buffer.c

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/*! \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;
}

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