/* Defines: */
/** Size of each ring buffer, in data elements - must be between 1 and 255. */
- #define BUFFER_SIZE 255
+ #define BUFFER_SIZE 255
/** Type of data to store into the buffer. */
- #define RingBuff_Data_t uint8_t
+ #define RingBuff_Data_t uint8_t
+
+ /** Datatype which may be used to store the count of data stored in a buffer, retrieved
+ * via a call to \ref RingBuffer_GetCount().
+ */
+ #if (BUFFER_SIZE <= 0xFF)
+ #define RingBuff_Count_t uint8_t
+ #else
+ #define RingBuff_Count_t uint16_t
+ #endif
/* Type Defines: */
/** Type define for a new ring buffer object. Buffers should be initialized via a call to
RingBuff_Data_t Buffer[BUFFER_SIZE]; /**< Internal ring buffer data, referenced by the buffer pointers. */
RingBuff_Data_t* In; /**< Current storage location in the circular buffer */
RingBuff_Data_t* Out; /**< Current retrieval location in the circular buffer */
- uint8_t Count; /**< Total number of bytes stored in the circular buffer */
+ RingBuff_Count_t Count;
} RingBuff_t;
/* Inline Functions: */
- /** Initialises a ring buffer ready for use. Buffers must be initialized via this function
+ /** Initializes a ring buffer ready for use. Buffers must be initialized via this function
* before any operations are called upon them. Already initialized buffers may be reset
* by re-initializing them using this function.
*
*/
static inline void RingBuffer_InitBuffer(RingBuff_t* const Buffer)
{
- Buffer->In = Buffer->Buffer;
- Buffer->Out = Buffer->Buffer;
- Buffer->Count = 0;
+ ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+ {
+ Buffer->In = Buffer->Buffer;
+ Buffer->Out = Buffer->Buffer;
+ }
}
- /** Atomically determines if the specified ring buffer contains any free space. This should
- * be tested before storing data to the buffer, to ensure that no data is lost due to a
- * buffer overrun.
+ /** Retrieves the minimum number of bytes stored in a particular buffer. This value is computed
+ * by entering an atomic lock on the buffer while the IN and OUT locations are fetched, so that
+ * the buffer cannot be modified while the computation takes place. This value should be cached
+ * when reading out the contents of the buffer, so that as small a time as possible is spent
+ * in an atomic lock.
*
- * \param[in,out] Buffer Pointer to a ring buffer structure to insert into
+ * \note The value returned by this function is guaranteed to only be the minimum number of bytes
+ * stored in the given buffer; this value may change as other threads write new data and so
+ * the returned number should be used only to determine how many successive reads may safely
+ * be performed on the buffer.
*
- * \return Boolean true if the buffer contains no free space, false otherwise
- */
- static inline bool RingBuffer_IsFull(RingBuff_t* const Buffer)
+ * \param[in] Buffer Pointer to a ring buffer structure whose count is to be computed
+ */
+ static inline RingBuff_Count_t RingBuffer_GetCount(RingBuff_t* const Buffer)
{
- bool IsFull;
+ RingBuff_Count_t Count;
ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
{
- IsFull = (Buffer->Count == BUFFER_SIZE);
+ Count = Buffer->Count;
}
- return IsFull;
+ return Count;
}
- /** Atomically inserts an element into the ring buffer.
+ /** Atomically determines if the specified ring buffer contains any free space. This should
+ * be tested before storing data to the buffer, to ensure that no data is lost due to a
+ * buffer overrun.
*
* \param[in,out] Buffer Pointer to a ring buffer structure to insert into
- * \param[in] Data Data element to insert into the buffer
- */
- static inline void RingBuffer_AtomicInsert(RingBuff_t* const Buffer,
- const RingBuff_Data_t Data)
+ *
+ * \return Boolean true if the buffer contains no free space, false otherwise
+ */
+ static inline bool RingBuffer_IsFull(RingBuff_t* const Buffer)
{
- ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
- {
- *Buffer->In = Data;
-
- if (++Buffer->In == &Buffer->Buffer[BUFFER_SIZE])
- Buffer->In = Buffer->Buffer;
-
- Buffer->Count++;
- }
+ return (RingBuffer_GetCount(Buffer) == BUFFER_SIZE);
}
- /** Atomically retrieves an element from the ring buffer.
+ /** Atomically determines if the specified ring buffer contains any data. This should
+ * be tested before removing data from the buffer, to ensure that the buffer does not
+ * underflow.
*
- * \param[in,out] Buffer Pointer to a ring buffer structure to retrieve from
+ * If the data is to be removed in a loop, store the total number of bytes stored in the
+ * buffer (via a call to the \ref RingBuffer_GetCount() function) in a temporary variable
+ * to reduce the time spent in atomicity locks.
*
- * \return Next data element stored in the buffer
- */
- static inline RingBuff_Data_t RingBuffer_AtomicRemove(RingBuff_t* const Buffer)
+ * \param[in,out] Buffer Pointer to a ring buffer structure to insert into
+ *
+ * \return Boolean true if the buffer contains no free space, false otherwise
+ */
+ static inline bool RingBuffer_IsEmpty(RingBuff_t* const Buffer)
{
- RingBuff_Data_t Data;
-
- ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
- {
- Data = *Buffer->Out;
-
- if (++Buffer->Out == &Buffer->Buffer[BUFFER_SIZE])
- Buffer->Out = Buffer->Buffer;
-
- Buffer->Count--;
- }
-
- return Data;
+ return (RingBuffer_GetCount(Buffer) == 0);
}
/** Inserts an element into the ring buffer.
*
+ * \note Only one execution thread (main program thread or an ISR) may insert into a single buffer
+ * otherwise data corruption may occur. Insertion and removal may occur from different execution
+ * threads.
+ *
* \param[in,out] Buffer Pointer to a ring buffer structure to insert into
* \param[in] Data Data element to insert into the buffer
*/
if (++Buffer->In == &Buffer->Buffer[BUFFER_SIZE])
Buffer->In = Buffer->Buffer;
-
- Buffer->Count++;
+
+ ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+ {
+ Buffer->Count++;
+ }
}
- /** Retrieves an element from the ring buffer.
+ /** Removes an element from the ring buffer.
+ *
+ * \note Only one execution thread (main program thread or an ISR) may remove from a single buffer
+ * otherwise data corruption may occur. Insertion and removal may occur from different execution
+ * threads.
*
* \param[in,out] Buffer Pointer to a ring buffer structure to retrieve from
*
if (++Buffer->Out == &Buffer->Buffer[BUFFER_SIZE])
Buffer->Out = Buffer->Buffer;
-
- Buffer->Count--;
+ ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+ {
+ Buffer->Count--;
+ }
+
return Data;
}
#endif
-
projects / pub / USBasp.git / blobdiff