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

   1 /**
   2  ******************************************************************************
   3  *
   4  * @file       buffer.c
   5  * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
   6  * @brief      see below
   7  *             As with all modules only the initialize function is exposed all other
   8  *             interactions with the module take place through the event queue and
   9  *             objects.
  10  * @see        The GNU Public License (GPL) Version 3
  11  *
  12  *****************************************************************************/
  13
  14 /*
  15  * This program is free software; you can redistribute it and/or modify
  16  * it under the terms of the GNU General Public License as published by
  17  * the Free Software Foundation; either version 3 of the License, or
  18  * (at your option) any later version.
  19  *
  20  * This program is distributed in the hope that it will be useful, but
  21  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  22  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  23  * for more details.
  24  *
  25  * You should have received a copy of the GNU General Public License along
  26  * with this program; if not, write to the Free Software Foundation, Inc.,
  27  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  28  */
  29
  30 /*! \file buffer.c \brief Multipurpose byte buffer structure and methods. */
  31 // *****************************************************************************
  32 //
  33 // File Name    : 'buffer.c'
  34 // Title                : Multipurpose byte buffer structure and methods
  35 // Author               : Pascal Stang - Copyright (C) 2001-2002
  36 // Created              : 9/23/2001
  37 // Revised              : 9/23/2001
  38 // Version              : 1.0
  39 // Target MCU   : any
  40 // Editor Tabs  : 4
  41 //
  42 // This code is distributed under the GNU Public License
  43 // which can be found at http://www.gnu.org/licenses/gpl.txt
  44 //
  45 // *****************************************************************************
  46
  47 #include "buffer.h"
  48
  49 // global variables
  50
  51 // initialization
  52
  53 void bufferInit(cBuffer *buffer, unsigned char *start, unsigned short size)
  54 {
  55     // set start pointer of the buffer
  56     buffer->dataptr    = start;
  57     buffer->size       = size;
  58     // initialize index and length
  59     buffer->dataindex  = 0;
  60     buffer->datalength = 0;
  61 }
  62
  63 // access routines
  64 unsigned char  bufferGetFromFront(cBuffer *buffer)
  65 {
  66     unsigned char data = 0;
  67
  68     // check to see if there's data in the buffer
  69     if (buffer->datalength) {
  70         // get the first character from buffer
  71         data = buffer->dataptr[buffer->dataindex];
  72         // move index down and decrement length
  73         buffer->dataindex++;
  74         if (buffer->dataindex >= buffer->size) {
  75             buffer->dataindex %= buffer->size;
  76         }
  77         buffer->datalength--;
  78     }
  79     // return
  80     return data;
  81 }
  82
  83 void bufferDumpFromFront(cBuffer *buffer, unsigned short numbytes)
  84 {
  85     // dump numbytes from the front of the buffer
  86     // are we dumping less than the entire buffer?
  87     if (numbytes < buffer->datalength) {
  88         // move index down by numbytes and decrement length by numbytes
  89         buffer->dataindex += numbytes;
  90         if (buffer->dataindex >= buffer->size) {
  91             buffer->dataindex %= buffer->size;
  92         }
  93         buffer->datalength -= numbytes;
  94     } else {
  95         // flush the whole buffer
  96         buffer->datalength = 0;
  97     }
  98 }
  99
 100 unsigned char bufferGetAtIndex(cBuffer *buffer, unsigned short index)
 101 {
 102     // return character at index in buffer
 103     return buffer->dataptr[(buffer->dataindex + index) % (buffer->size)];
 104 }
 105
 106 unsigned char bufferAddToEnd(cBuffer *buffer, unsigned char data)
 107 {
 108     // make sure the buffer has room
 109     if (buffer->datalength < buffer->size) {
 110         // save data byte at end of buffer
 111         buffer->dataptr[(buffer->dataindex + buffer->datalength) % buffer->size] = data;
 112         // increment the length
 113         buffer->datalength++;
 114         // return success
 115         return -1;
 116     } else { return 0; }
 117 }
 118
 119 unsigned char bufferIsNotFull(cBuffer *buffer)
 120 {
 121     // check to see if the buffer has room
 122     // return true if there is room
 123     return buffer->datalength < buffer->size;
 124 }
 125
 126 void bufferFlush(cBuffer *buffer)
 127 {
 128     // flush contents of the buffer
 129     buffer->datalength = 0;
 130 }