obs-studio/libobs/util/circlebuf.h

/*
 * Copyright (c) 2013 Hugh Bailey <obs.jim@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#pragma once

#include "c99defs.h"
#include <string.h>
#include <stdlib.h>
#include <assert.h>

#include "bmem.h"

#ifdef __cplusplus
extern "C" {
#endif

/* Dynamic circular buffer */

struct circlebuf {
	void   *data;
	size_t size;

	size_t start_pos;
	size_t end_pos;
	size_t capacity;
};

static inline void circlebuf_init(struct circlebuf *cb)
{
	memset(cb, 0, sizeof(struct circlebuf));
}

static inline void circlebuf_free(struct circlebuf *cb)
{
	bfree(cb->data);
	memset(cb, 0, sizeof(struct circlebuf));
}

static inline void circlebuf_reorder_data(struct circlebuf *cb,
		size_t new_capacity)
{
	size_t difference;
	uint8_t *data;

	if (!cb->size || !cb->start_pos || cb->end_pos > cb->start_pos)
		return;

	difference = new_capacity - cb->capacity;
	data = (uint8_t*)cb->data + cb->start_pos;
	memmove(data+difference, data, cb->capacity - cb->start_pos);
	cb->start_pos += difference;
}

static inline void circlebuf_ensure_capacity(struct circlebuf *cb)
{
	size_t new_capacity;
	if (cb->size <= cb->capacity)
		return;

	new_capacity = cb->capacity*2;
	if (cb->size > new_capacity)
		new_capacity = cb->size;

	cb->data = brealloc(cb->data, new_capacity);
	circlebuf_reorder_data(cb, new_capacity);
	cb->capacity = new_capacity;
}

static inline void circlebuf_reserve(struct circlebuf *cb, size_t capacity)
{
	if (capacity <= cb->capacity)
		return;

	cb->data = brealloc(cb->data, capacity);
	circlebuf_reorder_data(cb, capacity);
	cb->capacity = capacity;
}

static inline void circlebuf_upsize(struct circlebuf *cb, size_t size)
{
	size_t add_size = size - cb->size;
	size_t new_end_pos = cb->end_pos + add_size;

	if (size <= cb->size)
		return;

	cb->size = size;
	circlebuf_ensure_capacity(cb);

	if (new_end_pos > cb->capacity) {
		size_t back_size = cb->capacity - cb->end_pos;
		size_t loop_size = add_size - back_size;

		if (back_size)
			memset((uint8_t*)cb->data + cb->end_pos, 0, back_size);

		memset(cb->data, 0, loop_size);
		new_end_pos -= cb->capacity;
	} else {
		memset((uint8_t*)cb->data + cb->end_pos, 0, add_size);
	}

	cb->end_pos = new_end_pos;
}

/** Overwrites data at a specific point in the buffer (relative).  */
static inline void circlebuf_place(struct circlebuf *cb, size_t position,
		const void *data, size_t size)
{
	size_t end_point = position + size;
	size_t data_end_pos;

	if (end_point > cb->size)
		circlebuf_upsize(cb, end_point);

	position += cb->start_pos;
	if (position >= cb->capacity)
		position -= cb->capacity;

	data_end_pos = position + size;
	if (data_end_pos > cb->capacity) {
		size_t back_size = data_end_pos - cb->capacity;
		size_t loop_size = size - back_size;

		if (back_size)
			memcpy((uint8_t*)cb->data + position, data, loop_size);
		memcpy(cb->data, (uint8_t*)data + loop_size, back_size);
	} else {
		memcpy((uint8_t*)cb->data + position, data, size);
	}
}

static inline void circlebuf_push_back(struct circlebuf *cb, const void *data,
		size_t size)
{
	size_t new_end_pos = cb->end_pos + size;

	cb->size += size;
	circlebuf_ensure_capacity(cb);

	if (new_end_pos > cb->capacity) {
		size_t back_size = cb->capacity - cb->end_pos;
		size_t loop_size = size - back_size;

		if (back_size)
			memcpy((uint8_t*)cb->data + cb->end_pos, data,
					back_size);
		memcpy(cb->data, (uint8_t*)data + back_size, loop_size);

		new_end_pos -= cb->capacity;
	} else {
		memcpy((uint8_t*)cb->data + cb->end_pos, data, size);
	}

	cb->end_pos = new_end_pos;
}

static inline void circlebuf_pop_front(struct circlebuf *cb, void *data,
		size_t size)
{
	size_t start_size;
	assert(size <= cb->size);

	start_size = cb->capacity - cb->start_pos;

	if (data) {
		if (start_size < size) {
			memcpy(data, (uint8_t*)cb->data + cb->start_pos,
					start_size);
			memcpy((uint8_t*)data + start_size, cb->data,
					size - start_size);
		} else {
			memcpy(data, (uint8_t*)cb->data + cb->start_pos, size);
		}
	}

	cb->size -= size;
	cb->start_pos += size;
	if (cb->start_pos >= cb->capacity)
		cb->start_pos -= cb->capacity;
}

#ifdef __cplusplus
}
#endif