LibrePilot/ground/openpilotgcs/src/plugins/gpsdisplay/buffer.cpp

/**
 ******************************************************************************
 *
 * @file       buffer.c
 * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
 * @brief      see below
 *             As with all modules only the initialize function is exposed all other
 *             interactions with the module take place through the event queue and
 *             objects.
 * @see        The GNU Public License (GPL) Version 3
 *
 *****************************************************************************/

/*
 * 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 3 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.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

/*! \file buffer.c \brief Multipurpose byte buffer structure and methods. */
// *****************************************************************************
//
// File Name	: 'buffer.c'
// Title		: Multipurpose byte buffer structure and methods
// Author		: Pascal Stang - Copyright (C) 2001-2002
// Created		: 9/23/2001
// Revised		: 9/23/2001
// Version		: 1.0
// Target MCU	: any
// Editor Tabs	: 4
//
// This code is distributed under the GNU Public License
// which can be found at http://www.gnu.org/licenses/gpl.txt
//
// *****************************************************************************

#include "buffer.h"

// global variables

// initialization

void bufferInit(cBuffer *buffer, unsigned char *start, unsigned short size)
{
    // set start pointer of the buffer
    buffer->dataptr    = start;
    buffer->size       = size;
    // initialize index and length
    buffer->dataindex  = 0;
    buffer->datalength = 0;
}

// access routines
unsigned char  bufferGetFromFront(cBuffer *buffer)
{
    unsigned char data = 0;

    // check to see if there's data in the buffer
    if (buffer->datalength) {
        // get the first character from buffer
        data = buffer->dataptr[buffer->dataindex];
        // move index down and decrement length
        buffer->dataindex++;
        if (buffer->dataindex >= buffer->size) {
            buffer->dataindex %= buffer->size;
        }
        buffer->datalength--;
    }
    // return
    return data;
}

void bufferDumpFromFront(cBuffer *buffer, unsigned short numbytes)
{
    // dump numbytes from the front of the buffer
    // are we dumping less than the entire buffer?
    if (numbytes < buffer->datalength) {
        // move index down by numbytes and decrement length by numbytes
        buffer->dataindex += numbytes;
        if (buffer->dataindex >= buffer->size) {
            buffer->dataindex %= buffer->size;
        }
        buffer->datalength -= numbytes;
    } else {
        // flush the whole buffer
        buffer->datalength = 0;
    }
}

unsigned char bufferGetAtIndex(cBuffer *buffer, unsigned short index)
{
    // return character at index in buffer
    return buffer->dataptr[(buffer->dataindex + index) % (buffer->size)];
}

unsigned char bufferAddToEnd(cBuffer *buffer, unsigned char data)
{
    // make sure the buffer has room
    if (buffer->datalength < buffer->size) {
        // save data byte at end of buffer
        buffer->dataptr[(buffer->dataindex + buffer->datalength) % buffer->size] = data;
        // increment the length
        buffer->datalength++;
        // return success
        return -1;
    } else { return 0; }
}

unsigned char bufferIsNotFull(cBuffer *buffer)
{
    // check to see if the buffer has room
    // return true if there is room
    return buffer->datalength < buffer->size;
}

void bufferFlush(cBuffer *buffer)
{
    // flush contents of the buffer
    buffer->datalength = 0;
}