Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I'd do it with a <code>BSTR</code> since it means you don't have to call into native twice per string, once to get the length and then once to get the contents.</p> <p>With a <code>BSTR</code> the marshaller will take care of deallocating the <code>BSTR</code> with the right memory manager so you can safely pass it out of your C++ code.</p> <p><strong>C++</strong></p> <pre><code>#include &lt;comutil.h&gt; BSTR GetSomeText() { return ::SysAllocString(L"Greetings from the native world!"); } </code></pre> <p><strong>C#</strong></p> <pre><code>[DllImport(@"test.dll", CallingConvention = CallingConvention.Cdecl)] [return: MarshalAs(UnmanagedType.BStr)] private static extern string GetSomeText(); </code></pre> <p>There is one minor drawback of the <code>BSTR</code>, namely that it carries a UTF-16 payload but your source data may well be <code>char*</code>.</p> <p>To overcome this you can wrap up the conversion from <code>char*</code> to <code>BSTR</code> like this:</p> <pre><code>BSTR ANSItoBSTR(const char* input) { BSTR result = NULL; int lenA = lstrlenA(input); int lenW = ::MultiByteToWideChar(CP_ACP, 0, input, lenA, NULL, 0); if (lenW &gt; 0) { result = ::SysAllocStringLen(0, lenW); ::MultiByteToWideChar(CP_ACP, 0, input, lenA, result, lenW); } return result; } </code></pre> <p>That's the hardest one out of the way, and now it's easy to add other wrappers to convert to <code>BSTR</code> from <code>LPWSTR</code>, <code>std::string</code>, <code>std::wstring</code> etc.</p>
    singulars
    1. This table or related slice is empty.
    1. POHow to return text from Native (C++) code
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USDavid Heffernan
    1. USDavid Heffernan
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POHow to return text from Native (C++) code
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CO@rturrado Many thanks indeed for your corrections in the edit.
      singulars
      1. PO
      1. USDavid Heffernan
    2. COthe answer is very helpful, so it deserves it. BTW, just realising that 'may well char*' is missing a 'be'.
      singulars
      1. PO
      1. USrturrado
    3. COYou can pass `-1` as the fourth argument to `MultiByteToWideChar` to have the function calculate the length of the string automatically; avoids the need to call `lstrlenA` yourself.
      singulars
      1. PO
      1. USFrerich Raabe
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload