QCString Class Reference

Detailed Description

QCString inherits QByteArray, which is defined as QMemArray<char>. Since QCString is a QMemArray, it uses explicit sharing with a reference count.

QCString tries to behave like a more convenient const char *. The price of doing this is that some algorithms will perform badly. For example, append() is O(length()) since it scans for a null terminator. Although you might use QCString for text that is never exposed to the user, for most purposes, and especially for user-visible text, you should use QString. QString provides implicit sharing, Unicode and other internationalization support, and is well optimized.

Note that for the QCString methods that take a const char * parameter the const char * must either be 0 (null) or not-null and '\0' (NUL byte) terminated; otherwise the results are undefined.

A QCString that has not been assigned to anything is null, i.e. both the length and the data pointer is 0. A QCString that references the empty string ("", a single '\0' char) is empty. Both null and empty QCStrings are legal parameters to the methods. Assigning const char * 0 to QCString produces a null QCString.

The length() function returns the length of the string; resize() resizes the string and truncate() truncates the string. A string can be filled with a character using fill(). Strings can be left or right padded with characters using leftJustify() and rightJustify(). Characters, strings and regular expressions can be searched for using find() and findRev(), and counted using contains().

Strings and characters can be inserted with insert() and appended with append(). A string can be prepended with prepend(). Characters can be removed from the string with remove() and replaced with replace().

Portions of a string can be extracted using left(), right() and mid(). Whitespace can be removed using stripWhiteSpace() and simplifyWhiteSpace(). Strings can be converted to uppercase or lowercase with upper() and lower() respectively.

Strings that contain numbers can be converted to numbers with toShort(), toInt(), toLong(), toULong(), toFloat() and toDouble(). Numbers can be converted to strings with setNum().

Many operators are overloaded to work with QCStrings. QCString also supports some more obscure functions, e.g. sprintf(), setStr() and setExpand().

Note on Character Comparisons

In QCString the notion of uppercase and lowercase and of which character is greater than or less than another character is locale dependent. This affects functions which support a case insensitive option or which compare or lowercase or uppercase their arguments. Case insensitive operations and comparisons will be accurate if both strings contain only ASCII characters. (If $LC_CTYPE is set, most Unix systems do "the right thing".) Functions that this affects include contains(), find(), findRev(), operator<(), operator<=(), operator>(), operator>=(), lower() and upper().

This issue does not apply to QStrings since they represent characters using Unicode.

Performance note: The QCString methods for QRegExp searching are implemented by converting the QCString to a QString and performing the search on that. This implies a deep copy of the QCString data. If you are going to perform many QRegExp searches on a large QCString, you will get better performance by converting the QCString to a QString yourself, and then searching in the QString.

See also Collection Classes, Implicitly and Explicitly Shared Classes, Text Related Classes, and Non-GUI Classes.

Member Function Documentation

QCString::QCString ()

Constructs a null string.

See also isNull().

QCString::QCString ( int size )

If size > 0, then the first and last characters in the string are initialized to '\0'. All other characters are uninitialized.

See also resize() and isNull().

QCString::QCString ( const QCString & s )

Constructs a shallow copy s.

See also assign().

QCString::QCString ( const char * str )

If str is 0 a null string is created.

See also isNull().

QCString::QCString ( const char * str, uint maxsize )

Example:

    QCString str( "helloworld", 6 ); // assigns "hello" to str
    

If str contains a 0 byte within the first maxsize bytes, the resulting QCString will be terminated by this 0. If str is 0 a null string is created.

See also isNull().

QCString & QCString::append ( const char * str )

Appends string str to the string and returns a reference to the string. Equivalent to operator+=().

int QCString::contains ( char c, bool cs = TRUE ) const

The match is case sensitive if cs is TRUE, or case insensitive if cs if FALSE.

See also Note on character comparisons.

int QCString::contains ( const char * str, bool cs = TRUE ) const

Returns the number of times str occurs in the string.

The match is case sensitive if cs is TRUE, or case insensitive if cs if FALSE.

This function counts overlapping substrings, for example, "banana" contains two occurrences of "ana".

See also findRev() and Note on character comparisons.

int QCString::contains ( const QRegExp & rx ) const

Counts the number of overlapping occurrences of rx in the string.

Example:

    QString s = "banana and panama";
    QRegExp r = QRegExp( "a[nm]a", TRUE, FALSE );
    s.contains( r ); // 4 matches
    

See also find() and findRev().

Warning: If you want to apply this function repeatedly to the same string it is more efficient to convert the string to a QString and apply the function to that.

