Cleanup of bitstring.h:

1) Add FreeBSD: tag.
2) Add parenthesis around macro args.
3) Add parenthesis around macros which are expressions.
4) Add do { ... } while (0) around macros which are compound statements.
5) Sync bitstr_size and bit_alloc with neater versions from NetBSD.
6) Fix bit_ffs and bit_ffc so that they don't search off the end of the
	bitstirng.
7) Try to avoid rightshifting signed ints.

I didn't take NetBSD's version directly as the macros are significantly
slower for long bitstrings. Bruce reviewed a previous version of
this patch.

PR:		21204
Submitted by:	bob@immure.com
Reviewed by:	bde

1 files changed, 46 insertions, 39 deletions

diff --git a/sys/sys/bitstring.h b/sys/sys/bitstring.h
index 88437e7fb9f7..eafdba18b098 100644
--- a/sys/sys/bitstring.h
+++ b/sys/sys/bitstring.h
@@ -33,7 +33,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)bitstring.h	8.1 (Berkeley) 7/19/93
+ * $FreeBSD$
  */
 
 #ifndef _BITSTRING_H_
@@ -53,16 +53,15 @@ typedef	unsigned char bitstr_t;
 /* external macros */
 				/* bytes in a bitstring of nbits bits */
 #define	bitstr_size(nbits) \
-	((((nbits) - 1) >> 3) + 1)
+	(((nbits) + 7) >> 3)
 
 				/* allocate a bitstring */
 #define	bit_alloc(nbits) \
-	(bitstr_t *)calloc(1, \
-	    (unsigned int)bitstr_size(nbits) * sizeof(bitstr_t))
+	(bitstr_t *)calloc((size_t)bitstr_size(nbits), sizeof(bitstr_t))
 
 				/* allocate a bitstring on the stack */
 #define	bit_decl(name, nbits) \
-	(name)[bitstr_size(nbits)]
+	((name)[bitstr_size(nbits)])
 
 				/* is bit N of bitstring name set? */
 #define	bit_test(name, bit) \
@@ -70,16 +69,16 @@ typedef	unsigned char bitstr_t;
 
 				/* set bit N of bitstring name */
 #define	bit_set(name, bit) \
-	(name)[_bit_byte(bit)] |= _bit_mask(bit)
+	((name)[_bit_byte(bit)] |= _bit_mask(bit))
 
 				/* clear bit N of bitstring name */
 #define	bit_clear(name, bit) \
-	(name)[_bit_byte(bit)] &= ~_bit_mask(bit)
+	((name)[_bit_byte(bit)] &= ~_bit_mask(bit))
 
 				/* clear bits start ... stop in bitstring */
-#define	bit_nclear(name, start, stop) { \
-	register bitstr_t *_name = name; \
-	register int _start = start, _stop = stop; \
+#define	bit_nclear(name, start, stop) do { \
+	register bitstr_t *_name = (name); \
+	register int _start = (start), _stop = (stop); \
 	register int _startbyte = _bit_byte(_start); \
 	register int _stopbyte = _bit_byte(_stop); \
 	if (_startbyte == _stopbyte) { \
@@ -91,12 +90,12 @@ typedef	unsigned char bitstr_t;
 			_name[_startbyte] = 0; \
 		_name[_stopbyte] &= 0xff << ((_stop&0x7) + 1); \
 	} \
-}
+} while (0)
 
 				/* set bits start ... stop in bitstring */
-#define	bit_nset(name, start, stop) { \
-	register bitstr_t *_name = name; \
-	register int _start = start, _stop = stop; \
+#define	bit_nset(name, start, stop) do { \
+	register bitstr_t *_name = (name); \
+	register int _start = (start), _stop = (stop); \
 	register int _startbyte = _bit_byte(_start); \
 	register int _stopbyte = _bit_byte(_stop); \
 	if (_startbyte == _stopbyte) { \
@@ -108,36 +107,44 @@ typedef	unsigned char bitstr_t;
 	    		_name[_startbyte] = 0xff; \
 		_name[_stopbyte] |= 0xff >> (7 - (_stop&0x7)); \
 	} \
-}
+} while (0)
 
 				/* find first bit clear in name */
-#define	bit_ffc(name, nbits, value) { \
-	register bitstr_t *_name = name; \
-	register int _byte, _nbits = nbits; \
-	register int _stopbyte = _bit_byte(_nbits), _value = -1; \
-	for (_byte = 0; _byte <= _stopbyte; ++_byte) \
-		if (_name[_byte] != 0xff) { \
-			_value = _byte << 3; \
-			for (_stopbyte = _name[_byte]; (_stopbyte&0x1); \
-			    ++_value, _stopbyte >>= 1); \
-			break; \
-		} \
+#define	bit_ffc(name, nbits, value) do { \
+	register bitstr_t *_name = (name); \
+	register int _byte, _nbits = (nbits); \
+	register int _stopbyte = _bit_byte(_nbits - 1), _value = -1; \
+	if (_nbits > 0) \
+		for (_byte = 0; _byte <= _stopbyte; ++_byte) \
+			if (_name[_byte] != 0xff) { \
+				bitstr_t _lb; \
+				_value = _byte << 3; \
+				for (_lb = _name[_byte]; (_lb&0x1); \
+				    ++_value, _lb >>= 1); \
+				break; \
+			} \
+	if (_value >= nbits) \
+		_value = -1; \
 	*(value) = _value; \
-}
+} while (0)
 
 				/* find first bit set in name */
-#define	bit_ffs(name, nbits, value) { \
-	register bitstr_t *_name = name; \
-	register int _byte, _nbits = nbits; \
-	register int _stopbyte = _bit_byte(_nbits), _value = -1; \
-	for (_byte = 0; _byte <= _stopbyte; ++_byte) \
-		if (_name[_byte]) { \
-			_value = _byte << 3; \
-			for (_stopbyte = _name[_byte]; !(_stopbyte&0x1); \
-			    ++_value, _stopbyte >>= 1); \
-			break; \
-		} \
+#define	bit_ffs(name, nbits, value) do { \
+	register bitstr_t *_name = (name); \
+	register int _byte, _nbits = (nbits); \
+	register int _stopbyte = _bit_byte(_nbits - 1), _value = -1; \
+	if (_nbits > 0) \
+		for (_byte = 0; _byte <= _stopbyte; ++_byte) \
+			if (_name[_byte]) { \
+				bitstr_t _lb; \
+				_value = _byte << 3; \
+				for (_lb = _name[_byte]; !(_lb&0x1); \
+				    ++_value, _lb >>= 1); \
+				break; \
+			} \
+	if (_value >= nbits) \
+		_value = -1; \
 	*(value) = _value; \
-}
+} while (0)
 
 #endif /* !_BITSTRING_H_ */