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162 lines
7.3 KiB
Plaintext
162 lines
7.3 KiB
Plaintext
POCO Zip User Guide
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Zip
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!!!Introduction
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POCO Zip adds support for parsing and creating Zip files. It offers the following features:
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* decompress from local files
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* decompress from network files while they are downloaded
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* compress to local files
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* compress directly to a network destination
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!!Restrictions
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* POCO Zip does not support the DEFLATE64 algorithm.
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* encrypted files are not supported
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!!!Main Classes
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Most users will work with two common classes: <*Compress*> and <*Decompress*>
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!!Compress
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Compress is a helper class that simplifies creation of Zip files.
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Creating a Zip file is a basically a three-step process:
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* Create the Compress object: Specify the output stream and define if it is seekable (set to true for local files, to false for network files)
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Compress(std::ostream& out, bool seekableOut);
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----
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* Add entries: either add single files or directory entries
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void addFile(std::istream& input,
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const Poco::DateTime& lastModifiedAt,
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const Poco::Path& fileName,
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ZipCommon::CompressionMethod cm = ZipCommon::CM_DEFLATE,
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ZipCommon::CompressionLevel cl = ZipCommon::CL_MAXIMUM);
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/// Adds a single file to the Zip File. fileName must not be a directory name.
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void addFile(const Poco::Path& file,
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const Poco::Path& fileName,
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ZipCommon::CompressionMethod cm = ZipCommon::CM_DEFLATE,
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ZipCommon::CompressionLevel cl = ZipCommon::CL_MAXIMUM);
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/// Adds a single file to the Zip File. fileName must not be a directory name. The file must exist physically!
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void addDirectory(const Poco::Path& entryName, const Poco::DateTime& lastModifiedAt);
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/// Adds a directory entry excluding all children to the Zip file, entryName must not be empty.
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void addRecursive(const Poco::Path& entry,
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ZipCommon::CompressionLevel cl = ZipCommon::CL_MAXIMUM,
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bool excludeRoot = true,
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const Poco::Path& name = Poco::Path());
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/// Adds a directory entry recursively to the zip file, set excludeRoot to false to exclude the parent directory.
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/// The name specifies under which path the entries are added in the Zip file.
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----
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Note that one must always define a name when adding a file entry, otherwise the compresser can not decide if the file should be added with an absolute or a relative path.
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Assume you are adding the file <*c:\\data\\hello.txt*> twice to a Zip:
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// MUST use binary!
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std::ofstream out("test.zip", std::ios::binary);
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Compress c(out, true);
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Poco::Path aFile("c:\\data\\hello.txt");
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c.addFile(theFile, "hello.txt");
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c.addFile(theFile, theFile);
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c.close(); // MUST be done to finalize the Zip file
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----
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A Zip file stores entries internally in UNIX path style. The Zip file created above will contain the following entries:
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hello.txt
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data/
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data/hello.txt
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----
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The directory entry <*data/*> was automatically added.
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When adding directories recursively, the same principle applies. You specify the root directory that should be added and an optional path name where entries are added in the Zip file.
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Assume you have the following directory structure:
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data/
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run1/
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result1.txt
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run2/
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result2.txt
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----
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The following call will add all subdirectories and all files of data to the Zip but not the root entry <*data*>:
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Poco::Path data("data");
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data.makeDirectory();
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c.addRecursive(data);
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----
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Or if you want the files to be added under the directory name <*20070401*> (you basically <*rename*> data to 20070401):
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Poco::Path data("data");
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Poco::Path name("20070401);
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data.makeDirectory();
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name.makeDirectory();
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c.addRecursive(data, ZipCommon::CL_NORMAL, false, name);
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----
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Note that <*makeDirectory*> does not create a directory, it simply assures that the Path is treated as a directory not as a file.
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Also using NORMAL compression instead of MAXIMUM (which is the default) has the benefit of improved performance.
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To get notified about the entries that are added during <*addRecursive*> register to the <!EDone!> event of the Compress object:
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Poco::FIFOEvent<const ZipLocalFileHeader> EDone;
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----
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* Closing the Zip file: It is mandatory to manually close Compress objects. This guarantees that the Zip directory is written, thus creating a valid Zip file. It is safe to call <*close*> multiple times, only the first call takes effect.
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ZipArchive close();
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----
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<*close*> returns a ZipArchive which describes all entries inside a Zip file.
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!!Decompress
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Decompress can be used to decompress all files from a Zip file or to decompress single files only.
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!Decompress All
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The following sample code shows how all entries can be extracted from a Zip file:
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std::ifstream inp("test.zip", std::ios::binary);
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poco_assert (inp);
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// decompress to current working dir
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Decompress dec(inp, Poco::Path());
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// if an error happens invoke the ZipTest::onDecompressError method
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dec.EError += Poco::Delegate<ZipTest, std::pair<const Poco::Zip::ZipLocalFileHeader, const std::string> >(this, &ZipTest::onDecompressError);
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dec.decompressAllFiles();
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dec.EError -= Poco::Delegate<ZipTest, std::pair<const Poco::Zip::ZipLocalFileHeader, const std::string> >(this, &ZipTest::onDecompressError);
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----
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The onDecompressError method:
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void ZipTest::onDecompressError(const void* pSender, std::pair<const Poco::Zip::ZipLocalFileHeader, const std::string>& info)
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{
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// inform user about error
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[...]
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}
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----
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Decompressing directly from the net works similar:
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Poco::URI uri("http://www.appinf.com/test.zip");
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HTTPClientSession session(uri.getHost(), uri.getPort());
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HTTPRequest req(HTTPRequest::HTTP_GET, path, HTTPMessage::HTTP_1_1);
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session.sendRequest(req);
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HTTPResponse res;
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std::istream& rs = session.receiveResponse(res);
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Decompress dec(rs, Poco::Path());
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// if an error happens invoke the ZipTest::onDecompressError method
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dec.EError += Poco::Delegate<ZipTest, std::pair<const Poco::Zip::ZipLocalFileHeader, const std::string> >(this, &ZipTest::onDecompressError);
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dec.decompressAllFiles();
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dec.EError -= Poco::Delegate<ZipTest, std::pair<const Poco::Zip::ZipLocalFileHeader, const std::string> >(this, &ZipTest::onDecompressError);
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----
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Furthermore, Decompress supports additional parameters:
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Decompress(std::istream& in, const Poco::Path& outputDir, bool flattenDirs = false, bool keepIncompleteFiles = false);
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----
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If <*flattenDirs*> is set to true no subdirs are extracted, if <*keepIncompleteFiles*> is set to true, corrupt files (i.e. wrong CRC, wrong size on disk) will not be deleted.
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!Decompress Single Files
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To decompress single files you must first parse a Zip file, and then decompress the file which happens transparently inside the <*ZipInputStream*>:
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std::ifstream inp("test.zip", std::ios::binary);
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poco_assert (inp);
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ZipArchive arch(inp);
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ZipArchive::FileHeaders::const_iterator it = arch.findHeader("data/hello.txt");
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poco_assert (it != arch.headerEnd());
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ZipInputStream zipin (inp, it->second);
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std::ostringstream out(std::ios::binary);
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Poco::StreamCopier::copyStream(zipin, out);
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----
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Note that this will only work with local files which allow us to seek inside the file.
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Directly extracting single entries from a network file is currently not possible via the Decompress class.
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