lwip-1.3.2/src/include/lwip/pbuf.h File Reference

#include "lwip/opt.h"
#include "lwip/err.h"

Data Structures
struct	pbuf

Macros
#define	PBUF_FLAG_PUSH   0x01U
	indicates this packet's data should be immediately passed to the application More...
#define	pbuf_init()
#define	PBUF_IP_HLEN   20
#define	PBUF_TRANSPORT_HLEN   20

Enumerations
enum	pbuf_layer {   PBUF_TRANSPORT,   PBUF_IP,   PBUF_LINK,   PBUF_RAW,   PBUF_TRANSPORT,   PBUF_IP,   PBUF_LINK,   PBUF_RAW,   PBUF_TRANSPORT,   PBUF_IP,   PBUF_LINK,   PBUF_RAW }
enum	pbuf_type {   PBUF_RAM,   PBUF_ROM,   PBUF_REF,   PBUF_POOL,   PBUF_RAM,   PBUF_ROM,   PBUF_REF,   PBUF_POOL,   PBUF_RAM,   PBUF_ROM,   PBUF_REF,   PBUF_POOL }

Functions
struct pbuf *	pbuf_alloc (pbuf_layer l, u16_t size, pbuf_type type)
	Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type). More...
void	pbuf_cat (struct pbuf *head, struct pbuf *tail)
	Concatenate two pbufs (each may be a pbuf chain) and take over the caller's reference of the tail pbuf. More...
void	pbuf_chain (struct pbuf *head, struct pbuf *tail)
	Chain two pbufs (or pbuf chains) together. More...
u8_t	pbuf_clen (struct pbuf *p)
	Count number of pbufs in a chain. More...
struct pbuf *	pbuf_coalesce (struct pbuf *p, pbuf_layer layer)
	Creates a single pbuf out of a queue of pbufs. More...
err_t	pbuf_copy (struct pbuf *p_to, struct pbuf *p_from)
	Create PBUF_RAM copies of pbufs. More...
u16_t	pbuf_copy_partial (struct pbuf *p, void *dataptr, u16_t len, u16_t offset)
	Copy (part of) the contents of a packet buffer to an application supplied buffer. More...
struct pbuf *	pbuf_dechain (struct pbuf *p)
	Dechains the first pbuf from its succeeding pbufs in the chain. More...
u8_t	pbuf_free (struct pbuf *p)
	Dereference a pbuf chain or queue and deallocate any no-longer-used pbufs at the head of this chain or queue. More...
u8_t	pbuf_header (struct pbuf *p, s16_t header_size)
	Adjusts the payload pointer to hide or reveal headers in the payload. More...
void	pbuf_realloc (struct pbuf *p, u16_t size)
	Shrink a pbuf chain to a desired length. More...
void	pbuf_ref (struct pbuf *p)
	Increment the reference count of the pbuf. More...
void	pbuf_ref_chain (struct pbuf *p)
err_t	pbuf_take (struct pbuf *buf, const void *dataptr, u16_t len)
	Copy application supplied data into a pbuf. More...

#define PBUF_FLAG_PUSH   0x01U

indicates this packet's data should be immediately passed to the application

#define pbuf_init

(

)

#define PBUF_IP_HLEN   20

#define PBUF_TRANSPORT_HLEN   20

enum pbuf_layer

Enumerator
PBUF_TRANSPORT
PBUF_IP
PBUF_LINK
PBUF_RAW
PBUF_TRANSPORT
PBUF_IP
PBUF_LINK
PBUF_RAW
PBUF_TRANSPORT
PBUF_IP
PBUF_LINK
PBUF_RAW

enum pbuf_type

Enumerator
PBUF_RAM
PBUF_ROM
PBUF_REF
PBUF_POOL
PBUF_RAM
PBUF_ROM
PBUF_REF
PBUF_POOL
PBUF_RAM
PBUF_ROM
PBUF_REF
PBUF_POOL

struct pbuf* pbuf_alloc	(	pbuf_layer	layer,
		u16_t	length,
		pbuf_type	type
	)

Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).

The actual memory allocated for the pbuf is determined by the layer at which the pbuf is allocated and the requested size (from the size parameter).

Parameters

layer	flag to define header size
length	size of the pbuf's payload
type	this parameter decides how and where the pbuf should be allocated as follows:

• PBUF_RAM: buffer memory for pbuf is allocated as one large chunk. This includes protocol headers as well.
• PBUF_ROM: no buffer memory is allocated for the pbuf, even for protocol headers. Additional headers must be prepended by allocating another pbuf and chain in to the front of the ROM pbuf. It is assumed that the memory used is really similar to ROM in that it is immutable and will not be changed. Memory which is dynamic should generally not be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
• PBUF_REF: no buffer memory is allocated for the pbuf, even for protocol headers. It is assumed that the pbuf is only being used in a single thread. If the pbuf gets queued, then pbuf_take should be called to copy the buffer.
• PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from the pbuf pool that is allocated during pbuf_init().

Returns

the allocated pbuf. If multiple pbufs where allocated, this is the first pbuf of a pbuf chain.

void pbuf_cat	(	struct pbuf *	h,
		struct pbuf *	t
	)

Concatenate two pbufs (each may be a pbuf chain) and take over the caller's reference of the tail pbuf.

Note

The caller MAY NOT reference the tail pbuf afterwards. Use pbuf_chain() for that purpose.

See Also

pbuf_chain()

void pbuf_chain	(	struct pbuf *	h,
		struct pbuf *	t
	)

Chain two pbufs (or pbuf chains) together.

