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 of bytes.
  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  *  \brief Lightweight ring buffer, for fast insertion/deletion of bytes.
  46  *
  47  *  \section Sec_Dependencies Module Source Dependencies
  48  *  The following files must be built with any user project that uses this module:
  49  *    - None
  50  *
  51  *  \section Sec_ModDescription Module Description
  52  *  Lightweight ring buffer, for fast insertion/deletion. Multiple buffers can be created of
  53  *  different sizes to suit different needs.
  54  *
  55  *  Note that for each buffer, insertion and removal operations may occur at the same time (via
  56  *  a multi-threaded ISR based system) however the same kind of operation (two or more insertions
  57  *  or deletions) must not overlap. If there is possibility of two or more of the same kind of
  58  *  operating occurring at the same point in time, atomic (mutex) locking should be used.
  59  *
  60  *  \section Sec_ExampleUsage Example Usage
  61  *  The following snippet is an example of how this module may be used within a typical
  62  *  application.
  63  *
  64  *  \code
  65  *      // Create the buffer structure and its underlying storage array
  66  *      RingBuffer_t Buffer;
  67  *      uint8_t      BufferData[128];
  68  *
  69  *      // Initialize the buffer with the created storage array
  70  *      RingBuffer_InitBuffer(&Buffer, BufferData, sizeof(BufferData));
  71  *
  72  *      // Insert some data into the buffer
  73  *      RingBuffer_Insert(Buffer, 'H');
  74  *      RingBuffer_Insert(Buffer, 'E');
  75  *      RingBuffer_Insert(Buffer, 'L');
  76  *      RingBuffer_Insert(Buffer, 'L');
  77  *      RingBuffer_Insert(Buffer, 'O');
  78  *
  79  *      // Cache the number of stored bytes in the buffer
  80  *      uint16_t BufferCount = RingBuffer_GetCount(&Buffer);
  81  *
  82  *      // Printer stored data length
  83  *      printf("Buffer Length: %d, Buffer Data: \r\n", BufferCount);
  84  *
  85  *      // Print contents of the buffer one character at a time
  86  *      while (BufferCount--)
  87  *        putc(RingBuffer_Remove(&Buffer));
  88  *  \endcode
  89  *
  90  *  @{
  91  */
  92
  93 #ifndef __RING_BUFFER_H__
  94 #define __RING_BUFFER_H__
  95
  96         /* Includes: */
  97                 #include "../../Common/Common.h"
  98
  99         /* Enable C linkage for C++ Compilers: */
 100                 #if defined(__cplusplus)
 101                         extern "C" {
 102                 #endif
 103
 104         /* Type Defines: */
 105                 /** \brief Ring Buffer Management Structure.
 106                  *
 107                  *  Type define for a new ring buffer object. Buffers should be initialized via a call to
 108                  *  \ref RingBuffer_InitBuffer() before use.
 109                  */
 110                 typedef struct
 111                 {
 112                         uint8_t* In; /**< Current storage location in the circular buffer. */
 113                         uint8_t* Out; /**< Current retrieval location in the circular buffer. */
 114                         uint8_t* Start; /**< Pointer to the start of the buffer's underlying storage array. */
 115                         uint8_t* End; /**< Pointer to the end of the buffer's underlying storage array. */
 116                         uint8_t  Size; /**< Size of the buffer's underlying storage array. */
 117                         uint16_t Count; /**< Number of bytes currently stored in the buffer. */
 118                 } RingBuffer_t;
 119
 120         /* Inline Functions: */
 121                 /** Initializes a ring buffer ready for use. Buffers must be initialized via this function
 122                  *  before any operations are called upon them. Already initialized buffers may be reset
 123                  *  by re-initializing them using this function.
 124                  *
 125                  *  \param[out] Buffer   Pointer to a ring buffer structure to initialize.
 126                  *  \param[out] DataPtr  Pointer to a global array that will hold the data stored into the ring buffer.
 127                  *  \param[out] Size     Maximum number of bytes that can be stored in the underlying data array.
 128                  */
 129                 static inline void RingBuffer_InitBuffer(RingBuffer_t* Buffer, uint8_t* const DataPtr, const uint16_t Size)
 130                 {
 131                         GCC_FORCE_POINTER_ACCESS(Buffer);
 132
 133                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 134                         GlobalInterruptDisable();
 135
 136                         Buffer->In     = DataPtr;
 137                         Buffer->Out    = DataPtr;
 138                         Buffer->Start  = &DataPtr[0];
 139                         Buffer->End    = &DataPtr[Size];
 140                         Buffer->Size   = Size;
 141                         Buffer->Count  = 0;
 142
 143                         SetGlobalInterruptMask(CurrentGlobalInt);
 144                 }
 145
 146                 /** Retrieves the minimum number of bytes stored in a particular buffer. This value is computed
 147                  *  by entering an atomic lock on the buffer while the IN and OUT locations are fetched, so that
 148                  *  the buffer cannot be modified while the computation takes place. This value should be cached
 149                  *  when reading out the contents of the buffer, so that as small a time as possible is spent
 150                  *  in an atomic lock.