QCString QCString::copy () const

Returns a deep copy of this string.

See also detach().

bool QCString::fill ( char c, int len = -1 )

If len is negative, then the current string length is used.

Returns FALSE is len is nonnegative and there is not enough memory to resize the string; otherwise returns TRUE.

int QCString::find ( char c, int index = 0, bool cs = TRUE ) const

The search is case sensitive if cs is TRUE, or case insensitive if cs is FALSE.

Returns the position of c, or -1 if c could not be found.

See also Note on character comparisons.

Example: network/networkprotocol/nntp.cpp.

int QCString::find ( const char * str, int index = 0, bool cs = TRUE ) const

Finds the first occurrence of the string str, starting at position index.

The search is case sensitive if cs is TRUE, or case insensitive if cs is FALSE.

Returns the position of str, or -1 if str could not be found.

See also Note on character comparisons.

int QCString::find ( const QRegExp & rx, int index = 0 ) const

Finds the first occurrence of the regular expression rx, starting at position index.

Returns the position of the next match, or -1 if rx was not found.

Warning: If you want to apply this function repeatedly to the same string it is more efficient to convert the string to a QString and apply the function to that.

int QCString::findRev ( char c, int index = -1, bool cs = TRUE ) const

The search is case sensitive if cs is TRUE, or case insensitive if cs is FALSE.

Returns the position of c, or -1 if c could not be found.

See also Note on character comparisons.

int QCString::findRev ( const char * str, int index = -1, bool cs = TRUE ) const

Finds the first occurrence of the string str, starting at position index and searching backwards.

The search is case sensitive if cs is TRUE, or case insensitive if cs is FALSE.

Returns the position of str, or -1 if str could not be found.

See also Note on character comparisons.

int QCString::findRev ( const QRegExp & rx, int index = -1 ) const

Finds the first occurrence of the regular expression rx, starting at position index and searching backwards.

Returns the position of the next match (backwards), or -1 if rx was not found.

Warning: If you want to apply this function repeatedly to the same string it is more efficient to convert the string to a QString and apply the function to that.

QCString & QCString::insert ( uint index, char c )

If index is beyond the end of the string, the string is padded with spaces (ASCII 32) to length index and then c is appended.

Example:

    QCString s = "Yes";
    s.insert( 3, '!');   // s == "Yes!"
    

See also remove() and replace().

QCString & QCString::insert ( uint index, const char * s )

Inserts string s into the string at position index.

If index is beyond the end of the string, the string is padded with spaces (ASCII 32) to length index and then s is appended.

    QCString s = "I like fish";
    s.insert( 2, "don't ");     // s == "I don't like fish"

    s = "x";                    // index 01234
    s.insert( 3, "yz" );        // s == "x  yz"
    

bool QCString::isEmpty () const

Returns TRUE if the string is empty, i.e. if length() == 0; otherwise returns FALSE. An empty string is not always a null string.

See example in isNull().

See also isNull(), length(), and size().

bool QCString::isNull () const

Returns TRUE if the string is null, i.e. if data() == 0; otherwise returns FALSE. A null string is also an empty string.

Example:

    QCString a;         // a.data() == 0,  a.size() == 0, a.length() == 0
    QCString b == "";   // b.data() == "", b.size() == 1, b.length() == 0
    a.isNull();         // TRUE  because a.data() == 0
    a.isEmpty();        // TRUE  because a.length() == 0
    b.isNull();         // FALSE because b.data() == ""
    b.isEmpty();        // TRUE  because b.length() == 0
    

See also isEmpty(), length(), and size().

QCString QCString::left ( uint len ) const

The whole string is returned if len exceeds the length of the string.

Example:

    QCString s = "Pineapple";
    QCString t = s.left( 4 );  // t == "Pine"
    

See also right() and mid().

Example: network/networkprotocol/nntp.cpp.

QCString QCString::leftJustify ( uint width, char fill = ' ', bool truncate = FALSE ) const

If the length of the string exceeds width and truncate is FALSE (the default), then the returned string is a copy of the string. If the length of the string exceeds width and truncate is TRUE, then the returned string is a left(width).

Example:

    QCString s("apple");
    QCString t = s.leftJustify(8, '.');  // t == "apple..."
    

See also rightJustify().

uint QCString::length () const

Returns the length of the string, excluding the '\0'-terminator. Equivalent to calling strlen(data()).

Null strings and empty strings have zero length.

See also size(), isNull(), and isEmpty().

