library

/*! \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"
#include "global.h"
#include "avr/io.h"

#ifndef CRITICAL_SECTION_START
#define CRITICAL_SECTION_START  unsigned char _sreg = SREG; cli()
#define CRITICAL_SECTION_END    SREG = _sreg
#endif

// global variables

// initialization

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

// access routines
unsigned char  bufferGetFromFront(cBuffer* buffer)
{
        unsigned char data = 0;
        // begin critical section
        CRITICAL_SECTION_START;
        // 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--;
        }
        // end critical section
        CRITICAL_SECTION_END;
        // return
        return data;
}

void bufferDumpFromFront(cBuffer* buffer, unsigned short numbytes)
{
        // begin critical section
        CRITICAL_SECTION_START;
        // 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;
        }
        // end critical section
        CRITICAL_SECTION_END;
}

unsigned char bufferGetAtIndex(cBuffer* buffer, unsigned short index)
{
        // begin critical section
        CRITICAL_SECTION_START;
        // return character at index in buffer
        unsigned char data = buffer->dataptr[(buffer->dataindex+index)%(buffer->size)];
        // end critical section
        CRITICAL_SECTION_END;
        return data;
}

unsigned char bufferAddToEnd(cBuffer* buffer, unsigned char data)
{
        // begin critical section
        CRITICAL_SECTION_START;
        // 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++;
                // end critical section
                CRITICAL_SECTION_END;
                // return success
                return -1;
        }
        // end critical section
        CRITICAL_SECTION_END;
        // return failure
        return 0;
}

unsigned short bufferIsNotFull(cBuffer* buffer)
{
        // begin critical section
        CRITICAL_SECTION_START;
        // check to see if the buffer has room
        // return true if there is room
        unsigned short bytesleft = (buffer->size - buffer->datalength);
        // end critical section
        CRITICAL_SECTION_END;
        return bytesleft;
}

void bufferFlush(cBuffer* buffer)
{
        // begin critical section
        CRITICAL_SECTION_START;
        // flush contents of the buffer
        buffer->datalength = 0;
        // end critical section
        CRITICAL_SECTION_END;
}