lnav/src/big_array.hh

/**
 * Copyright (c) 2017, Timothy Stack
 *
 * All rights reserved.
 *
 * 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.
 * * Neither the name of Timothy Stack nor the names of its contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 * @file big_array.hh
 */

#ifndef lnav_big_array_hh
#define lnav_big_array_hh

#include <sys/mman.h>

#include "base/math_util.hh"

template<typename T>
struct big_array {
    static const size_t DEFAULT_INCREMENT = 100 * 1000;

    big_array() : ba_ptr(nullptr), ba_size(0), ba_capacity(0) {

    };

    bool reserve(size_t size) {
        if (size < this->ba_capacity) {
            return false;
        }

        if (this->ba_ptr) {
            munmap(this->ba_ptr,
                   roundup_size(this->ba_capacity * sizeof(T), getpagesize()));
        }

        this->ba_capacity = size + DEFAULT_INCREMENT;
        void *result = mmap(nullptr,
                            roundup_size(this->ba_capacity * sizeof(T),
                                         getpagesize()),
                            PROT_READ|PROT_WRITE,
                            MAP_ANONYMOUS|MAP_PRIVATE,
                            -1,
                            0);

        ensure(result != MAP_FAILED);

        this->ba_ptr = (T *) result;

        return true;
    };

    void clear() {
        this->ba_size = 0;
    };

    size_t size() const {
        return this->ba_size;
    };

    void shrink_to(size_t new_size) {
        require(new_size <= this->ba_size);

        this->ba_size = new_size;
    }

    bool empty() const {
        return this->ba_size == 0;
    };

    void push_back(const T &val) {
        this->ba_ptr[this->ba_size] = val;
        this->ba_size += 1;
    };

    T &operator[](size_t index) {
        return this->ba_ptr[index];
    };

    const T &operator[](size_t index) const {
        return this->ba_ptr[index];
    };

    T &back() {
        return this->ba_ptr[this->ba_size - 1];
    }

    typedef T *iterator;

    iterator begin() {
        return this->ba_ptr;
    };

    iterator end() {
        return this->ba_ptr + this->ba_size;
    };

    T *ba_ptr;
    size_t ba_size;
    size_t ba_capacity;
};

#endif