Most-significant-byte-first ordering is traditionally called "big endian" -ordering and the least-significant-byte-first is traditionally called +ordering and least-significant-byte-first is traditionally called "little-endian" ordering. The names are derived from Jonathan Swift's satirical novel @@ -135,7 +135,7 @@ And programmers may also want to use the library when minimizing either internal external data sizes is advantageous.
The Boost.Endian library provides three different approaches to dealing with +
Boost.Endian provides three different approaches to dealing with
endianness. All three approaches support integers, floating point types
except long double, and user-define types (UDTs).
Endian buffer types - The application uses the provided endian buffer types to hold values, and explicitly converts to and from the built-in integer and -floating point types to perform arithmetic. Buffer lengths of 1 through 8 bytes -are supported, rather than just 2, 4, and 8 bytes. The types may be aligned or -unaligned.
+floating point types. Buffer sizes of 8, 16, 24, 32, 40, 48, 56, and 64 bits (i.e. +1, 2, 3, 4, 5, 6, 7, and 8 bytes) are provided. Unaligned integer buffer types +are provided for all sizes, unaligned floating point buffer types are provided +for 32 and 64 bit sizes, and aligned buffer types are provided for 16, 32, and +64-bit sizes. The provided specific types are typedefs for a generic class +template that may be used directly for less common use cases. -Endian arithmetic types - The application uses the provided endian -arithmetic types, which supply the same operations as the built-in C++ -arithmetic types. All conversions are implicit. Arithmetic integer types with -lengths of 1 through 8 bytes are supported, rather than just 2, 4, and 8 byte -integers. The types may be aligned.
+Endian arithmetic types - The +application uses the provided endian arithmetic types, which supply the same +operations as the built-in C++ arithmetic types. All conversions are implicit. +Arithmetic sizes of 8, 16, 24, 32, 40, 48, 56, and 64 bits (i.e. 1, 2, 3, 4, 5, +6, 7, and 8 bytes) are provided. Unaligned integer types are provided for all +sizes, unaligned floating point types are provided for 32 and 64 bit sizes, and aligned +arithmetic types are provided for 16, 32, and 64-bit sizes. The provided +specific types are typedefs for a generic class template that may be used +directly for less common use cases.
@@ -178,15 +185,16 @@ Choosing the Approach page.Most compilers, including GCC, Clang, and Visual C++, supply built-in support for byte swapping intrinsics. -The Endian library uses these intrinsics when available since they may result in smaller and faster generated code, particularly for release +The Endian library uses these intrinsics when available since they may result in smaller and faster generated code, particularly for +optimized builds.
Defining the macro BOOST_ENDIAN_NO_INTRINSICS will suppress use
-of the intrinsics. Useful when intrinsic headers such as
-byteswap.h are not being found by your compiler, perhaps because it
+of the intrinsics. This is useful when a compiler has no intrinsic support or
+fails to locate the appropriate header, perhaps because it
is an older release or has very limited supporting libraries.
The macro BOOST_ENDIAN_INTRINSIC_MSG is defined as
either "no byte swap intrinsics" or a string describing the
-particular set of intrinsics being used. Useful for eliminating missing
+particular set of intrinsics being used. This is useful for eliminating missing
intrinsics as a source of performance issues.
Does endianness have any uses outside of portable binary file or network I/O formats?
-Using the unaligned integer types to save internal or external -memory space is a minor secondary use.
+Using the unaligned integer types with a size tailored to the application's +needs is a minor secondary use that saves internal or external memory space. For +example, using
big_int40_buf_utorbig_int40_utin a +large array saves a lot of space compared to one of the 64-bit types.
Why bother with binary I/O? Why not just use C++ Standard Library stream inserters and extractors?
@@ -583,7 +593,7 @@ Blechmann, Tim Moore, tymofey, Tomas Puverle, Vincente Botet, Yuval Ronen and Vitaly Budovsk. Apologies if anyone has been missed.Last revised: -09 February, 2015
+12 February, 2015© Copyright Beman Dawes, 2011, 2013
Distributed under the Boost Software License, Version 1.0. See www.boost.org/ LICENSE_1_0.txt