+/////////////////////////////////////////////////////////////////////////////
+// Name: archive.h
+// Purpose: topic overview
+// Author: wxWidgets team
+// RCS-ID: $Id$
+// Licence: wxWindows license
+/////////////////////////////////////////////////////////////////////////////
+
+/*!
+
+ @page overview_arc Archive formats such as zip
+
+ The archive classes handle archive formats such as zip, tar, rar and cab.
+ Currently wxZip and wxTar classes are included.
+
+ For each archive type, there are the following classes (using zip here
+ as an example):
+
+ @li wxZipInputStream: input stream
+ @li wxZipOutputStream: output stream
+ @li wxZipEntry: holds the meta-data for an entry (e.g. filename, timestamp, etc.)
+
+ There are also abstract wxArchive classes that can be used to write code
+ that can handle any of the archive types, see @ref overview_arc_generic.
+
+ Also see wxFileSystem for a higher level interface that
+ can handle archive files in a generic way.
+
+ The classes are designed to handle archives on both seekable streams such
+ as disk files, or non-seekable streams such as pipes and sockets
+ (see @ref overview_arc_noseek).
+
+ See also wxFileSystem.
+
+ @li @ref overview_arc_create
+ @li @ref overview_arc_extract
+ @li @ref overview_arc_modify
+ @li @ref overview_arc_byname
+ @li @ref overview_arc_generic
+ @li @ref overview_arc_noseek
+
+
+ <hr>
+
+
+ @section overview_arc_create Creating an archive
+
+ Call wxArchiveOutputStream::PutNextEntry() to create each new entry in the archive,
+ then write the entry's data.
+ Another call to PutNextEntry() closes the current entry and begins the next.
+ For example:
+
+ @code
+ wxFFileOutputStream out(_T("test.zip"));
+ wxZipOutputStream zip(out);
+ wxTextOutputStream txt(zip);
+ wxString sep(wxFileName::GetPathSeparator());
+
+ zip.PutNextEntry(_T("entry1.txt"));
+ txt << _T("Some text for entry1.txt\n");
+
+ zip.PutNextEntry(_T("subdir") + sep + _T("entry2.txt"));
+ txt << _T("Some text for subdir/entry2.txt\n");
+ @endcode
+
+ The name of each entry can be a full path, which makes it possible to
+ store entries in subdirectories.
+
+
+ @section overview_arc_extract Extracting an archive
+
+ wxArchiveInputStream::GetNextEntry() returns a pointer to entry object containing the
+ meta-data for the next entry in the archive (and gives away ownership).
+
+ Reading from the input stream then returns the entry's data.
+ Eof() becomes @true after an attempt has been made to read past the end of the entry's data.
+
+ When there are no more entries, GetNextEntry() returns @NULL and sets Eof().
+
+ @code
+ auto_ptr<wxZipEntry> entry;
+
+ wxFFileInputStream in(_T("test.zip"));
+ wxZipInputStream zip(in);
+
+ while (entry.reset(zip.GetNextEntry()), entry.get() != NULL)
+ {
+ // access meta-data
+ wxString name = entry->GetName();
+ // read 'zip' to access the entry's data
+ }
+ @endcode
+
+
+
+ @section overview_arc_modify Modifying an archive
+
+ To modify an existing archive, write a new copy of the archive to a new file,
+ making any necessary changes along the way and transferring any unchanged
+ entries using wxArchiveOutputStream::CopyEntry().
+
+ For archive types which compress entry data, CopyEntry() is likely to be
+ much more efficient than transferring the data using Read() and Write()
+ since it will copy them without decompressing and recompressing them.
+
+ In general modifications are not possible without rewriting the archive,
+ though it may be possible in some limited cases. Even then, rewriting the
+ archive is usually a better choice since a failure can be handled without
+ losing the whole archive. wxTempFileOutputStream can be helpful to do this.
