diff options
author | Jack Humbert <jack.humb@gmail.com> | 2017-07-07 21:33:29 +0200 |
---|---|---|
committer | GitHub <noreply@github.com> | 2017-07-07 21:33:29 +0200 |
commit | 9de443cbf10ac41bc15762c9c83f138f51dd3b9a (patch) | |
tree | d8ddcb428e0b7d9773a1e52c42b60bdca2658beb /lib/lufa/Projects/Magstripe/Lib/CircularBitBuffer.c | |
parent | 88b3d051b21cb1ddacc6353c5d59b19f03f3a242 (diff) | |
parent | 1c26468ad5a0701e244c99cbcbc547c93b75d515 (diff) | |
download | qmk_firmware-9de443cbf10ac41bc15762c9c83f138f51dd3b9a.tar.gz qmk_firmware-9de443cbf10ac41bc15762c9c83f138f51dd3b9a.tar.xz |
Merge pull request #1471 from qmk/lufa_lib
Update LUFA and move it to /lib/lufa
Diffstat (limited to 'lib/lufa/Projects/Magstripe/Lib/CircularBitBuffer.c')
-rw-r--r-- | lib/lufa/Projects/Magstripe/Lib/CircularBitBuffer.c | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/lib/lufa/Projects/Magstripe/Lib/CircularBitBuffer.c b/lib/lufa/Projects/Magstripe/Lib/CircularBitBuffer.c new file mode 100644 index 000000000..802d040c5 --- /dev/null +++ b/lib/lufa/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; +} + |