From 84faaa7bbf38f61bc27e35604e4d5c8e6f9bf9ce Mon Sep 17 00:00:00 2001 From: Beman Date: Thu, 20 Nov 2014 15:38:25 -0500 Subject: [PATCH] Rename the conversion functions to discourage unthinking use of the in-place versions as these are unsafe in that they effectively break the type system by treating the buffer as an undescriminated union. Remove the synonym functions based on names popularized by BSD, OS X, and Linux since these are permitted to be implemented as macros, which would cause endless difficulties if encountered. --- doc/buffers.html | 688 ++++++++++++++++++++++++++++ include/boost/endian/conversion.hpp | 108 +++-- 2 files changed, 739 insertions(+), 57 deletions(-) create mode 100644 doc/buffers.html diff --git a/doc/buffers.html b/doc/buffers.html new file mode 100644 index 0000000..aaf7a72 --- /dev/null +++ b/doc/buffers.html @@ -0,0 +1,688 @@ + + + + + + + +Endian Arithmetic Types + + + + + + + + + + + + +
+ +boost.png (6897 bytes) + + Endian Buffer Types +
+ + + + + +
Boost Home     + Endian Home     + Conversion Functions     + Arithmetic Types     + Buffer Types
+ +

+ + + + + + + + + + + + + + +
+ Contents
+ Introduction
+ Example
+ Limitations
+ Feature set
+ Enums and typedefs
+ Class template endian
+     + Synopsis
+     Members
+    Stream inserter
+    Stream extractor
+ FAQ
+ Design
+ Experience
+ Motivating use cases
+ C++11
+ Compilation
+ Acknowledgements +
+ Headers
+ <boost/endian/conversion.hpp>
+ <boost/endian/arithmetic.hpp>
+

Introduction

+

Header boost/endian/buffers.hpp +provides integer and floating point binary types with control over +byte order, value type, size, and alignment. Typedefs provide easy-to-use names +for common configurations.

+

These types provide portable byte-holders for integer data, independent of +particular computer architectures. Use cases almost always involve I/O, either via files or +network connections. Although data portability is the primary motivation, these +integer byte-holders may +also be used to reduce memory use, file size, or network activity since they +provide binary integer sizes not otherwise available.

+

Such integer byte-holder types are traditionally called +endian types. See the +Wikipedia for +a full +exploration of endianness, including definitions of big +endian and little endian.

+

Boost endian integers provide the same full set of C++ assignment, +arithmetic, and relational operators as C++ standard integral types, with +the standard semantics.

+

Unary arithmetic operators are +, -, ~, +!, prefix and postfix -- and ++. Binary +arithmetic operators are +, +=, -, +-=, *, *=, /, /=, +%/ %=, &, &=, |, |=, +^, ^=, <<, <<=, >>, +>>=. Binary relational operators are ==, !=, +<, <=, >, >=.

+

Automatic implicit conversion to the underlying value type is provided. An +conversion constructor from the underlying value type is provided.

+

Example

+

The endian_example.cpp program writes a +binary file containing four byte big-endian and little-endian integers:

+
+ 
#include <iostream>
+#include <cstdio>
+#include <boost/endian/arithmetic.hpp>
+#include <boost/static_assert.hpp>
+
+using namespace boost::endian;
+
+namespace 
+{
+  //  This is an extract from a very widely used GIS file format. It seems odd
+  //  to mix big and little endians in the same file - but this is a real-world
+  //  format and users wishing to write low level code manipulating these files
+  //  must deal with the mixed endianness.
+
+  struct header
+  {
+    big_int32_t     file_code;
+    big_int32_t     file_length;
+    little_int32_t  version;
+    little_int32_t  shape_type;
+  };
+
+  const char* filename = "test.dat";
+}
+
+int main(int, char* [])
+{
+  BOOST_STATIC_ASSERT(sizeof(header) == 16U);  // reality check
+  
+  header h;
+
+  h.file_code   = 0x01020304;
+  h.file_length = sizeof(header);
+  h.version     = 1;
+  h.shape_type  = 0x01020304;
+
+  //  Low-level I/O such as POSIX read/write or <cstdio> fread/fwrite is sometimes
+  //  used for binary file operations when ultimate efficiency is important. Such
+  //  I/O is often performed in some C++ wrapper class, but to drive home the
+  //  point that endian integers are often used in fairly low-level code that does
+  //  bulk I/O operations, <cstdio> fopen/fwrite is used for I/O in this example.
+
+  std::FILE* fi = std::fopen(filename, "wb");  // MUST BE BINARY
+  
+  if (!fi)
+  {
+    std::cout << "could not open " << filename << '\n';
+    return 1;
+  }
+
+  if (std::fwrite(&h, sizeof(header), 1, fi)!= 1)
+  {
+    std::cout << "write failure for " << filename << '\n';
+    return 1;
+  }
+
+  std::fclose(fi);
+
+  std::cout << "created file " << filename << '\n';
+
+  return 0;
+}
+
+
+

