timestamp.cpp

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/* xoreos - A reimplementation of BioWare's Aurora engine
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/* Based on ScummVM (<http://scummvm.org>) code, which is released
 * under the terms of version 2 or later of the GNU General Public
 * License.
 *
 * The original copyright note in ScummVM reads as follows:
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program 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.
 *
 * This program 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 more 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 Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

#include "src/common/algorithm.h"
#include "src/common/error.h"
#include "src/common/rational.h"
#include "src/common/timestamp.h"

namespace Common {

Timestamp::Timestamp(uint64 ms, uint64 fr) {
    if (fr == 0)
        throw Exception("Invalid frame rate 0");

    _secs = ms / 1000;
    _framerateFactor = 1000 / gcd<uint64>(1000, fr);
    _framerate = fr * _framerateFactor;

    // Note that _framerate is always divisible by 1000.
    _numFrames = (ms % 1000) * (_framerate / 1000);
}

Timestamp::Timestamp(uint64 s, uint64 frames, uint64 fr) {
    if (fr == 0)
        throw Exception("Invalid frame rate 0");

    _secs = s + (frames / fr);
    _framerateFactor = 1000 / gcd<uint64>(1000, fr);
    _framerate = fr * _framerateFactor;
    _numFrames = (frames % fr) * _framerateFactor;
}

Timestamp::Timestamp(uint64 s, uint64 frames, const Rational &newFramerate) {
    if (newFramerate <= 0)
        throw Exception("Invalid frame rate %d/%d", newFramerate.getNumerator(), newFramerate.getDenominator());

    uint64 fr;
    if (newFramerate.getDenominator() == 1) {
        fr = newFramerate.getNumerator();
    } else {
        Rational time = newFramerate.getInverse() * frames;
        frames = time.getNumerator();
        fr = time.getDenominator();
    }

    _secs = s + (frames / fr);
    _framerateFactor = 1000 / gcd<uint64>(1000, fr);
    _framerate = fr * _framerateFactor;
    _numFrames = (frames % fr) * _framerateFactor;
}

Timestamp Timestamp::convertToFramerate(uint64 newFramerate) const {
    assert(_framerate != 0);
    assert(newFramerate != 0);

    Timestamp ts(*this);

    if (ts.framerate() != newFramerate) {
        ts._framerateFactor = 1000 / gcd<uint64>(1000, newFramerate);
        ts._framerate = newFramerate * ts._framerateFactor;

        const uint64 g = gcd(_framerate, ts._framerate);
        const uint64 p = _framerate / g;
        const uint64 q = ts._framerate / g;

        // Convert the frame offset to the new framerate.
        // We round to the nearest (as opposed to always
        // rounding down), to minimize rounding errors during
        // round trip conversions.
        ts._numFrames = (ts._numFrames * q + p/2) / p;

        ts.normalize();
    }

    return ts;
}

void Timestamp::normalize() {
    // Convert negative _numFrames values to positive ones by adjusting _secs
    if (_numFrames < 0) {
        int64 secsub = 1 + (-_numFrames / _framerate);

        _numFrames += _framerate * secsub;
        _secs -= secsub;
    }

    // Wrap around if necessary
    _secs += (_numFrames / _framerate);
    _numFrames %= _framerate;
}

bool Timestamp::operator==(const Timestamp &ts) const {
    return cmp(ts) == 0;
}

bool Timestamp::operator!=(const Timestamp &ts) const {
    return cmp(ts) != 0;
}

bool Timestamp::operator<(const Timestamp &ts) const {
    return cmp(ts) < 0;
}

bool Timestamp::operator<=(const Timestamp &ts) const {
    return cmp(ts) <= 0;
}

bool Timestamp::operator>(const Timestamp &ts) const {
    return cmp(ts) > 0;
}

bool Timestamp::operator>=(const Timestamp &ts) const {
    return cmp(ts) >= 0;
}

int64 Timestamp::cmp(const Timestamp &ts) const {
    assert(_framerate != 0);
    assert(ts._framerate != 0);

    int64 delta = _secs - ts._secs;
    if (!delta) {
        const uint64 g = gcd(_framerate, ts._framerate);
        const uint64 p = _framerate / g;
        const uint64 q = ts._framerate / g;

        delta = (_numFrames * q - ts._numFrames * p);
    }

    return delta;
}


Timestamp Timestamp::addFrames(int64 frames) const {
    Timestamp ts(*this);

    // The frames are given in the original framerate, so we have to
    // adjust by _framerateFactor accordingly.
    ts._numFrames += frames * _framerateFactor;
    ts.normalize();

    return ts;
}

Timestamp Timestamp::addMsecs(int64 ms) const {
    Timestamp ts(*this);
    ts._secs += ms / 1000;
    // Add the remaining frames. Note that _framerate is always divisible by 1000.
    ts._numFrames += (ms % 1000) * (ts._framerate / 1000);

    ts.normalize();

    return ts;
}

void Timestamp::addIntern(const Timestamp &ts) {
    if (_framerate != ts._framerate)
        throw Exception("Cannot add two timestamps of different frame rates");

    _secs += ts._secs;
    _numFrames += ts._numFrames;

    normalize();
}

Timestamp Timestamp::operator-() const {
    Timestamp result(*this);
    result._secs = -_secs;
    result._numFrames = -_numFrames;
    result.normalize();
    return result;
}

Timestamp Timestamp::operator+(const Timestamp &ts) const {
    Timestamp result(*this);
    result.addIntern(ts);
    return result;
}

Timestamp Timestamp::operator-(const Timestamp &ts) const {
    Timestamp result(*this);
    result.addIntern(-ts);
    return result;
}

int64 Timestamp::frameDiff(const Timestamp &ts) const {
    assert(_framerate != 0);
    assert(ts._framerate != 0);

    int64 delta = 0;
    if (_secs != ts._secs)
        delta = (_secs - ts._secs) * _framerate;

    delta += _numFrames;

    if (_framerate == ts._framerate) {
        delta -= ts._numFrames;
    } else {
        // We need to multiply by the quotient of the two framerates.
        // We cancel the GCD in this fraction to reduce the risk of
        // overflows.
        const uint64 g = gcd(_framerate, ts._framerate);
        const uint64 p = _framerate / g;
        const uint64 q = ts._framerate / g;

        delta -= ((long)ts._numFrames * p + q/2) / (long)q;
    }

    return delta / (int64)_framerateFactor;
}

int64 Timestamp::msecsDiff(const Timestamp &ts) const {
    return msecs() - ts.msecs();
}

int64 Timestamp::msecs() const {
    // Note that _framerate is always divisible by 1000.
    return _secs * 1000 + _numFrames / (_framerate / 1000);
}


} // End of namespace Common