include/net/buf.h

/** @file
 *  @brief Buffer management.
 */

/*
 * Copyright (c) 2015 Intel Corporation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef __NET_BUF_H
#define __NET_BUF_H

#include <stddef.h>
#include <stdint.h>
#include <toolchain.h>
#include <misc/util.h>
#include <nanokernel.h>

#ifdef __cplusplus
extern "C" {
#endif

/* Alignment needed for various parts of the buffer definition */
#define __net_buf_align __aligned(sizeof(int))

/** @def NET_BUF_SIMPLE
 *  @brief Define a net_buf_simple stack variable and get a pointer to it.
 *
 *  This is a helper macro which is used to define a net_buf_simple object on
 *  the stack and the get a pointer to it as follows:
 *
 *  struct net_buf_simple *my_buf = NET_BUF_SIMPLE(10);
 *
 *  After creating the object it needs to be initialized by calling
 *  net_buf_simple_init().
 *
 *  @param _size Maximum data storage for the buffer.
 *
 *  @return Pointer to stack-allocated net_buf_simple object.
 */
#define NET_BUF_SIMPLE(_size)                        \
	((struct net_buf_simple *)(&(struct {        \
		struct net_buf_simple buf;           \
		uint8_t data[_size] __net_buf_align; \
	}) {                                         \
		.buf.size = _size,                   \
	}))

/** @brief Simple network buffer representation.
 *
 *  This is a simpler variant of the net_buf object (in fact net_buf uses
 *  net_buf_simple internally). It doesn't provide any kind of reference
 *  counting, user data, dynamic allocation, or in general the ability to
 *  pass through nano-kernel objects such as FIFOs.
 *
 *  The main use of this is for scenarios where the meta-data of the normal
 *  net_buf isn't needed and causes too much overhead. This could be e.g.
 *  when the buffer only needs to be allocated on the stack or when the
 *  access to and lifetime of the buffer is well controlled and constrained.
 *
 */
struct net_buf_simple {
	/** Pointer to the start of data in the buffer. */
	uint8_t *data;

	/** Length of the data behind the data pointer. */
	uint16_t len;

	/** Amount of data that this buffer can store. */
	const uint16_t size;

	/** Start of the data storage. Not to be accessed directly
	 *  (the data pointer should be used instead).
	 */
	uint8_t __buf[0] __net_buf_align;
};

/** @brief Initialize a net_buf_simple object.
 *
 *  This needs to be called after creating a net_buf_simple object e.g. using
 *  the NET_BUF_SIMPLE macro.
 *
 *  @param buf Buffer to initialize.
 *  @param reserve_head Headroom to reserve.
 */
static inline void net_buf_simple_init(struct net_buf_simple *buf,
				       size_t reserve_head)
{
	buf->data = buf->__buf + reserve_head;
	buf->len = 0;
}

/**
 *  @brief Prepare data to be added at the end of the buffer
 *
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param len Number of bytes to increment the length with.
 *
 *  @return The original tail of the buffer.
 */
void *net_buf_simple_add(struct net_buf_simple *buf, size_t len);

/**
 *  @brief Add (8-bit) byte at the end of the buffer
 *
 *  Adds a byte at the end of the buffer. Increments the data length of
 *  the  buffer to account for more data at the end.
 *
 *  @param buf Buffer to update.
 *  @param val byte value to be added.
 *
 *  @return Pointer to the value added
 */
uint8_t *net_buf_simple_add_u8(struct net_buf_simple *buf, uint8_t val);

/**
 *  @brief Add 16-bit value at the end of the buffer
 *
 *  Adds 16-bit value in little endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be added.
 */
void net_buf_simple_add_le16(struct net_buf_simple *buf, uint16_t val);

/**
 *  @brief Add 16-bit value at the end of the buffer
 *
 *  Adds 16-bit value in big endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be added.
 */
void net_buf_simple_add_be16(struct net_buf_simple *buf, uint16_t val);

/**
 *  @brief Add 32-bit value at the end of the buffer
 *
 *  Adds 32-bit value in little endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 32-bit value to be added.
 */
void net_buf_simple_add_le32(struct net_buf_simple *buf, uint32_t val);

/**
 *  @brief Add 32-bit value at the end of the buffer
 *
 *  Adds 32-bit value in big endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 32-bit value to be added.
 */
void net_buf_simple_add_be32(struct net_buf_simple *buf, uint32_t val);