After compiling and executing endian_example.cpp, +a hex dump of test.dat shows:

+
+ 
01020304 00000010 01000000 04030201
+
+

Notice that the first two 32-bit integers are big endian while the second two +are little endian, even though the machine this was compiled and run on was +little endian.

+

Limitations

+

Requires <climits> CHAR_BIT == 8. If CHAR_BIT +is some other value, compilation will result in an #error. This +restriction is in place because the design, implementation, testing, and +documentation has only considered issues related to 8-bit bytes, and there have +been no real-world use cases presented for other sizes.

+

In C++03, endian does not meet the requirements for POD types +because it has constructors, private data members, and a base class. This means +that common use cases are relying on unspecified behavior in that the C++ +Standard does not guarantee memory layout for non-POD types. This has not been a +problem in practice since all known C++ compilers do layout memory as if +endian were a POD type. In C++11, it is possible to specify the +default constructor as trivial, and private data members and base classes will +no longer disqualify a type from being a POD. Thus under C++11, endian +will no longer be relying on unspecified behavior.

+

Feature set

+ +

Enums and typedefs

+

Two scoped enums are provided:

+
+ 
enum class order {big, little, native};
+
+enum class align {no, yes};
+
+

One class template is provided:

+
+ 
template <order Order, typename T, std::size_t n_bits, align A = align::no>
+  class endian_arithmetic;
+
+
+

Typedefs, such as big_int32_t, provide convenient naming +conventions for common use cases:

+
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
NameEndiannessAlignmentSignSizes in bits (n)
big_intn_tbigyessigned16,32,64
big_uintn_tbigyesunsigned16,32,64
big_floatn_tbigyessigned32,64
big_intn_utbignosigned8,16,24,32,40,48,56,64
big_uintn_utbignounsigned8,16,24,32,40,48,56,64
big_floatn_utbignosigned32,64
little_intn_tlittleyessigned16,32,64
little_uintn_tlittleyesunsigned16,32,64
little_floatn_tlittleyessigned32,64
little_intn_utlittlenosigned8,16,24,32,40,48,56,64
little_uintn_utlittlenounsigned8,16,24,32,40,48,56,64
little_floatn_utlittlenosigned32,64
native_floatn_tnativeyessigned32,64
native_intn_utnativenosigned8,16,24,32,40,48,56,64
native_uintn_utnativenounsigned8,16,24,32,40,48,56,64
native_floatn_utnativenosigned32,64
+
+

The unaligned types do not cause compilers to insert padding bytes in classes +and structs. This is an important characteristic that can be exploited to minimize wasted space in +memory, files, and network transmissions.

+

Warning: +Code that uses aligned types is possibly non-portable because alignment +requirements vary between hardware architectures and because alignment may be +affected by compiler switches or pragmas. For example, alignment of an 64-bit +integer may be to a 32-bit boundary on a 32-bit machine. Furthermore, aligned types +are only available on architectures with 16, 32, and 64-bit integer types.

+

Note: One-byte types +have identical +functionality. They are provided to improve code readability and searchability.

