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Overview |
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Group |
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Quick Info
Windows NT
| Yes
| Win95
| Yes
| Win32s
| Yes
| Import Library
| kernel32.lib
| Header File
| winnls.h
| Unicode
| WinNT
| Platform Notes
| None
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CompareString
The
CompareString function compares two character strings, using the locale specified by the
given identifier as the basis for the comparison.
int CompareString(
LCID Locale,
| // locale identifier
|
DWORD dwCmpFlags,
| // comparison-style options
|
LPCTSTR lpString1,
| // pointer to first string
|
int cchCount1,
| // size, in bytes or characters, of first string
|
LPCTSTR lpString2,
| // pointer to second string
|
int cchCount2
| // size, in bytes or characters, of second string
|
);
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|
Parameters
Locale
Specifies the locale used for the comparison. This parameter can be one of the
following predefined locale identifiers:
Value
| Meaning
|
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
A 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:
Value
| Meaning
|
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
Points to the first string to be compared.
cchCount1
Specifies the size, in bytes (ANSI version) or characters (Unicode version),
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
Points to the second string to be compared.
cchCount2
Specifies the size, in bytes (ANSI version) or characters (Unicode version),
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 Values
If the function succeeds, the return value is one of the following values:
Value
| Meaning
|
-
| The string pointed to by the lpString1 parameter is less in lexical value than the string pointed to by the lpString2 parameter.
|
-
| The string pointed to by lpString1 is equal in lexical value to the string pointed to by lpString2.
|
-
| The string pointed to by lpString1 is greater in lexical value than the string pointed to by lpString2.
|
If the function fails, the return value is zero. To get extended error
information, call
GetLastError.
GetLastError may return one of the following error codes:
ERROR_INVALID_FLAGS
|
ERROR_INVALID_PARAMETER
|
Remarks
Notice that if the return value is 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
Locale Identifiers.
Typically, strings are compared using what is called a "word sort" technique.
In a word sort, all punctuation marks and other nonalphanumeric characters,
except for the hyphen and the apostrophe, come before any alphanumeric character.
The hyphen and the apostrophe are treated differently than the other
nonalphanumeric symbols, in order to ensure that words such as "coop" and "co-op" stay
together within a sorted list.
If the SORT_STRINGSORT flag is specified, 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 table shows a list of words sorted both ways:
Word Sort
| String Sort
|
| Word Sort
| String Sort
|
billet
| bill's
|
| t-ant
| t-ant
|
bills
| billet
|
| tanya
| t-aria
|
bill's
| bills
|
| t-aria
| tanya
|
cannot
| can't
|
| sued
| sue's
|
cant
| cannot
|
| sues
| sued
|
can't
| cant
|
| sue's
| sues
|
con
| co-op
|
| went
| we're
|
coop
| con
|
| were
| went
|
co-op
| coop
|
| we're
| were
|
The
lstrcmp and
lstrcmpi functions use a word sort. The
CompareString and
LCMapString functions default to using a word sort, but use 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 0 or NORM_IGNORECASE, and
cchCount1 and
cchCount2 have the value -1.
The
CompareString function ignores Arabic Kashidas during the comparison. Thus, if two strings
are identical save for the presence of Kashidas,
CompareString returns a value of 2; the strings are considered "equal" in the collation
sense, though they are not necessarily identical.
See Also
FoldString,
GetSystemDefaultLCID,
GetUserDefaultLCID,
LCMapString,
lstrcmp,
lstrcmpi,
MAKELCID
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