1 /* Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
3 /** \file ringbuffer.c Simple ringbuffer implementation */
8 #include "ringbuffer.h"
12 * Holds all information about one ring buffer
14 * It is intentionally not exported via ringbuffer.h. Think abstract.
18 /** The size of this ring buffer. */
20 /** The actual entries of the ringbuffer. */
22 /** The next entry will be added at this position. */
24 /** How many entries the ring buffer contains. */
29 * Initialize a new ringbuffer.
31 * \param size The number of entries the ringbuffer holds.
33 * This function initializes a circular ring buffer which can hold up to \a
34 * size entries of arbitrary type. If performance is an issue, \a size should
35 * be a power of two to make the underlying modulo operations cheap. Arbitrary
36 * many ringbuffers may be initialized via this function. Each ringbuffer is
37 * identified by a 'cookie'.
39 * \return A 'cookie' which identifies the ringbuffer just created and
40 * which must be passed to ringbuffer_add() and ringbuffer_get().
42 struct ringbuffer
*ringbuffer_new(unsigned size
)
44 struct ringbuffer
*rb
= para_calloc(sizeof(struct ringbuffer
));
45 rb
->entries
= para_calloc(size
* sizeof(void *));
51 * Add one entry to a ringbuffer.
53 * \param rb The ringbuffer identifier.
54 * \param data The data to be inserted.
56 * Insert \a data into the ringbuffer associated with \a cookie. As soon as
57 * the ringbuffer fills up, its oldest entry is disregarded and replaced by \a
60 * \return The old \a data pointer which is going to be disregarded, or
61 * NULL if the ringbuffer is not yet full.
63 void *ringbuffer_add(struct ringbuffer
*rb
, void *data
)
65 void *ret
= rb
->entries
[rb
->head
];
66 rb
->entries
[rb
->head
] = data
;
67 rb
->head
= (rb
->head
+ 1) % rb
->size
;
68 if (rb
->filled
< rb
->size
)
74 * Get one entry from a ringbuffer.
76 * \param rb The ringbuffer identifier.
77 * \param num The number of the entry.
79 * \return A pointer to data previously added, or NULL if entry number
80 * \a num is not available. \a num counts backwards from zero, i.e.
81 * ringbuffer_get_entry(0) gets the entry which was added most recently.
83 void *ringbuffer_get(struct ringbuffer
*rb
, int num
)
85 int pos
= (rb
->head
+ rb
->size
- 1 - num
) % rb
->size
;
86 // fprintf(stderr, "pos = %d\n", pos);
87 return rb
->entries
[pos
];
91 * Get the number of entries in the ring buffer.
93 * \param rb The ringbuffer identifier
95 * \return This function always succeeds. It returns a number less than the
96 * size of the ring buffer.
98 unsigned ringbuffer_filled(struct ringbuffer
*rb
)