+

Class template endian_arithmetic

+

An endian is an integer byte-holder with user-specified +endianness, value type, size, and alignment. The +usual operations on integers are supplied.

+

Synopsis

+
namespace boost
+{
+  namespace endian
+  {
+    //  C++11 features emulated if not available
+   
+    enum class order
+    {
+      big,                             // big-endian
+      little,                          // little-endian
+      native = implementation-defined  // same as order::big or order::little
+    };
+
+    enum class align {no, yes};            
+
+    template <order Order, class T, std::size_t n_bits, align A = align::no>
+    class endian
+    {
+    public:
+      typedef T value_type;
+
+      // if BOOST_ENDIAN_FORCE_PODNESS is defined && C++11 POD's are not
+      // available then these two constructors will not be present
+      endian() noexcept = default;
+      endian(T v) noexcept;
+
+      endian& operator=(T v) noexcept;
+      operator T() const noexcept;
+      const char* data() const noexcept;
+
+      // arithmetic operations
+      //   note that additional operations are provided by the value_type 
+      value_type operator+(const endian& x) noexcept;
+      endian& operator+=(endian& x, value_type y) noexcept;
+      endian& operator-=(endian& x, value_type y) noexcept;
+      endian& operator*=(endian& x, value_type y) noexcept;
+      endian& operator/=(endian& x, value_type y) noexcept;
+      endian& operator%=(endian& x, value_type y) noexcept;
+      endian& operator&=(endian& x, value_type y) noexcept;
+      endian& operator|=(endian& x, value_type y) noexcept;
+      endian& operator^=(endian& x, value_type y) noexcept;
+      endian& operator<<=(endian& x, value_type y) noexcept;
+      endian& operator>>=(endian& x, value_type y noexcept;
+      value_type operator<<(const endian& x, value_type y) noexcept;
+      value_type operator>>(const endian& x, value_type y) noexcept;
+      endian& operator++(endian& x) noexcept;
+      endian& operator--(endian& x) noexcept;
+      endian operator++(endian& x, int) noexcept;
+      endian operator--(endian& x, int) noexcept;
+
+      // Stream inserter
+      template <class charT, class traits>
+      friend std::basic_ostream<charT, traits>&
+        operator<<(std::basic_ostream<charT, traits>& os, const T& x);
+
+      // Stream extractor 
+      template <class charT, class traits>
+      friend std::basic_istream<charT, traits>&
+        operator>>(std::basic_istream<charT, traits>& is, T& x);
+    };
+
+    // typedefs  
+
+    // aligned big endian floating point types
+    typedef endian<order::big, float, 32, align::yes>       big_float32_t;
+    typedef endian<order::big, double, 64, align::yes>      big_float64_t;
+
+    // aligned little endian floating point types
+    typedef endian<order::little, float, 32, align::yes>    little_float32_t;
+    typedef endian<order::little, double, 64, align::yes>   little_float64_t;
+
+    // unaligned big endian floating point types
+    typedef endian<order::big, float, 32, align::no>        big_float32un_t;
+    typedef endian<order::big, double, 64, align::no>       big_float64un_t;
+  
+    // unaligned little endian floating point types
+    typedef endian<order::little, float, 32, align::no>     little_float32un_t;
+    typedef endian<order::little, double, 64, align::no>    little_float64un_t;
+  
+    // aligned big endian signed integer types
+    typedef endian<order::big, int16_t, 16, align::yes>     big_int16_t;
+    typedef endian<order::big, int32_t, 32, align::yes>     big_int32_t;
+    typedef endian<order::big, int64_t, 64, align::yes>     big_int64_t;
+
+    // aligned big endian unsigned integer types
+    typedef endian<order::big, uint16_t, 16, align::yes>    big_uint16_t;
+    typedef endian<order::big, uint32_t, 32, align::yes>    big_uint32_t;
+    typedef endian<order::big, uint64_t, 64, align::yes>    big_uint64_t;
+
+    // aligned little endian signed integer types
+    typedef endian<order::little, int16_t, 16, align::yes>  little_int16_t;
+    typedef endian<order::little, int32_t, 32, align::yes>  little_int32_t;
