1 files changed, 115 insertions, 0 deletions
diff --git a/Projects/Magstripe/Lib/CircularBitBuffer.c b/Projects/Magstripe/Lib/CircularBitBuffer.c
new file mode 100644
index 000000000..802d040c5
--- /dev/null
+++ b/Projects/Magstripe/Lib/CircularBitBuffer.c
@@ -0,0 +1,115 @@
+/*
+             LUFA Library
+     Copyright (C) Dean Camera, 2017.
+
+  dean [at] fourwalledcubicle [dot] com
+           www.lufa-lib.org
+*/
+
+/*
+  Copyright 2010  Denver Gingerich (denver [at] ossguy [dot] com)
+  Copyright 2017  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;
+}
+