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lotusny78@yahoo.com
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 Posted: Wed Apr 27, 2005 8:49 am Post subject: vectors and legacy APIs: what next |
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After you pass a vector to a legacy function, how do you use it if
other legacy functions expect a different type?
A Win32 example:
//The first call to DocumentProperties tells us the required
//buffer size in bytes
long bufferSizeNeeded =
DocumentProperties(0, hPrinter, printerName, 0, 0, 0);
vector<BYTE> resultDevMode(bufferSizeNeeded);
//Is this line OK??? Otherwise, how do we pass it back to API
PDEVMODE pResult = reinterpret_cast<PDEVMODE>(&resultDevMode[0]);
//DocumentProperties expects a PDEVMODE, but we used a vector
if(IDOK != DocumentProperties(0, hPrinter, printerName,
pResult, 0, DM_OUT_BUFFER))
throw(runtime_error("Can't get document properties"));
Thanks.
- Sean
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Nickolay Merkin
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| Posted: Thu Apr 28, 2005 12:32 pm Post subject: Re: vectors and legacy APIs: what next |
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Just an idea (I never used it):
template<class T, class U>
T* reinterpret_bytes( vector<U>& vec )
{
assert( vec.size() * sizeof(U) >= sizeof(T) );
return (T*) &vec[0];
}
template<class T, class U>
const T* reinterpret_cbytes( const vector<U>& vec )
{
assert( vec.size() * sizeof(U) >= sizeof(T) );
return (const T*) &vec[0];
}
///////////////////////////////
PDEVMODE pResult = reinterpret_bytes<PDEVMODE>(resultDevMode);
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unspammable@gmail.com
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| Posted: Fri Apr 29, 2005 1:39 am Post subject: Re: vectors and legacy APIs: what next |
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The line appears to be Ok. But if the only reaon you're using a vector
is that it manages its own memory you can use a smart pointer (like
auto_ptr) instead.
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Carl Barron
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| Posted: Sat Apr 30, 2005 3:58 pm Post subject: Re: vectors and legacy APIs: what next |
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[email]unspammable (AT) gmail (DOT) com[/email] <unspammable (AT) gmail (DOT) com> wrote:
| Quote: | The line appears to be Ok. But if the only reaon you're using a vector
is that it manages its own memory you can use a smart pointer (like
auto_ptr) instead.
void test() |
{
auto_ptr does not suport arrays example this is won't work
std::auto_ptr<char> foo(new char[256]);
std::strcpy(foo.get(),"Hello World");
// ouch dtr of auto_ptr usse delete not delete [].
}
struct array_deleter
{
template <class T> void operator () (T *x) {delete [] x;}
};
boost::shared_ptr<T> p(new T[256],array_deleter());
void get_data(p.get());
is better solution but it too has about two longs and a deleter
overhead so it is easier to use std::vector and be done with it...
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Seungbeom Kim
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| Posted: Sun May 01, 2005 11:05 am Post subject: Re: vectors and legacy APIs: what next |
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Carl Barron wrote:
| Quote: |
void test()
{
auto_ptr does not suport arrays example this is won't work
std::auto_ptr<char> foo(new char[256]);
std::strcpy(foo.get(),"Hello World");
// ouch dtr of auto_ptr usse delete not delete [].
}
struct array_deleter
{
template <class T> void operator () (T *x) {delete [] x;}
};
boost::shared_ptr<T> p(new T[256],array_deleter());
void get_data(p.get());
is better solution but it too has about two longs and a deleter
overhead so it is easier to use std::vector and be done with it...
|
Why not use boost::shared_array which does that for you?
--
Seungbeom Kim
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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