pbuf.c File Reference
Packet buffer management. More...
|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). |
|void||pbuf_realloc (struct pbuf *p, u16_t new_len)|
|Shrink a pbuf chain to a desired length. |
|u8_t||pbuf_header (struct pbuf *p, s16_t header_size_increment)|
|Adjusts the payload pointer to hide or reveal headers in the payload. |
|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. |
|u8_t||pbuf_clen (struct pbuf *p)|
|Count number of pbufs in a chain. |
|void||pbuf_ref (struct pbuf *p)|
|Increment the reference count of the pbuf. |
|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. |
|void||pbuf_chain (struct pbuf *h, struct pbuf *t)|
|Chain two pbufs (or pbuf chains) together. |
|struct pbuf *||pbuf_dechain (struct pbuf *p)|
|Dechains the first pbuf from its succeeding pbufs in the chain. |
|err_t||pbuf_copy (struct pbuf *p_to, struct pbuf *p_from)|
|Create PBUF_RAM copies of pbufs. |
|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. |
|err_t||pbuf_take (struct pbuf *buf, const void *dataptr, u16_t len)|
|Copy application supplied data into a pbuf. |
|struct pbuf *||pbuf_coalesce (struct pbuf *p, pbuf_layer layer)|
|Creates a single pbuf out of a queue of pbufs. |
|u8_t||pbuf_get_at (struct pbuf *p, u16_t offset)|
|Get one byte from the specified position in a pbuf WARNING: returns zero for offset >= p->tot_len. |
|u16_t||pbuf_memcmp (struct pbuf *p, u16_t offset, const void *s2, u16_t n)|
|Compare pbuf contents at specified offset with memory s2, both of length n. |
|u16_t||pbuf_memfind (struct pbuf *p, const void *mem, u16_t mem_len, u16_t start_offset)|
|Find occurrence of mem (with length mem_len) in pbuf p, starting at offset start_offset. |
|u16_t||pbuf_strstr (struct pbuf *p, const char *substr)|
|Find occurrence of substr with length substr_len in pbuf p, start at offset start_offset WARNING: in contrast to strstr(), this one does not stop at the first \0 in the pbuf/source string! |
Packet buffer management.
Packets are built from the pbuf data structure. It supports dynamic memory allocation for packet contents or can reference externally managed packet contents both in RAM and ROM. Quick allocation for incoming packets is provided through pools with fixed sized pbufs.
A packet may span over multiple pbufs, chained as a singly linked list. This is called a "pbuf chain".
Multiple packets may be queued, also using this singly linked list. This is called a "packet queue".
So, a packet queue consists of one or more pbuf chains, each of which consist of one or more pbufs. CURRENTLY, PACKET QUEUES ARE NOT SUPPORTED!!! Use helper structs to queue multiple packets.
The differences between a pbuf chain and a packet queue are very precise but subtle.
The last pbuf of a packet has a ->tot_len field that equals the ->len field. It can be found by traversing the list. If the last pbuf of a packet has a ->next field other than NULL, more packets are on the queue.
Therefore, looping through a pbuf of a single packet, has an loop end condition (tot_len == p->len), NOT (next == NULL).
Definition in file pbuf.c.
|struct pbuf* pbuf_alloc||(||pbuf_layer||layer,|
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).
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().
- 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|
|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.
h head pbuf (chain) t tail pbuf (chain)
- 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 )|
|struct pbuf* pbuf_coalesce||(||struct pbuf *||p,|
Creates a single pbuf out of a queue of pbufs.
- : 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!
p the source pbuf layer pbuf_layer of the new pbuf
- 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.
- You MUST explicitly use p = pbuf_take(p);
- Only one packet is copied, no packet queue!
p_to pbuf destination of the copy p_from pbuf source of the copy
- 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,|
Copy (part of) the contents of a packet buffer to an application supplied buffer.
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
- the number of bytes copied, or 0 on failure
|struct pbuf* pbuf_dechain||(||struct pbuf *||p )||
|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.
p The pbuf (chain) to be dereferenced.
- the number of pbufs that were de-allocated from the head of the chain.
- 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).
|u8_t pbuf_get_at||(||struct pbuf *||p,|
|u8_t pbuf_header||(||struct pbuf *||p,|
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.
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.
- non-zero on failure, zero on success.
|u16_t pbuf_memcmp||(||struct pbuf *||p,|
|const void *||s2,|
Compare pbuf contents at specified offset with memory s2, both of length n.
p pbuf to compare offset offset into p at wich to start comparing s2 buffer to compare n length of buffer to compare
- zero if equal, nonzero otherwise (0xffff if p is too short, diffoffset+1 otherwise)
|u16_t pbuf_memfind||(||struct pbuf *||p,|
|const void *||mem,|
Find occurrence of mem (with length mem_len) in pbuf p, starting at offset start_offset.
p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as return value 'not found' mem search for the contents of this buffer mem_len length of 'mem' start_offset offset into p at which to start searching
- 0xFFFF if substr was not found in p or the index where it was found
|void pbuf_realloc||(||struct pbuf *||p,|
Shrink a pbuf chain to a desired length.
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.
- 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 )|
|u16_t pbuf_strstr||(||struct pbuf *||p,|
|const char *||substr|
Find occurrence of substr with length substr_len in pbuf p, start at offset start_offset WARNING: in contrast to strstr(), this one does not stop at the first \0 in the pbuf/source string!
p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as return value 'not found' substr string to search for in p, maximum length is 0xFFFE
- 0xFFFF if substr was not found in p or the index where it was found
|err_t pbuf_take||(||struct pbuf *||buf,|
|const void *||dataptr,|
Copy application supplied data into a pbuf.
This function can only be used to copy the equivalent of buf->tot_len data.
buf pbuf to fill with data dataptr application supplied data buffer len length of the application supplied data buffer
- ERR_OK if successful, ERR_MEM if the pbuf is not big enough