+    typedef endian<order::little, int64_t, 64, align::yes>  little_int64_t;
+
+    // aligned little endian unsigned integer types
+    typedef endian<order::little, uint16_t, 16, align::yes> little_uint16_t;
+    typedef endian<order::little, uint32_t, 32, align::yes> little_uint32_t;
+    typedef endian<order::little, uint64_t, 64, align::yes> little_uint64_t;
+
+    // aligned native endian typedefs are not provided because
+    // <cstdint> types are superior for that use case
+  
+    // unaligned big endian signed integer types
+    typedef endian<order::big, int_least8_t, 8>        big_int8_ut;
+    typedef endian<order::big, int_least16_t, 16>      big_int16_ut;
+    typedef endian<order::big, int_least32_t, 24>      big_int24_ut;
+    typedef endian<order::big, int_least32_t, 32>      big_int32_ut;
+    typedef endian<order::big, int_least64_t, 40>      big_int40_ut;
+    typedef endian<order::big, int_least64_t, 48>      big_int48_ut;
+    typedef endian<order::big, int_least64_t, 56>      big_int56_ut;
+    typedef endian<order::big, int_least64_t, 64>      big_int64_ut;
+  
+    // unaligned big endian unsigned integer types
+    typedef endian<order::big, uint_least8_t, 8>       big_uint8_ut;
+    typedef endian<order::big, uint_least16_t, 16>     big_uint16_ut;
+    typedef endian<order::big, uint_least32_t, 24>     big_uint24_ut;
+    typedef endian<order::big, uint_least32_t, 32>     big_uint32_ut;
+    typedef endian<order::big, uint_least64_t, 40>     big_uint40_ut;
+    typedef endian<order::big, uint_least64_t, 48>     big_uint48_ut;
+    typedef endian<order::big, uint_least64_t, 56>     big_uint56_ut;
+    typedef endian<order::big, uint_least64_t, 64>     big_uint64_ut;
+  
+    // unaligned little endian signed integer types
+    typedef endian<order::little, int_least8_t, 8>     little_int8_ut;
+    typedef endian<order::little, int_least16_t, 16>   little_int16_ut;
+    typedef endian<order::little, int_least32_t, 24>   little_int24_ut;
+    typedef endian<order::little, int_least32_t, 32>   little_int32_ut;
+    typedef endian<order::little, int_least64_t, 40>   little_int40_ut;
+    typedef endian<order::little, int_least64_t, 48>   little_int48_ut;
+    typedef endian<order::little, int_least64_t, 56>   little_int56_ut;
+    typedef endian<order::little, int_least64_t, 64>   little_int64_ut;
+  
+    // unaligned little endian unsigned integer types
+    typedef endian<order::little, uint_least8_t, 8>    little_uint8_ut;
+    typedef endian<order::little, uint_least16_t, 16>  little_uint16_ut;
+    typedef endian<order::little, uint_least32_t, 24>  little_uint24_ut;
+    typedef endian<order::little, uint_least32_t, 32>  little_uint32_ut;
+    typedef endian<order::little, uint_least64_t, 40>  little_uint40_ut;
+    typedef endian<order::little, uint_least64_t, 48>  little_uint48_ut;
+    typedef endian<order::little, uint_least64_t, 56>  little_uint56_ut;
+    typedef endian<order::little, uint_least64_t, 64>  little_uint64_ut;
+  
+  // unaligned native endian signed integer types
+    typedef implementation-defined_int8_t   native_int8_ut;
+    typedef implementation-defined_int16_t  native_int16_ut;
+    typedef implementation-defined_int24_t  native_int24_ut;
+    typedef implementation-defined_int32_t  native_int32_ut;
+    typedef implementation-defined_int40_t  native_int40_ut;
+    typedef implementation-defined_int48_t  native_int48_ut;
+    typedef implementation-defined_int56_t  native_int56_ut;
+    typedef implementation-defined_int64_t  native_int64_ut;
+
+  // unaligned native endian unsigned integer types
+    typedef implementation-defined_uint8_t   native_uint8_ut;
+    typedef implementation-defined_uint16_t  native_uint16_ut;
+    typedef implementation-defined_uint24_t  native_uint24_ut;
+    typedef implementation-defined_uint32_t  native_uint32_ut;
+    typedef implementation-defined_uint40_t  native_uint40_ut;
+    typedef implementation-defined_uint48_t  native_uint48_ut;
+    typedef implementation-defined_uint56_t  native_uint56_ut;
+    typedef implementation-defined_uint64_t  native_uint64_ut;
+
+  } // namespace endian
+} // namespace boost
+

