lib/os/ring_buffer.c

/* ring_buffer.c: Simple ring buffer API */

/*
 * Copyright (c) 2015 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <ring_buffer.h>
#include <string.h>

/**
 * Internal data structure for a buffer header.
 *
 * We want all of this to fit in a single u32_t. Every item stored in the
 * ring buffer will be one of these headers plus any extra data supplied
 */
struct ring_element {
	u32_t  type   :16; /**< Application-specific */
	u32_t  length :8;  /**< length in 32-bit chunks */
	u32_t  value  :8;  /**< Room for small integral values */
};

int ring_buf_item_put(struct ring_buf *buf, u16_t type, u8_t value,
		      u32_t *data, u8_t size32)
{
	u32_t i, space, index, rc;

	space = ring_buf_space_get(buf);
	if (space >= (size32 + 1)) {
		struct ring_element *header =
			(struct ring_element *)&buf->buf.buf32[buf->tail];
		header->type = type;
		header->length = size32;
		header->value = value;

		if (likely(buf->mask)) {
			for (i = 0U; i < size32; ++i) {
				index = (i + buf->tail + 1) & buf->mask;
				buf->buf.buf32[index] = data[i];
			}
			buf->tail = (buf->tail + size32 + 1) & buf->mask;
		} else {
			for (i = 0U; i < size32; ++i) {
				index = (i + buf->tail + 1) % buf->size;
				buf->buf.buf32[index] = data[i];
			}
			buf->tail = (buf->tail + size32 + 1) % buf->size;
		}
		rc = 0U;
	} else {
		buf->misc.item_mode.dropped_put_count++;
		rc = -EMSGSIZE;
	}

	return rc;
}

int ring_buf_item_get(struct ring_buf *buf, u16_t *type, u8_t *value,
		      u32_t *data, u8_t *size32)
{
	struct ring_element *header;
	u32_t i, index;

	if (ring_buf_is_empty(buf)) {
		return -EAGAIN;
	}

	header = (struct ring_element *) &buf->buf.buf32[buf->head];

	if (header->length > *size32) {
		*size32 = header->length;
		return -EMSGSIZE;
	}

	*size32 = header->length;
	*type = header->type;
	*value = header->value;

	if (likely(buf->mask)) {
		for (i = 0U; i < header->length; ++i) {
			index = (i + buf->head + 1) & buf->mask;
			data[i] = buf->buf.buf32[index];
		}
		buf->head = (buf->head + header->length + 1) & buf->mask;
	} else {
		for (i = 0U; i < header->length; ++i) {
			index = (i + buf->head + 1) % buf->size;
			data[i] = buf->buf.buf32[index];
		}
		buf->head = (buf->head + header->length + 1) % buf->size;
	}

	return 0;
}

/** @brief Wraps index if it exceeds the limit.
 *
 * @param val  Value
 * @param max  Max.
 *
 * @return value % max.
 */
static inline u32_t wrap(u32_t val, u32_t max)
{
	return val >= max ? (val - max) : val;
}

u32_t ring_buf_put_claim(struct ring_buf *buf, u8_t **data, u32_t size)
{
	u32_t space, trail_size, allocated;

	space = z_ring_buf_custom_space_get(buf->size, buf->head,
					    buf->misc.byte_mode.tmp_tail);

	/* Limit requested size to available size. */
	size = MIN(size, space);
	trail_size = buf->size - buf->misc.byte_mode.tmp_tail;

	/* Limit allocated size to trail size. */
	allocated = MIN(trail_size, size);

	*data = &buf->buf.buf8[buf->misc.byte_mode.tmp_tail];
	buf->misc.byte_mode.tmp_tail =
		wrap(buf->misc.byte_mode.tmp_tail + allocated, buf->size);

	return allocated;
}

int ring_buf_put_finish(struct ring_buf *buf, u32_t size)
{
	if (size > ring_buf_space_get(buf)) {
		return -EINVAL;
	}

	buf->tail = wrap(buf->tail + size, buf->size);
	buf->misc.byte_mode.tmp_tail = buf->tail;

	return 0;
}

u32_t ring_buf_put(struct ring_buf *buf, const u8_t *data, u32_t size)
{
	u8_t *dst;
	u32_t partial_size;
	u32_t total_size = 0U;
	int err;

	do {
		partial_size = ring_buf_put_claim(buf, &dst, size);
		memcpy(dst, data, partial_size);
		total_size += partial_size;
		size -= partial_size;
		data += partial_size;
	} while (size && partial_size);

	err = ring_buf_put_finish(buf, total_size);
	__ASSERT_NO_MSG(err == 0);

	return total_size;
}

u32_t ring_buf_get_claim(struct ring_buf *buf, u8_t **data, u32_t size)
{
	u32_t space, granted_size, trail_size;

	space = (buf->size - 1) -
		z_ring_buf_custom_space_get(buf->size,
					    buf->misc.byte_mode.tmp_head,
					    buf->tail);
	trail_size = buf->size - buf->misc.byte_mode.tmp_head;

	/* Limit requested size to available size. */
	granted_size = MIN(size, space);

	/* Limit allocated size to trail size. */
	granted_size = MIN(trail_size, granted_size);

	*data = &buf->buf.buf8[buf->misc.byte_mode.tmp_head];
	buf->misc.byte_mode.tmp_head =
		wrap(buf->misc.byte_mode.tmp_head + granted_size, buf->size);

	return granted_size;
}

int ring_buf_get_finish(struct ring_buf *buf, u32_t size)
{
	u32_t allocated = (buf->size - 1) - ring_buf_space_get(buf);

	if (size > allocated) {
		return -EINVAL;
	}

	buf->head = wrap(buf->head + size, buf->size);
	buf->misc.byte_mode.tmp_head = buf->head;

	return 0;
}

u32_t ring_buf_get(struct ring_buf *buf, u8_t *data, u32_t size)
{
	u8_t *src;
	u32_t partial_size;
	u32_t total_size = 0U;
	int err;

	do {
		partial_size = ring_buf_get_claim(buf, &src, size);
		memcpy(data, src, partial_size);
		total_size += partial_size;
		size -= partial_size;
		data += partial_size;
	} while (size && partial_size);

	err = ring_buf_get_finish(buf, total_size);
	__ASSERT_NO_MSG(err == 0);

	return total_size;
}