summaryrefslogtreecommitdiff
path: root/digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c
diff options
context:
space:
mode:
Diffstat (limited to 'digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c')
-rw-r--r--digital/avr/modules/usb/lufa/Projects/Magstripe/CircularBitBuffer.c113
1 files changed, 113 insertions, 0 deletions
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;
+}