The caller MUST call pbuf_free(t) once it has stopped using it. Use pbuf_cat() instead if you no longer use t.

Parameters

h	head pbuf (chain)
t	tail pbuf (chain)

Note

The pbufs MUST belong to the same packet.

MAY NOT be called on a packet queue.

The ->tot_len fields of all pbufs of the head chain are adjusted. The ->next field of the last pbuf of the head chain is adjusted. The ->ref field of the first pbuf of the tail chain is adjusted.

u8_t pbuf_clen

(

struct pbuf *

p

)

Count number of pbufs in a chain.

Parameters

p	first pbuf of chain

Returns

the number of pbufs in a chain

struct pbuf* pbuf_coalesce	(	struct pbuf *	p,
		pbuf_layer	layer
	)

Creates a single pbuf out of a queue of pbufs.

Remarks

: Either the source pbuf 'p' is freed by this function or the original pbuf 'p' is returned, therefore the caller has to check the result!

Parameters

p	the source pbuf
layer	pbuf_layer of the new pbuf

Returns

a new, single pbuf (p->next is NULL) or the old pbuf if allocation fails

Remarks

: The source pbuf 'p' is not freed by this function because that can be illegal in some places!

Parameters

p	the source pbuf
layer	pbuf_layer of the new pbuf

Returns

a new, single pbuf (p->next is NULL) or the old pbuf if allocation fails

err_t pbuf_copy	(	struct pbuf *	p_to,
		struct pbuf *	p_from
	)

Create PBUF_RAM copies of pbufs.

Used to queue packets on behalf of the lwIP stack, such as ARP based queueing.

Note

You MUST explicitly use p = pbuf_take(p);

Only one packet is copied, no packet queue!

Parameters

p_to	pbuf destination of the copy
p_from	pbuf source of the copy

Returns

ERR_OK if pbuf was copied ERR_ARG if one of the pbufs is NULL or p_to is not big enough to hold p_from

u16_t pbuf_copy_partial	(	struct pbuf *	buf,
		void *	dataptr,
		u16_t	len,
		u16_t	offset
	)

Copy (part of) the contents of a packet buffer to an application supplied buffer.

Parameters

buf	the pbuf from which to copy data
dataptr	the application supplied buffer
len	length of data to copy (dataptr must be big enough). No more than buf->tot_len will be copied, irrespective of len
offset	offset into the packet buffer from where to begin copying len bytes

Returns

the number of bytes copied, or 0 on failure

struct pbuf* pbuf_dechain

(

struct pbuf *

p

)

Dechains the first pbuf from its succeeding pbufs in the chain.

Makes p->tot_len field equal to p->len.

Parameters

p	pbuf to dechain

Returns

remainder of the pbuf chain, or NULL if it was de-allocated.

Note

May not be called on a packet queue.

u8_t pbuf_free

(

struct pbuf *

p

)

Dereference a pbuf chain or queue and deallocate any no-longer-used pbufs at the head of this chain or queue.

Decrements the pbuf reference count. If it reaches zero, the pbuf is deallocated.

For a pbuf chain, this is repeated for each pbuf in the chain, up to the first pbuf which has a non-zero reference count after decrementing. So, when all reference counts are one, the whole chain is free'd.

Parameters

p	The pbuf (chain) to be dereferenced.

Returns

the number of pbufs that were de-allocated from the head of the chain.

Note

MUST NOT be called on a packet queue (Not verified to work yet).

the reference counter of a pbuf equals the number of pointers that refer to the pbuf (or into the pbuf).

examples:

Assuming existing chains a->b->c with the following reference counts, calling pbuf_free(a) results in:

1->2->3 becomes ...1->3 3->3->3 becomes 2->3->3 1->1->2 becomes ......1 2->1->1 becomes 1->1->1 1->1->1 becomes .......

u8_t pbuf_header	(	struct pbuf *	p,
		s16_t	header_size_increment
	)

Adjusts the payload pointer to hide or reveal headers in the payload.

Adjusts the ->payload pointer so that space for a header (dis)appears in the pbuf payload.

The ->payload, ->tot_len and ->len fields are adjusted.

Parameters

p	pbuf to change the header size.
header_size_increment	Number of bytes to increment header size which increases the size of the pbuf. New space is on the front. (Using a negative value decreases the header size.) If hdr_size_inc is 0, this function does nothing and returns succesful.

PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so the call will fail. A check is made that the increase in header size does not move the payload pointer in front of the start of the buffer.

Returns

non-zero on failure, zero on success.

void pbuf_realloc	(	struct pbuf *	p,
		u16_t	new_len
	)

Shrink a pbuf chain to a desired length.

Parameters

p	pbuf to shrink.
new_len	desired new length of pbuf chain

Depending on the desired length, the first few pbufs in a chain might be skipped and left unchanged. The new last pbuf in the chain will be resized, and any remaining pbufs will be freed.

Note

If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.

May not be called on a packet queue.

Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).

void pbuf_ref

(

struct pbuf *

p

)

Increment the reference count of the pbuf.

Parameters

p	pbuf to increase reference counter of

void pbuf_ref_chain

(

struct pbuf *

p

)

err_t pbuf_take	(	struct pbuf *	buf,
		const void *	dataptr,
		u16_t	len
	)

Copy application supplied data into a pbuf.

This function can only be used to copy the equivalent of buf->tot_len data.

Parameters

buf	pbuf to fill with data
dataptr	application supplied data buffer
len	length of the application supplied data buffer

Returns

ERR_OK if successful, ERR_MEM if the pbuf is not big enough