+
+ For example to delete all entries matching the pattern "*.txt":
+
+ @code
+ auto_ptr<wxFFileInputStream> in(new wxFFileInputStream(_T("test.zip")));
+ wxTempFileOutputStream out(_T("test.zip"));
+
+ wxZipInputStream inzip(*in);
+ wxZipOutputStream outzip(out);
+
+ auto_ptr<wxZipEntry> entry;
+
+ // transfer any meta-data for the archive as a whole (the zip comment
+ // in the case of zip)
+ outzip.CopyArchiveMetaData(inzip);
+
+ // call CopyEntry for each entry except those matching the pattern
+ while (entry.reset(inzip.GetNextEntry()), entry.get() != NULL)
+ if (!entry->GetName().Matches(_T("*.txt")))
+ if (!outzip.CopyEntry(entry.release(), inzip))
+ break;
+
+ // close the input stream by releasing the pointer to it, do this
+ // before closing the output stream so that the file can be replaced
+ in.reset();
+
+ // you can check for success as follows
+ bool success = inzip.Eof() && outzip.Close() && out.Commit();
+ @endcode
+
+
+
+ @section overview_arc_byname Looking up an archive entry by name
+
+ Also see wxFileSystem for a higher level interface that is
+ more convenient for accessing archive entries by name.
+
+ To open just one entry in an archive, the most efficient way is
+ to simply search for it linearly by calling wxArchiveInputStream::GetNextEntry()
+ until the required entry is found. This works both for archives on seekable and
+ non-seekable streams.
+
+ The format of filenames in the archive is likely to be different
+ from the local filename format. For example zips and tars use
+ unix style names, with forward slashes as the path separator,
+ and absolute paths are not allowed. So if on Windows the file
+ "C:\MYDIR\MYFILE.TXT" is stored, then when reading the entry back
+ wxArchiveEntry::GetName() will return "MYDIR\MYFILE.TXT".
+ The conversion into the internal format and back has lost some information.
+
+ So to avoid ambiguity when searching for an entry matching a local name,
+ it is better to convert the local name to the archive's internal format
+ and search for that:
+
+ @code
+ auto_ptr<wxZipEntry> entry;
+
+ // convert the local name we are looking for into the internal format
+ wxString name = wxZipEntry::GetInternalName(localname);
+
+ // open the zip
+ wxFFileInputStream in(_T("test.zip"));
+ wxZipInputStream zip(in);
+
+ // call GetNextEntry() until the required internal name is found
+ do {
+ entry.reset(zip.GetNextEntry());
+ }
+ while (entry.get() != NULL && entry->GetInternalName() != name);
+
+ if (entry.get() != NULL) {
+ // read the entry's data...
+ }
+ @endcode
+
+ To access several entries randomly, it is most efficient to transfer the
+ entire catalogue of entries to a container such as a std::map or a
+ wxHashMap then entries looked up by name can be opened using the
+ wxArchiveInputStream::OpenEntry() method.
+
+ @code
+ WX_DECLARE_STRING_HASH_MAP(wxZipEntry*, ZipCatalog);
+ ZipCatalog::iterator it;
+ wxZipEntry *entry;
+ ZipCatalog cat;
+
+ // open the zip
+ wxFFileInputStream in(_T("test.zip"));
+ wxZipInputStream zip(in);
+
+ // load the zip catalog
+ while ((entry = zip.GetNextEntry()) != NULL) {
+ wxZipEntry*& current = cat[entry->GetInternalName()];
+ // some archive formats can have multiple entries with the same name
+ // (e.g. tar) though it is an error in the case of zip
+ delete current;
+ current = entry;
+ }
+
+ // open an entry by name
+ if ((it = cat.find(wxZipEntry::GetInternalName(localname))) != cat.end()) {
+ zip.OpenEntry(*it->second);
+ // ... now read entry's data
+ }
+ @endcode
+
+ To open more than one entry simultaneously you need more than one
+ underlying stream on the same archive:
+
+ @code
+ // opening another entry without closing the first requires another
+ // input stream for the same file
+ wxFFileInputStream in2(_T("test.zip"));
+ wxZipInputStream zip2(in2);
+ if ((it = cat.find(wxZipEntry::GetInternalName(local2))) != cat.end())
+ zip2.OpenEntry(*it->second);
+ @endcode
+
+
+
+ @section overview_arc_generic Generic archive programming
+
+ Also see wxFileSystem for a higher level interface that
+ can handle archive files in a generic way.
