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[iobuf] Add iob_split() to split an I/O buffer into portions 

RNDIS devices may provide multiple packets encapsulated into a single
message.  Provide an API to allow the RNDIS driver to split an I/O
buffer into smaller portions.

The current implementation will always copy the underlying data,
rather than splitting the buffer in situ.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/33/head
Michael Brown 2014-12-11 17:10:01 +00:00
parent d83fb45b66
commit c86b22221d
2 changed files with 31 additions and 0 deletions
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30
src/core/iobuf.c
View File

@ -200,3 +200,33 @@ struct io_buffer * iob_concatenate ( struct list_head *list ) {
return concatenated;
}
/**
* Split I/O buffer
*
* @v iobuf I/O buffer
* @v len Length to split into a new I/O buffer
* @ret split New I/O buffer, or NULL on allocation failure
*
* Split the first @c len bytes of the existing I/O buffer into a
* separate I/O buffer. The resulting buffers are likely to have no
* headroom or tailroom.
*
* If this call fails, then the original buffer will be unmodified.
*/
struct io_buffer * iob_split ( struct io_buffer *iobuf, size_t len ) {
struct io_buffer *split;
/* Sanity checks */
assert ( len <= iob_len ( iobuf ) );
/* Allocate new I/O buffer */
split = alloc_iob ( len );
if ( ! split )
return NULL;
/* Copy in data */
memcpy ( iob_put ( split, len ), iobuf->data, len );
iob_pull ( iobuf, len );
return split;
}

1
src/include/ipxe/iobuf.h
View File

@ -217,5 +217,6 @@ extern void free_iob ( struct io_buffer *iobuf );
extern void iob_pad ( struct io_buffer *iobuf, size_t min_len );
extern int iob_ensure_headroom ( struct io_buffer *iobuf, size_t len );
extern struct io_buffer * iob_concatenate ( struct list_head *list );
extern struct io_buffer * iob_split ( struct io_buffer *iobuf, size_t len );
#endif /* _IPXE_IOBUF_H */