From 149c82a8ec8b1faed2ae722852042ba9d603b552 Mon Sep 17 00:00:00 2001
From: Pawel Dziepak <pdziepak@quarnos.org>
Date: Thu, 3 Oct 2013 04:27:49 +0200
Subject: [PATCH] kernel/util: Add bitmap implementation

---
 headers/private/kernel/util/BitUtils.h | 18 ++++++
 headers/private/kernel/util/Bitmap.h   | 81 ++++++++++++++++++++++++++
 src/system/kernel/util/Bitmap.cpp      | 68 +++++++++++++++++++++
 src/system/kernel/util/Jamfile         |  1 +
 4 files changed, 168 insertions(+)
 create mode 100644 headers/private/kernel/util/Bitmap.h
 create mode 100644 src/system/kernel/util/Bitmap.cpp

diff --git a/headers/private/kernel/util/BitUtils.h b/headers/private/kernel/util/BitUtils.h
index 60cbcb0a0a..1a0e08dc61 100644
--- a/headers/private/kernel/util/BitUtils.h
+++ b/headers/private/kernel/util/BitUtils.h
@@ -38,5 +38,23 @@ countSetBits(uint32 v)
 }
 
 
+static inline uint32
+log2(uint32 v)
+{
+	static const int MultiplyDeBruijnBitPosition[32] = {
+		0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30,
+		8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31
+	};
+
+	v |= v >> 1;
+	v |= v >> 2;
+	v |= v >> 4;
+	v |= v >> 8;
+	v |= v >> 16;
+
+	return MultiplyDeBruijnBitPosition[(uint32)(v * 0x07C4ACDDU) >> 27];
+}
+
+
 #endif	// KERNEL_UTIL_RANDOM_H
 
diff --git a/headers/private/kernel/util/Bitmap.h b/headers/private/kernel/util/Bitmap.h
new file mode 100644
index 0000000000..b47854cc61
--- /dev/null
+++ b/headers/private/kernel/util/Bitmap.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2013 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Paweł Dziepak, pdziepak@quarnos.org
+ */
+#ifndef KERNEL_UTIL_BITMAP_H
+#define KERNEL_UTIL_BITMAP_H
+
+
+#include <Debug.h>
+#include <SupportDefs.h>
+
+
+class Bitmap {
+public:
+						Bitmap(int bitCount);
+						~Bitmap();
+
+	inline	status_t	GetInitStatus();
+
+	inline	bool		Get(int index) const;
+	inline	void		Set(int index);
+	inline	void		Clear(int index);
+
+			int			GetHighestSet() const;
+
+private:
+			status_t	fInitStatus;
+
+			int			fElementsCount;
+			int			fSize;
+			addr_t*		fBits;
+
+	static	const int	kBitsPerElement;
+};
+
+
+status_t
+Bitmap::GetInitStatus()
+{
+	return fInitStatus;
+}
+
+
+bool
+Bitmap::Get(int index) const
+{
+	ASSERT(index < fSize);
+
+	const int kArrayElement = index / kBitsPerElement;
+	const addr_t kBitMask = addr_t(1) << (index % kBitsPerElement);
+	return fBits[kArrayElement] & kBitMask;
+}
+
+
+void
+Bitmap::Set(int index)
+{
+	ASSERT(index < fSize);
+
+	const int kArrayElement = index / kBitsPerElement;
+	const addr_t kBitMask = addr_t(1) << (index % kBitsPerElement);
+	fBits[kArrayElement] |= kBitMask;
+}
+
+
+void
+Bitmap::Clear(int index)
+{
+	ASSERT(index < fSize);
+
+	const int kArrayElement = index / kBitsPerElement;
+	const addr_t kBitMask = addr_t(1) << (index % kBitsPerElement);
+	fBits[kArrayElement] &= ~addr_t(kBitMask);
+}
+
+
+#endif	// KERNEL_UTIL_BITMAP_H
+
diff --git a/src/system/kernel/util/Bitmap.cpp b/src/system/kernel/util/Bitmap.cpp
new file mode 100644
index 0000000000..588e996006
--- /dev/null
+++ b/src/system/kernel/util/Bitmap.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2013 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Paweł Dziepak, pdziepak@quarnos.org
+ */
+
+
+#include <util/Bitmap.h>
+
+#include <new>
+
+#include <string.h>
+
+#include <util/BitUtils.h>
+
+
+const int Bitmap::kBitsPerElement = sizeof(addr_t) * 8;
+
+
+Bitmap::Bitmap(int bitCount)
+	:
+	fInitStatus(B_OK),
+	fElementsCount(0),
+	fSize(bitCount)
+{
+	int count = fSize + kBitsPerElement - 1;
+	count /= kBitsPerElement;
+
+	fBits = new(std::nothrow) addr_t[count];
+	if (fBits == NULL) {
+		fSize = 0;
+		fInitStatus = B_NO_MEMORY;
+	}
+
+	fElementsCount = count;
+	memset(fBits, 0, sizeof(addr_t) * count);
+}
+
+
+Bitmap::~Bitmap()
+{
+	delete[] fBits;
+}
+
+
+int
+Bitmap::GetHighestSet() const
+{
+	int i = fElementsCount - 1;
+	while (i >= 0 && fBits[i] == 0)
+		i--;
+
+	if (i < 0)
+		return -1;
+
+	STATIC_ASSERT(sizeof(addr_t) == sizeof(uint64)
+		|| sizeof(addr_t) == sizeof(uint32));
+	if (sizeof(addr_t) == sizeof(uint32))
+		return log2(fBits[i]) + i * kBitsPerElement;
+
+	uint32 v = fBits[i] >> 32;
+	if (v != 0)
+		return log2(v) + sizeof(uint32) * 8 + i * kBitsPerElement;
+	return log2(fBits[i]) + i * kBitsPerElement;
+}
+
diff --git a/src/system/kernel/util/Jamfile b/src/system/kernel/util/Jamfile
index a8f49b9d2a..6b89e4121c 100644
--- a/src/system/kernel/util/Jamfile
+++ b/src/system/kernel/util/Jamfile
@@ -4,6 +4,7 @@ UsePrivateHeaders [ FDirName kernel util ] ;
 
 KernelMergeObject kernel_util.o :
 	AVLTreeBase.cpp
+	Bitmap.cpp
 	hostname.cpp
 	inet_addr.c
 	inet_ntop.c