On Wed, Dec 13, 2006 at 11:19:40PM -0800, Angus Leeming wrote:
> Enrico Forestieri wrote:
[...]
> It's more efficient to create a string of the desired size...
>
> std::string s(64, std::string::value_type());
> See
> http://www.dinkumware.com/manuals/?manual=compleat&page=string2.html#basic_string::basic_string
>
> I guess that
> std::string s(64, char());
> would also work...
Yes, indeed. I am using that now.
> but why are you using a std::string rather than a std::vector<char>? Not
> that it matters, I guess, but the semantics of the latter as a buffer store
> are rather clearer.
No, I can't use std::vector<char>. I have to use the types exactly matching
the implementation as found in the compiler include files.
Indeed, when trying this solution you get a load of errors.
> Given that these two functions are identical, would it not make sense to
> define a helper function template and invoke that:
Yes, this is the right thing to do! Many thanks Angus. Now I implemented
all the missing types, just to avoid future problems. The only thing that
remains to do is adjusting the do_get methods, but I'll postpone this task
until I find an optimal solution. For the moment that lonely do_get method
is sufficient.
> Given that the only difference between the different do_put functions is
> the size of the std::string needed to store the data from
> string_num_put_facet.put, I'd suggest that you extend the helper function
> to take a std::size_t argument too...
The problem here is that I don't know the needed size in advance. Looking
at how the do_put methods are implemented in the STLport library, I came
to the conclusion that 64 is a safe value.
--
Enrico
Index: src/support/docstring.C
===================================================================
--- src/support/docstring.C (revision 16272)
+++ src/support/docstring.C (working copy)
@@ -440,52 +440,65 @@ public:
protected:
iter_type
- do_put(iter_type oit, std::ios_base & b, char_type fill, long v) const
+ do_put(iter_type oit, std::ios_base & b, char_type fill, bool v) const
{
- if (fill >= 0x80)
- throw num_put_failure();
-
- std::string s;
- // 64 is large enough
- s.resize(64);
- string_num_put_facet f;
- std::string::const_iterator cit = s.begin();
- std::string::const_iterator end =
- f.put(s.begin(), b, fill, v);
- for (; cit != end; ++cit, ++oit)
- *oit = *cit;
+ return do_put_helper(oit, b, fill, v);
+ }
- return oit;
+ iter_type
+ do_put(iter_type oit, std::ios_base & b, char_type fill, long v) const
+ {
+ return do_put_helper(oit, b, fill, v);
}
iter_type
do_put(iter_type oit, std::ios_base & b, char_type fill, unsigned long
v) const
{
- if (fill >= 0x80)
- throw num_put_failure();
+ return do_put_helper(oit, b, fill, v);
+ }
- std::string s;
- // 64 is large enough
- s.resize(64);
- string_num_put_facet f;
- std::string::const_iterator cit = s.begin();
- std::string::const_iterator end =
- f.put(s.begin(), b, fill, v);
- for (; cit != end; ++cit, ++oit)
- *oit = *cit;
+#ifdef _GLIBCXX_USE_LONG_LONG
+ iter_type
+ do_put(iter_type oit, std::ios_base & b, char_type fill, long long v)
const
+ {
+ return do_put_helper(oit, b, fill, v);
+ }
- return oit;
+ iter_type
+ do_put(iter_type oit, std::ios_base & b, char_type fill, unsigned long
long v) const
+ {
+ return do_put_helper(oit, b, fill, v);
}
+#endif
iter_type
do_put(iter_type oit, std::ios_base & b, char_type fill, double v) const
{
+ return do_put_helper(oit, b, fill, v);
+ }
+
+ iter_type
+ do_put(iter_type oit, std::ios_base & b, char_type fill, long double v)
const
+ {
+ return do_put_helper(oit, b, fill, v);
+ }
+
+ iter_type
+ do_put(iter_type oit, std::ios_base & b, char_type fill, void const *
v) const
+ {
+ return do_put_helper(oit, b, fill, v);
+ }
+
+private:
+ template <typename ValueType>
+ iter_type
+ do_put_helper(iter_type oit, std::ios_base & b, char_type fill,
ValueType v) const
+ {
if (fill >= 0x80)
throw num_put_failure();
- std::string s;
// 64 is large enough
- s.resize(64);
+ std::string s(64, '\0');
string_num_put_facet f;
std::string::const_iterator cit = s.begin();
std::string::const_iterator end =
