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/*! \file buffer.c \brief Multipurpose byte buffer structure and methods. */
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//*****************************************************************************
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//
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// File Name	: 'buffer.c'
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// Title		: Multipurpose byte buffer structure and methods
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// Author		: Pascal Stang - Copyright (C) 2001-2002
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// Created		: 9/23/2001
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// Revised		: 9/23/2001
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// Version		: 1.0
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// Target MCU	: any
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// Editor Tabs	: 4
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//
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// This code is distributed under the GNU Public License
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//		which can be found at http://www.gnu.org/licenses/gpl.txt
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//
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//*****************************************************************************
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#include "buffer.h"
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#include "global.h"
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#include "avr/io.h"
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#ifndef CRITICAL_SECTION_START
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#define CRITICAL_SECTION_START	unsigned char _sreg = SREG; cli()
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#define CRITICAL_SECTION_END	SREG = _sreg
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#endif
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// global variables
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// initialization
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void bufferInit(cBuffer* buffer, unsigned char *start, unsigned short size)
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{
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	// begin critical section
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	CRITICAL_SECTION_START;
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	// set start pointer of the buffer
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	buffer->dataptr = start;
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	buffer->size = size;
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	// initialize index and length
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	buffer->dataindex = 0;
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	buffer->datalength = 0;
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	// end critical section
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	CRITICAL_SECTION_END;
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}
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// access routines
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unsigned char  bufferGetFromFront(cBuffer* buffer)
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{
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	unsigned char data = 0;
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	// begin critical section
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	CRITICAL_SECTION_START;
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	// check to see if there's data in the buffer
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	if(buffer->datalength)
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	{
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		// get the first character from buffer
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		data = buffer->dataptr[buffer->dataindex];
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		// move index down and decrement length
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		buffer->dataindex++;
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		if(buffer->dataindex >= buffer->size)
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		{
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			buffer->dataindex -= buffer->size;
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		}
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		buffer->datalength--;
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	}
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	// end critical section
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	CRITICAL_SECTION_END;
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	// return
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	return data;
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}
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void bufferDumpFromFront(cBuffer* buffer, unsigned short numbytes)
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{
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	// begin critical section
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	CRITICAL_SECTION_START;
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	// dump numbytes from the front of the buffer
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	// are we dumping less than the entire buffer?
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	if(numbytes < buffer->datalength)
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	{
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		// move index down by numbytes and decrement length by numbytes
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		buffer->dataindex += numbytes;
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		if(buffer->dataindex >= buffer->size)
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		{
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			buffer->dataindex -= buffer->size;
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		}
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		buffer->datalength -= numbytes;
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	}
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	else
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	{
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		// flush the whole buffer
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		buffer->datalength = 0;
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	}
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	// end critical section
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	CRITICAL_SECTION_END;
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}
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unsigned char bufferGetAtIndex(cBuffer* buffer, unsigned short index)
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{
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	// begin critical section
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	CRITICAL_SECTION_START;
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	// return character at index in buffer
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	unsigned char data = buffer->dataptr[(buffer->dataindex+index)%(buffer->size)];
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	// end critical section
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	CRITICAL_SECTION_END;
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	return data;
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}
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unsigned char bufferAddToEnd(cBuffer* buffer, unsigned char data)
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{
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	// begin critical section
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	CRITICAL_SECTION_START;
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	// make sure the buffer has room
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	if(buffer->datalength < buffer->size)
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	{
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		// save data byte at end of buffer
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		buffer->dataptr[(buffer->dataindex + buffer->datalength) % buffer->size] = data;
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		// increment the length
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		buffer->datalength++;
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		// end critical section
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		CRITICAL_SECTION_END;
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		// return success
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		return -1;
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	}
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	// end critical section
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	CRITICAL_SECTION_END;
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	// return failure
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	return 0;
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}
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unsigned short bufferIsNotFull(cBuffer* buffer)
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{
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	// begin critical section
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	CRITICAL_SECTION_START;
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	// check to see if the buffer has room
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	// return true if there is room
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	unsigned short bytesleft = (buffer->size - buffer->datalength);
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	// end critical section
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	CRITICAL_SECTION_END;
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	return bytesleft;
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}
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void bufferFlush(cBuffer* buffer)
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{
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	// begin critical section
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	CRITICAL_SECTION_START;
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	// flush contents of the buffer
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	buffer->datalength = 0;
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	// end critical section
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	CRITICAL_SECTION_END;
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}
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