Example: network/networkprotocol/nntp.cpp.

QCString QCString::lower () const

Example:

    QCString s("Credit");
    QCString t = s.lower();  // t == "credit"
    

See also upper() and Note on character comparisons.

QCString QCString::mid ( uint index, uint len = 0xffffffff ) const

Returns a null string if the string is empty or if index is out of range. Returns the whole string from index if index+len exceeds the length of the string.

Example:

    QCString s = "Two pineapples";
    QCString t = s.mid( 4, 3 );     // t == "pin"
    

See also left() and right().

Example: network/networkprotocol/nntp.cpp.

QCString::operator const char * () const

Returns the string data.

QCString & QCString::operator+= ( const char * str )

QCString & QCString::operator+= ( char c )

Appends character c to the string and returns a reference to the string.

QCString & QCString::operator= ( const QCString & s )

Assigns a shallow copy of s to this string and returns a reference to this string.

QCString & QCString::operator= ( const char * str )

Assigns a deep copy of str to this string and returns a reference to this string.

If str is 0 a null string is created.

See also isNull().

QCString & QCString::prepend ( const char * s )

Prepend s to the string. Equivalent to insert(0, s).

See also insert().

QCString & QCString::remove ( uint index, uint len )

If index is out of range, nothing happens. If index is valid, but index + len is larger than the length of the string, the string is truncated at position index.

    QCString s = "Montreal";
    s.remove( 1, 4 );         // s == "Meal"
    

See also insert() and replace().

Example: network/networkprotocol/nntp.cpp.

QCString & QCString::replace ( uint index, uint len, const char * str )

If index is out of range, nothing is removed and str is appended at the end of the string. If index is valid, but index + len is larger than the length of the string, str replaces the rest of the string from position index.

    QCString s = "Say yes!";
    s.replace( 4, 3, "NO" );  // s == "Say NO!"
    

See also insert() and remove().

QCString & QCString::replace ( const QRegExp & rx, const char * str )

Replaces every occurrence of rx in the string with str. Returns a reference to the string.

Example:

    QString s = "banana";
    s.replace( QRegExp("a.*a"), "" );     // becomes "b"

    s = "banana";
    s.replace( QRegExp("^[bn]a"), "X" );  // becomes "Xnana"

    s = "banana";
    s.replace( QRegExp("^[bn]a"), "" );   // becomes "nana"
    

Warning: If you want to apply this function repeatedly to the same string it is more efficient to convert the string to a QString and apply the function to that.

QCString & QCString::replace ( char c, const char * after )

Replaces every occurrence of the character c in the string with after. Returns a reference to the string.

Example:

    QCString s = "a,b,c";
    s.replace( ',', " or " );
    // s == "a or b or c"
    

QCString & QCString::replace ( const char * before, const char * after )

Replaces every occurrence of the string before in the string with the string after. Returns a reference to the string.

Example:

    QCString s = "Greek is Greek";
    s.replace( "Greek", "English" );
    // s == "English is English"
    

QCString & QCString::replace ( char c1, char c2 )

Replaces every occurrence of c1 with the char c2. Returns a reference to the string.

bool QCString::resize ( uint len )

A '\0'-terminator is set at position len - 1 unless len == 0.

Example:

    QCString s = "resize this string";
    s.resize( 7 );                      // s == "resize"
    

See also truncate().

Example: network/networkprotocol/nntp.cpp.

QCString QCString::right ( uint len ) const

The whole string is returned if len exceeds the length of the string.

Example:

    QCString s = "Pineapple";
    QCString t = s.right( 5 );  // t == "apple"
    

See also left() and mid().

Example: network/networkprotocol/nntp.cpp.

QCString QCString::rightJustify ( uint width, char fill = ' ', bool truncate = FALSE ) const

If the length of the string exceeds width and truncate is FALSE (the default), then the returned string is a copy of the string. If the length of the string exceeds width and truncate is TRUE, then the returned string is a left(width).

Example:

    QCString s("pie");
    QCString t = s.rightJustify(8, '.');  // t == ".....pie"
    

See also leftJustify().

bool QCString::setExpand ( uint index, char c )

Returns FALSE if index was out of range and the string could not be expanded; otherwise returns TRUE.

QCString & QCString::setNum ( double n, char f = 'g', int prec = 6 )

The format of the string representation is specified by the format character f, and the precision (number of digits after the decimal point) is specified with prec.

The valid formats for f are 'e', 'E', 'f', 'g' and 'G'. The formats are the same as for sprintf(); they are explained in QString::arg().

