LocalArray.h revision b5fc5ecd3fe5315fc2756c0c25adc458cc8c8d91 
1/*
2 * Copyright (C) 2009 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef LOCAL_ARRAY_H_included
18#define LOCAL_ARRAY_H_included
19
20#include <cstddef>
21#include <new>
22
23/**
24 * A fixed-size array with a size hint. That number of bytes will be allocated
25 * on the stack, and used if possible, but if more bytes are requested at
26 * construction time, a buffer will be allocated on the heap (and deallocated
27 * by the destructor).
28 *
29 * The API is intended to be a compatible subset of C++0x's std::array.
30 */
31template <size_t STACK_BYTE_COUNT>
32class LocalArray {
33public:
34    /**
35     * Allocates a new fixed-size array of the given size. If this size is
36     * less than or equal to the template parameter STACK_BYTE_COUNT, an
37     * internal on-stack buffer will be used. Otherwise a heap buffer will
38     * be allocated.
39     */
40    LocalArray(size_t desiredByteCount) : mSize(desiredByteCount) {
41        if (desiredByteCount > STACK_BYTE_COUNT) {
42            mPtr = new char[mSize];
43        } else {
44            mPtr = &mOnStackBuffer[0];
45        }
46    }
47
48    /**
49     * Frees the heap-allocated buffer, if there was one.
50     */
51    ~LocalArray() {
52        if (mPtr != &mOnStackBuffer[0]) {
53            delete[] mPtr;
54        }
55    }
56
57    // Capacity.
58    size_t size() { return mSize; }
59    bool empty() { return mSize == 0; }
60
61    // Element access.
62    char& operator[](size_t n) { return mPtr[n]; }
63    const char& operator[](size_t n) const { return mPtr[n]; }
64
65private:
66    char mOnStackBuffer[STACK_BYTE_COUNT];
67    char* mPtr;
68    size_t mSize;
69};
70
71#endif // LOCAL_ARRAY_H_included
72