tinyQ.h

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