diff options
Diffstat (limited to 'modules/README')
| -rw-r--r-- | modules/README | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/modules/README b/modules/README new file mode 100644 index 0000000..537ff2d --- /dev/null +++ b/modules/README @@ -0,0 +1,33 @@ +This file describes the protocol used for communicating packets. +See include/pdp.h and the sources in this directory for more info. + +There are 3 kinds of pdp messages: + +[pdp register_ro <packet_id>] +[pdp register_rw <packet_id>] +[pdp process] + +An object can receive a packet by catching the 3 kinds of messages: + +When a register_ro message is received, the object can call +pdp_packet_copy_ro(packet) to reseve a read only copy for itself. +The only operations on the packet at that time are read only +operations. + +The same goes for handling the register_rw message. You can +reserve a read/write copy by using pdp_packet_copy_rw(packet) + +When a process message is received, the object is allowed to start +processing the data. + +In the register_ro or register_rw phases, the object can inspect +the packet to see if it wants to register it (using pdp_packet_header +and pdp_packet_data operations) but it is not allowed to allocate other objects +in that phase. This is only allowed in the process phase. (or after +the receiving packet is registerd.) + +An object can send out a pdp message using the outlet_pdp(outlet, packet) +function. This sends out these 3 messages in sequence. It is best to +unregister a packet using pdp_packet_mark_unused(packet) before sending it out, +if it is no longer used by the sending object. This eliminates one extra +copy operation on the data. |