/**
 *  @brief Push data to the beginning of the buffer.
 *
 *  Modifies the data pointer and buffer length to account for more data
 *  in the beginning of the buffer.
 *
 *  @param buf Buffer to update.
 *  @param len Number of bytes to add to the beginning.
 *
 *  @return The new beginning of the buffer data.
 */
void *net_buf_simple_push(struct net_buf_simple *buf, size_t len);

/**
 *  @brief Push 16-bit value to the beginning of the buffer
 *
 *  Adds 16-bit value in little endian format to the beginning of the
 *  buffer.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be pushed to the buffer.
 */
void net_buf_simple_push_le16(struct net_buf_simple *buf, uint16_t val);

/**
 *  @brief Push 16-bit value to the beginning of the buffer
 *
 *  Adds 16-bit value in little endian format to the beginning of the
 *  buffer.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be pushed to the buffer.
 */
void net_buf_simple_push_be16(struct net_buf_simple *buf, uint16_t val);

/**
 *  @brief Push 8-bit value to the beginning of the buffer
 *
 *  Adds 8-bit value the beginning of the buffer.
 *
 *  @param buf Buffer to update.
 *  @param val 8-bit value to be pushed to the buffer.
 */
void net_buf_simple_push_u8(struct net_buf_simple *buf, uint8_t val);

/**
 *  @brief Remove data from the beginning of the buffer.
 *
 *  Removes data from the beginnig of the buffer by modifying the data
 *  pointer and buffer length.
 *
 *  @param buf Buffer to update.
 *  @param len Number of bytes to remove.
 *
 *  @return New beginning of the buffer data.
 */
void *net_buf_simple_pull(struct net_buf_simple *buf, size_t len);

/**
 *  @brief Remove a 8-bit value from the beginning of the buffer
 *
 *  Same idea as with net_buf_simple_pull(), but a helper for operating
 *  on 8-bit values.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return The 8-bit removed value
 */
uint8_t net_buf_simple_pull_u8(struct net_buf_simple *buf);

/**
 *  @brief Remove and convert 16 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_simple_pull(), but a helper for operating
 *  on 16-bit little endian data.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return 16-bit value converted from little endian to host endian.
 */
uint16_t net_buf_simple_pull_le16(struct net_buf_simple *buf);

/**
 *  @brief Remove and convert 16 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_simple_pull(), but a helper for operating
 *  on 16-bit big endian data.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return 16-bit value converted from big endian to host endian.
 */
uint16_t net_buf_simple_pull_be16(struct net_buf_simple *buf);

/**
 *  @brief Remove and convert 32 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_simple_pull(), but a helper for operating
 *  on 32-bit little endian data.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return 32-bit value converted from little endian to host endian.
 */
uint32_t net_buf_simple_pull_le32(struct net_buf_simple *buf);

/**
 *  @brief Remove and convert 32 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_simple_pull(), but a helper for operating
 *  on 32-bit big endian data.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return 32-bit value converted from big endian to host endian.
 */
uint32_t net_buf_simple_pull_be32(struct net_buf_simple *buf);

/**
 *  @brief Get the tail pointer for a buffer.
 *
 *  Get a pointer to the end of the data in a buffer.
 *
 *  @param buf Buffer.
 *
 *  @return Tail pointer for the buffer.
 */
static inline uint8_t *net_buf_simple_tail(struct net_buf_simple *buf)
{
	return buf->data + buf->len;
}

/**
 *  @brief Check buffer headroom.
 *
 *  Check how much free space there is in the beginning of the buffer.
 *
 *  buf A valid pointer on a buffer
 *
 *  @return Number of bytes available in the beginning of the buffer.
 */
size_t net_buf_simple_headroom(struct net_buf_simple *buf);

/**
 *  @brief Check buffer tailroom.
 *
 *  Check how much free space there is at the end of the buffer.
 *
 *  @param buf A valid pointer on a buffer
 *
 *  @return Number of bytes available at the end of the buffer.
 */
size_t net_buf_simple_tailroom(struct net_buf_simple *buf);

/**
 *  @brief Parsing state of a buffer.
 *
 *  This is used for temporarily storing the parsing state of a buffer
 *  while giving control of the parsing to a routing which we don't
 *  control.
 */
struct net_buf_simple_state {
	/** Offset of the data pointer from the beginning of the storage */
	uint16_t offset;
	/** Length of data */
	uint16_t len;
};

