X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/f6bcfd974ef26faf6f91a62cac09827e09463fd1..daf5b37afdda9e8ab7f909e01ffd6387219a80ea:/docs/latex/wx/tstring.tex diff --git a/docs/latex/wx/tstring.tex b/docs/latex/wx/tstring.tex index e57912e91a..fa25faee5e 100644 --- a/docs/latex/wx/tstring.tex +++ b/docs/latex/wx/tstring.tex @@ -2,15 +2,16 @@ Classes: \helpref{wxString}{wxstring}, \helpref{wxArrayString}{wxarraystring}, \helpref{wxStringTokenizer}{wxstringtokenizer} -\subsection{Introduction} +\subsection{Introduction}\label{introductiontowxstring} wxString is a class which represents a character string of arbitrary length (limited by {\it MAX\_INT} which is usually 2147483647 on 32 bit machines) and containing -arbitrary characters. The ASCII NUL character is allowed, although care should be -taken when passing strings containing it to other functions. +arbitrary characters. The ASCII NUL character is allowed, but be aware that +in the current string implementation some methods might not work correctly +in this case. -wxString only works with ASCII (8 bit characters) strings as of this release, -but support for UNICODE (16 but characters) is planned for the next one. +wxString works with both ASCII (traditional, 7 or 8 bit, characters) as well as +Unicode (wide characters) strings. This class has all the standard operations you can expect to find in a string class: dynamic memory management (string extends to accommodate new characters), @@ -21,7 +22,7 @@ replacing and both C-like \helpref{Printf()}{wxstringprintf} and stream-like insertion functions as well as much more - see \helpref{wxString}{wxstring} for a list of all functions. -\subsection{Comparison of wxString to other string classes} +\subsection{Comparison of wxString to other string classes}\label{otherstringclasses} The advantages of using a special string class instead of working directly with C strings are so obvious that there is a huge number of such classes available. @@ -40,7 +41,7 @@ It also provides performance \helpref{statistics gathering code}{wxstringtuning} which may be enabled to fine tune the memory allocation strategy for your particular application - and the gain might be quite big. \item {\bf Compatibility} This class tries to combine almost full compatibility -with the old wxWindows 1.xx wxString class, some reminiscence to MFC CString +with the old wxWidgets 1.xx wxString class, some reminiscence to MFC CString class and 90\% of the functionality of std::string class. \item {\bf Rich set of functions} Some of the functions present in wxString are very useful but don't exist in most of other string classes: for example, @@ -48,13 +49,14 @@ very useful but don't exist in most of other string classes: for example, \helpref{BeforeLast}{wxstringbeforelast}, \helpref{operator<<}{wxstringoperatorout} or \helpref{Printf}{wxstringprintf}. Of course, all the standard string operations are supported as well. -\item {\bf UNICODE} In this release, wxString only supports {\it construction} from -a UNICODE string, but in the next one it will be capable of also storing its -internal data in either ASCII or UNICODE format. -\item {\bf Used by wxWindows} And, of course, this class is used everywhere -inside wxWindows so there is no performance loss which would result from +\item {\bf Unicode} wxString is Unicode friendly: it allows to easily convert +to and from ANSI and Unicode strings in any build mode (see the +\helpref{Unicode overview}{unicode} for more details) and maps to either +{\tt string} or {\tt wstring} transparently depending on the current mode. +\item {\bf Used by wxWidgets} And, of course, this class is used everywhere +inside wxWidgets so there is no performance loss which would result from conversions of objects of any other string class (including std::string) to -wxString internally by wxWindows. +wxString internally by wxWidgets. \end{enumerate} However, there are several problems as well. The most important one is probably @@ -63,18 +65,18 @@ example, to get the length of the string either one of length(), \helpref{Len()}{wxstringlen} or \helpref{Length()}{wxstringlength} may be used. The first function, as almost all the other functions in lowercase, is std::string compatible. The second one -is "native" wxString version and the last one is wxWindows 1.xx way. So the +is "native" wxString version and the last one is wxWidgets 1.xx way. So the question is: which one is better to use? And the answer is that: {\bf The usage of std::string compatible functions is strongly advised!