ringbuffer.h

A utility for storing and retrieving byte data using a ring buffer.

The ringbuffer is useful for buffering data in the same thread context but it is not thread-safe. For a thread-safe ring buffer, see Thread safe ringbuffer in the System library.

RINGBUFFER_INIT( BUF)

Initialize a ringbuffer.

{ (BUF), sizeof (BUF), 0, 0 }

This macro is meant for static ringbuffers.

Parameters

BUF:Buffer to use for the ringbuffer. The size is deduced through sizeof (BUF).

Return values

• The static initializer.

void ringbuffer_init(ringbuffer_t *__restrict rb, char * buffer, unsigned bufsize)

Initialize a ringbuffer.

Parameters

rb:Datum to initialize. buffer:Buffer to use by rb. bufsize:sizeof (buffer)

int ringbuffer_add_one(ringbuffer_t *__restrict rb, char c)

Add an element to the ringbuffer.

If rb is full, then the oldest element gets overwritten. Test ringbuffer.h::ringbuffer_full() first if overwriting is not intended.

Parameters

rb:Ringbuffer to operate on. c:Element to add.

Return values

• The element that was dropped, iff the buffer was full. -1 iff the buffer was not full.

unsigned ringbuffer_add(ringbuffer_t *__restrict rb, const char * buf, unsigned n)

Add a number of elements to the ringbuffer.

Only so many elements are added as fit in the ringbuffer. No elements get overwritten. If this is not the intended behavior, then use ringbuffer.h::ringbuffer_add_one() in a loop instead.

Parameters

rb:Ringbuffer to operate on. buf:Buffer to add elements from. n:Maximum number of elements to add.

Return values

• Number of elements actually added. 0 if rb is full.

int ringbuffer_get_one(ringbuffer_t *__restrict rb)

Peek and remove oldest element from the ringbuffer.

Parameters

rb:Ringbuffer to operate on.

Return values

• The oldest element that was added, or -1 if rb is empty.

unsigned ringbuffer_get(ringbuffer_t *__restrict rb, char * buf, unsigned n)

Read and remove a number of elements from the ringbuffer.

Parameters

rb:Ringbuffer to operate on. buf:Buffer to write into. n:Read at most n elements.

Return values

• Number of elements actually read.

unsigned ringbuffer_remove(ringbuffer_t *__restrict rb, unsigned n)

Remove a number of elements from the ringbuffer.

Parameters

rb:Ringbuffer to operate on. n:Read at most n elements.

Return values

• Number of elements actually removed.

int ringbuffer_empty(const ringbuffer_t *__restrict rb)

Test if the ringbuffer is empty.

Parameters

rb:Ringbuffer to operate on.

Return values

• 0 iff not empty

int ringbuffer_full(const ringbuffer_t *__restrict rb)

Test if the ringbuffer is full.

Parameters

rb:Ringbuffer to operate on.

Return values

• 0 iff not full

unsigned int ringbuffer_get_free(const ringbuffer_t *__restrict rb)

Return available space in ringbuffer.

Parameters

rb:Ringbuffer to query.

Return values

• number of available bytes

int ringbuffer_peek_one(const ringbuffer_t *__restrict rb)

Read, but don’t remove, the oldest element in the buffer.

Parameters

rb:Ringbuffer to operate on.

Return values

• Same as ringbuffer.h::ringbuffer_get_one()

unsigned ringbuffer_peek(const ringbuffer_t *__restrict rb, char * buf, unsigned n)

Read, but don’t remove, the a number of element of the buffer.

Parameters

rb:Ringbuffer to operate on. buf:Buffer to write into. n:Read at most n elements.

Return values

• Same as ringbuffer.h::ringbuffer_get()

struct ringbuffer_t

Ringbuffer.

Non thread-safe FIFO ringbuffer implementation around a char array.

char * buf

Buffer to operate on.

unsigned int size

Size of buf.

unsigned int start

Current read position in the ring buffer.

unsigned int avail

Number of elements available for reading.