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/*
* Copyright (C) 2013-2017 Max Kellermann <max.kellermann@gmail.com>
*
* 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 "Compiler.h"
#include <utility>
#include <stddef.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 = nullptr;
size_t capacity = 0;
public:
ReusableArray() = default;
ReusableArray(ReusableArray &&src)
:buffer(std::exchange(src.buffer, nullptr)),
capacity(std::exchange(src.capacity, 0)) {}
ReusableArray &operator=(ReusableArray &&src) {
std::swap(buffer, src.buffer);
std::swap(capacity, src.capacity);
return *this;
}
~ReusableArray() {
delete[] buffer;
}
size_t GetCapacity() const {
return capacity;
}
/**
* 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
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