h \
       $(top_srcdir)/include/erofs/xattr.h \
-- 
2.43.5