c++ - How do I call the UrlCanonicalize API function correctly? -

hresult urlcanonicalize(   _in_     pctstr pszurl,   _out_    ptstr pszcanonicalized,   _inout_  dword *pcchcanonicalized,   dword dwflags ); 

example:

lpctstr pszurl  = url.c_str(); lpstr pszoutput = new char[ strurl.length ]; dword* dwcount = new dword[  strurl.length ]; hres =  urlcanonicalize( pszurl, pszoutput,dwcount, url_escape_unsafe ); 

output:

e_invalidarg 

this api fails , returns e_invalidarg every time try call it. please give me working code snippet call urlcanonicalize function.

if know c++ language, the sdk documentation function pretty tells need know:

• you pass c-style nul-terminated string contains url.
• you pass pointer buffer receive output string.
• you pass 1 or more flags customize function's behavior.
• and finally, returns hresult value, error code. if succeeds, value s_ok. if fails, other error code.

it works this:

std::wstring originalurl(l"http://www.example.com/hello/cruel/../world/");  // allocate buffer of appropriate length. // needs @ least long input string. std::wstring canonicalurl(originalurl.length() + 1, l'\0'); dword length = originalurl.length() + 1;  // call function modify string. hresult hr = urlcanonicalize(originalurl.c_str(), // input string                              &canonicalurl[0],    // buffer                              &length,             // pointer dword contains length of buffer                              url_unescape | url_escape_unsafe); if (succeeded(hr)) {     // function succeeded.     // canonicalized url in canonicalurl string.     messagebox(nullptr, canonicalurl.c_str(), l"the url is:", mb_ok);    } else {     // function failed.     // hr variable contains error code.     throw std::runtime_error("the urlcanonicalize function failed."); } 

if want make sure buffer sufficiently long (and avoid having handle error), use constant internet_max_url_length (declared in wininet.h) when allocating it:

std::wstring canonicalurl(internet_max_url_length, l'\0'); dword length = internet_max_url_length; 

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the code tried has couple of problems:

1. you've incorrectly initialized dwcount variable. function wants pointer, doesn't mean should declare variable pointer. nor want array; single dword value. need declare regular dword, , use address-of operator (&) pass function pointer variable. right now, you're passing function garbage, it's failing.

2. you're using c-style strings, should avoid in c++ code. use c++ string class (std::wstring windows code), exception safe , manages memory you. know, c_str() member function gives easy access c-style nul-terminated string c apis want. works fine, not need use raw character arrays yourself. avoid new whenever possible.

potentially, third problem you're trying use c++ string type std::string instead of std::wstring. former 8-bit string type , doesn't support unicode in windows environment. want std::wstring, wide string unicode support. it's windows api functions expect if have unicode symbol defined project (which default).