/** \page usage Usage

 * 

 * This page provides general information on QuaZIP usage. See classes

 * QuaZip and QuaZipFile for the detailed documentation on what can

 * QuaZIP do and what can not. Also, reading comments in the zip.h and

 * unzip.h files (taken from the original ZIP/UNZIP package) is always a

 * good idea too. After all, QuaZIP is just a wrapper with a few

 * convenience extensions and reimplementations.

 *

 * QuaZip is a class representing ZIP archive, QuaZipFile represents a

 * file inside archive and subclasses QIODevice as well.

 *

 * \section terminology Terminology

 *

 * "QuaZIP" means whole this library, while "QuaZip" (not case

 * difference) is just one class in it.

 *

 * "ZIP/UNZIP API" means the original API of the Gilles Vollant's

 * ZIP/UNZIP package. I did not alter it in any way to make it easier to

 * port to the future ZIP/UNZIP versions.

 *

 * "ZIP", "ZIP archive" or "ZIP file" means any ZIP archive. Typically

 * this is a plain file with ".zip" (or ".ZIP") file name suffix.

 *

 * "A file inside archive", "a file inside ZIP" or something like that

 * means file either being read or written from/to some ZIP archive.

 *

 * \section error-handling Error handling

 *

 * Almost any call to ZIP/UNZIP API return some error code. Most of the

 * original API's error checking could be done in this wrapper as well,

 * but it would cause unnecessary code bloating without any benefit. So,

 * QuaZIP only checks for situations that ZIP/UNZIP API can not check

 * for. For example, ZIP/UNZIP API has no "ZIP open mode" concept

 * because read and write modes are completely separated. On the other

 * hand, to avoid creating classes like "QuaZipReader", "QuaZipWriter"

 * or something like that, QuaZIP introduces "ZIP open mode" concept

 * instead, thus making it possible to use one class (QuaZip) for both

 * reading and writing. But this leads to additional open mode checks

 * which are not done in ZIP/UNZIP package.

 *

 * Therefore, error checking is two-level (QuaZIP's level and ZIP/UNZIP

 * API level), which sometimes can be confusing, so here are some

 * advices on how the error checking should be properly done:

 *

 * - Both QuaZip and QuaZipFile have getZipError() function, which return

 *   error code of the last ZIP/UNZIP API call. Most function calls

 *   reset error code to UNZ_OK on success and set error code on

 *   failure. Some functions do not reset error code. Most of them are

 *   \c const and do not access ZIP archive in any way. Some, on the

 *   other hand, \em do access ZIP archive, but do not reset or set

 *   error code. For example, QuaZipFile::pos() function. Such functions

 *   are explicitly marked in the documentation.

 * - Most functions have its own way to report errors, by returning a

 *   null string, negative value or \c false. If such a function returns

 *   error value, call getZipError() to get more information about

 *   error. See "zip.h" and "unzip.h" of the ZIP/UNZIP package for error

 *   codes.

 * - If the function returns error-stating value (like \c false), but

 *   getZipError() returns UNZ_OK, it means that you did something

 *   obviously wrong. For example, tried to write in the archive open

 *   for reading or not open at all. You better just do not do that!

 *   Most functions also issue a warning using qWarning() function in

 *   such cases. See documentation for a specific function for details

 *   on when it should not be called.

 *

 * I know that this is somewhat messy, but I could not find a better way

 * to do all the error handling.

 **/