mirror of https://github.com/ArduPilot/ardupilot
198 lines
6.8 KiB
C
198 lines
6.8 KiB
C
/*
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LUFA Library
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Copyright (C) Dean Camera, 2010.
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dean [at] fourwalledcubicle [dot] com
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www.fourwalledcubicle.com
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*/
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/*
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Copyright 2010 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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*
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* Ultra lightweight ring buffer, for fast insertion/deletion.
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*/
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#ifndef _ULW_RING_BUFF_H_
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#define _ULW_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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/* Defines: */
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/** Size of each ring buffer, in data elements - must be between 1 and 255. */
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#define BUFFER_SIZE 128
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/** Maximum number of data elements to buffer before forcing a flush.
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* Must be less than BUFFER_SIZE
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*/
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#define BUFFER_NEARLY_FULL 96
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/** Type of data to store into the buffer. */
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#define RingBuff_Data_t uint8_t
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/** Datatype which may be used to store the count of data stored in a buffer, retrieved
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* via a call to \ref RingBuffer_GetCount().
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*/
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#if (BUFFER_SIZE <= 0xFF)
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#define RingBuff_Count_t uint8_t
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#else
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#define RingBuff_Count_t uint16_t
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#endif
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/* Type Defines: */
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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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RingBuff_Data_t Buffer[BUFFER_SIZE]; /**< Internal ring buffer data, referenced by the buffer pointers. */
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RingBuff_Data_t* In; /**< Current storage location in the circular buffer */
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RingBuff_Data_t* Out; /**< Current retrieval location in the circular buffer */
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RingBuff_Count_t Count;
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} RingBuff_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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*/
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static inline void RingBuffer_InitBuffer(RingBuff_t* const Buffer)
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{
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ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
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{
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Buffer->In = Buffer->Buffer;
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Buffer->Out = Buffer->Buffer;
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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 RingBuff_Count_t RingBuffer_GetCount(RingBuff_t* const Buffer)
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{
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RingBuff_Count_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 true if the buffer contains no free space, false otherwise
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*/
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static inline bool RingBuffer_IsFull(RingBuff_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 true if the buffer contains no free space, false otherwise
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*/
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static inline bool RingBuffer_IsEmpty(RingBuff_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(RingBuff_t* const Buffer,
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const RingBuff_Data_t Data)
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{
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*Buffer->In = Data;
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if (++Buffer->In == &Buffer->Buffer[BUFFER_SIZE])
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Buffer->In = Buffer->Buffer;
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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 RingBuff_Data_t RingBuffer_Remove(RingBuff_t* const Buffer)
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{
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RingBuff_Data_t Data = *Buffer->Out;
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if (++Buffer->Out == &Buffer->Buffer[BUFFER_SIZE])
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Buffer->Out = Buffer->Buffer;
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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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#endif
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