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264 lines
9.8 KiB
264 lines
9.8 KiB
/*
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LUFA Library
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Copyright (C) Dean Camera, 2011.
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dean [at] fourwalledcubicle [dot] com
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www.lufa-lib.org
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*/
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/*
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Copyright 2011 Dean Camera (dean [at] fourwalledcubicle [dot] com)
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Permission to use, copy, modify, distribute, and sell this
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software and its documentation for any purpose is hereby granted
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without fee, provided that the above copyright notice appear in
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all copies and that both that the copyright notice and this
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permission notice and warranty disclaimer appear in supporting
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documentation, and that the name of the author not be used in
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advertising or publicity pertaining to distribution of the
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software without specific, written prior permission.
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The author disclaim all warranties with regard to this
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software, including all implied warranties of merchantability
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and fitness. In no event shall the author be liable for any
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special, indirect or consequential damages or any damages
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whatsoever resulting from loss of use, data or profits, whether
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in an action of contract, negligence or other tortious action,
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arising out of or in connection with the use or performance of
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this software.
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*/
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/** \file
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* \brief Lightweight ring buffer, for fast insertion/deletion.
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*
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* Lightweight ring buffer, for fast insertion/deletion. Multiple buffers can be created of
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* different sizes to suit different needs.
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*
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* Note that for each buffer, insertion and removal operations may occur at the same time (via
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* a multi-threaded ISR based system) however the same kind of operation (two or more insertions
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* or deletions) must not overlap. If there is possibility of two or more of the same kind of
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* operating occurring at the same point in time, atomic (mutex) locking should be used.
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*/
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/** \ingroup Group_MiscDrivers
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* @defgroup Group_RingBuff Generic Byte Ring Buffer - LUFA/Drivers/Misc/RingBuffer.h
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*
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* \section Sec_Dependencies Module Source Dependencies
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* The following files must be built with any user project that uses this module:
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* - None
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*
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* \section Sec_ModDescription Module Description
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* Lightweight ring buffer, for fast insertion/deletion. Multiple buffers can be created of
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* different sizes to suit different needs.
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*
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* Note that for each buffer, insertion and removal operations may occur at the same time (via
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* a multi-threaded ISR based system) however the same kind of operation (two or more insertions
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* or deletions) must not overlap. If there is possibility of two or more of the same kind of
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* operating occurring at the same point in time, atomic (mutex) locking should be used.
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*
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* \section Sec_ExampleUsage Example Usage
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* The following snippet is an example of how this module may be used within a typical
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* application.
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*
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* \code
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* // Create the buffer structure and its underlying storage array
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* RingBuffer_t Buffer;
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* uint8_t BufferData[128];
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*
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* // Initialise the buffer with the created storage array
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* RingBuffer_InitBuffer(&Buffer, BufferData, sizeof(BufferData));
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*
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* // Insert some data into the buffer
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* RingBuffer_Insert(Buffer, 'H');
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* RingBuffer_Insert(Buffer, 'E');
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* RingBuffer_Insert(Buffer, 'L');
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* RingBuffer_Insert(Buffer, 'L');
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* RingBuffer_Insert(Buffer, 'O');
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*
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* // Cache the number of stored bytes in the buffer
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* uint16_t BufferCount = RingBuffer_GetCount(&Buffer);
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*
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* // Printer stored data length
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* printf("Buffer Length: %d, Buffer Data: \r\n", BufferCount);
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*
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* // Print contents of the buffer one character at a time
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* while (BufferCount--)
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* putc(RingBuffer_Remove(&Buffer));
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* \endcode
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*
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* @{
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*/
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#ifndef __RING_BUFF_H__
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#define __RING_BUFF_H__
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/* Includes: */
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#include <util/atomic.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <LUFA/Common/Common.h>
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/* Type Defines: */
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/** \brief Ring Buffer Management Structure.
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*
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* Type define for a new ring buffer object. Buffers should be initialized via a call to
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* \ref RingBuffer_InitBuffer() before use.
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*/
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typedef struct
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{
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uint8_t* In; /**< Current storage location in the circular buffer */
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uint8_t* Out; /**< Current retrieval location in the circular buffer */
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uint8_t* Start; /**< Pointer to the start of the buffer's underlying storage array */
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uint8_t* End; /**< Pointer to the end of the buffer's underlying storage array */
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uint8_t Size; /**< Size of the buffer's underlying storage array */
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uint16_t Count; /**< Number of bytes currently stored in the buffer */
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} RingBuffer_t;
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/* Inline Functions: */
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/** Initializes a ring buffer ready for use. Buffers must be initialized via this function
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* before any operations are called upon them. Already initialized buffers may be reset
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* by re-initializing them using this function.
