Userland: tar: support extracting gzipped files

Author: https://github.com/petelliott
Commit: https://github.com/SerenityOS/serenity/commit/1b3f9c170c6
Pull-request: https://github.com/SerenityOS/serenity/pull/3660
Reviewed-by: https://github.com/asynts

Libraries/LibTar/Tar.h

@@ -46,6 +46,7 @@ enum FileType {
 };
 
 constexpr size_t block_size = 512;
+constexpr const char* ustar_magic = "ustar ";
 
 class Header {
 public:
@@ -59,14 +60,14 @@ public:
     time_t timestamp() const { return get_tar_field(m_timestamp); }
     FileType type_flag() const { return FileType(m_type_flag); }
     const StringView link_name() const { return m_link_name; }
-    const StringView magic() const { return m_magic; }
-    const StringView version() const { return m_version; }
+    const StringView magic() const { return StringView(m_magic, sizeof(m_magic)); }
+    const StringView version() const { return StringView(m_version, sizeof(m_version)); }
     const StringView owner_name() const { return m_owner_name; }
     const StringView group_name() const { return m_group_name; }
     int major() const { return get_tar_field(m_major); }
     int minor() const { return get_tar_field(m_minor); }
 
-    //private:
+private:
     char m_file_name[100];
     char m_mode[8];
     char m_uid[8];

Libraries/LibTar/TarStream.cpp

@@ -111,7 +111,7 @@ void TarStream::advance()
         m_finished = true;
         return;
     }
-    if (m_header.magic() == "") {
+    if (!valid()) {
         m_finished = true;
         return;
     }
@@ -119,6 +119,11 @@ void TarStream::advance()
     ASSERT(m_stream.discard_or_error(block_size - sizeof(Header)));
 }
 
+bool TarStream::valid() const
+{
+    return header().magic() == ustar_magic;
+}
+
 TarFileStream TarStream::file_contents()
 {
     ASSERT(!m_finished);

Libraries/LibTar/TarStream.h

@@ -55,6 +55,7 @@ public:
     TarStream(InputStream&);
     void advance();
     bool finished() const { return m_finished; }
+    bool valid() const;
     const Header& header() const { return m_header; }
     TarFileStream file_contents();
 

Userland/CMakeLists.txt

@@ -35,7 +35,7 @@ target_link_libraries(passwd LibCrypt)
 target_link_libraries(paste LibGUI)
 target_link_libraries(pro LibProtocol)
 target_link_libraries(su LibCrypt)
-target_link_libraries(tar LibTar)
+target_link_libraries(tar LibTar LibCompress)
 target_link_libraries(test-crypto LibCrypto LibTLS LibLine)
 target_link_libraries(test-compress LibCompress)
 target_link_libraries(test-js LibJS LibLine LibCore)

Userland/tar.cpp

@@ -26,6 +26,7 @@
 
 #include <AK/LogStream.h>
 #include <AK/Vector.h>
+#include <LibCompress/Gzip.h>
 #include <LibCore/ArgsParser.h>
 #include <LibCore/FileStream.h>
 #include <LibTar/TarStream.h>
@@ -41,6 +42,7 @@ int main(int argc, char** argv)
     bool extract = false;
     bool list = false;
     bool verbose = false;
+    bool gzip = false;
     const char* archive_file = nullptr;
     Vector<const char*> paths;
 
@@ -49,6 +51,7 @@ int main(int argc, char** argv)
     args_parser.add_option(extract, "Extract archive", "extract", 'x');
     args_parser.add_option(list, "List contents", "list", 't');
     args_parser.add_option(verbose, "Print paths", "verbose", 'v');
+    args_parser.add_option(gzip, "compress or uncompress file using gzip", "gzip", 'z');
     args_parser.add_option(archive_file, "Archive file", "file", 'f', "FILE");
     args_parser.add_positional_argument(paths, "Paths", "PATHS", Core::ArgsParser::Required::No);
     args_parser.parse(argc, argv);
@@ -69,8 +72,17 @@ int main(int argc, char** argv)
             }
             file = maybe_file.value();
         }
-        Core::InputFileStream input_stream(file);
-        Tar::TarStream tar_stream(input_stream);
+
+        Core::InputFileStream file_stream(file);
+        Compress::GzipDecompressor gzip_stream(file_stream);
+
+        InputStream& file_input_stream = file_stream;
+        InputStream& gzip_input_stream = gzip_stream;
+        Tar::TarStream tar_stream((gzip) ? gzip_input_stream : file_input_stream);
+        if (!tar_stream.valid()) {
+            warn() << "the provided file is not a well-formatted ustar file";
+            return 1;
+        }
         for (; !tar_stream.finished(); tar_stream.advance()) {
             if (list || verbose)
                 out() << tar_stream.header().file_name();
@@ -112,7 +124,7 @@ int main(int argc, char** argv)
                 }
             }
         }
-        input_stream.close();
+        file_stream.close();
         return 0;
     }