Moved all source to the trunk directory.

[pub/lufa.git] / Projects / Magstripe / CircularBitBuffer.c

diff --git a/Projects/Magstripe/CircularBitBuffer.c b/Projects/Magstripe/CircularBitBuffer.c
new file mode 100644 (file)
index 0000000..5d23762
--- /dev/null
+++ b/Projects/Magstripe/CircularBitBuffer.c
@@ -0,0 +1,113 @@
+/*\r
+             LUFA Library\r
+     Copyright (C) Dean Camera, 2009.\r
+              \r
+  dean [at] fourwalledcubicle [dot] com\r
+      www.fourwalledcubicle.com\r
+*/\r
+\r
+/*\r
+  Copyright 2009  Denver Gingerich (denver [at] ossguy [dot] com)\r
+  Copyright 2009  Dean Camera (dean [at] fourwalledcubicle [dot] com)\r
+\r
+  Permission to use, copy, modify, and distribute this software\r
+  and its documentation for any purpose and without fee is hereby\r
+  granted, provided that the above copyright notice appear in all\r
+  copies and that both that the copyright notice and this\r
+  permission notice and warranty disclaimer appear in supporting\r
+  documentation, and that the name of the author not be used in\r
+  advertising or publicity pertaining to distribution of the\r
+  software without specific, written prior permission.\r
+\r
+  The author disclaim all warranties with regard to this\r
+  software, including all implied warranties of merchantability\r
+  and fitness.  In no event shall the author be liable for any\r
+  special, indirect or consequential damages or any damages\r
+  whatsoever resulting from loss of use, data or profits, whether\r
+  in an action of contract, negligence or other tortious action,\r
+  arising out of or in connection with the use or performance of\r
+  this software.\r
+*/\r
+\r
+/** Circular bit buffer library. This will allow for individual bits\r
+ *  to be stored in packed form inside circular buffers, to reduce\r
+ *  overall RAM usage.\r
+ */\r
+\r
+#include "CircularBitBuffer.h"\r
+\r
+/** Function to initialize or reset a bit buffer, ready for data to be stored into it. */\r
+void BitBuffer_Init(BitBuffer_t* Buffer)\r
+{\r
+       /* Reset the number of stored bits in the buffer */\r
+       Buffer->Elements        = 0;\r
+       \r
+       /* Reset the data in and out pointer structures in the buffer to the first buffer bit */\r
+       Buffer->In.CurrentByte  = Buffer->Data;\r
+       Buffer->In.ByteMask     = (1 << 0);\r
+       Buffer->Out.CurrentByte = Buffer->Data;\r
+       Buffer->Out.ByteMask    = (1 << 0);\r
+}\r
+\r
+/** Function to store the given bit into the given bit buffer. */\r
+void BitBuffer_StoreNextBit(BitBuffer_t* Buffer, bool Bit)\r
+{\r
+       /* If the bit to store is true, set the next bit in the buffer */\r
+       if (Bit)\r
+         *Buffer->In.CurrentByte |= Buffer->In.ByteMask;\r
+       \r
+       /* Increment the number of stored bits in the buffer counter */\r
+       Buffer->Elements++;\r
+       \r
+       /* Check if the current buffer byte is full of stored bits */\r
+       if (Buffer->In.ByteMask == (1 << 7))\r
+       {\r
+               /* Check if the end of the buffer has been reached, if so reset to start of buffer, otherwise advance to next bit */\r
+               if (Buffer->In.CurrentByte != &Buffer->Data[sizeof(Buffer->Data) - 1])\r
+                 Buffer->In.CurrentByte++;\r
+               else\r
+                 Buffer->In.CurrentByte = Buffer->Data;\r
+                 \r
+               /* Reset the storage bit mask in the current buffer byte to the first bit */            \r
+               Buffer->In.ByteMask = (1 << 0);\r
+       }\r
+       else\r
+       {\r
+               /* Shift the current storage bit mask to the next bit in the current byte */\r
+               Buffer->In.ByteMask <<= 1;\r
+       }\r
+}\r
+\r
+/** Function to retrieve the next bit stored in the given bit buffer. */\r
+bool BitBuffer_GetNextBit(BitBuffer_t* Buffer)\r
+{      \r
+       /* Retrieve the value of the next bit stored in the buffer */\r
+       bool Bit = ((*Buffer->Out.CurrentByte & Buffer->Out.ByteMask) != 0);\r
+\r
+       /* Clear the buffer bit */\r
+       *Buffer->Out.CurrentByte &= ~Buffer->Out.ByteMask;\r
+\r
+       /* Decrement the number of stored bits in the buffer counter */\r
+       Buffer->Elements--;\r
+       \r
+       /* Check if the current buffer byte is empty of stored bits */  \r
+       if (Buffer->Out.ByteMask == (1 << 7))\r
+       {\r
+               /* Check if the end of the buffer has been reached, if so reset to start of buffer, otherwise advance to next bit */\r
+               if (Buffer->Out.CurrentByte != &Buffer->Data[sizeof(Buffer->Data) - 1])\r
+                 Buffer->Out.CurrentByte++;\r
+               else\r
+                 Buffer->Out.CurrentByte = Buffer->Data;               \r
+               \r
+               /* Reset the retrieval bit mask in the current buffer byte to the first bit */          \r
+               Buffer->Out.ByteMask = (1 << 0);\r
+       }\r
+       else\r
+       {\r
+               /* Shift the current retrieval bit mask to the next bit in the current byte */\r
+               Buffer->Out.ByteMask <<= 1;\r
+       }\r
+\r
+       /* Return the retrieved bit from the buffer */\r
+       return Bit;\r
+}\r