What kind of string is a bstr string?

A BSTR (Basic string or binary string) is a string data type that is used by COM, Automation, and Interop functions. Use the BSTR data type in all interfaces that will be accessed from script.
Indeed, what kind of data type is a BSTR?
A BSTR (Basic string or binary string) is a string data type that is used by COM, Automation, and Interop functions.
In fact, which is BSTR wrapper for the Visual Basic string type? _bstr_t -- A C++ class wrapper for the Visual Basic string type CComBSTR -- Yet another C++ class wrapper for the Visual Basic string type used predominately in ATL code
Similarly, where does a BSTR point in a string?
A BSTR is a pointer. The pointer points to the first character of the data string, not to the length prefix. BSTRs are allocated using COM memory allocation functions, so they can be returned from methods without concern for memory allocation. The following code is incorrect:
In this manner, when do you need to convert a C string to BSTR?
BSTR /C String conversions are required if: You are writing multiple language applications, such as C++ DLL's accessed by Visual Basic applications. This article deals with the following C/MFC/ATL string types: The demo project is just an MFC dialog based application with buttons for each type of conversion.

20 Similar Question Found

How to construct a bstr wrapped by a _ bstr _ t?

Constructs a _bstr_t object. Copies a BSTR into the BSTR wrapped by a _bstr_t. Links a _bstr_t wrapper to a BSTR. Constructs a copy of the encapsulated BSTR. Returns the BSTR wrapped by a _bstr_t and detaches the BSTR from the _bstr_t. Points to the BSTR wrapped by a _bstr_t. Points to the beginning of the BSTR wrapped by the _bstr_t.

How does the _ bstr _ t class work in bstr?

A _bstr_t object encapsulates the BSTR data type. The class manages resource allocation and deallocation through function calls to SysAllocString and SysFreeString and other BSTR APIs when appropriate. The _bstr_t class uses reference counting to avoid excessive overhead. Constructs a _bstr_t object.

How to return the bstr wrapped by a _ bstr _ t?

Returns the BSTR wrapped by a _bstr_t and detaches the BSTR from the _bstr_t. Points to the BSTR wrapped by a _bstr_t.

How to convert a string to a bstr string?

The _bstr_t object is a way to encapsulate wide character BSTR strings. A BSTR string has a length value and does not use a null character to terminate the string, but the string type you convert to may require a terminating null.

Can a bstr be stored as a utf-16 encoded string?

That's lossy since BSTR stores a utf-16 encoded Unicode string. Unless you want to encode in utf-8. You'll find helper methods to do this, as well as manipulate the resulting string, in the ICU library. That truncates any strings containing null characters, even though BSTR and std::wstring can both store them correctly. – JoeG Jul 6 '11 at 13:57

Is there standard code snippet to convert bstr to std : : string?

Someone can use BSTR wrapper like CComBSTR or MS's CString. But because I can't use ATL or MFC in MinGW compiler, is there standard code snippet to convert BSTR to std::string (or std::wstring) and vice versa? Are there also some non-MS wrappers for BSTR similar to CComBSTR? Thanks to everyone who helped me out in any way!

Can a bstr string be terminated by null?

A BSTR string has a length value and does not use a null character to terminate the string, but the string type you convert to may require a terminating null.

What is the length of a string in bstr?

A debugger that examines the memory location of this variable will now reveal a length prefix containing the value 34. This is the expected value for a 17-byte character string that is represented as a wide-string literal through the inclusion of the "L" string prefix. The debugger will also show the terminator that appears after the data string.

How to free the bstr string in cstring class?

CString class also contains a member function AllocSysString () which returns the BSTR string corresponding to the CString object. Use the API SysFreeString to free the BSTR string when we no longer need the BSTR string. void f (BSTR bStr) { CString csStr = bStr; //or csStr (bStr); ...

When do you need to convert a vb string to bstr?

So a VB string knows it's own length. In addition, all VB strings are Unicode (16 bits per character). BSTR /C String conversions are required if: You are writing multiple language applications, such as C++ DLL's accessed by Visual Basic applications. This article deals with the following C/MFC/ATL string types:

How to convert bstr to c string in atl code?

CComBSTR -- Yet another C++ class wrapper for the Visual Basic string type used predominately in ATL code The demo project is just an MFC dialog based application with buttons for each type of conversion. It is built using VC++ 6.0. It uses a couple of support functions you may find helpful:

How to convert std string to bstr in c + +?

Below are the functions I use to convert BSTR to std::string and std::string to BSTR respectively:

How to convert a securestring string to a bstr?

Marshal.SecureStringToBSTR, which converts the SecureString string value to a binary string (BSTR) recognized by COM. Marshal.SecureStringToCoTaskMemAnsi and Marshal.SecureStringToGlobalAllocAnsi, which copy the SecureString string value to an ANSI string in unmanaged memory.

Where does a bstr point in a string?

A BSTR is a pointer. The pointer points to the first character of the data string, not to the length prefix. BSTRs are allocated using COM memory allocation functions, so they can be returned from methods without concern for memory allocation. The following code is incorrect:

Is the bstr variable the same as the string?

However, for the purposes of this article, I will not consider such cases.) A BSTR variable in C++ is actually a pointer to the first character of the string. In fact, the type BSTR is defined this way: This is very unfortunate, because in reality a BSTR is not the same as a Unicode string.

How to check if a bstr is a null string?

Checks if the encapsulated BSTR is a NULL string. Compares two _bstr_t objects. Extract the pointers to the encapsulated Unicode or multibyte BSTR object. Header: <comutil.h>

What's the difference between bstr and basic string?

A BSTR (Basic string or binary string) is a string data type that is used by COM, Automation, and Interop functions. Use the BSTR data type in all interfaces that will be accessed from script. A BSTR is a composite data type that consists of a length prefix, a data string, and a terminator. The following table describes these components.

What to do with string pointed to by bstr?

String pointed to by BSTR must be allocated with SysAllocString () family functions. String pointed to by LPOLESTR is usually to be allocated with CoTaskMemAlloc () (this should be looked up in the documentation to the COM call accepting/returning it).

How to append string to string in string builder?

Append (StringBuilder) Appends the string representation of a specified string builder to this instance.

How is the memory allocated for a bstr?

BSTRs are allocated using COM memory allocation functions, so they can be returned from methods without concern for memory allocation. The following code is incorrect: This code builds (compiles and links) correctly, but it will not function properly because the string does not have a length prefix.