RtlInitAnsiString function (wdm.h)

The RtlInitAnsiString routine initializes a counted string of ANSI characters.


NTSYSAPI VOID RtlInitAnsiString(
  [out]          PANSI_STRING          DestinationString,
  [in, optional] __drv_aliasesMem PCSZ SourceString


[out] DestinationString

A pointer to the ANSI_STRING structure to be initialized.

[in, optional] SourceString

A pointer to a null-terminated character string. This string is used to initialize the counted string pointed to by DestinationString.

Return value



This routine initializes a counted character string.

The routine copies the SourceString pointer value to the Buffer member of the ANSI_STRING structure pointed to by DestinationString. The Length member of this structure is set to the length, in bytes, of the source string, excluding the terminating null. The MaximumLength member of the structure is set to the length, in bytes, of the source string, including the terminating null. If SourceString is NULL, Length and MaximumLength are both set to zero.

RtlInitAnsiString does not alter the source string pointed to by SourceString.

Note  If the source string is longer than MAXUSHORT - 1 bytes, RtlInitAnsiString sets the Length member of the ANSI_STRING structure pointed to by DestinationString to MAXUSHORT - 1, and sets the MaximumLength member of this structure to MAXUSHORT. In this case, the Length and MaximumLength values misrepresent the length of the null-terminated source string, and relying on the accuracy of these values is potentially dangerous.
Callers of RtlInitAnsiString can be running at IRQL <= DISPATCH_LEVEL if the DestinationString buffer is nonpageable. Usually, callers run at IRQL = PASSIVE_LEVEL because most other RtlXxxString routines cannot be called at IRQL > PASSIVE_LEVEL.

The RTL_CONSTANT_STRING macro creates a string or Unicode string structure to hold a counted string.

  [in]  PCSZ SourceString

  [in]  PCWSTR SourceString

RTL_CONSTANT_STRING returns either a string structure or Unicode string structure.

The RTL_CONSTANT_STRING macro replaces the RtlInitAnsiString, RtlInitString, and RtlInitUnicodeString routines when passing a constant string.

You can use RTL_CONSTANT_STRING to initialize global variables.


Minimum supported client Available starting with Windows 2000.
Target Platform Universal
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
IRQL Any level (See Remarks section)

See also