07.03.2014 11:53, Alex Peshkoff wrote: > Main reason is performance compromise. It's faster to store required > information from IMessageMetadata somewhere in end-user code and use it > to access data instead of calling dozens of virtual functions.
There is no difference if you store offset got from a virtual function or a pointer got from other virtual function. In any case you'll have to perform "buffer+offset" operation every time you use the same or different buffer. With pointer you can receive new pointer only if buffer is changed. No difference between "buffer+Metadata.getOffset(i)" and "Buffer.getData(i)" which has the same "buffer+Metadata.getOffset(i)" inside. Calling of virtual function is cheaper than copying of kilobytes of data. > Currently one > can just pass single pointer to next buffer to fetch() - and this job is > done. Access to fields is usually performed by other layer of component. > I have no idea how can IBuffer performing offset-to-pointer conversions > help here. Exactly the same way: one just pass next (descendant of) IBuffer to fetch() and there is no need to worry how this IBuffer keeps information internally. Default TPlainBuffer can keep all values in single piece of memory, someone can invent TScatteredBuffer for any reason and so on. Polymorphism will allow server code to work with all of them. > Not sure it's possible for SQLDA where memory for fields allocated by > user. It is. If you have in engine a piece of code that looks like this: "p = Buffer.getData(i)", then in plain buffer object getData() can be implemented as "return buffer+Metadata.getOffset(i)" while in SQLDA-based buffer if will be "return sqlda->sqlvars[i].sqldata". No difference for calling code, no need in gathering data from user buffers into internal one. "Zero copy" is a good thing. -- WBR, SD. ------------------------------------------------------------------------------ Subversion Kills Productivity. Get off Subversion & Make the Move to Perforce. With Perforce, you get hassle-free workflows. Merge that actually works. Faster operations. Version large binaries. Built-in WAN optimization and the freedom to use Git, Perforce or both. Make the move to Perforce. http://pubads.g.doubleclick.net/gampad/clk?id=122218951&iu=/4140/ostg.clktrk Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