} It will both make your code more familiar to other C++ programmers (who are supposed to have knowledge of std::string but not of wxString), let you reuse the same code -in both wxWindows and other programs (by just typedefing wxString as std::string -when used outside wxWindows) and by staying compatible with future versions of -wxWindows which will probably start using std::string sooner or later too. +in both wxWidgets and other programs (by just typedefing wxString as std::string +when used outside wxWidgets) and by staying compatible with future versions of +wxWidgets which will probably start using std::string sooner or later too. In the situations where there is no corresponding std::string function, please -try to use the new wxString methods and not the old wxWindows 1.xx variants +try to use the new wxString methods and not the old wxWidgets 1.xx variants which are deprecated and may disappear in future versions. \subsection{Some advice about using wxString}\label{wxstringadvices} @@ -129,20 +131,21 @@ strings inside the function faster because of strings should return {\it wxString} - this makes it safe to return local variables. -\subsection{Other string related functions and classes} - -As most programs use character strings, the standard C library provides quite a -few functions to work with them. Unfortunately, some of them have rather -counter-intuitive behaviour (like strncpy() which doesn't always terminate the resulting -string with a NULL) and are in general not very safe (passing NULL to them will -probably lead to program crash). Moreover, some very useful functions are not -standard at all. This is why in addition to all wxString functions, there are -also a few global string functions which try to correct these problems: -\helpref{IsEmpty()}{IsEmpty} verifies whether the string is empty (returning -TRUE for NULL pointers), \helpref{Strlen()}{Strlen} also handles NULLs correctly -and returns 0 for them and \helpref{Stricmp()}{Stricmp} is just a -platform-independent version of case-insensitive string comparison function -known either as stricmp() or strcasecmp() on different platforms. +\subsection{Other string related functions and classes}\label{relatedtostring} + +As most programs use character strings, the standard C library provides quite +a few functions to work with them. Unfortunately, some of them have rather +counter-intuitive behaviour (like strncpy() which doesn't always terminate the +resulting string with a NULL) and are in general not very safe (passing NULL +to them will probably lead to program crash). Moreover, some very useful +functions are not standard at all. This is why in addition to all wxString +functions, there are also a few global string functions which try to correct +these problems: \helpref{wxIsEmpty()}{wxisempty} verifies whether the string +is empty (returning {\tt true} for {\tt NULL} pointers), +\helpref{wxStrlen()}{wxstrlen} also handles NULLs correctly and returns 0 for +them and \helpref{wxStricmp()}{wxstricmp} is just a platform-independent +version of case-insensitive string comparison function known either as +stricmp() or strcasecmp() on different platforms. The {\tt } header also defines \helpref{wxSnprintf}{wxsnprintf} and \helpref{wxVsnprintf}{wxvsnprintf} functions which should be used instead @@ -164,20 +167,8 @@ vastly better from a performance point of view than a wxObjectArray of wxStrings \subsection{Reference counting and why you shouldn't care about it}\label{wxstringrefcount} -wxString objects use a technique known as {\it copy on write} (COW). This means -that when a string is assigned to another, no copying really takes place: only -the reference count on the shared string data is incremented and both strings -share the same data. - -But as soon as one of the two (or more) strings is modified, the data has to be -copied because the changes to one of the strings shouldn't be seen in the -others. As data copying only happens when the string is written to, this is -known as COW. - -What is important to understand is that all this happens absolutely -transparently to the class users and that whether a string is shared or not is -not seen from the outside of the class - in any case, the result of any -operation on it is the same. +All considerations for wxObject-derived \helpref{reference counted}{trefcount} objects +are valid also for wxString, even if it does not derive from wxObject. Probably the unique case when you might want to think about reference counting is when a string character is taken from a string which is not a