IsTextUnicode function (winbase.h)

Article
10/13/2021

Determines if a buffer is likely to contain a form of Unicode text.

Syntax

BOOL IsTextUnicode(
  [in]                const VOID *lpv,
  [in]                int        iSize,
  [in, out, optional] LPINT      lpiResult
);

Parameters

[in] lpv

Pointer to the input buffer to examine.

[in] iSize

Size, in bytes, of the input buffer indicated by lpv.

[in, out, optional] lpiResult

On input, pointer to the tests to apply to the input buffer text. On output, this parameter receives the results of the specified tests: 1 if the contents of the buffer pass a test, 0 for failure. Only flags that are set upon input to the function are significant upon output.

If lpiResult is NULL, the function uses all available tests to determine if the data in the buffer is likely to be Unicode text.

This parameter can be one or more of the following values. Values can be combined with binary "OR".

Value	Meaning
IS_TEXT_UNICODE_ASCII16	The text is Unicode, and contains only zero-extended ASCII values/characters.
IS_TEXT_UNICODE_REVERSE_ASCII16	Same as the preceding, except that the Unicode text is byte-reversed.
IS_TEXT_UNICODE_STATISTICS	The text is probably Unicode, with the determination made by applying statistical analysis. Absolute certainty is not guaranteed. See the Remarks section.
IS_TEXT_UNICODE_REVERSE_STATISTICS	Same as the preceding, except that the text that is probably Unicode is byte-reversed.
IS_TEXT_UNICODE_CONTROLS	The text contains Unicode representations of one or more of these nonprinting characters: RETURN, LINEFEED, SPACE, CJK_SPACE, TAB.
IS_TEXT_UNICODE_REVERSE_CONTROLS	Same as the preceding, except that the Unicode characters are byte-reversed.
IS_TEXT_UNICODE_BUFFER_TOO_SMALL	There are too few characters in the buffer for meaningful analysis (fewer than two bytes).
IS_TEXT_UNICODE_SIGNATURE	The text contains the Unicode byte-order mark (BOM) 0xFEFF as its first character.
IS_TEXT_UNICODE_REVERSE_SIGNATURE	The text contains the Unicode byte-reversed byte-order mark (Reverse BOM) 0xFFFE as its first character.
IS_TEXT_UNICODE_ILLEGAL_CHARS	The text contains one of these Unicode-illegal characters: embedded Reverse BOM, UNICODE_NUL, CRLF (packed into one word), or 0xFFFF.
IS_TEXT_UNICODE_ODD_LENGTH	The number of characters in the string is odd. A string of odd length cannot (by definition) be Unicode text.
IS_TEXT_UNICODE_NULL_BYTES	The text contains null bytes, which indicate non-ASCII text.
IS_TEXT_UNICODE_UNICODE_MASK	The value is a combination of IS_TEXT_UNICODE_ASCII16, IS_TEXT_UNICODE_STATISTICS, IS_TEXT_UNICODE_CONTROLS, IS_TEXT_UNICODE_SIGNATURE.
IS_TEXT_UNICODE_REVERSE_MASK	The value is a combination of IS_TEXT_UNICODE_REVERSE_ASCII16, IS_TEXT_UNICODE_REVERSE_STATISTICS, IS_TEXT_UNICODE_REVERSE_CONTROLS, IS_TEXT_UNICODE_REVERSE_SIGNATURE.
IS_TEXT_UNICODE_NOT_UNICODE_MASK	The value is a combination of IS_TEXT_UNICODE_ILLEGAL_CHARS, IS_TEXT_UNICODE_ODD_LENGTH, and two currently unused bit flags.
IS_TEXT_UNICODE_NOT_ASCII_MASK	The value is a combination of IS_TEXT_UNICODE_NULL_BYTES and three currently unused bit flags.

Return value

Returns a nonzero value if the data in the buffer passes the specified tests. The function returns 0 if the data in the buffer does not pass the specified tests.

Remarks

This function uses various statistical and deterministic methods to make its determination, under the control of flags passed in the lpiResult parameter. When the function returns, the results of such tests are reported using the same parameter.

The IS_TEXT_UNICODE_STATISTICS and IS_TEXT_UNICODE_REVERSE_STATISTICS tests use statistical analysis. These tests are not foolproof. The statistical tests assume certain amounts of variation between low and high bytes in a string, and some ASCII strings can slip through. For example, if lpv indicates the ASCII string 0x41, 0x0A, 0x0D, 0x1D (A\n\r^Z), the string passes the IS_TEXT_UNICODE_STATISTICS test, although failure would be preferable.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winbase.h (include Windows.h)
Library	Advapi32.lib
DLL	Advapi32.dll