1 files changed, 58 insertions, 3 deletions
diff --git a/include/utils/LinearAllocator.h b/include/utils/LinearAllocator.h
index cd2521d..4772bc8 100644
--- a/include/utils/LinearAllocator.h
+++ b/include/utils/LinearAllocator.h
@@ -30,11 +30,66 @@
 
 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:
-    void* alloc(size_t size) { return 0; }
-    void rewindIfLastAlloc(void* ptr, size_t allocSize) {}
-    void dumpMemoryStats(const char* prefix = "") {}
+    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