LUFA/Drivers/Misc/RingBuffer.h

   1 /*
   2              LUFA Library
   3      Copyright (C) Dean Camera, 2012.
   4
   5   dean [at] fourwalledcubicle [dot] com
   6            www.lufa-lib.org
   7 */
   8
   9 /*
  10   Copyright 2012  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 disclaims 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 (circular) 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                         uint16_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,
 130                                                          uint8_t* const DataPtr,
 131                                                          const uint16_t Size) ATTR_NON_NULL_PTR_ARG(1) ATTR_NON_NULL_PTR_ARG(2);
 132                 static inline void RingBuffer_InitBuffer(RingBuffer_t* Buffer,
 133                                                          uint8_t* const DataPtr,
 134                                                          const uint16_t Size)
 135                 {
 136                         GCC_FORCE_POINTER_ACCESS(Buffer);
 137
 138                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 139                         GlobalInterruptDisable();
 140
 141                         Buffer->In     = DataPtr;
 142                         Buffer->Out    = DataPtr;
 143                         Buffer->Start  = &DataPtr[0];
 144                         Buffer->End    = &DataPtr[Size];
 145                         Buffer->Size   = Size;
 146                         Buffer->Count  = 0;
 147
 148                         SetGlobalInterruptMask(CurrentGlobalInt);
 149                 }
 150
 151                 /** Retrieves the current number of bytes stored in a particular buffer. This value is computed
 152                  *  by entering an atomic lock on the buffer, so that the buffer cannot be modified while the
 153                  *  computation takes place. This value should be cached when reading out the contents of the buffer,
 154                  *  so that as small a time as possible is spent in an atomic lock.
 155                  *
 156                  *  \note The value returned by this function is guaranteed to only be the minimum number of bytes
 157                  *        stored in the given buffer; this value may change as other threads write new data, thus
 158                  *        the returned number should be used only to determine how many successive reads may safely
 159                  *        be performed on the buffer.
 160                  *
 161                  *  \param[in] Buffer  Pointer to a ring buffer structure whose count is to be computed.
 162                  *
 163                  *  \return Number of bytes currently stored in the buffer.
 164                  */
 165                 static inline uint16_t RingBuffer_GetCount(RingBuffer_t* const Buffer) ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(1);
 166                 static inline uint16_t RingBuffer_GetCount(RingBuffer_t* const Buffer)
 167                 {
 168                         uint16_t Count;
 169
 170                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 171                         GlobalInterruptDisable();
 172
 173                         Count = Buffer->Count;
 174
 175                         SetGlobalInterruptMask(CurrentGlobalInt);
 176                         return Count;
 177                 }
 178
 179                 /** Retrieves the free space in a particular buffer. This value is computed by entering an atomic lock
 180                  *  on the buffer, so that the buffer cannot be modified while the computation takes place.
 181                  *
 182                  *  \note The value returned by this function is guaranteed to only be the maximum number of bytes
 183                  *        free in the given buffer; this value may change as other threads write new data, thus
 184                  *        the returned number should be used only to determine how many successive writes may safely
 185                  *        be performed on the buffer when there is a single writer thread.
 186                  *
 187                  *  \param[in] Buffer  Pointer to a ring buffer structure whose free count is to be computed.
 188                  *
 189                  *  \return Number of free bytes in the buffer.
 190                  */
 191                 static inline uint16_t RingBuffer_GetFreeCount(RingBuffer_t* const Buffer) ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(1);
 192                 static inline uint16_t RingBuffer_GetFreeCount(RingBuffer_t* const Buffer)
 193                 {
 194                         return (Buffer->Size - RingBuffer_GetCount(Buffer));
 195                 }
 196
 197                 /** Atomically determines if the specified ring buffer contains any data. This should
 198                  *  be tested before removing data from the buffer, to ensure that the buffer does not
 199                  *  underflow.
 200                  *
 201                  *  If the data is to be removed in a loop, store the total number of bytes stored in the
 202                  *  buffer (via a call to the \ref RingBuffer_GetCount() function) in a temporary variable
 203                  *  to reduce the time spent in atomicity locks.