+
+ The specific archive classes, such as the wxZip classes, inherit from
+ the following abstract classes which can be used to write code that can
+ handle any of the archive types:
+
+ @li wxArchiveInputStream: input stream
+ @li wxArchiveOutputStream: output stream
+ @li wxArchiveEntry: holds the meta-data for an entry (e.g. filename)
+
+ In order to able to write generic code it's necessary to be able to create
+ instances of the classes without knowing which archive type is being used.
+
+ To allow this there is a class factory for each archive type, derived from
+ wxArchiveClassFactory, that can create the other classes.
+
+ For example, given @e wxArchiveClassFactory* factory, streams and
+ entries can be created like this:
+
+ @code
+ // create streams without knowing their type
+ auto_ptr<wxArchiveInputStream> inarc(factory->NewStream(in));
+ auto_ptr<wxArchiveOutputStream> outarc(factory->NewStream(out));
+
+ // create an empty entry object
+ auto_ptr<wxArchiveEntry> entry(factory->NewEntry());
+ @endcode
+
+ For the factory itself, the static member wxArchiveClassFactory::Find().
+ can be used to find a class factory that can handle a given file
+ extension or mime type. For example, given @e filename:
+
+ @code
+ const wxArchiveClassFactory *factory;
+ factory = wxArchiveClassFactory::Find(filename, wxSTREAM_FILEEXT);
+
+ if (factory)
+ stream = factory->NewStream(new wxFFileInputStream(filename));
+ @endcode
+
+ @e Find does not give away ownership of the returned pointer, so it
+ does not need to be deleted.
+
+ There are similar class factories for the filter streams that handle the
+ compression and decompression of a single stream, such as wxGzipInputStream.
+ These can be found using wxFilterClassFactory::Find().
+
+ For example, to list the contents of archive @e filename:
+
+ @code
+ auto_ptr<wxInputStream> in(new wxFFileInputStream(filename));
+
+ if (in->IsOk())
+ {
+ // look for a filter handler, e.g. for '.gz'
+ const wxFilterClassFactory *fcf;
+ fcf = wxFilterClassFactory::Find(filename, wxSTREAM_FILEEXT);
+ if (fcf) {
+ in.reset(fcf->NewStream(in.release()));
+ // pop the extension, so if it was '.tar.gz' it is now just '.tar'
+ filename = fcf->PopExtension(filename);
+ }
+
+ // look for a archive handler, e.g. for '.zip' or '.tar'
+ const wxArchiveClassFactory *acf;
+ acf = wxArchiveClassFactory::Find(filename, wxSTREAM_FILEEXT);
+ if (acf) {
+ auto_ptr<wxArchiveInputStream> arc(acf->NewStream(in.release()));
+ auto_ptr<wxArchiveEntry> entry;
+
+ // list the contents of the archive
+ while ((entry.reset(arc->GetNextEntry())), entry.get() != NULL)
+ std::wcout << entry->GetName().c_str() << "\n";
+ }
+ else {
+ wxLogError(_T("can't handle '%s'"), filename.c_str());
+ }
+ }
+ @endcode
+
+
+
+ @section overview_arc_noseek Archives on non-seekable streams
+
+ In general, handling archives on non-seekable streams is done in the same
+ way as for seekable streams, with a few caveats.
+
+ The main limitation is that accessing entries randomly using
+ wxArchiveInputStream::OpenEntry() is not possible, the entries can only be
+ accessed sequentially in the order they are stored within the archive.
+
+ For each archive type, there will also be other limitations which will
+ depend on the order the entries' meta-data is stored within the archive.
+ These are not too difficult to deal with, and are outlined below.
+
+ @subsection overview_arc_noseek_entrysize PutNextEntry and the entry size
+
+ When writing archives, some archive formats store the entry size before
+ the entry's data (tar has this limitation, zip doesn't). In this case
+ the entry's size must be passed to wxArchiveOutputStream::PutNextEntry()
+ or an error occurs.
+
+ This is only an issue on non-seekable streams, since otherwise the archive
+ output stream can seek back and fix up the header once the size of the
+ entry is known.
+
+ For generic programming, one way to handle this is to supply the size
+ whenever it is known, and rely on the error message from the output
+ stream when the operation is not supported.
