CompareString
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4/8/2010
This function compares two character strings, using the locale specified by the given identifier as the basis for the comparison.
Note
If you specify a locale with the LCID (Locale ID) parameter and that locale is not installed or available on the Windows® phone, the function fails with ERROR_INVALID_PARAMETER. To determine whether the locale is supported or not, call IsValidLocale.
Syntax
int CompareString(
LCID Locale,
DWORD dwCmpFlags,
LPCTSTR lpString1,
int cchCount1,
LPCTSTR lpString2,
int cchCount2
);
Parameters
Locale
[in] Value that specifies the locale used for the comparison. This parameter can be one of the following predefined locale identifiers. The following table shows the values this parameter can take.Value Description LOCALE_SYSTEM_DEFAULT
The system's default locale.
LOCALE_USER_DEFAULT
The current user's default locale.
This parameter can also be a locale identifier created by the MAKELCID macro.
dwCmpFlags
[in] Set of flags that indicate how the function compares the two strings. By default, these flags are not set. This parameter can specify zero to get the default behavior, or it can be any combination of the following values. The following table shows the values this parameter can take.Value Description NORM_IGNORECASE
Ignore case.
NORM_IGNOREKANATYPE
Do not differentiate between Hiragana and Katakana characters. Corresponding Hiragana and Katakana characters compare as equal.
NORM_IGNORENONSPACE
Ignore nonspacing characters.
NORM_IGNORESYMBOLS
Ignore symbols.
NORM_IGNOREWIDTH
Do not differentiate between a single-byte character and the same character as a double-byte character.
SORT_STRINGSORT
Treat punctuation the same as symbols.
- lpString1
[in] Pointer to the first string to be compared.
- cchCount1
[in] Size, in characters, of the string pointed to by the lpString1 parameter. If this parameter is –1, the string is assumed to be null terminated and the length is calculated automatically.
- lpString2
[in] Pointer to the second string to be compared.
- cchCount2
[in] Size, in characters, of the string pointed to by the lpString2 parameter. If this parameter is –1, the string is assumed to be null terminated and the length is calculated automatically.
Return Value
If the function succeeds, the return value is one of the following values.
| Value | Description |
|---|---|
CSTR_LESS_THAN |
The string pointed to by the lpString1 parameter is less in lexical value than the string pointed to by the lpString2 parameter. |
CSTR_EQUAL |
The string pointed to by lpString1 is equal in lexical value to the string pointed to by lpString2. |
CSTR_GREATER_THAN |
The string pointed to by lpString1 is greater in lexical value than the string pointed to by lpString2. |
Zero indicates failure. To get extended error information, call the GetLastError function. Possible values for GetLastError include the following:
- ERROR_INVALID_FLAGS
- ERROR_INVALID_PARAMETER
Remarks
Notice that if the return value is CSTR_EQUAL, which is the value 2, the two strings are "equal" in the collation sense, though not necessarily identical.
To maintain the C run-time convention of comparing strings, the value 2 can be subtracted from a nonzero return value. The meaning of < 0, ==0 and > 0 is then consistent with the C run times.
If the two strings are of different lengths, they are compared up to the length of the shortest one. If they are equal to that point, then the return value will indicate that the longer string is greater. For more information about locale identifiers, see National Language support (NLS) Locale Identifiers.
Strings are compared using what is called a "string sort" technique. In a string sort, the hyphen and apostrophe are treated just like any other nonalphanumeric symbols: they come before the alphanumeric symbols.
The following list of words is sorted using a string sort.
bill's |
t-ant |
billet |
t-aria |
bills |
tanya |
can't |
sue's |
cannot |
sued |
cant |
sues |
co-op |
we're |
con |
went |
coop |
were |
The LCMapString function defaults to using a word sort, but uses a string sort if their caller sets the SORT_STRINGSORT flag.
The CompareString function is optimized to run at the highest speed when dwCmpFlags is set to zero or NORM_IGNORECASE, and cchCount1 and cchCount2 have the value –1.
Requirements
| Header | winnls.h |
| Library | Coreloc.lib |
| Windows Embedded CE | Windows CE 1.0 and later |
| Windows Mobile | Windows Mobile Version 5.0 and later |