LUFA/Drivers/Misc/RingBuffer.h

   1 /*
   2              LUFA Library
   3      Copyright (C) Dean Camera, 2011.
   4
   5   dean [at] fourwalledcubicle [dot] com
   6            www.lufa-lib.org
   7 */
   8
   9 /*
  10   Copyright 2011  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  11
  12   Permission to use, copy, modify, distribute, and sell this
  13   software and its documentation for any purpose is hereby granted
  14   without fee, provided that the above copyright notice appear in
  15   all copies and that both that the copyright notice and this
  16   permission notice and warranty disclaimer appear in supporting
  17   documentation, and that the name of the author not be used in
  18   advertising or publicity pertaining to distribution of the
  19   software without specific, written prior permission.
  20
  21   The author disclaim all warranties with regard to this
  22   software, including all implied warranties of merchantability
  23   and fitness.  In no event shall the author be liable for any
  24   special, indirect or consequential damages or any damages
  25   whatsoever resulting from loss of use, data or profits, whether
  26   in an action of contract, negligence or other tortious action,
  27   arising out of or in connection with the use or performance of
  28   this software.
  29 */
  30
  31 /** \file
  32  *  \brief Lightweight ring buffer, for fast insertion/deletion.
  33  *
  34  *  Lightweight ring buffer, for fast insertion/deletion. Multiple buffers can be created of
  35  *  different sizes to suit different needs.
  36  *
  37  *  Note that for each buffer, insertion and removal operations may occur at the same time (via
  38  *  a multi-threaded ISR based system) however the same kind of operation (two or more insertions
  39  *  or deletions) must not overlap. If there is possibility of two or more of the same kind of
  40  *  operating occurring at the same point in time, atomic (mutex) locking should be used.
  41  */
  42
  43 /** \ingroup Group_MiscDrivers
  44  *  @defgroup Group_RingBuff Generic Byte Ring Buffer - LUFA/Drivers/Misc/RingBuffer.h
  45  *
  46  *  \section Sec_Dependencies Module Source Dependencies
  47  *  The following files must be built with any user project that uses this module:
  48  *    - None
  49  *
  50  *  \section Sec_ModDescription Module Description
  51  *  Lightweight ring buffer, for fast insertion/deletion. Multiple buffers can be created of
  52  *  different sizes to suit different needs.
  53  *
  54  *  Note that for each buffer, insertion and removal operations may occur at the same time (via
  55  *  a multi-threaded ISR based system) however the same kind of operation (two or more insertions
  56  *  or deletions) must not overlap. If there is possibility of two or more of the same kind of
  57  *  operating occurring at the same point in time, atomic (mutex) locking should be used.
  58  *
  59  *  \section Sec_ExampleUsage Example Usage
  60  *  The following snippet is an example of how this module may be used within a typical
  61  *  application.
  62  *
  63  *  \code
  64  *      // Create the buffer structure and its underlying storage array
  65  *      RingBuffer_t Buffer;
  66  *      uint8_t      BufferData[128];
  67  *
  68  *      // Initialise the buffer with the created storage array
  69  *      RingBuffer_InitBuffer(&Buffer, BufferData, sizeof(BufferData));
  70  *
  71  *      // Insert some data into the buffer
  72  *      RingBuffer_Insert(Buffer, 'H');
  73  *      RingBuffer_Insert(Buffer, 'E');
  74  *      RingBuffer_Insert(Buffer, 'L');
  75  *      RingBuffer_Insert(Buffer, 'L');
  76  *      RingBuffer_Insert(Buffer, 'O');
  77  *
  78  *      // Cache the number of stored bytes in the buffer
  79  *      uint16_t BufferCount = RingBuffer_GetCount(&Buffer);
  80  *
  81  *      // Printer stored data length
  82  *      printf("Buffer Length: %d, Buffer Data: \r\n", BufferCount);
  83  *
  84  *      // Print contents of the buffer one character at a time
  85  *      while (BufferCount--)
  86  *        putc(RingBuffer_Remove(&Buffer));
  87  *  \endcode
  88  *
  89  *  @{
  90  */
  91
  92 #ifndef __RING_BUFF_H__
  93 #define __RING_BUFF_H__
  94
  95         /* Includes: */
  96                 #include <util/atomic.h>
  97                 #include <stdint.h>
  98                 #include <stdbool.h>
  99
 100                 #include <LUFA/Common/Common.h>
 101
 102         /* Type Defines: */
 103                 /** \brief Ring Buffer Management Structure.
 104                  *
 105                  *  Type define for a new ring buffer object. Buffers should be initialized via a call to
 106                  *  \ref RingBuffer_InitBuffer() before use.
 107                  */
 108                 typedef struct
 109                 {
 110                         uint8_t* In; /**< Current storage location in the circular buffer */
 111                         uint8_t* Out; /**< Current retrieval location in the circular buffer */
 112                         uint8_t* Start; /**< Pointer to the start of the buffer's underlying storage array */
 113                         uint8_t* End; /**< Pointer to the end of the buffer's underlying storage array */
 114                         uint8_t  Size; /**< Size of the buffer's underlying storage array */
 115                         uint16_t Count; /**< Number of bytes currently stored in the buffer */
 116                 } RingBuffer_t;
 117
 118         /* Inline Functions: */
 119                 /** Initializes a ring buffer ready for use. Buffers must be initialized via this function
 120                  *  before any operations are called upon them. Already initialized buffers may be reset
 121                  *  by re-initializing them using this function.