QCString & QCString::setNum ( short n )

Sets the string to the string representation of the number n and returns a reference to the string.

QCString & QCString::setNum ( ushort n )

Sets the string to the string representation of the number n and returns a reference to the string.

QCString & QCString::setNum ( int n )

Sets the string to the string representation of the number n and returns a reference to the string.

QCString & QCString::setNum ( uint n )

Sets the string to the string representation of the number n and returns a reference to the string.

QCString & QCString::setNum ( long n )

Sets the string to the string representation of the number n and returns a reference to the string.

QCString & QCString::setNum ( ulong n )

Sets the string to the string representation of the number n and returns a reference to the string.

QCString & QCString::setNum ( float n, char f = 'g', int prec = 6 )

QCString & QCString::setStr ( const char * str )

QCString QCString::simplifyWhiteSpace () const

White space means the decimal ASCII codes 9, 10, 11, 12, 13 and 32.

    QCString s = "  lots\t of\nwhite    space ";
    QCString t = s.simplifyWhiteSpace(); // t == "lots of white space"
    

See also stripWhiteSpace().

QCString & QCString::sprintf ( const char * format, ... )

If the string is shorter than 256 characters, this sprintf() calls resize(256) to decrease the chance of memory corruption. The string is resized back to its actual length before sprintf() returns.

Example:

    QCString s;
    s.sprintf( "%d - %s", 1, "first" );         // result < 256 chars

    QCString big( 25000 );                      // very long string
    big.sprintf( "%d - %s", 2, longString );    // result < 25000 chars
    

Warning: All vsprintf() implementations will write past the end of the target string (*this) if the format specification and arguments happen to be longer than the target string, and some will also fail if the target string is longer than some arbitrary implementation limit.

Giving user-supplied arguments to sprintf() is risky: Sooner or later someone will paste a huge line into your application.

QCString QCString::stripWhiteSpace () const

White space means the decimal ASCII codes 9, 10, 11, 12, 13 and 32.

Example:

    QCString s = " space ";
    QCString t = s.stripWhiteSpace();           // t == "space"
    

See also simplifyWhiteSpace().

double QCString::toDouble ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, or if it has trailing garbage; otherwise *ok is set to TRUE.

float QCString::toFloat ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, or if it has trailing garbage; otherwise *ok is set to TRUE.

int QCString::toInt ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, or if it has trailing garbage; otherwise *ok is set to TRUE.

long QCString::toLong ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, or if it has trailing garbage; otherwise *ok is set to TRUE.

short QCString::toShort ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, is out of range, or if it has trailing garbage; otherwise *ok is set to TRUE.

uint QCString::toUInt ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, or if it has trailing garbage; otherwise *ok is set to TRUE.

ulong QCString::toULong ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, or if it has trailing garbage; otherwise *ok is set to TRUE.

ushort QCString::toUShort ( bool * ok = 0 ) const

If ok is not 0: *ok is set to FALSE if the string is not a number, is out of range, or if it has trailing garbage; otherwise *ok is set to TRUE.

bool QCString::truncate ( uint pos )

Truncates the string at position pos.

Equivalent to calling resize(pos+1).

Example:

    QCString s = "truncate this string";
    s.truncate( 5 );                      // s == "trunc"
    

See also resize().

QCString QCString::upper () const

Example:

    QCString s( "Debit" );
    QCString t = s.upper();  // t == "DEBIT"
    

See also lower() and Note on character comparisons.

Related Functions

bool operator!= ( const QCString & s1, const QCString & s2 )

Returns TRUE if s1 and s2 are different; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) != 0.

bool operator!= ( const QCString & s1, const char * s2 )

Returns TRUE if s1 and s2 are different; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) != 0.

bool operator!= ( const char * s1, const QCString & s2 )

Returns TRUE if s1 and s2 are different; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) != 0.

const QCString operator+ ( const QCString & s1, const QCString & s2 )

Returns a string which consists of the concatenation of s1 and s2.

const QCString operator+ ( const QCString & s1, const char * s2 )

Returns a string which consists of the concatenation of s1 and s2.

const QCString operator+ ( const char * s1, const QCString & s2 )

Returns a string which consists of the concatenation of s1 and s2.

const QCString operator+ ( const QCString & s, char c )

Returns a string which consists of the concatenation of s and c.

const QCString operator+ ( char c, const QCString & s )

Returns a string which consists of the concatenation of c and s.

bool operator< ( const QCString & s1, const char * s2 )

Returns TRUE if s1 is less than s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) < 0.