/**
 *  @brief Save the parsing state of a buffer.
 *
 *  Saves the parsing state of a buffer so it can be restored later.
 *
 *  @param buf Buffer from which the state should be saved.
 *  @param state Storage for the state.
 */
static inline void net_buf_simple_save(struct net_buf_simple *buf,
				       struct net_buf_simple_state *state)
{
	state->offset = net_buf_simple_headroom(buf);
	state->len = buf->len;
}

/**
 *  @brief Restore the parsing state of a buffer.
 *
 *  Restores the parsing state of a buffer from a state previously stored
 *  by net_buf_simple_save().
 *
 *  @param buf Buffer to which the state should be restored.
 *  @param state Stored state.
 */
static inline void net_buf_simple_restore(struct net_buf_simple *buf,
					  struct net_buf_simple_state *state)
{
	buf->data = buf->__buf + state->offset;
	buf->len = state->len;
}

/** Flag indicating that the buffer has associated fragments. Only used
  * internally by the buffer handling code while the buffer is inside a
  * FIFO, meaning this never needs to be explicitly set or unset by the
  * net_buf API user. As long as the buffer is outside of a FIFO, i.e.
  * in practice always for the user for this API, the buf->frags pointer
  * should be used instead.
  */
#define NET_BUF_FRAGS        BIT(0)

/** @brief Network buffer representation.
  *
  * This struct is used to represent network buffers. Such buffers are
  * normally defined through the NET_BUF_POOL() API and allocated using
  * the net_buf_get() and net_buf_get_timeout() APIS.
  */
struct net_buf {
	union {
		/** FIFO uses first 4 bytes itself, reserve space */
		int _unused;

		/** Fragments associated with this buffer. */
		struct net_buf *frags;
	};

	/** Size of the user data associated with this buffer. */
	const uint16_t user_data_size;

	/** Reference count. */
	uint8_t ref;

	/** Bit-field of buffer flags. */
	uint8_t flags;

	/** Where the buffer should go when freed up. */
	struct nano_fifo * const free;

	/** Function to be called when the buffer is freed. */
	void (*const destroy)(struct net_buf *buf);

	/* Union for convenience access to the net_buf_simple members, also
	 * preserving the old API.
	 */
	union {
		/* The ABI of this struct must match net_buf_simple */
		struct {
			/** Pointer to the start of data in the buffer. */
			uint8_t *data;

			/** Length of the data behind the data pointer. */
			uint16_t len;

			/** Amount of data that this buffer can store. */
			const uint16_t size;
		};

		struct net_buf_simple b;
	};

	/** Start of the data storage. Not to be accessed directly
	 *  (the data pointer should be used instead).
	 */
	uint8_t __buf[0] __net_buf_align;
};

/**
 *  @brief Define a pool of buffers of a certain amount and size.
 *
 *  Defines the necessary memory space (array of structs) for the needed
 *  amount of buffers. After this the net_buf_pool_init() API still
 *  needs to be used (at runtime), after which the buffers can be
 *  accessed using the fifo given as one of the parameters.
 *
 *  If provided with a custom destroy callback this callback is
 *  responsible for eventually returning the buffer back to the free
 *  buffers FIFO through nano_fifo_put(buf->free, buf).
 *
 *  @param _name     Name of buffer pool.
 *  @param _count    Number of buffers in the pool.
 *  @param _size     Maximum data size for each buffer.
 *  @param _fifo     FIFO for the buffers when they are unused.
 *  @param _destroy  Optional destroy callback when buffer is freed.
 *  @param _ud_size  Amount of user data space to reserve.
 */
#define NET_BUF_POOL(_name, _count, _size, _fifo, _destroy, _ud_size)	\
	struct {							\
		struct net_buf buf;					\
		uint8_t data[_size] __net_buf_align;	                \
		uint8_t ud[ROUND_UP(_ud_size, 4)] __net_buf_align;	\
	} _name[_count] = {						\
		[0 ... (_count - 1)] = { .buf = {			\
			.user_data_size = ROUND_UP(_ud_size, 4),	\
			.free = _fifo,					\
			.destroy = _destroy,				\
			.size = _size } },			        \
	}