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*
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* \param[out] Buffer Pointer to a ring buffer structure to initialize.
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* \param[out] DataPtr Pointer to a global array that will hold the data stored into the ring buffer.
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* \param[out] Size Maximum number of bytes that can be stored in the underlying data array.
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*/
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static inline void RingBuffer_InitBuffer(RingBuffer_t* Buffer, uint8_t* const DataPtr, const uint16_t Size)
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{
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GCC_FORCE_POINTER_ACCESS(Buffer);
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ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
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{
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Buffer->In = DataPtr;
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Buffer->Out = DataPtr;
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Buffer->Start = &DataPtr[0];
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Buffer->End = &DataPtr[Size];
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Buffer->Size = Size;
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Buffer->Count = 0;
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}
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}
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/** Retrieves the minimum number of bytes stored in a particular buffer. This value is computed
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* by entering an atomic lock on the buffer while the IN and OUT locations are fetched, so that
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* the buffer cannot be modified while the computation takes place. This value should be cached
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* when reading out the contents of the buffer, so that as small a time as possible is spent
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* in an atomic lock.
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*
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* \note The value returned by this function is guaranteed to only be the minimum number of bytes
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* stored in the given buffer; this value may change as other threads write new data and so
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* the returned number should be used only to determine how many successive reads may safely
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* be performed on the buffer.
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*
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* \param[in] Buffer Pointer to a ring buffer structure whose count is to be computed.
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*/
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static inline uint16_t RingBuffer_GetCount(RingBuffer_t* const Buffer)
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{
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uint16_t Count;
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ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
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{
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Count = Buffer->Count;
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}
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return Count;
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}
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/** Atomically determines if the specified ring buffer contains any free space. This should
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* be tested before storing data to the buffer, to ensure that no data is lost due to a
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* buffer overrun.
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*
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* \param[in,out] Buffer Pointer to a ring buffer structure to insert into.
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*
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* \return Boolean \c true if the buffer contains no free space, false otherwise.
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*/
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static inline bool RingBuffer_IsFull(RingBuffer_t* const Buffer)
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{
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return (RingBuffer_GetCount(Buffer) == Buffer->Size);
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}
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/** Atomically determines if the specified ring buffer contains any data. This should
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* be tested before removing data from the buffer, to ensure that the buffer does not
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* underflow.
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*
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* If the data is to be removed in a loop, store the total number of bytes stored in the
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* buffer (via a call to the \ref RingBuffer_GetCount() function) in a temporary variable
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* to reduce the time spent in atomicity locks.
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*
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* \param[in,out] Buffer Pointer to a ring buffer structure to insert into.
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*
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* \return Boolean \c true if the buffer contains no free space, false otherwise.
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*/
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static inline bool RingBuffer_IsEmpty(RingBuffer_t* const Buffer)
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{
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return (RingBuffer_GetCount(Buffer) == 0);
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}
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/** Inserts an element into the ring buffer.
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*
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* \note Only one execution thread (main program thread or an ISR) may insert into a single buffer
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* otherwise data corruption may occur. Insertion and removal may occur from different execution
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* threads.
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*
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* \param[in,out] Buffer Pointer to a ring buffer structure to insert into.
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* \param[in] Data Data element to insert into the buffer.
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*/
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static inline void RingBuffer_Insert(RingBuffer_t* Buffer,
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const uint8_t Data)
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{
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GCC_FORCE_POINTER_ACCESS(Buffer);
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*Buffer->In = Data;
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if (++Buffer->In == Buffer->End)
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Buffer->In = Buffer->Start;
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ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
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{
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Buffer->Count++;
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}
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}
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/** Removes an element from the ring buffer.
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*
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* \note Only one execution thread (main program thread or an ISR) may remove from a single buffer
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* otherwise data corruption may occur. Insertion and removal may occur from different execution
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* threads.
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*
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* \param[in,out] Buffer Pointer to a ring buffer structure to retrieve from.
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*
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* \return Next data element stored in the buffer.
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*/
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static inline uint8_t RingBuffer_Remove(RingBuffer_t* Buffer)
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{
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GCC_FORCE_POINTER_ACCESS(Buffer);
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uint8_t Data = *Buffer->Out;
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if (++Buffer->Out == Buffer->End)
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Buffer->Out = Buffer->Start;
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ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
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{
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Buffer->Count--;
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}
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return Data;
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}
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/** Returns the next element stored in the ring buffer, without removing it.
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*
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* \param[in,out] Buffer Pointer to a ring buffer structure to retrieve from.
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*
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* \return Next data element stored in the buffer.
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*/
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static inline uint8_t RingBuffer_Peek(RingBuffer_t* const Buffer)
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{
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return *Buffer->Out;
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}
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#endif
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/** @} */
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