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116 lines
3.9 KiB
116 lines
3.9 KiB
/*
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LUFA Library
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Copyright (C) Dean Camera, 2012.
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dean [at] fourwalledcubicle [dot] com
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www.lufa-lib.org
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*/
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/*
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Copyright 2010 Denver Gingerich (denver [at] ossguy [dot] com)
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Copyright 2012 Dean Camera (dean [at] fourwalledcubicle [dot] com)
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Permission to use, copy, modify, distribute, and sell this
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software and its documentation for any purpose is hereby granted
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without fee, provided that the above copyright notice appear in
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all copies and that both that the copyright notice and this
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permission notice and warranty disclaimer appear in supporting
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documentation, and that the name of the author not be used in
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advertising or publicity pertaining to distribution of the
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software without specific, written prior permission.
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The author disclaims all warranties with regard to this
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software, including all implied warranties of merchantability
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and fitness. In no event shall the author be liable for any
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special, indirect or consequential damages or any damages
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whatsoever resulting from loss of use, data or profits, whether
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in an action of contract, negligence or other tortious action,
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arising out of or in connection with the use or performance of
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this software.
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*/
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/** Circular bit buffer library. This will allow for individual bits
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* to be stored in packed form inside circular buffers, to reduce
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* overall RAM usage.
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*/
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#include "CircularBitBuffer.h"
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/** Function to initialize or reset a bit buffer, ready for data to be stored into it. */
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void BitBuffer_Init(BitBuffer_t* const Buffer)
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{
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/* Reset the number of stored bits in the buffer */
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Buffer->Elements = 0;
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/* Reset the data in and out pointer structures in the buffer to the first buffer bit */
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Buffer->In.CurrentByte = Buffer->Data;
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Buffer->In.ByteMask = (1 << 0);
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Buffer->Out.CurrentByte = Buffer->Data;
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Buffer->Out.ByteMask = (1 << 0);
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}
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/** Function to store the given bit into the given bit buffer. */
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void BitBuffer_StoreNextBit(BitBuffer_t* const Buffer,
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const bool Bit)
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{
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/* If the bit to store is true, set the next bit in the buffer */
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if (Bit)
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*Buffer->In.CurrentByte |= Buffer->In.ByteMask;
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/* Increment the number of stored bits in the buffer counter */
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Buffer->Elements++;
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/* Check if the current buffer byte is full of stored bits */
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if (Buffer->In.ByteMask == (1 << 7))
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{
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/* Check if the end of the buffer has been reached, if so reset to start of buffer, otherwise advance to next bit */
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if (Buffer->In.CurrentByte != &Buffer->Data[sizeof(Buffer->Data) - 1])
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Buffer->In.CurrentByte++;
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else
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Buffer->In.CurrentByte = Buffer->Data;
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/* Reset the storage bit mask in the current buffer byte to the first bit */
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Buffer->In.ByteMask = (1 << 0);
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}
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else
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{
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/* Shift the current storage bit mask to the next bit in the current byte */
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Buffer->In.ByteMask <<= 1;
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}
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}
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/** Function to retrieve the next bit stored in the given bit buffer. */
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bool BitBuffer_GetNextBit(BitBuffer_t* const Buffer)
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{
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/* Retrieve the value of the next bit stored in the buffer */
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bool Bit = ((*Buffer->Out.CurrentByte & Buffer->Out.ByteMask) != 0);
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/* Clear the buffer bit */
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*Buffer->Out.CurrentByte &= ~Buffer->Out.ByteMask;
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/* Decrement the number of stored bits in the buffer counter */
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Buffer->Elements--;
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/* Check if the current buffer byte is empty of stored bits */
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if (Buffer->Out.ByteMask == (1 << 7))
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{
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/* Check if the end of the buffer has been reached, if so reset to start of buffer, otherwise advance to next bit */
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if (Buffer->Out.CurrentByte != &Buffer->Data[sizeof(Buffer->Data) - 1])
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Buffer->Out.CurrentByte++;
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else
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Buffer->Out.CurrentByte = Buffer->Data;
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/* Reset the retrieval bit mask in the current buffer byte to the first bit */
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Buffer->Out.ByteMask = (1 << 0);
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}
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else
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{
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/* Shift the current retrieval bit mask to the next bit in the current byte */
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Buffer->Out.ByteMask <<= 1;
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}
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/* Return the retrieved bit from the buffer */
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return Bit;
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}
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