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Author SHA1 Message Date
922ce7b8ae Branch at revision 46530
[SVN r46531]
2008-06-19 18:57:10 +00:00
bacb5d6752 Attempt to work around problem with allocator casts in Boost.Function
[SVN r46446]
2008-06-17 13:59:04 +00:00
04040ae566 Improve documentation on the size/efficiency of boost::function objects
[SVN r44852]
2008-04-28 14:11:46 +00:00
2 changed files with 5 additions and 5 deletions

View File

@ -24,7 +24,7 @@
<para> And, of course, function pointers have several advantages over Boost.Function:
<itemizedlist spacing="compact">
<listitem><para> Function pointers are smaller (the size of one pointer instead of three) </para></listitem>
<listitem><para> Function pointers are smaller (the size of one pointer instead of four or more) </para></listitem>
<listitem><para> Function pointers are faster (Boost.Function may require two calls through function pointers) </para></listitem>
<listitem><para> Function pointers are backward-compatible with C libraries.</para></listitem>
<listitem><para> More readable error messages. </para></listitem>
@ -37,12 +37,12 @@
<section>
<title>Function object wrapper size</title>
<para> Function object wrappers will be the size of two function pointers plus one function pointer or data pointer (whichever is larger). On common 32-bit platforms, this amounts to 12 bytes per wrapper. Additionally, the function object target will be allocated on the heap.</para>
<para> Function object wrappers will be the size of a struct containing a member function pointer and two data pointers. The actual size can vary significantly depending on the underlying platform; on 32-bit Mac OS X with GCC, this amounts to 16 bytes, while it is 32 bytes Windows with Visual C++. Additionally, the function object target may be allocated on the heap, if it cannot be placed into the small-object buffer in the <code>boost::function</code> object.</para>
</section>
<section>
<title>Copying efficiency</title>
<para> Copying function object wrappers may require allocating memory for a copy of the function object target. The default allocator may be replaced with a faster custom allocator or one may choose to allow the function object wrappers to only store function object targets by reference (using <computeroutput>ref</computeroutput>) if the cost of this cloning becomes prohibitive.</para>
<para> Copying function object wrappers may require allocating memory for a copy of the function object target. The default allocator may be replaced with a faster custom allocator or one may choose to allow the function object wrappers to only store function object targets by reference (using <computeroutput>ref</computeroutput>) if the cost of this cloning becomes prohibitive. Small function objects can be stored within the <code>boost::function</code> object itself, improving copying efficiency.</para>
</section>
<section>

View File

@ -432,7 +432,7 @@ namespace boost {
// can't do the static_cast that we should do.
const functor_wrapper_type* f =
(const functor_wrapper_type*)(in_buffer.obj_ptr);
wrapper_allocator_type wrapper_allocator(static_cast<wrapper_allocator_type const &>(*f));
wrapper_allocator_type wrapper_allocator(static_cast<Allocator const &>(*f));
wrapper_allocator_pointer_type copy = wrapper_allocator.allocate(1);
wrapper_allocator.construct(copy, *f);
@ -443,7 +443,7 @@ namespace boost {
/* Cast from the void pointer to the functor_wrapper_type */
functor_wrapper_type* victim =
static_cast<functor_wrapper_type*>(in_buffer.obj_ptr);
wrapper_allocator_type wrapper_allocator(static_cast<wrapper_allocator_type const &>(*victim));
wrapper_allocator_type wrapper_allocator(static_cast<Allocator const &>(*victim));
wrapper_allocator.destroy(victim);
wrapper_allocator.deallocate(victim,1);
out_buffer.obj_ptr = 0;