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/* SPDX-License-Identifier: GPL-2.0 */
/** \file ringbuffer.c Simple ringbuffer implementation */
#include "para.h"
#include "ringbuffer.h"
#include "string.h"
/*
* Represents an instance of a ringbuffer. Opaque to the users of the
* ringbuffer API.
*/
struct ringbuffer {
/* The size of this ringbuffer. */
unsigned size;
/* The actual entries of the ringbuffer. */
void **entries;
/* The next entry will be added at this position. */
int head;
/* How many entries the ringbuffer contains. */
unsigned filled;
};
/**
* Initialize a new ringbuffer.
*
* \param size The number of entries the ringbuffer holds.
*
* This function initializes a circular buffer which can store up to the given
* number of entries. The entries can be of arbitrary type. Each ringbuffer
* is identified by an opaque handle which is returned by this function.
*
* \return An opaque handle which identifies the new ringbuffer. Other
* functions of the ringbuffer API such as to \ref ringbuffer_add() and \ref
* ringbuffer_get() take a handle as their first argument.
*/
struct ringbuffer *ringbuffer_new(unsigned size)
{
struct ringbuffer *rb = zalloc(sizeof(struct ringbuffer));
rb->entries = zalloc(size * sizeof(void *));
rb->size = size;
return rb;
}
/**
* Add an entry to a ringbuffer.
*
* \param rb The handle which identifies the ringbuffer instance.
* \param data Pointer to the data to be inserted.
*
* If the ringbuffer is full, the data pointer of the oldest entry is replaced
* by the given pointer.
*
* \return The data pointer which is was disregarded, or NULL if the ringbuffer
* was not full yet.
*/
void *ringbuffer_add(struct ringbuffer *rb, void *data)
{
void *ret = rb->entries[rb->head];
rb->entries[rb->head] = data;
rb->head = (rb->head + 1) % rb->size;
if (rb->filled < rb->size)
rb->filled++;
return ret;
}
/**
* Get one entry from a ringbuffer.
*
* \param rb The handle which identifies the ringbuffer instance.
* \param num The number of the entry.
*
* \return A pointer to data previously added, or NULL if there is no entry
* corresponding to the given number. The number counts entries starting
* at the newest entry so that ringbuffer_get_entry(rb, 0) gets the entry
* which was added most recently.
*/
void *ringbuffer_get(struct ringbuffer *rb, int num)
{
int pos = (rb->head + rb->size - 1 - num) % rb->size;
// fprintf(stderr, "pos = %d\n", pos);
return rb->entries[pos];
}
/**
* Get the number of entries in the ringbuffer.
*
* \param rb The handle which identifies the ringbuffer instance.
*
* \return This function always succeeds and returns a number between zero
* and one less than the size of the ringbuffer, inclusively.
*/
unsigned ringbuffer_filled(struct ringbuffer *rb)
{
return rb->filled;
}
/**
* Remove all entries from a ringbuffer.
*
* \param rb The handle which identifies the ringbuffer instance.
* \param free_func Called on each existing entry.
*/
void ringbuffer_flush(struct ringbuffer *rb, void (*free_func)(void *))
{
for (int i = 0; i < rb->filled; i++) {
int pos = (rb->head + rb->size - 1 - i) % rb->size;
free_func(rb->entries[pos]);
}
memset(rb->entries, 0, rb->size * sizeof(void *));
rb->filled = 0;
rb->head = 0;
}
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