/*
* This file is originally from JACK Audio Connection Kit
*
* Copyright (C) 2000 Paul Davis
* Copyright (C) 2003 Rohan Drape
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#ifndef RINGBUF_H
#define RINGBUF_H
#include "os_compat.h"
/** @file ringbuf.h
*
* A set of library functions to make lock-free ringbuffers available
* to JACK clients. The `capture_client.c' (in the example_clients
* directory) is a fully functioning user of this API.
*
* The key attribute of a ringbuffer is that it can be safely accessed
* by two threads simultaneously -- one reading from the buffer and
* the other writing to it -- without using any synchronization or
* mutual exclusion primitives. For this to work correctly, there can
* only be a single reader and a single writer thread. Their
* identities cannot be interchanged.
*/
struct ringbuf {
void *buf;
size_t write_ptr;
size_t read_ptr;
size_t size;
size_t size_mask;
};
/**
* Allocates a ringbuffer data structure of a specified size. The
* caller must arrange for a call to ringbuf_free() to release
* the memory associated with the ringbuffer.
*
* @param sz the ringbuffer size in bytes.
*
* @return a pointer to a new struct ringbuf, if successful; NULL
* otherwise.
*/
struct ringbuf *ringbuf_create(size_t sz);
/**
* Frees the ringbuffer data structure allocated by an earlier call to
* ringbuf_create().
*
* @param rb a pointer to the ringbuffer structure.
*/
void ringbuf_free(struct ringbuf * rb);
/**
* Fill a data structure with a description of the current readable
* data held in the ringbuffer. This description is returned in a two
* element array of struct iovec. Two elements are needed
* because the data to be read may be split across the end of the
* ringbuffer.
*
* The first element will always contain a valid @a len field, which
* may be zero or greater. If the @a len field is non-zero, then data
* can be read in a contiguous fashion using the address given in the
* corresponding @a buf field.
*
* If the second element has a non-zero @a len field, then a second
* contiguous stretch of data can be read from the address given in
* its corresponding @a buf field.
*
* @param rb a pointer to the ringbuffer structure.
* @param vec a pointer to a 2 element array of struct iovec.
*
* @return total number of bytes readable into both vec elements
*/
size_t ringbuf_get_read_vector(const struct ringbuf * rb, struct iovec * vec);
/**
* Fill a data structure with a description of the current writable
* space in the ringbuffer. The description is returned in a two
* element array of struct iovec. Two elements are needed
* because the space available for writing may be split across the end
* of the ringbuffer.
*
* The first element will always contain a valid @a len field, which
* may be zero or greater. If the @a len field is non-zero, then data
* can be written in a contiguous fashion using the address given in
* the corresponding @a buf field.
*
* If the second element has a non-zero @a len field, then a second
* contiguous stretch of data can be written to the address given in
* the corresponding @a buf field.
*
* @param rb a pointer to the ringbuffer structure.
* @param vec a pointer to a 2 element array of struct iovec.
*
* @return total number of bytes writable in both vec elements
*/
size_t ringbuf_get_write_vector(const struct ringbuf * rb, struct iovec * vec);
/**
* Read data from the ringbuffer.
*
* @param rb a pointer to the ringbuffer structure.
* @param dest a pointer to a buffer where data read from the
* ringbuffer will go.
* @param cnt the number of bytes to read.
*
* @return the number of bytes read, which may range from 0 to cnt.
*/
size_t ringbuf_read(struct ringbuf * rb, void *dest, size_t cnt);
/**
* Read data from the ringbuffer. Opposed to ringbuf_read()
* this function does not move the read pointer. Thus it's
* a convenient way to inspect data in the ringbuffer in a
* continous fashion. The price is that the data is copied
* into a user provided buffer. For "raw" non-copy inspection
* of the data in the ringbuffer use ringbuf_get_read_vector().
*
* @param rb a pointer to the ringbuffer structure.
* @param dest a pointer to a buffer where data read from the
* ringbuffer will go.
* @param cnt the number of bytes to read.
*
* @return the number of bytes read, which may range from 0 to cnt.
*/
size_t ringbuf_peek(struct ringbuf * rb, void *dest, size_t cnt);
/**
* Advance the read pointer.
*
* After data have been read from the ringbuffer using the pointers
* returned by ringbuf_get_read_vector(), use this function to
* advance the buffer pointers, making that space available for future
* write operations.
*
* @param rb a pointer to the ringbuffer structure.
* @param cnt the number of bytes read.
*/
void ringbuf_read_advance(struct ringbuf * rb, size_t cnt);
/**
* Return the number of bytes available for reading.
*
* @param rb a pointer to the ringbuffer structure.
*
* @return the number of bytes available to read.
*/
size_t ringbuf_read_space(const struct ringbuf * rb);
/**
* Reset the read and write pointers, making an empty buffer.
*
* This is not thread safe.
*
* @param rb a pointer to the ringbuffer structure.
*/
void ringbuf_reset(struct ringbuf * rb);
/**
* Write data into the ringbuffer.
*
* @param rb a pointer to the ringbuffer structure.
* @param src a pointer to the data to be written to the ringbuffer.
* @param cnt the number of bytes to write.
*
* @return the number of bytes write, which may range from 0 to cnt
*/
size_t ringbuf_write(struct ringbuf * rb, const void *src, size_t cnt);
/**
* Advance the write pointer.
*
* After data have been written the ringbuffer using the pointers
* returned by ringbuf_get_write_vector(), use this function
* to advance the buffer pointer, making the data available for future
* read operations.
*
* @param rb a pointer to the ringbuffer structure.
* @param cnt the number of bytes written.
*/
void ringbuf_write_advance(struct ringbuf * rb, size_t cnt);
/**
* Return the number of bytes available for writing.
*
* @param rb a pointer to the ringbuffer structure.
*
* @return the amount of free space (in bytes) available for writing.
*/
size_t ringbuf_write_space(const struct ringbuf * rb);
#endif /* RINGBUF_H */
