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-rw-r--r--src/util/ReusableArray.hxx88
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+/*
+ * Copyright (C) 2013 Max Kellermann <max@duempel.org>
+ *
+ * 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 AND CONTRIBUTORS
+ * ``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
+ * FOUNDATION 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 REUSABLE_ARRAY_HXX
+#define REUSABLE_ARRAY_HXX
+
+#include <stddef.h>
+
+#include "gcc.h"
+
+/**
+ * Manager for a temporary array which grows as needed. This attempts
+ * to reduce the number of consecutive heap allocations and
+ * deallocations.
+ *
+ * @param T the array element type
+ * @param M always allocate multiples of this number; must be a power of 2
+ */
+template<typename T, size_t M=1>
+class ReusableArray {
+ T *buffer;
+ size_t capacity;
+
+public:
+ ReusableArray():buffer(nullptr), capacity(0) {}
+
+ ReusableArray(const ReusableArray &other) = delete;
+ ReusableArray &operator=(const ReusableArray &other) = delete;
+
+ ~ReusableArray() {
+ delete[] buffer;
+ }
+
+ /**
+ * Free resources allocated by this object. This invalidates
+ * the buffer returned by Get().
+ */
+ void Clear() {
+ delete[] buffer;
+ buffer = nullptr;
+ capacity = 0;
+ }
+
+ /**
+ * Get the buffer, and guarantee a minimum size. This buffer
+ * becomes invalid with the next Get() call.
+ */
+ gcc_malloc
+ T *Get(size_t size) {
+ if (gcc_unlikely(size > capacity)) {
+ /* too small: grow */
+ delete[] buffer;
+
+ capacity = ((size - 1) | (M - 1)) + 1;
+ buffer = new T[capacity];
+ }
+
+ return buffer;
+ }
+};
+
+#endif