116 lines
3.9 KiB
C
116 lines
3.9 KiB
C
/*
|
|
LUFA Library
|
|
Copyright (C) Dean Camera, 2019.
|
|
|
|
dean [at] fourwalledcubicle [dot] com
|
|
www.lufa-lib.org
|
|
*/
|
|
|
|
/*
|
|
Copyright 2010 Denver Gingerich (denver [at] ossguy [dot] com)
|
|
Copyright 2019 Dean Camera (dean [at] fourwalledcubicle [dot] com)
|
|
|
|
Permission to use, copy, modify, distribute, and sell this
|
|
software and its documentation for any purpose is hereby granted
|
|
without fee, provided that the above copyright notice appear in
|
|
all copies and that both that the copyright notice and this
|
|
permission notice and warranty disclaimer appear in supporting
|
|
documentation, and that the name of the author not be used in
|
|
advertising or publicity pertaining to distribution of the
|
|
software without specific, written prior permission.
|
|
|
|
The author disclaims all warranties with regard to this
|
|
software, including all implied warranties of merchantability
|
|
and fitness. In no event shall the author be liable for any
|
|
special, indirect or consequential damages or any damages
|
|
whatsoever resulting from loss of use, data or profits, whether
|
|
in an action of contract, negligence or other tortious action,
|
|
arising out of or in connection with the use or performance of
|
|
this software.
|
|
*/
|
|
|
|
/** Circular bit buffer library. This will allow for individual bits
|
|
* to be stored in packed form inside circular buffers, to reduce
|
|
* overall RAM usage.
|
|
*/
|
|
|
|
#include "CircularBitBuffer.h"
|
|
|
|
/** Function to initialize or reset a bit buffer, ready for data to be stored into it. */
|
|
void BitBuffer_Init(BitBuffer_t* const Buffer)
|
|
{
|
|
/* Reset the number of stored bits in the buffer */
|
|
Buffer->Elements = 0;
|
|
|
|
/* Reset the data in and out pointer structures in the buffer to the first buffer bit */
|
|
Buffer->In.CurrentByte = Buffer->Data;
|
|
Buffer->In.ByteMask = (1 << 0);
|
|
Buffer->Out.CurrentByte = Buffer->Data;
|
|
Buffer->Out.ByteMask = (1 << 0);
|
|
}
|
|
|
|
/** Function to store the given bit into the given bit buffer. */
|
|
void BitBuffer_StoreNextBit(BitBuffer_t* const Buffer,
|
|
const bool Bit)
|
|
{
|
|
/* If the bit to store is true, set the next bit in the buffer */
|
|
if (Bit)
|
|
*Buffer->In.CurrentByte |= Buffer->In.ByteMask;
|
|
|
|
/* Increment the number of stored bits in the buffer counter */
|
|
Buffer->Elements++;
|
|
|
|
/* Check if the current buffer byte is full of stored bits */
|
|
if (Buffer->In.ByteMask == (1 << 7))
|
|
{
|
|
/* Check if the end of the buffer has been reached, if so reset to start of buffer, otherwise advance to next bit */
|
|
if (Buffer->In.CurrentByte != &Buffer->Data[sizeof(Buffer->Data) - 1])
|
|
Buffer->In.CurrentByte++;
|
|
else
|
|
Buffer->In.CurrentByte = Buffer->Data;
|
|
|
|
/* Reset the storage bit mask in the current buffer byte to the first bit */
|
|
Buffer->In.ByteMask = (1 << 0);
|
|
}
|
|
else
|
|
{
|
|
/* Shift the current storage bit mask to the next bit in the current byte */
|
|
Buffer->In.ByteMask <<= 1;
|
|
}
|
|
}
|
|
|
|
/** Function to retrieve the next bit stored in the given bit buffer. */
|
|
bool BitBuffer_GetNextBit(BitBuffer_t* const Buffer)
|
|
{
|
|
/* Retrieve the value of the next bit stored in the buffer */
|
|
bool Bit = ((*Buffer->Out.CurrentByte & Buffer->Out.ByteMask) != 0);
|
|
|
|
/* Clear the buffer bit */
|
|
*Buffer->Out.CurrentByte &= ~Buffer->Out.ByteMask;
|
|
|
|
/* Decrement the number of stored bits in the buffer counter */
|
|
Buffer->Elements--;
|
|
|
|
/* Check if the current buffer byte is empty of stored bits */
|
|
if (Buffer->Out.ByteMask == (1 << 7))
|
|
{
|
|
/* Check if the end of the buffer has been reached, if so reset to start of buffer, otherwise advance to next bit */
|
|
if (Buffer->Out.CurrentByte != &Buffer->Data[sizeof(Buffer->Data) - 1])
|
|
Buffer->Out.CurrentByte++;
|
|
else
|
|
Buffer->Out.CurrentByte = Buffer->Data;
|
|
|
|
/* Reset the retrieval bit mask in the current buffer byte to the first bit */
|
|
Buffer->Out.ByteMask = (1 << 0);
|
|
}
|
|
else
|
|
{
|
|
/* Shift the current retrieval bit mask to the next bit in the current byte */
|
|
Buffer->Out.ByteMask <<= 1;
|
|
}
|
|
|
|
/* Return the retrieved bit from the buffer */
|
|
return Bit;
|
|
}
|
|
|