 122                  *
 123                  *  \param[out] Buffer   Pointer to a ring buffer structure to initialize.
 124                  *  \param[out] DataPtr  Pointer to a global array that will hold the data stored into the ring buffer.
 125                  *  \param[out] Size     Maximum number of bytes that can be stored in the underlying data array.
 126                  */
 127                 static inline void RingBuffer_InitBuffer(RingBuffer_t* Buffer, uint8_t* const DataPtr, const uint16_t Size)
 128                 {
 129                         GCC_FORCE_POINTER_ACCESS(Buffer);
 130
 131                         ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
 132                         {
 133                                 Buffer->In     = DataPtr;
 134                                 Buffer->Out    = DataPtr;
 135                                 Buffer->Start  = &DataPtr[0];
 136                                 Buffer->End    = &DataPtr[Size];
 137                                 Buffer->Size   = Size;
 138                                 Buffer->Count  = 0;
 139                         }
 140                 }
 141
 142                 /** Retrieves the minimum number of bytes stored in a particular buffer. This value is computed
 143                  *  by entering an atomic lock on the buffer while the IN and OUT locations are fetched, so that
 144                  *  the buffer cannot be modified while the computation takes place. This value should be cached
 145                  *  when reading out the contents of the buffer, so that as small a time as possible is spent
 146                  *  in an atomic lock.
 147                  *
 148                  *  \note The value returned by this function is guaranteed to only be the minimum number of bytes
 149                  *        stored in the given buffer; this value may change as other threads write new data and so
 150                  *        the returned number should be used only to determine how many successive reads may safely
 151                  *        be performed on the buffer.
 152                  *
 153                  *  \param[in] Buffer  Pointer to a ring buffer structure whose count is to be computed.
 154                  */
 155                 static inline uint16_t RingBuffer_GetCount(RingBuffer_t* const Buffer)
 156                 {
 157                         uint16_t Count;
 158
 159                         ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
 160                         {
 161                                 Count = Buffer->Count;
 162                         }
 163
 164                         return Count;
 165                 }
 166
 167                 /** Atomically determines if the specified ring buffer contains any free space. This should
 168                  *  be tested before storing data to the buffer, to ensure that no data is lost due to a
 169                  *  buffer overrun.
 170                  *
 171                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 172                  *
 173                  *  \return Boolean \c true if the buffer contains no free space, false otherwise.
 174                  */
 175                 static inline bool RingBuffer_IsFull(RingBuffer_t* const Buffer)
 176                 {
 177                         return (RingBuffer_GetCount(Buffer) == Buffer->Size);
 178                 }
 179
 180                 /** Atomically determines if the specified ring buffer contains any data. This should
 181                  *  be tested before removing data from the buffer, to ensure that the buffer does not
 182                  *  underflow.
 183                  *
 184                  *  If the data is to be removed in a loop, store the total number of bytes stored in the
 185                  *  buffer (via a call to the \ref RingBuffer_GetCount() function) in a temporary variable
 186                  *  to reduce the time spent in atomicity locks.
 187                  *
 188                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 189                  *
 190                  *  \return Boolean \c true if the buffer contains no free space, false otherwise.
 191                  */
 192                 static inline bool RingBuffer_IsEmpty(RingBuffer_t* const Buffer)
 193                 {
 194                         return (RingBuffer_GetCount(Buffer) == 0);
 195                 }
 196
 197                 /** Inserts an element into the ring buffer.
 198                  *
 199                  *  \note Only one execution thread (main program thread or an ISR) may insert into a single buffer
 200                  *        otherwise data corruption may occur. Insertion and removal may occur from different execution
 201                  *        threads.
 202                  *
 203                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 204                  *  \param[in]     Data    Data element to insert into the buffer.
 205                  */
 206                 static inline void RingBuffer_Insert(RingBuffer_t* Buffer,
 207                                                      const uint8_t Data)
 208                 {
 209                         GCC_FORCE_POINTER_ACCESS(Buffer);
 210
 211                         *Buffer->In = Data;
 212
 213                         if (++Buffer->In == Buffer->End)
 214                           Buffer->In = Buffer->Start;
 215
 216                         ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
 217                         {
 218                                 Buffer->Count++;
 219                         }
 220                 }
 221
 222                 /** Removes an element from the ring buffer.
 223                  *
 224                  *  \note Only one execution thread (main program thread or an ISR) may remove from a single buffer
 225                  *        otherwise data corruption may occur. Insertion and removal may occur from different execution
 226                  *        threads.
 227                  *
 228                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from.
 229                  *
 230                  *  \return Next data element stored in the buffer.
 231                  */
 232                 static inline uint8_t RingBuffer_Remove(RingBuffer_t* Buffer)
 233                 {
 234                         GCC_FORCE_POINTER_ACCESS(Buffer);
 235
 236                         uint8_t Data = *Buffer->Out;
 237
 238                         if (++Buffer->Out == Buffer->End)
 239                           Buffer->Out = Buffer->Start;
 240
 241                         ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
 242                         {
 243                                 Buffer->Count--;
 244                         }
 245
 246                         return Data;
 247                 }
 248
 249                 /** Returns the next element stored in the ring buffer, without removing it.
 250                  *
 251                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from.
 252                  *
 253                  *  \return Next data element stored in the buffer.
 254                  */
 255                 static inline uint8_t RingBuffer_Peek(RingBuffer_t* const Buffer)
 256                 {
 257                         return *Buffer->Out;
 258                 }
 259
 260 #endif
 261
 262 /** @} */
 263