qpcpp/qs/source/qs_byte.cpp

//****************************************************************************
// Product: QS/C++
// Last Updated for Version: 5.1.0
// Date of the Last Update:  Sep 23, 2013
//
//                    Q u a n t u m     L e a P s
//                    ---------------------------
//                    innovating embedded systems
//
// Copyright (C) 2002-2013 Quantum Leaps, LLC. All rights reserved.
//
// This program is open source 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.
//
// Alternatively, this program may be distributed and modified under the
// terms of Quantum Leaps commercial licenses, which expressly supersede
// the GNU General Public License and are specifically designed for
// licensees interested in retaining the proprietary status of their code.
//
// 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, see <http://www.gnu.org/licenses/>.
//
// Contact information:
// Quantum Leaps Web sites: http://www.quantum-leaps.com
//                          http://www.state-machine.com
// e-mail:                  info@quantum-leaps.com
//****************************************************************************
#include "qs_pkg.h"

/// \file
/// \ingroup qs
/// \brief QS::getByte() implementation

namespace QP {

//............................................................................
uint16_t QS::getByte(void) {
    uint16_t ret;
    if (priv_.used == static_cast<QSCtr>(0)) {
        ret = QS_EOD;                                       // set End-Of-Data
    }
    else {
        uint8_t *buf_ = priv_.buf;            // put in a temporary (register)
        QSCtr tail_   = priv_.tail;           // put in a temporary (register)
        ret = static_cast<uint16_t>(*QS_PTR_AT_(tail_)); // the byte to return
        ++tail_;                                           // advance the tail
        if (tail_ == priv_.end) {                         // tail wrap around?
            tail_ = static_cast<QSCtr>(0);
        }
        priv_.tail = tail_;                                 // update the tail
        --priv_.used;                                    // one less byte used
    }
    return ret;                                      // return the byte or EOD
}

}                                                              // namespace QP