 151                  *
 152                  *  \note The value returned by this function is guaranteed to only be the minimum number of bytes
 153                  *        stored in the given buffer; this value may change as other threads write new data and so
 154                  *        the returned number should be used only to determine how many successive reads may safely
 155                  *        be performed on the buffer.
 156                  *
 157                  *  \param[in] Buffer  Pointer to a ring buffer structure whose count is to be computed.
 158                  */
 159                 static inline uint16_t RingBuffer_GetCount(RingBuffer_t* const Buffer)
 160                 {
 161                         uint16_t Count;
 162
 163                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 164                         GlobalInterruptDisable();
 165
 166                         Count = Buffer->Count;
 167
 168                         SetGlobalInterruptMask(CurrentGlobalInt);
 169                         return Count;
 170                 }
 171
 172                 /** Atomically determines if the specified ring buffer contains any free space. This should
 173                  *  be tested before storing data to the buffer, to ensure that no data is lost due to a
 174                  *  buffer overrun.
 175                  *
 176                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 177                  *
 178                  *  \return Boolean \c true if the buffer contains no free space, false otherwise.
 179                  */
 180                 static inline bool RingBuffer_IsFull(RingBuffer_t* const Buffer)
 181                 {
 182                         return (RingBuffer_GetCount(Buffer) == Buffer->Size);
 183                 }
 184
 185                 /** Atomically determines if the specified ring buffer contains any data. This should
 186                  *  be tested before removing data from the buffer, to ensure that the buffer does not
 187                  *  underflow.
 188                  *
 189                  *  If the data is to be removed in a loop, store the total number of bytes stored in the
 190                  *  buffer (via a call to the \ref RingBuffer_GetCount() function) in a temporary variable
 191                  *  to reduce the time spent in atomicity locks.
 192                  *
 193                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 194                  *
 195                  *  \return Boolean \c true if the buffer contains no free space, false otherwise.
 196                  */
 197                 static inline bool RingBuffer_IsEmpty(RingBuffer_t* const Buffer)
 198                 {
 199                         return (RingBuffer_GetCount(Buffer) == 0);
 200                 }
 201
 202                 /** Inserts an element into the ring buffer.
 203                  *
 204                  *  \note Only one execution thread (main program thread or an ISR) may insert into a single buffer
 205                  *        otherwise data corruption may occur. Insertion and removal may occur from different execution
 206                  *        threads.
 207                  *
 208                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 209                  *  \param[in]     Data    Data element to insert into the buffer.
 210                  */
 211                 static inline void RingBuffer_Insert(RingBuffer_t* Buffer,
 212                                                      const uint8_t Data)
 213                 {
 214                         GCC_FORCE_POINTER_ACCESS(Buffer);
 215
 216                         *Buffer->In = Data;
 217
 218                         if (++Buffer->In == Buffer->End)
 219                           Buffer->In = Buffer->Start;
 220
 221                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 222                         GlobalInterruptDisable();
 223
 224                         Buffer->Count++;
 225
 226                         SetGlobalInterruptMask(CurrentGlobalInt);
 227                 }
 228
 229                 /** Removes an element from the ring buffer.
 230                  *
 231                  *  \note Only one execution thread (main program thread or an ISR) may remove from a single buffer
 232                  *        otherwise data corruption may occur. Insertion and removal may occur from different execution
 233                  *        threads.
 234                  *
 235                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from.
 236                  *
 237                  *  \return Next data element stored in the buffer.
 238                  */
 239                 static inline uint8_t RingBuffer_Remove(RingBuffer_t* Buffer)
 240                 {
 241                         GCC_FORCE_POINTER_ACCESS(Buffer);
 242
 243                         uint8_t Data = *Buffer->Out;
 244
 245                         if (++Buffer->Out == Buffer->End)
 246                           Buffer->Out = Buffer->Start;
 247
 248                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 249                         GlobalInterruptDisable();
 250
 251                         Buffer->Count--;
 252
 253                         SetGlobalInterruptMask(CurrentGlobalInt);
 254
 255                         return Data;
 256                 }
 257
 258                 /** Returns the next element stored in the ring buffer, without removing it.
 259                  *
 260                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from.
 261                  *
 262                  *  \return Next data element stored in the buffer.
 263                  */
 264                 static inline uint8_t RingBuffer_Peek(RingBuffer_t* const Buffer)
 265                 {
 266                         return *Buffer->Out;
 267                 }
 268
 269         /* Disable C linkage for C++ Compilers: */
 270                 #if defined(__cplusplus)
 271                         }
 272                 #endif
 273
 274 #endif
 275
 276 /** @} */
 277