The implementation-defined text above is either +big or little according to the endianness of the +platform.

+

Members

+
+ 
endian() = default;  // C++03: endian(){}
+
+
+

Effects: Constructs an object of type endian<E, T, n_bits, A>.

+
+
endian(T v);
+
+

Effects: Constructs an object of type endian<E, T, n_bits, A>.

+

Postcondition: x == v, where x is the +constructed object.

+
+
endian& operator=(T v);
+
+

Postcondition: x == v, where x is the + constructed object.

+

Returns: *this.

+
+
operator T() const;
+
+

Returns: The current value stored in *this, converted to +value_type.

+
+
const char* data() const;
+
+

Returns: A pointer to the first byte of the endian binary value stored +in *this.

+
+

Other operators

+

Other operators on endian objects are forwarded to the equivalent +operator on value_type.

+

Stream inserter

+
template <class charT, class traits>
+friend std::basic_ostream<charT, traits>&
+  operator<<(std::basic_ostream<charT, traits>& os, const T& x);
+
+
+

Returns: os << +x.

+
+

Stream extractor

+
template <class charT, class traits>
+friend std::basic_istream<charT, traits>&
+  operator>>(std::basic_istream<charT, traits>& is, T& x);
+
+
+

Effects: As if:

+
+ 
T i;
+if (is >> i)
+  x = i;
+
+
+

Returns: is.

+
+

FAQ

+ +

See the Endian home page FAQ for a library-wide +FAQ.

+ +

Why not just use Boost.Serialization? Serialization involves a +conversion for every object involved in I/O. Endian integers require no +conversion or copying. They are already in the desired format for binary I/O. +Thus they can be read or written in bulk.

+

Are endian types POD's? Yes for C++11. No for C++03, although several +macros are available to force PODness in all cases.

+

What are the implications of endian integer types not being POD's with C++03 +compilers? They +can't be used in unions. Also, compilers aren't required to align or lay +out storage in portable ways, although this potential problem hasn't prevented +use of Boost.Endian with +real compilers.

+

What good is native endianness? It provides alignment and +size guarantees not available from the built-in types. It eases generic +programming.

+

Why bother with the aligned endian types? Aligned integer operations +may be faster (as much as 10 to 20 times faster) if the endianness and alignment of +the type matches the endianness and alignment requirements of the machine. The code, +however, is +likely to be somewhat less portable than with the unaligned types.

+

Why provide the arithmetic operations? Providing a full set of operations reduces program +clutter and makes code both easier to write and to read. Consider +incrementing a variable in a record. It is very convenient to write:

+
    ++record.foo;
+

Rather than:

+
    int temp(record.foo);
+    ++temp;
+    record.foo = temp;
+

Design considerations for Boost.Endian types

+ +

Experience

+

Classes with similar functionality have been independently developed by +several Boost programmers and used very successful in high-value, high-use +applications for many years. These independently developed endian libraries +often evolved from C libraries that were also widely used. Endian types have proven widely useful across a wide +range of computer architectures and applications.

+

Motivating use cases

+

Neil Mayhew writes: "I can also provide a meaningful use-case for this +library: reading TrueType font files from disk and processing the contents. The +data format has fixed endianness (big) and has unaligned values in various +places. Using Boost.Endian simplifies and cleans the code wonderfully."

+

C++11

+

The availability of the C++11 + +Defaulted Functions feature is detected automatically, and will be used if +present to ensure that objects of class endian are trivial, and +thus POD's.

