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+
+ |
+ + Endian Library | +
| Boost Home Conversion Reference + Types Reference Tutorial | +
The Boost Endian Library provides facilities to deal with endianness. See +Introduction to endianness below for +the basics of endianness.
+ +The library provides two approaches to dealing with integer endianness:
+ ++ ++ +Endian conversions for native integers - The application uses the +built-in integer types, and calls the provided conversion functions to swap +bytes as needed. Both mutating and non-mutating conversions are supplied, and +each comes in unconditional and conditional variants. This approach is simple +and efficient, but is less flexible in terms of size and alignment, and can be +hard to manage in code with many logical paths involving endianness transitions.
+ +Endian integer types
+ +
Consider a C++ program that defines variables x, y, and z as 16, 32, and +64-bit integers, respectively. There are several ways a processor might layout +the individual bytes for these variables in memory:
+ +| int16_t x = 0x0A0B; | +|||||
| Big Endian | +Little Endian | +||||
| Value | +0A | +0B | +Value | +0B | +0A | +
| Address | +...0 | +...1 | +Address | +...0 | +...1 | +
| int32_t y = 0x0A0B0C0D; | +|||||||||
| Big Endian | +Little Endian | +||||||||
| Value | +0A | +0B | +0C | +0D | +Value | +0D | +0C | +0B | +0A | +
| Address | +...0 | +...1 | +...2 | +...3 | +Address | +...0 | +...1 | +...2 | +...3 | +
| int64_t z = 0x0A0B0C0D0E0F0102; | +|||||||||||||||||
| Big Endian | +Little Endian | +||||||||||||||||
| Value | +0A | +0B | +0C | +0D | +0E | +0F | +01 | +02 | +Value | +02 | +01 | +0F | +0E | +0D | +0C | +0B | +0A | +
| Address | +...0 | +...1 | +...2 | +...3 | +...4 | +...5 | +...6 | +...7 | +Address | +...0 | +...1 | +...2 | +...3 | +...4 | +...5 | +...6 | +...7 | +
The most-significant byte first ordering is traditionally called "big endian" +ordering and the least-significant byte first is traditionally called +"little-endian" ordering. Although some other orderings are possible, most +modern uses are as shown above. The names are derived from + +Jonathan Swift's satirical novel + +Gulliver’s Travels, where rival kingdom's opened their soft-boiled eggs +at different ends.
+ +Intel processors are traditionally little endian while many others are big +endian. Some processors can switch endianness, so which is in use depends on the +operating system. The Wikipedia's +Endianness entry lists +details for many processors and operating systems.
+ +External memory, such as disks, generally uses the same endianness as the +operating system. Networks traditionally use big endian ordering, so this is +sometimes referred as network endianness.
+Last revised: +27 May, 2011
+© Copyright Beman Dawes, 2011
+Distributed under the Boost Software License, Version 1.0. See +www.boost.org/ LICENSE_1_0.txt
+ ++ + + + \ No newline at end of file diff --git a/libs/endian/doc/integers.html b/libs/endian/doc/types.html similarity index 98% rename from libs/endian/doc/integers.html rename to libs/endian/doc/types.html index 0cd0893..d968153 100644 --- a/libs/endian/doc/integers.html +++ b/libs/endian/doc/types.html @@ -6,7 +6,7 @@
Last revised: -25 March, 2009
+27 May, 2011© Copyright Beman Dawes, 2006-2009
-Distributed under the Boost Software License, Version 1.0. (See accompanying -file LICENSE_1_0.txt or copy at -www.boost.org/ LICENSE_1_0.txt)
+Distributed under the Boost Software License, Version 1.0. See +www.boost.org/ LICENSE_1_0.txt
diff --git a/libs/endian/index.html b/libs/endian/index.html new file mode 100644 index 0000000..3ebbb5a --- /dev/null +++ b/libs/endian/index.html @@ -0,0 +1,14 @@ + + + + + +Automatic redirection failed, please go to +doc/index.html.© Copyright Beman Dawes, 2001
+Distributed under the Boost Software License, Version 1.0. +(See www.boost.org/LICENSE_1_0.txt) + +
+ + \ No newline at end of file