RingBuffer.hpp

/* This file is part of Raul.
 * Copyright (C) 2007-2009 David Robillard <http://drobilla.net>
 *
 * Raul is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * Raul is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef RAUL_RING_BUFFER_HPP
#define RAUL_RING_BUFFER_HPP

#include <stdint.h>

#include <cassert>
#include <cstdlib>
#include <cstring>
#include <iostream>

#include <glib.h>

#include "raul/log.hpp"

namespace Raul {


class RingBuffer {
public:
    explicit RingBuffer(uint32_t size)
        : _buf(static_cast<char*>(malloc(size)))
        , _size(size)
    {
        reset();
        assert(read_space() == 0);
        assert(write_space() == size - 1);
    }

    virtual ~RingBuffer() {
        free(_buf);
    }

    void reset() {
        g_atomic_int_set(&_write_ptr, 0);
        g_atomic_int_set(&_read_ptr, 0);
    }

    uint32_t write_space() const {
        const uint32_t w = g_atomic_int_get(&_write_ptr);
        const uint32_t r = g_atomic_int_get(&_read_ptr);

        if (w > r) {
            return ((r - w + _size) % _size) - 1;
        } else if (w < r) {
            return (r - w) - 1;
        } else {
            return _size - 1;
        }
    }

    uint32_t read_space() const {
        const uint32_t w = g_atomic_int_get(&_write_ptr);
        const uint32_t r = g_atomic_int_get(&_read_ptr);

        if (w > r) {
            return w - r;
        } else {
            return (w - r + _size) % _size;
        }
    }

    uint32_t capacity() const { return _size; }

    uint32_t peek(uint32_t size, void* dst);
    bool     full_peek(uint32_t size, void* dst);

    uint32_t read(uint32_t size, void* dst);
    bool     full_read(uint32_t size, void* dst);

    bool     skip(uint32_t size);

    void     write(uint32_t size, const void* src);

protected:
    mutable uint32_t _write_ptr;
    mutable uint32_t _read_ptr;

    char* const    _buf;  
    const uint32_t _size; 
};


inline uint32_t
RingBuffer::peek(uint32_t size, void* dst)
{
    const uint32_t priv_read_ptr = g_atomic_int_get(&_read_ptr);

    const uint32_t read_size = (priv_read_ptr + size < _size)
            ? size
            : _size - priv_read_ptr;

    memcpy(dst, &_buf[priv_read_ptr], read_size);

    return read_size;
}


inline bool
RingBuffer::full_peek(uint32_t size, void* dst)
{
    if (read_space() < size) {
        return false;
    }

    const uint32_t read_size = peek(size, dst);

    if (read_size < size) {
        peek(size - read_size, (char*)dst + read_size);
    }

    return true;
}


inline uint32_t
RingBuffer::read(uint32_t size, void* dst)
{
    const uint32_t priv_read_ptr = g_atomic_int_get(&_read_ptr);

    const uint32_t read_size = (priv_read_ptr + size < _size)
            ? size
            : _size - priv_read_ptr;

    memcpy(dst, &_buf[priv_read_ptr], read_size);

    g_atomic_int_set(&_read_ptr, (priv_read_ptr + read_size) % _size);

    return read_size;
}


inline bool
RingBuffer::full_read(uint32_t size, void* dst)
{
    if (read_space() < size) {
        return false;
    }

    const uint32_t read_size = read(size, dst);

    if (read_size < size) {
        read(size - read_size, (char*)dst + read_size);
    }

    return true;
}


inline bool
RingBuffer::skip(uint32_t size)
{
    if (read_space() < size) {
        warn << "Attempt to skip past end of RingBuffer" << std::endl;
        return false;
    }

    const uint32_t priv_read_ptr = g_atomic_int_get(&_read_ptr);
    g_atomic_int_set(&_read_ptr, (priv_read_ptr + size) % _size);

    return true;
}


inline void
RingBuffer::write(uint32_t size, const void* src)
{
    const uint32_t priv_write_ptr = g_atomic_int_get(&_write_ptr);

    if (priv_write_ptr + size <= _size) {
        memcpy(&_buf[priv_write_ptr], src, size);
        g_atomic_int_set(&_write_ptr, (priv_write_ptr + size) % _size);
    } else {
        const uint32_t this_size = _size - priv_write_ptr;
        assert(this_size < size);
        assert(priv_write_ptr + this_size <= _size);
        memcpy(&_buf[priv_write_ptr], src, this_size);
        memcpy(&_buf[0], (char*)src + this_size, size - this_size);
        g_atomic_int_set(&_write_ptr, size - this_size);
    }
}


} // namespace Raul

#endif // RAUL_RING_BUFFER_HPP