+

Compilation

+

Boost.Endian is implemented entirely within headers, with no need to link to +any Boost object libraries.

+

Several macros allow user control over features:

+ +

Acknowledgements

+

Original design developed by Darin Adler based on classes developed by Mark +Borgerding. Four original class templates combined into a single endian +class template by Beman Dawes, who put the library together, provided +documentation, added the typedefs, and also added the unrolled_byte_loops +sign partial specialization to correctly extend the sign when cover integer size +differs from endian representation size. Vicente Botet and other reviewers +suggested supporting floating point types.

+
+

Last revised: +20 November, 2014

+

© Copyright Beman Dawes, 2006-2009, 2013

+

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/include/boost/endian/conversion.hpp b/include/boost/endian/conversion.hpp index d1ceecb..5e43319 100644 --- a/include/boost/endian/conversion.hpp +++ b/include/boost/endian/conversion.hpp @@ -41,91 +41,85 @@ namespace endian // suggested by Phil Endecott // //--------------------------------------------------------------------------------------// - // reverse byte order (i.e. endianness) - // - inline int8_t reverse_value(int8_t x) BOOST_NOEXCEPT; - inline int16_t reverse_value(int16_t x) BOOST_NOEXCEPT; - inline int32_t reverse_value(int32_t x) BOOST_NOEXCEPT; - inline int64_t reverse_value(int64_t x) BOOST_NOEXCEPT; - inline uint8_t reverse_value(uint8_t x) BOOST_NOEXCEPT; - inline uint16_t reverse_value(uint16_t x) BOOST_NOEXCEPT; - inline uint32_t reverse_value(uint32_t x) BOOST_NOEXCEPT; - inline uint64_t reverse_value(uint64_t x) BOOST_NOEXCEPT; - - // reverse_value overloads for floating point types as requested by Vicente - // Botet and others. + // reverse byte order (i.e. endianness) + + inline int8_t reverse(int8_t x) BOOST_NOEXCEPT; + inline int16_t reverse(int16_t x) BOOST_NOEXCEPT; + inline int32_t reverse(int32_t x) BOOST_NOEXCEPT; + inline int64_t reverse(int64_t x) BOOST_NOEXCEPT; + inline uint8_t reverse(uint8_t x) BOOST_NOEXCEPT; + inline uint16_t reverse(uint16_t x) BOOST_NOEXCEPT; + inline uint32_t reverse(uint32_t x) BOOST_NOEXCEPT; + inline uint64_t reverse(uint64_t x) BOOST_NOEXCEPT; // TODO: Track progress of Floating-Point Typedefs Having Specified Widths proposal (N3626) - inline float reverse_value(float x) BOOST_NOEXCEPT; - inline double reverse_value(double x) BOOST_NOEXCEPT; + inline float reverse(float x) BOOST_NOEXCEPT; + inline double reverse(double x) BOOST_NOEXCEPT; + + // The conversion function templates, both value returning and in-place, are specified + // and implemented by calling the preceding overloads of reverse(). As a consequence, + // there is no need for explicit overloads in addition to the generic templates. + + // generic byte order reverse + template + ReversibleValue reverse(ReversibleValue from) BOOST_NOEXCEPT; + + // reverse byte order unless native endianness is big - // reverse bytes unless native endianness is big - // possible names: reverse_unless_native_big, reverse_value_unless_big, reverse_unless_big template - inline ReversibleValue big_endian_value(ReversibleValue x) BOOST_NOEXCEPT; - // Return: x if native endian order is big, otherwise reverse_value(x) + inline ReversibleValue big(ReversibleValue x) BOOST_NOEXCEPT; + // Returns: x if native endian order is big, otherwise reverse(x) + + // reverse byte order unless native endianness is little - // reverse bytes unless native endianness is little - // possible names: reverse_unless_native_little, reverse_value_unless_little, reverse_unless_little template - inline ReversibleValue little_endian_value(ReversibleValue x) BOOST_NOEXCEPT; - // Return: x if native endian order is little, otherwise reverse_value(x); + inline ReversibleValue little(ReversibleValue x) BOOST_NOEXCEPT; + // Returns: