"Cliff Green" <cliffg@codewrangler.net> wrote in message news:web-41870932@bk2.webmaillogin.com...
I've dealt with (and written) endian utilities for many years, since almost my full career has involved writing software for heterogeneous distributed systems. I definitely think Boost needs a library to ease and simplify byte endian issues.
But I'm curious as to the rationale for these endian integer types - I've always written utilities to transform native (or user-defined) types into a serializable binary format - including the option for big-endian, little-endian (or in one project, for "receiver makes right" endianness). I've never had a need for code that performs operations on endian types, other than as "placeholders" for performing I/O with them (whether over a network, or disk I/O). Are there application use cases where the application never transforms into / out of native / UDT's, and always uses these (endian) types instead?
Sure. The usual application for me is a record (or page) oriented disk file. The app works with a record, but often only touches a portion of that record. The rest remains unchanged. Doing a byte-reversing copy of the entire record into a buffer would kill performance. Perhaps the best-known example of this is a page in a B-Tree. While the app using the B-tree may possible work with native or UDT types, the B-tree structural information on the page always uses the endian types. There is no reason to ever convert out of the endian types.
Specifically, I've written (templatized generic) utilities that take integers and append them to a character (byte) buffer in a specified endian format (and the converse transformation). (Non-integral types are also supported, with lots of caveats and warnings - floating point type swapping is full of pitfalls, and any endian / byte swapping on a UDT has the expected restrictions - POD single element, no pointers or references, etc.) I would expect these types of utilities to be used in some form of serialization design (e.g. with Boost.Serialization).
Yes, but those are a somewhat different set of needs.
Anyway, I'm just trying to expand my awareness of various endian related designs.
Yes, they are lots of fun. In industrial database applications there is also a lot of money riding on getting endianess right. You have to be able to build files in one environment, and sell them to folks in other environments without the buyers ever realizing you aren't building with their favorite platform. --Beman