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The Boost Endian library manipulates the
endianness of integers
and user-defined types. It provides three approaches to dealing with endianness:
-conversion functions, buffer classes, and full arithmetic types. Each approach
+conversion functions, buffer classes, and arithmetic classes. Each approach
has use cases where it is preferred over the other approaches. The purpose of
-this RFC is to determine interest in adding all or any of these approaches to
-the C++ standard library.
+this RFC is to determine interest in adding all or any of these components to
+the C++ standard library or a library TS.
Introduction
+The Boost Endian documentation (www.boost.org/libs/endian/doc)
+provides an overview
+and detailed technical specifications for the
+conversion
+functions,
+arithmetic types, and
+buffer types.
+
+A separate discussion covers
+choosing
+between the three approaches provided by the library.
+For those not interested in plowing through the entire documentation, the
+Overall FAQ,
+Conversion
+FAQ,
+Arithmetic FAQ, and
+Buffers FAQ
+answer a lot of question likely to arise during standardization.
Motivation for standardization
+
+ - Lack of any one de facto standard endianness capability in either C or
+ C++. While most platforms provides some way to handle endianness in C, the
+ mechanism varies from platform to platform.
+ - Commonly used endian handling functions are extremely error prone. While
+ the Boost Endian conversion functions have the same problems, the buffer and
+ arithmetic classes do not.
+ - Surprisingly difficult to write and test yourself in a portable yet
+ efficient (i.e. using intrinsics) way.
+ - Explicit requests for standardization from Boost Endian users.
+ - The Boost library is existing practice with years of both implementation
+ and end-user experience.
+ - The committee has already failed once to standardize endian conversion
+ functions; perhaps now is time to do it right.
+
Impact on the standard library
+All three proposed approaches to endianness would be a pure additions to the
+standard library and would break no existing user code (modulo the usual
+namespace caveats).
Proposed wording
+The Boost Endian reference documentation for
+
+Conversion,
+
+Arithmetic, and
+Buffer
+approaches follows the standard library's Method of description
+[description], so provides a fairly close approximation of what proposed wording
+would look like. Actual proposed wording will be provided in a proposal document
+for any portions of the library of interest to the committee. Names will need
+the usual bikeshedding.
Questions for the Library Evolution Group
+
+ - How would you likely vote on a fully-worded and reviewed proposal to add a
+ standardized version of the Boost Endian conversion functions to the standard
+ library or a library TS?
+
+ - How would you likely vote on a fully-worded and reviewed proposal to add a
+ standardized version of the Boost Endian buffer classes to the standard
+ library or a library TS?
+
+ - How would you likely vote on a fully-worded and reviewed proposal to add a
+ standardized version of the Boost Endian arithmetic classes to the standard
+ library or a library TS?
+
Acknowledgements
+The original design for the arithmetic classes was developed by Darin Adler
+based on work by Mark Borgerding. The Boost documentation acknowledges
+45+
+other people.