 204                  *
 205                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 206                  *
 207                  *  \return Boolean \c true if the buffer contains no free space, false otherwise.
 208                  */
 209                 static inline bool RingBuffer_IsEmpty(RingBuffer_t* const Buffer) ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(1);
 210                 static inline bool RingBuffer_IsEmpty(RingBuffer_t* const Buffer)
 211                 {
 212                         return (RingBuffer_GetCount(Buffer) == 0);
 213                 }
 214
 215                 /** Atomically determines if the specified ring buffer contains any free space. This should
 216                  *  be tested before storing data to the buffer, to ensure that no data is lost due to a
 217                  *  buffer overrun.
 218                  *
 219                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into.
 220                  *
 221                  *  \return Boolean \c true if the buffer contains no free space, false otherwise.
 222                  */
 223                 static inline bool RingBuffer_IsFull(RingBuffer_t* const Buffer) ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(1);
 224                 static inline bool RingBuffer_IsFull(RingBuffer_t* const Buffer)
 225                 {
 226                         return (RingBuffer_GetCount(Buffer) == Buffer->Size);
 227                 }
 228
 229                 /** Inserts an element into the ring buffer.
 230                  *
 231                  *  \warning Only one execution thread (main program thread or an ISR) may insert into 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 insert into.
 236                  *  \param[in]     Data    Data element to insert into the buffer.
 237                  */
 238                 static inline void RingBuffer_Insert(RingBuffer_t* Buffer, const uint8_t Data) ATTR_NON_NULL_PTR_ARG(1);
 239                 static inline void RingBuffer_Insert(RingBuffer_t* Buffer, const uint8_t Data)
 240                 {
 241                         GCC_FORCE_POINTER_ACCESS(Buffer);
 242
 243                         *Buffer->In = Data;
 244
 245                         if (++Buffer->In == Buffer->End)
 246                           Buffer->In = Buffer->Start;
 247
 248                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 249                         GlobalInterruptDisable();
 250
 251                         Buffer->Count++;
 252
 253                         SetGlobalInterruptMask(CurrentGlobalInt);
 254                 }
 255
 256                 /** Removes an element from the ring buffer.
 257                  *
 258                  *  \warning Only one execution thread (main program thread or an ISR) may remove from a single buffer
 259                  *           otherwise data corruption may occur. Insertion and removal may occur from different execution
 260                  *           threads.
 261                  *
 262                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from.
 263                  *
 264                  *  \return Next data element stored in the buffer.
 265                  */
 266                 static inline uint8_t RingBuffer_Remove(RingBuffer_t* Buffer) ATTR_NON_NULL_PTR_ARG(1);
 267                 static inline uint8_t RingBuffer_Remove(RingBuffer_t* Buffer)
 268                 {
 269                         GCC_FORCE_POINTER_ACCESS(Buffer);
 270
 271                         uint8_t Data = *Buffer->Out;
 272
 273                         if (++Buffer->Out == Buffer->End)
 274                           Buffer->Out = Buffer->Start;
 275
 276                         uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
 277                         GlobalInterruptDisable();
 278
 279                         Buffer->Count--;
 280
 281                         SetGlobalInterruptMask(CurrentGlobalInt);
 282
 283                         return Data;
 284                 }
 285
 286                 /** Returns the next element stored in the ring buffer, without removing it.
 287                  *
 288                  *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from.
 289                  *
 290                  *  \return Next data element stored in the buffer.
 291                  */
 292                 static inline uint8_t RingBuffer_Peek(RingBuffer_t* const Buffer) ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(1);
 293                 static inline uint8_t RingBuffer_Peek(RingBuffer_t* const Buffer)
 294                 {
 295                         return *Buffer->Out;
 296                 }
 297
 298         /* Disable C linkage for C++ Compilers: */
 299                 #if defined(__cplusplus)
 300                         }
 301                 #endif
 302
 303 #endif
 304
 305 /** @} */
 306