Introduce four new APIs that support efficient sharing of portions of packets.
odp_packet_splice() creates a reference to a base packet by splicing a supplied header packet onto it at a specified offset. If multiple splices are created then each shares the base packet that was spliced. odp_packet_ref() creates a reference to a base packet by splicing a zero-length header onto it at a specified offset. This allows an application to "hold onto" a pointer to a packet so that it will not be freed until all references to it are freed. odp_packet_is_a_splice() allows an application to determine whether a packet is a splice and if so how many individual packets are contained within it. odp_packet_is_spliced() allows an application to determine whether a packet has a splice on it and if so how many splices are based on it. Signed-off-by: Bill Fischofer <bill.fischo...@linaro.org> --- include/odp/api/spec/packet.h | 103 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) diff --git a/include/odp/api/spec/packet.h b/include/odp/api/spec/packet.h index 4a14f2d..8e147a3 100644 --- a/include/odp/api/spec/packet.h +++ b/include/odp/api/spec/packet.h @@ -844,6 +844,109 @@ int odp_packet_concat(odp_packet_t *dst, odp_packet_t src); */ int odp_packet_split(odp_packet_t *pkt, uint32_t len, odp_packet_t *tail); +/** + * Splice a packet + * + * Create a new packet by splicing a header onto an existing packet. The + * spliced packet consists of the header followed by a shared reference to the + * base packet receiving the splice starting at a designated offset. If + * multiple splices are created on the same base packet, it is the + * application's responsibility to coordinate any changes to the shared + * segment(s) of the splice, otherwise results are undefined. + * + * @param hdr Handle of the header packet to be spliced onto the base packet + * + * @param pkt Handle of the base packet that is to receive the splice + * + * @param offset Byte offset within the base packet at which the splice is + * to be made. + * + * @return Handle of the spliced packet. This may or may not be the + * same as the input hdr packet. The caller should use this + * for any future references to the splice. The original hdr + * packet no longer has any independent existence. + * + * @retval ODP_PACKET_INVALID If the splice failed. In this case both hdr + * and pkt are unchanged. + * + * @note The base pkt remains valid after the completion of the splice, + * however changes that affect its length may yield unpredictable + * results when viewed through the returned splice handle. For best + * portability and predictable behavior, applications should regard the + * base packet as read only following a successful splice, with the + * exception of tailroom manipulation (which still requires application + * coordination if multiple splices exist on the same base packet whose + * tail is being pushed or pulled). + * + * @note Either packet input to this routine may itself be a splice, however + * individual implementations may impose limits on how deeply splices + * may be nested and fail the attempted splice if those limits are + * exceeded. + * + * @note The packets used to create a splice may reside in different pools, + * however individual implementations may require that both reside in + * the same pool and fail the attempted splice if this restriction is + * not observed. Upon return odp_packet_pool() returns the pool id of + * the header packet. + * + * @note Once successfully spliced, the base packet may be freed via + * odp_packet_free(), however the storage used to represent it will not + * be released until all splices based on it have themselves been freed. + */ +odp_packet_t odp_packet_splice(odp_packet_t hdr, + odp_packet_t pkt, uint32_t offset); + +/** + * Create a reference to a packet + * + * Create a (shared) reference to a base packet starting at a specified + * byte offset. A reference is simply a splice with a zero-length header. + * + * @param pkt Handle of the base packet for which a reference is to be + * created. + * @param offset Byte offset in the base packet at which shared reference is + * to begin. + * + * @return Handle of the reference packet + * @retval ODP_PACKET_INVALID Operation failed. Base packet remains unchanged. + * + * @note The zero-length header used to create a packet reference is always + * drawn from the same pool as the base packet. + * + * @note Because references are a type of splice, any bytes pushed onto the + * head of a reference (via odp_packet_push_head() or + * odp_packet_extend_head() are unique to this reference and are not + * seen by any other reference to the same base packet. + */ +odp_packet_t odp_packet_ref(odp_packet_t pkt, uint32_t offset); + +/** + * Tests if a packet is a splice + * + * A packet is a splice if it was created by odp_packet_splice() or + * odp_packet_ref(). Note that a splice may be a simple splice or a + * compound splice (a splice created from another splice). + * + * @param pkt Packet Handle + * + * @retval 0 Packet is not a splice + * @retval >0 Packet is a splice containing N individual packets + */ +int odp_packet_is_a_splice(odp_packet_t pkt); + +/** + * Tests if a packet is spliced + * + * A packet is spliced if a splice was created on it by odp_packet_splice() + * or odp_packet_ref(). + * + * @param pkt Packet Handle + * + * @retval 0 Packet is not spliced + * @retval >0 Packet has N splices based on it + */ +int odp_packet_is_spliced(odp_packet_t pkt); + /* * * Copy -- 2.7.4