x if native endian order is little, otherwise reverse(x) - // synonyms based on names popularized by BSD, e.g. OS X, Linux - // "h" stands for "host" (i.e. native), "be" for "big endian", "le" for "little endian" - template inline T bswap(T x) BOOST_NOEXCEPT {return reverse_value(x);} - template inline T htobe(T host) BOOST_NOEXCEPT {return big_endian_value(host);} - template inline T htole(T host) BOOST_NOEXCEPT {return little_endian_value(host);} - template inline T betoh(T big) BOOST_NOEXCEPT {return big_endian_value(big);} - template inline T letoh(T little) BOOST_NOEXCEPT {return little_endian_value(little);} + // runtime byte order determination - // compile-time generic byte order conversion - template - ReversibleValue convert_value(ReversibleValue from) BOOST_NOEXCEPT; - - // runtime actual byte-order determination inline BOOST_SCOPED_ENUM(order) effective_order(BOOST_SCOPED_ENUM(order) o) BOOST_NOEXCEPT; - // Return: o if o != native, otherwise big or little depending on native ordering + // Return: o if o != native, otherwise big or little depending on native ordering - // runtime byte-order conversion + // runtime byte order reverse + template - ReversibleValue convert_value(ReversibleValue from, BOOST_SCOPED_ENUM(order) from_order, - BOOST_SCOPED_ENUM(order) to_order) BOOST_NOEXCEPT; + ReversibleValue reverse(ReversibleValue from, BOOST_SCOPED_ENUM(order) from_order, + BOOST_SCOPED_ENUM(order) to_order) BOOST_NOEXCEPT; + + // Q: What happended to bswap, htobe, and the other synonym functions based on names + // popularized by BSD, OS X, and Linux? + // A: Turned out these may be implemented as macros on some systems. Ditto POSIX names + // for such functionality. Since macros would cause endless problems with these + // function names, and these functions are just synonyms anyhow, they have been + // removed. //--------------------------------------------------------------------------------------// -// modify in place interface // +// in place interface // //--------------------------------------------------------------------------------------// - // reverse byte order (i.e. endianness) + // reverse byte order (i.e. endianness) // template - inline void reverse(Value& x) BOOST_NOEXCEPT; + inline void reverse_in_place(Value& x) BOOST_NOEXCEPT; // reverse unless native endianness is big template - inline void big_endian(Reversible& x) BOOST_NOEXCEPT; + inline void big_in_place(Reversible& x) BOOST_NOEXCEPT; // Effects: none if native endian order is big, otherwise reverse(x) // reverse unless native endianness is little template - inline void little_endian(Reversible& x) BOOST_NOEXCEPT; + inline void little_in_place(Reversible& x) BOOST_NOEXCEPT; // Effects: none if native endian order is little, otherwise reverse(x); - // synonyms based on names popularized by BSD, e.g. OS X, Linux. - // "h" stands for "host" (i.e. native), "be" for "big endian", - // "le" for "little endian", "m" for "modify in place" - template inline void mbswap(T& x) BOOST_NOEXCEPT {reverse(x);} - template inline void mhtobe(T& host) BOOST_NOEXCEPT {big_endian(host);} - template inline void mhtole(T& host) BOOST_NOEXCEPT {little_endian(host);} - template inline void mbetoh(T& big) BOOST_NOEXCEPT {big_endian(big);} - template inline void mletoh(T& little) BOOST_NOEXCEPT {little_endian(little);} - - // compile-time generic byte order conversion + // generic byte order conversion template - void convert(Reversible& x) BOOST_NOEXCEPT; + void reverse_in_place(Reversible& x) BOOST_NOEXCEPT; - // runtime byte-order conversion + // runtime byte-order reverse template - void convert(Reversible& x, BOOST_SCOPED_ENUM(order) from_order, + void reverse_in_place(Reversible& x, BOOST_SCOPED_ENUM(order) from_order, BOOST_SCOPED_ENUM(order) to_order) BOOST_NOEXCEPT; //----------------------------------- end synopsis -------------------------------------//