/**
 *  @brief Initialize an available buffers FIFO based on a pool.
 *
 *  Initializes a buffer pool created using NET_BUF_POOL(). After
 *  calling this API the buffers can ge accessed through the FIFO that
 *  was given to NET_BUF_POOL(), i.e. after this call there should be no
 *  need to access the buffer pool (struct array) directly anymore.
 *
 *  @param pool  Buffer pool to initialize.
 */
#define net_buf_pool_init(pool)						\
	do {								\
		int i;							\
									\
		nano_fifo_init(pool[0].buf.free);			\
									\
		for (i = 0; i < ARRAY_SIZE(pool); i++) {		\
			nano_fifo_put(pool[i].buf.free, &pool[i]);	\
		}							\
	} while (0)

/**
 *  @brief Get a new buffer from a FIFO.
 *
 *  Get buffer from a FIFO. The reserve_head parameter is only relevant
 *  if the FIFO in question is a free buffers pool, i.e. the buffer will
 *  end up being initialized upon return. If called for any other FIFO
 *  the reserve_head parameter will be ignored and should be set to 0.
 *
 *  @param fifo Which FIFO to take the buffer from.
 *  @param reserve_head How much headroom to reserve.
 *
 *  @return New buffer or NULL if out of buffers.
 *
 *  @warning If there are no available buffers and the function is
 *  called from a task or fiber the call will block until a buffer
 *  becomes available in the FIFO. If you want to make sure no blocking
 *  happens use net_buf_get_timeout() instead with TICKS_NONE.
 */
struct net_buf *net_buf_get(struct nano_fifo *fifo, size_t reserve_head);

/**
 *  @brief Get a new buffer from a FIFO.
 *
 *  Get buffer from a FIFO. The reserve_head parameter is only relevant
 *  if the FIFO in question is a free buffers pool, i.e. the buffer will
 *  end up being initialized upon return. If called for any other FIFO
 *  the reserve_head parameter will be ignored and should be set to 0.
 *
 *  @param fifo Which FIFO to take the buffer from.
 *  @param reserve_head How much headroom to reserve.
 *  @param timeout Affects the action taken should the FIFO be empty.
 *         If TICKS_NONE, then return immediately. If TICKS_UNLIMITED, then
 *         wait as long as necessary. Otherwise, wait up to the specified
 *         number of ticks before timing out.
 *
 *  @return New buffer or NULL if out of buffers.
 */
struct net_buf *net_buf_get_timeout(struct nano_fifo *fifo,
				    size_t reserve_head, int32_t timeout);

/**
 *  @brief Initialize buffer with the given headroom.
 *
 *  Initializes a buffer with a given headroom. The buffer is not expected to
 *  contain any data when this API is called.
 *
 *  @param buf Buffer to initialize.
 *  @param reserve How much headroom to reserve.
 */
void net_buf_reserve(struct net_buf *buf, size_t reserve);

/**
 *  @brief Put a buffer into a FIFO
 *
 *  Put a buffer to the end of a FIFO. If the buffer contains follow-up
 *  fragments this function will take care of inserting them as well
 *  into the FIFO.
 *
 *  @param fifo Which FIFO to put the buffer to.
 *  @param buf Buffer.
 */
void net_buf_put(struct nano_fifo *fifo, struct net_buf *buf);

/**
 *  @brief Decrements the reference count of a buffer.
 *
 *  Decrements the reference count of a buffer and puts it back into the
 *  pool if the count reaches zero.
 *
 *  @param buf A valid pointer on a buffer
 */
void net_buf_unref(struct net_buf *buf);

/**
 *  @brief Increment the reference count of a buffer.
 *
 *  @param buf A valid pointer on a buffer
 *
 *  @return the buffer newly referenced
 */
struct net_buf *net_buf_ref(struct net_buf *buf);

/**
 *  @brief Duplicate buffer
 *
 *  Duplicate given buffer including any data and headers currently stored.
 *
 *  @param buf A valid pointer on a buffer
 *
 *  @return Duplicated buffer or NULL if out of buffers.
 */
struct net_buf *net_buf_clone(struct net_buf *buf);

/**
 *  @brief Get a pointer to the user data of a buffer.
 *
 *  @param buf A valid pointer on a buffer
 *
 *  @return Pointer to the user data of the buffer.
 */
static inline void *net_buf_user_data(struct net_buf *buf)
{
	return (void *)ROUND_UP((buf->__buf + buf->size), sizeof(int));
}