+
+ @subsection overview_arc_noseek_weak GetNextEntry and the weak reference mechanism
+
+ Some archive formats do not store all an entry's meta-data before the
+ entry's data (zip is an example). In this case, when reading from a
+ non-seekable stream, wxArchiveInputStream::GetNextEntry() can only return
+ a partially populated wxArchiveEntry object - not all the fields are set.
+
+ The input stream then keeps a weak reference to the entry object and
+ updates it when more meta-data becomes available. A weak reference being
+ one that does not prevent you from deleting the wxArchiveEntry object - the
+ input stream only attempts to update it if it is still around.
+
+ The documentation for each archive entry type gives the details
+ of what meta-data becomes available and when. For generic programming,
+ when the worst case must be assumed, you can rely on all the fields
+ of wxArchiveEntry being fully populated when GetNextEntry() returns,
+ with the the following exceptions:
+
+ @li wxArchiveEntry::GetSize(): guaranteed to be available after the
+ entry has been read to wxInputStream::Eof(), or wxArchiveInputStream::CloseEntry()
+ has been called
+
+ @li wxArchiveEntry::IsReadOnly(): guaranteed to be available after the end of
+ the archive has been reached, i.e. after GetNextEntry() returns @NULL and
+ Eof() is @true
+
+ This mechanism allows wxArchiveOutputStream::CopyEntry() to always fully
+ preserve entries' meta-data. No matter what order order the meta-data occurs
+ within the archive, the input stream will always have read it before the output
+ stream must write it.
+
+ @subsection overview_arc_noseek_notifier wxArchiveNotifier
+
+ Notifier objects can be used to get a notification whenever an input
+ stream updates a wxArchiveEntry object's data via the weak reference mechanism.
+
+ Consider the following code which renames an entry in an archive.
+ This is the usual way to modify an entry's meta-data, simply set the
+ required field before writing it with wxArchiveOutputStream::CopyEntry():
+
+ @code
+ auto_ptr<wxArchiveInputStream> arc(factory->NewStream(in));
+ auto_ptr<wxArchiveOutputStream> outarc(factory->NewStream(out));
+ auto_ptr<wxArchiveEntry> entry;
+
+ outarc->CopyArchiveMetaData(*arc);
+
+ while (entry.reset(arc->GetNextEntry()), entry.get() != NULL) {
+ if (entry->GetName() == from)
+ entry->SetName(to);
+ if (!outarc->CopyEntry(entry.release(), *arc))
+ break;
+ }
+
+ bool success = arc->Eof() && outarc->Close();
+ @endcode
+
+ However, for non-seekable streams, this technique cannot be used for
+ fields such as wxArchiveEntry::IsReadOnly(), which are not necessarily set when
+ wxArchiveInputStream::GetNextEntry() returns.
+
+ In this case a wxArchiveNotifier can be used:
+
+ @code
+ class MyNotifier : public wxArchiveNotifier
+ {
+ public:
+ void OnEntryUpdated(wxArchiveEntry& entry) { entry.SetIsReadOnly(false); }
+ };
+ @endcode
+
+ The meta-data changes are done in your notifier's wxArchiveNotifier::OnEntryUpdated()
+ method, then wxArchiveEntry::SetNotifier() is called before CopyEntry():
+
+ @code
+ auto_ptr<wxArchiveInputStream> arc(factory->NewStream(in));
+ auto_ptr<wxArchiveOutputStream> outarc(factory->NewStream(out));
+ auto_ptr<wxArchiveEntry> entry;
+ MyNotifier notifier;
+
+ outarc->CopyArchiveMetaData(*arc);
+
+ while (entry.reset(arc->GetNextEntry()), entry.get() != NULL) {
+ entry->SetNotifier(notifier);
+ if (!outarc->CopyEntry(entry.release(), *arc))
+ break;
+ }
+
+ bool success = arc->Eof() && outarc->Close();
+ @endcode
+
+ SetNotifier() calls OnEntryUpdated() immediately, then the input
+ stream calls it again whenever it sets more fields in the entry. Since
+ OnEntryUpdated() will be called at least once, this technique always
+ works even when it is not strictly necessary to use it. For example,
+ changing the entry name can be done this way too and it works on seekable
+ streams as well as non-seekable.
+
+*/
+
projects / wxWidgets.git / commitdiff
