From 74298f8ca11dc8d3b0359d1d4e124d6494c3eeac Mon Sep 17 00:00:00 2001 From: Nicolas Schodet Date: Fri, 10 Apr 2009 01:15:42 +0200 Subject: * digital/avr/modules/usb: - imported LUFA. --- .../lufa/Projects/Magstripe/CircularBitBuffer.c | 113 +++++++++++++++++++++ 1 file changed, 113 insertions(+) create mode 100644 digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c (limited to 'digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c') diff --git a/digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c b/digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c new file mode 100644 index 00000000..5d23762e --- /dev/null +++ b/digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c @@ -0,0 +1,113 @@ +/* + LUFA Library + Copyright (C) Dean Camera, 2009. + + dean [at] fourwalledcubicle [dot] com + www.fourwalledcubicle.com +*/ + +/* + Copyright 2009 Denver Gingerich (denver [at] ossguy [dot] com) + Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com) + + Permission to use, copy, modify, and distribute this software + and its documentation for any purpose and without fee is hereby + granted, 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 disclaim 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* 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* Buffer, 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* 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; +} -- cgit v1.2.3