Add LinearAllocator
Moving from external/webkit/Source/WebCore/platform/graphics/android/utils/
Change-Id: If91830aa9b207dbc8692b2ca7c4a0b76778addd5
diff --git a/include/utils/LinearAllocator.h b/include/utils/LinearAllocator.h
new file mode 100644
index 0000000..4772bc8
--- /dev/null
+++ b/include/utils/LinearAllocator.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright 2012, The Android Open Source Project
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ANDROID_LINEARALLOCATOR_H
+#define ANDROID_LINEARALLOCATOR_H
+
+#include <stddef.h>
+
+namespace android {
+
+/**
+ * A memory manager that internally allocates multi-kbyte buffers for placing objects in. It avoids
+ * the overhead of malloc when many objects are allocated. It is most useful when creating many
+ * small objects with a similar lifetime, and doesn't add significant overhead for large
+ * allocations.
+ */
+class LinearAllocator {
+public:
+ LinearAllocator();
+ ~LinearAllocator();
+
+ /**
+ * Reserves and returns a region of memory of at least size 'size', aligning as needed.
+ * Typically this is used in an object's overridden new() method or as a replacement for malloc.
+ *
+ * The lifetime of the returned buffers is tied to that of the LinearAllocator. If calling
+ * delete() on an object stored in a buffer is needed, it should be overridden to use
+ * rewindIfLastAlloc()
+ */
+ void* alloc(size_t size);
+
+ /**
+ * Attempt to deallocate the given buffer, with the LinearAllocator attempting to rewind its
+ * state if possible. No destructors are called.
+ */
+ void rewindIfLastAlloc(void* ptr, size_t allocSize);
+
+ /**
+ * Dump memory usage statistics to the log (allocated and wasted space)
+ */
+ void dumpMemoryStats(const char* prefix = "");
+
+ /**
+ * The number of bytes used for buffers allocated in the LinearAllocator (does not count space
+ * wasted)
+ */
+ size_t usedSize() const { return mTotalAllocated - mWastedSpace; }
+
+private:
+ LinearAllocator(const LinearAllocator& other);
+
+ class Page;
+
+ Page* newPage(size_t pageSize);
+ bool fitsInCurrentPage(size_t size);
+ void ensureNext(size_t size);
+ void* start(Page *p);
+ void* end(Page* p);
+
+ size_t mPageSize;
+ size_t mMaxAllocSize;
+ void* mNext;
+ Page* mCurrentPage;
+ Page* mPages;
+
+ // Memory usage tracking
+ size_t mTotalAllocated;
+ size_t mWastedSpace;
+ size_t mPageCount;
+ size_t mDedicatedPageCount;
+};
+
+}; // namespace android
+
+#endif // ANDROID_LINEARALLOCATOR_H