See also Note on character comparisons.

bool operator< ( const char * s1, const QCString & s2 )

Returns TRUE if s1 is less than s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) < 0.

See also Note on character comparisons.

QDataStream & operator<< ( QDataStream & s, const QCString & str )

Writes string str to the stream s.

See also Format of the QDataStream operators.

bool operator<= ( const QCString & s1, const char * s2 )

Returns TRUE if s1 is less than or equal to s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) <= 0.

See also Note on character comparisons.

bool operator<= ( const char * s1, const QCString & s2 )

Returns TRUE if s1 is less than or equal to s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) <= 0.

See also Note on character comparisons.

bool operator== ( const QCString & s1, const QCString & s2 )

Returns TRUE if s1 and s2 are equal; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) == 0.

bool operator== ( const QCString & s1, const char * s2 )

Returns TRUE if s1 and s2 are equal; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) == 0.

bool operator== ( const char * s1, const QCString & s2 )

Returns TRUE if s1 and s2 are equal; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) == 0.

bool operator> ( const QCString & s1, const char * s2 )

Returns TRUE if s1 is greater than s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) > 0.

See also Note on character comparisons.

bool operator> ( const char * s1, const QCString & s2 )

Returns TRUE if s1 is greater than s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) > 0.

See also Note on character comparisons.

bool operator>= ( const QCString & s1, const char * s2 )

Returns TRUE if s1 is greater than or equal to s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) >= 0.

See also Note on character comparisons.

bool operator>= ( const char * s1, const QCString & s2 )

Returns TRUE if s1 is greater than or equal to s2; otherwise returns FALSE.

Equivalent to qstrcmp(s1, s2) >= 0.

See also Note on character comparisons.

QDataStream & operator>> ( QDataStream & s, QCString & str )

Reads a string into str from the stream s.

See also Format of the QDataStream operators.

void * qmemmove ( void * dst, const void * src, uint len )

This function is normally part of the C library. Qt implements memmove() for platforms that do not provide it.

memmove() copies len bytes from src into dst. The data is copied correctly even if src and dst overlap.

int qstrcmp ( const char * str1, const char * str2 )

A safe strcmp() function.

Compares str1 and str2. Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

Special case I: Returns 0 if str1 and str2 are both 0.

Special case II: Returns a random nonzero value if str1 is 0 or str2 is 0 (but not both).

See also qstrncmp(), qstricmp(), qstrnicmp(), and Note on character comparisons.

char * qstrcpy ( char * dst, const char * src )

A safe strcpy() function.

Copies all characters up to and including the '\0' from src into dst and returns a pointer to dst.

char * qstrdup ( const char * src )

Returns a duplicate string.

Allocates space for a copy of src, copies it, and returns a pointer to the copy. If src is 0, it immediately returns 0.

The returned string must be deleted using delete[].

int qstricmp ( const char * str1, const char * str2 )

A safe stricmp() function.

Compares str1 and str2 ignoring the case.

Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

Special case I: Returns 0 if str1 and str2 are both 0.

Special case II: Returns a random nonzero value if str1 is 0 or str2 is 0 (but not both).

See also qstrcmp(), qstrncmp(), qstrnicmp(), and Note on character comparisons.

uint qstrlen ( const char * str )

A safe strlen function.

Returns the number of characters that precede the terminating '\0'. or 0 if str is 0.

int qstrncmp ( const char * str1, const char * str2, uint len )

A safe strncmp() function.

Compares at most len bytes of str1 and str2.

Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

Special case I: Returns 0 if str1 and str2 are both 0.

Special case II: Returns a random nonzero value if str1 is 0 or str2 is 0 (but not both).

See also qstrcmp(), qstricmp(), qstrnicmp(), and Note on character comparisons.

char * qstrncpy ( char * dst, const char * src, uint len )

A safe strncpy() function.

Copies at most len bytes from src (stopping at len or the terminating '\0' whichever comes first) into dst and returns a pointer to dst. Guarantees that dst is '\0'-terminated. If src or dst is 0, returns 0 immediately.

See also qstrcpy().

int qstrnicmp ( const char * str1, const char * str2, uint len )

A safe strnicmp() function.

Compares at most len bytes of str1 and str2 ignoring the case.

Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

Special case I: Returns 0 if str1 and str2 are both 0.

Special case II: Returns a random nonzero value if str1 is 0 or str2 is 0 (but not both).

See also qstrcmp(), qstrncmp(), qstricmp(), and Note on character comparisons.

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