TinyQueue.h

00001 #ifndef TINYQ_H
00002 #define TINYQ_H
00003 
00004 /** \defgroup tinyQ Tiny Queue
00005  * Tiny Queues implements a 4 byte queue for iPhone events with just 1 byte of management overhead.
00006  * Head and Tail pointers both inherently wrap at the end of the buffer and no bounds checking is 
00007  * necesary IFF the buffer size is set as a power of 2 equal to the width of the pointers !!
00008  * i.e head is 2 bits wide so the buffer must be 2^2 = 4 bytes deep.
00009  * @{
00010  */
00011 /** NOTE: Q_SIZE MUST be == 2 ^ widthof( tinyQ_t.head ) */
00012 #define Q_SIZE 256
00013 
00014 /** a tinyQ tracks a 8 * queue with just 1 byte overhead */
00015 typedef struct
00016 {
00017     unsigned char head:8;  ///< the bit depth MUST be that power of 2 that is the Q_SIZE
00018     unsigned char tail:8;  ///< the bit depth MUST be that power of 2 that is the Q_SIZE
00019     unsigned char fill:9;  ///< Must be 1 bit bigger than the head and tail pointers
00020     void* data[Q_SIZE];     ///< NOTE: Q_SIZE MUST be == 2 ^ widthof( tinyQ_t.head )
00021 }tinyQ_t;
00022 
00023 
00024 /**
00025  * \brief Push an Accessibility Event onto our queue for sending to the iphone
00026  * \param q pointer to our tinyQ_t
00027  * \param c the Event to send to the iphone
00028  * \return null if Q full,  1 on success
00029  * \sa Qpop(), Qjump()
00030  * \ingroup tinyQ
00031  */
00032 int Qpush( tinyQ_t* q, void* p );
00033 
00034 /**
00035  * \brief Push an Accessibility Event onto front of our queue for sending to the iphone
00036  * \param q pointer to our tinyQ_t
00037  * \param c the Event to send to the iphone
00038  * \return null if Q full, 1 on success
00039  * \sa Qpush(), Qpop()
00040  * \ingroup tinyQ
00041  */
00042 int Qjump( tinyQ_t* q, void* p );
00043 
00044 /**
00045  * \brief Pop an Accessibility Event off our queue for sending to the iphone
00046  * \param q pointer to our tinyQ_t
00047  * \param c pointer to receive the Event
00048  * \return null if Q empty, 1 on success
00049  * \sa Qpop(), Qjump()
00050  * \ingroup tinyQ
00051  */
00052 int Qpop( tinyQ_t* q, void ** p);
00053 
00054 #endif