/**
 *  @def net_buf_add
 *  @brief Prepare data to be added at the end of the buffer
 *
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param len Number of bytes to increment the length with.
 *
 *  @return The original tail of the buffer.
 */
#define net_buf_add(buf, len) net_buf_simple_add(&(buf)->b, len)

/**
 *  @def net_buf_add_u8
 *  @brief Add (8-bit) byte at the end of the buffer
 *
 *  Adds a byte at the end of the buffer. Increments the data length of
 *  the  buffer to account for more data at the end.
 *
 *  @param buf Buffer to update.
 *  @param val byte value to be added.
 *
 *  @return Pointer to the value added
 */
#define net_buf_add_u8(buf, val) net_buf_simple_add_u8(&(buf)->b, val)

/**
 *  @def net_buf_add_le16
 *  @brief Add 16-bit value at the end of the buffer
 *
 *  Adds 16-bit value in little endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be added.
 */
#define net_buf_add_le16(buf, val) net_buf_simple_add_le16(&(buf)->b, val)

/**
 *  @def net_buf_add_be16
 *  @brief Add 16-bit value at the end of the buffer
 *
 *  Adds 16-bit value in big endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be added.
 */
#define net_buf_add_be16(buf, val) net_buf_simple_add_be16(&(buf)->b, val)

/**
 *  @def net_buf_add_le32
 *  @brief Add 32-bit value at the end of the buffer
 *
 *  Adds 32-bit value in little endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 32-bit value to be added.
 */
#define net_buf_add_le32(buf, val) net_buf_simple_add_le32(&(buf)->b, val)

/**
 *  @def net_buf_add_be32
 *  @brief Add 32-bit value at the end of the buffer
 *
 *  Adds 32-bit value in big endian format at the end of buffer.
 *  Increments the data length of a buffer to account for more data
 *  at the end.
 *
 *  @param buf Buffer to update.
 *  @param val 32-bit value to be added.
 */
#define net_buf_add_be32(buf, val) net_buf_simple_add_be32(&(buf)->b, val)

/**
 *  @def net_buf_push
 *  @brief Push data to the beginning of the buffer.
 *
 *  Modifies the data pointer and buffer length to account for more data
 *  in the beginning of the buffer.
 *
 *  @param buf Buffer to update.
 *  @param len Number of bytes to add to the beginning.
 *
 *  @return The new beginning of the buffer data.
 */
#define net_buf_push(buf, len) net_buf_simple_push(&(buf)->b, len)

/**
 *  @def net_buf_push_le16
 *  @brief Push 16-bit value to the beginning of the buffer
 *
 *  Adds 16-bit value in little endian format to the beginning of the
 *  buffer.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be pushed to the buffer.
 */
#define net_buf_push_le16(buf, val) net_buf_simple_push_le16(&(buf)->b, val)

/**
 *  @def net_buf_push_be16
 *  @brief Push 16-bit value to the beginning of the buffer
 *
 *  Adds 16-bit value in little endian format to the beginning of the
 *  buffer.
 *
 *  @param buf Buffer to update.
 *  @param val 16-bit value to be pushed to the buffer.
 */
#define net_buf_push_be16(buf, val) net_buf_simple_push_be16(&(buf)->b, val)

/**
 *  @def net_buf_push_u8
 *  @brief Push 8-bit value to the beginning of the buffer
 *
 *  Adds 8-bit value the beginning of the buffer.
 *
 *  @param buf Buffer to update.
 *  @param val 8-bit value to be pushed to the buffer.
 */
#define net_buf_push_u8(buf, val) net_buf_simple_push_u8(&(buf)->b, val)

/**
 *  @def net_buf_pull
 *  @brief Remove data from the beginning of the buffer.
 *
 *  Removes data from the beginnig of the buffer by modifying the data
 *  pointer and buffer length.
 *
 *  @param buf Buffer to update.
 *  @param len Number of bytes to remove.
 *
 *  @return New beginning of the buffer data.
 */
#define net_buf_pull(buf, len) net_buf_simple_pull(&(buf)->b, len)

