Mechanism and method for accessing data in a shared memory

摘要

In a shared memory data are allocated into topics 32, accessible through respective constant addresses. A number of buffers 36 is allocated to each topic, the number being equal to that of clients 40 accessing the topic plus two for each server 50. The clients and servers have active access pointers 42, 52 which are directed to the buffers by an active access pointer director 38 based on the transaction request. Director 38 identifies the buffer 58 containing the most recent data and directs newly communicating clients 40 to them. Server read/write transactions are directed to a further buffer 70 where the most recent data are copied. Most recent data is only guaranteed at the time of transaction. Zero-copy operations, whereby data is accessed without copying at operating system level, uses machine assembly language transactions only ensuring that the most recent data is lock free. Topics include airspeed, waypoints, flight plans.