#ifndef _LTTNG_RING_BUFFER_BACKEND_H

#define _LTTNG_RING_BUFFER_BACKEND_H

/*

 * libringbuffer/backend.h

 *

 * Ring buffer backend (API).

 *

 * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

 *

 * This library 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; only

 * version 2.1 of the License.

 *

 * This library 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 library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 *

 * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by

 * the reader in flight recorder mode.

 */

#include <unistd.h>

/* Internal helpers */

#include "backend_internal.h"

#include "frontend_internal.h"

/* Ring buffer backend API */

/* Ring buffer backend access (read/write) */

extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb,

				   size_t offset, void *dest, size_t len,

				   struct lttng_ust_shm_handle *handle);

extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb,

				     size_t offset, void *dest, size_t len,

				     struct lttng_ust_shm_handle *handle);

/*

 * Return the address where a given offset is located.

 * Should be used to get the current subbuffer header pointer. Given we know

 * it's never on a page boundary, it's safe to write directly to this address,

 * as long as the write is never bigger than a page size.

 */

extern void *

lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,

			       size_t offset,

			       struct lttng_ust_shm_handle *handle);

extern void *

lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,

				    size_t offset,

				    struct lttng_ust_shm_handle *handle);

/**

 * lib_ring_buffer_write - write data to a buffer backend

 * @config : ring buffer instance configuration

 * @ctx: ring buffer context. (input arguments only)

 * @src : source pointer to copy from

 * @len : length of data to copy

 *

 * This function copies "len" bytes of data from a source pointer to a buffer

 * backend, at the current context offset. This is more or less a buffer

 * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)

 * if copy is crossing a page boundary.

 */

static inline

void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config,

			   struct lttng_ust_lib_ring_buffer_ctx *ctx,

			   const void *src, size_t len)

{

	struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;

	struct channel_backend *chanb = &ctx->chan->backend;

	struct lttng_ust_shm_handle *handle = ctx->handle;

	size_t sbidx;

	size_t offset = ctx->buf_offset;

	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;

	unsigned long sb_bindex, id;

	if (caa_unlikely(!len))

		return;

	offset &= chanb->buf_size - 1;

	sbidx = offset >> chanb->subbuf_size_order;

	id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;

	sb_bindex = subbuffer_id_get_index(config, id);

	rpages = shmp_index(handle, bufb->array, sb_bindex);

	CHAN_WARN_ON(ctx->chan,

		     config->mode == RING_BUFFER_OVERWRITE

		     && subbuffer_id_is_noref(config, id));

	/*

	 * Underlying layer should never ask for writes across

	 * subbuffers.

	 */

	CHAN_WARN_ON(chanb, offset >= chanb->buf_size);

	lib_ring_buffer_do_copy(config,

				shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)),

				src, len);

	ctx->buf_offset += len;

}

/*

 * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL

 * terminating character is found in @src. Returns the number of bytes

 * copied. Does *not* terminate @dest with NULL terminating character.

 */

static inline

size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,

		char *dest, const char *src, size_t len)

{

	size_t count;

	for (count = 0; count < len; count++) {

		char c;

		/*

		 * Only read source character once, in case it is

		 * modified concurrently.

		 */

		c = CMM_LOAD_SHARED(src[count]);

		if (!c)

			break;

		lib_ring_buffer_do_copy(config, &dest[count], &c, 1);

	}

	return count;

}

/**

 * lib_ring_buffer_strcpy - write string data to a buffer backend

 * @config : ring buffer instance configuration

 * @ctx: ring buffer context. (input arguments only)

 * @src : source pointer to copy from

 * @len : length of data to copy

 * @pad : character to use for padding

 *

 * This function copies @len - 1 bytes of string data from a source

 * pointer to a buffer backend, followed by a terminating '\0'

 * character, at the current context offset. This is more or less a

 * buffer backend-specific strncpy() operation. If a terminating '\0'

 * character is found in @src before @len - 1 characters are copied, pad

 * the buffer with @pad characters (e.g. '#').

 */

static inline

void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,

			   struct lttng_ust_lib_ring_buffer_ctx *ctx,

			   const char *src, size_t len, int pad)

{

	struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;

	struct channel_backend *chanb = &ctx->chan->backend;

	struct lttng_ust_shm_handle *handle = ctx->handle;

	size_t sbidx, count;

	size_t offset = ctx->buf_offset;

	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;

	unsigned long sb_bindex, id;

	if (caa_unlikely(!len))

		return;

	offset &= chanb->buf_size - 1;

	sbidx = offset >> chanb->subbuf_size_order;

	id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;

	sb_bindex = subbuffer_id_get_index(config, id);

	rpages = shmp_index(handle, bufb->array, sb_bindex);

	CHAN_WARN_ON(ctx->chan,

		     config->mode == RING_BUFFER_OVERWRITE

		     && subbuffer_id_is_noref(config, id));

	/*

	 * Underlying layer should never ask for writes across

	 * subbuffers.

	 */

	CHAN_WARN_ON(chanb, offset >= chanb->buf_size);

	count = lib_ring_buffer_do_strcpy(config,

			shmp_index(handle, shmp(handle, rpages->shmp)->p,

				offset & (chanb->subbuf_size - 1)),

			src, len - 1);

	offset += count;

	/* Padding */

	if (caa_unlikely(count < len - 1)) {

		size_t pad_len = len - 1 - count;

		lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,

				offset & (chanb->subbuf_size - 1)),

			pad, pad_len);

		offset += pad_len;

	}

	/* Final '\0' */

	lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,

				offset & (chanb->subbuf_size - 1)),

			'\0', 1);

	ctx->buf_offset += len;

}

/*

 * This accessor counts the number of unread records in a buffer.

 * It only provides a consistent value if no reads not writes are performed

 * concurrently.

 */

static inline

unsigned long lib_ring_buffer_get_records_unread(

				const struct lttng_ust_lib_ring_buffer_config *config,

				struct lttng_ust_lib_ring_buffer *buf,

				struct lttng_ust_shm_handle *handle)

{

	struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;

	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages;

	unsigned long records_unread = 0, sb_bindex, id;

	unsigned int i;

	for (i = 0; i < shmp(handle, bufb->chan)->backend.num_subbuf; i++) {

		id = shmp_index(handle, bufb->buf_wsb, i)->id;

		sb_bindex = subbuffer_id_get_index(config, id);

		pages = shmp_index(handle, bufb->array, sb_bindex);

		records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread);

	}

	if (config->mode == RING_BUFFER_OVERWRITE) {

		id = bufb->buf_rsb.id;

		sb_bindex = subbuffer_id_get_index(config, id);

		pages = shmp_index(handle, bufb->array, sb_bindex);

		records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread);

	}

	return records_unread;

}

#endif /* _LTTNG_RING_BUFFER_BACKEND_H */