/**
 *  @def net_buf_pull_u8
 *  @brief Remove a 8-bit value from the beginning of the buffer
 *
 *  Same idea as with net_buf_pull(), but a helper for operating on
 *  8-bit values.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return The 8-bit removed value
 */
#define net_buf_pull_u8(buf) net_buf_simple_pull_u8(&(buf)->b)

/**
 *  @def net_buf_pull_le16
 *  @brief Remove and convert 16 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_pull(), but a helper for operating on
 *  16-bit little endian data.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return 16-bit value converted from little endian to host endian.
 */
#define net_buf_pull_le16(buf) net_buf_simple_pull_le16(&(buf)->b)

/**
 *  @def net_buf_pull_be16
 *  @brief Remove and convert 16 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_pull(), but a helper for operating on
 *  16-bit big endian data.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return 16-bit value converted from big endian to host endian.
 */
#define net_buf_pull_be16(buf) net_buf_simple_pull_be16(&(buf)->b)

/**
 *  @def net_buf_pull_le32
 *  @brief Remove and convert 32 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_pull(), but a helper for operating on
 *  32-bit little endian data.
 *
 *  @param buf A valid pointer on a buffer.
 *
 *  @return 32-bit value converted from little endian to host endian.
 */
#define net_buf_pull_le32(buf) net_buf_simple_pull_le32(&(buf)->b)

/**
 *  @def net_buf_pull_be32
 *  @brief Remove and convert 32 bits from the beginning of the buffer.
 *
 *  Same idea as with net_buf_pull(), but a helper for operating on
 *  32-bit big endian data.
 *
 *  @param buf A valid pointer on a buffer
 *
 *  @return 32-bit value converted from big endian to host endian.
 */
#define net_buf_pull_be32(buf) net_buf_simple_pull_be32(&(buf)->b)

/**
 *  @def net_buf_tailroom
 *  @brief Check buffer tailroom.
 *
 *  Check how much free space there is at the end of the buffer.
 *
 *  @param buf A valid pointer on a buffer
 *
 *  @return Number of bytes available at the end of the buffer.
 */
#define net_buf_tailroom(buf) net_buf_simple_tailroom(&(buf)->b)

/**
 *  @def net_buf_headroom
 *  @brief Check buffer headroom.
 *
 *  Check how much free space there is in the beginning of the buffer.
 *
 *  buf A valid pointer on a buffer
 *
 *  @return Number of bytes available in the beginning of the buffer.
 */
#define net_buf_headroom(buf) net_buf_simple_headroom(&(buf)->b)

/**
 *  @def net_buf_tail
 *  @brief Get the tail pointer for a buffer.
 *
 *  Get a pointer to the end of the data in a buffer.
 *
 *  @param buf Buffer.
 *
 *  @return Tail pointer for the buffer.
 */
#define net_buf_tail(buf) net_buf_simple_tail(&(buf)->b)

/** @brief Find the last fragment in the fragment list.
 *
 * @return Pointer to last fragment in the list.
 */
struct net_buf *net_buf_frag_last(struct net_buf *frags);

/** @brief Insert a new fragment to a chain of bufs.
 *
 *  @param parent Parent buffer/fragment.
 *  @param frag Fragment to insert.
 */
void net_buf_frag_insert(struct net_buf *parent, struct net_buf *frag);

/** @def net_buf_frag_add
 *  @brief Add a new fragment to the end of a chain of bufs.
 *
 *  @param parent Parent buffer/fragment.
 *  @param frag Fragment to add.
 */
#define net_buf_frag_add(parent, frag) \
	net_buf_frag_insert(net_buf_frag_last(parent), frag)

/** @brief Delete existing fragment from a chain of bufs.
 *
 *  @param parent Parent buffer/fragment.
 *  @param frag Fragment to delete.
 */
void net_buf_frag_del(struct net_buf *parent, struct net_buf *frag);

/** @brief Calculate amount of bytes stored in fragments.
 *
 *  Calculates the total amount of data stored in the given buffer and the
 *  fragments linked to it.
 *
 *  @param buf Buffer to start off with.
 *
 *  @return Number of bytes in the buffer and its fragments.
 */
static inline size_t net_buf_frags_len(struct net_buf *buf)
{
	size_t bytes = 0;

	while (buf) {
		bytes += buf->len;
		buf = buf->frags;
	}

	return bytes;
}

#ifdef __cplusplus
}
#endif

#endif /* __NET_BUF_H */