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WindowsCreateStringReference function (winstring.h)

  • Makale

Creates a new string reference based on the specified string.

Syntax

HRESULT WindowsCreateStringReference(
  PCWSTR         sourceString,
  UINT32         length,
  HSTRING_HEADER *hstringHeader,
  HSTRING        *string
);

Parameters

sourceString

Type: [in] PCWSTR

A null-terminated string to use as the source for the new HSTRING.

A value of NULL represents the empty string, if the value of length is 0. Should be allocated on the stack frame.

length

Type: [in] UINT32

The length of sourceString, in Unicode characters. Must be 0 if sourceString is NULL. If greater than 0, sourceString must have a terminating null character.

hstringHeader

Type: [out] HSTRING_HEADER*

A pointer to a structure that the Windows Runtime uses to identify string as a string reference, or fast-pass string.

string

Type: [out] HSTRING*

A pointer to the newly created string, or NULL if an error occurs. Any existing content in string is overwritten. The HSTRING is a standard handle type.

Return value

Type: HRESULT

This function can return one of these values.

Return code Description
S_OK
 The HSTRING was created successfully.
E_INVALIDARG
 Either string or hstringHeader is NULL, or string is not null-terminated.
E_OUTOFMEMORY
 Failed to allocate the new HSTRING.
E_POINTER
 sourceString is NULL and length is non-zero.

Remarks

Use the WindowsCreateStringReference function to create an HSTRING from an existing string. This kind of HSTRING is named a fast-pass string. Unlike an HSTRING created by the WindowsCreateString function, the lifetime of the backing buffer in the new HSTRING is not managed by the Windows Runtime. The caller allocates sourceString on the stack frame, together with an uninitialized HSTRING_HEADER, to avoid a heap allocation and eliminate the risk of a memory leak. The caller must ensure that sourceString and the contents of hstringHeader remain unchanged during the lifetime of the attached HSTRING.

You don't need to call the WindowsDeleteString function to de-allocate a fast-pass HSTRING created by the WindowsCreateStringReference function.

To create an empty HSTRING, pass NULL for sourceString and 0 for length.

The Windows Runtime tracks a fast-pass string by using an HSTRING_HEADER structure, which is returned in the hstringHeader out parameter. Do not change the contents of the HSTRING_HEADER.

Requirements

Requirement Value
Minimum supported client Windows 8 [desktop apps | UWP apps]
Minimum supported server Windows Server 2012 [desktop apps | UWP apps]
Target Platform Windows
Header winstring.h

See also

WindowsCreateString

WindowsDeleteString