gzippedinputstream.html

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<a name="288" href="#288">288</a>                             <em class="comment">// Found gzip header. Backup the stream the</em>
<a name="289" href="#289">289</a>                             <em class="comment">// bytes we just found and set result true.</em>
<a name="290" href="#290">290</a>                             getInputStream().reset();
<a name="291" href="#291">291</a>                             result = <strong>true</strong>;
<a name="292" href="#292">292</a>                             <strong>break</strong>;
<a name="293" href="#293">293</a>                         }
<a name="294" href="#294">294</a>                     }
<a name="295" href="#295">295</a>                     <em class="comment">// Didn't find gzip header.  Reset stream but one byte</em>
<a name="296" href="#296">296</a>                     <em class="comment">// futher on then redo header tests.</em>
<a name="297" href="#297">297</a>                     ps.position(ps.position() - headerRead);
<a name="298" href="#298">298</a>                 }
<a name="299" href="#299">299</a>             }
<a name="300" href="#300">300</a>         } <strong>catch</strong> (IOException e) {
<a name="301" href="#301">301</a>             <strong>throw</strong> <strong>new</strong> RuntimeException(<span class="string">"Failed i/o: "</span> + e.getMessage());
<a name="302" href="#302">302</a>         }
<a name="303" href="#303">303</a>         <strong>return</strong> result;
<a name="304" href="#304">304</a>     }
<a name="305" href="#305">305</a>     
<a name="306" href="#306">306</a>     <strong>protected</strong> <strong>boolean</strong> compareBytes(<strong>final</strong> <strong>int</strong> a, <strong>final</strong> <strong>int</strong> b) {
<a name="307" href="#307">307</a>     	<strong>return</strong> ((byte)(a &amp; 0xff)) == ((byte)(b &amp; 0xff));
<a name="308" href="#308">308</a>     }
<a name="309" href="#309">309</a>   
<a name="310" href="#310">310</a>     <strong>protected</strong> Inflater getInflater() {
<a name="311" href="#311">311</a>         <strong>return</strong> <strong>this</strong>.inf;
<a name="312" href="#312">312</a>     }
<a name="313" href="#313">313</a>     
<a name="314" href="#314">314</a>     <strong>protected</strong> InputStream getInputStream() {
<a name="315" href="#315">315</a>         <strong>return</strong> <strong>this</strong>.in;
<a name="316" href="#316">316</a>     }
<a name="317" href="#317">317</a>     
<a name="318" href="#318">318</a>     <strong>protected</strong> <a href="../../../org/archive/io/GzipHeader.html">GzipHeader</a> getGzipHeader() {
<a name="319" href="#319">319</a>         <strong>return</strong> <strong>this</strong>.gzipHeader;
<a name="320" href="#320">320</a>     }
<a name="321" href="#321">321</a>     
<a name="322" href="#322">322</a>     <em>/**<em>*</em></em>
<a name="323" href="#323">323</a> <em>     * Move to next gzip member in the file.</em>
<a name="324" href="#324">324</a> <em>     */</em>
<a name="325" href="#325">325</a>     <strong>protected</strong> <strong>void</strong> resetInflater() {
<a name="326" href="#326">326</a>         <strong>this</strong>.eos = false;
<a name="327" href="#327">327</a>         <strong>this</strong>.inf.reset();
<a name="328" href="#328">328</a>     }
<a name="329" href="#329">329</a>     
<a name="330" href="#330">330</a>     <em>/**<em>*</em></em>
<a name="331" href="#331">331</a> <em>     * Read in the gzip header.</em>
<a name="332" href="#332">332</a> <em>     * @throws IOException</em>
<a name="333" href="#333">333</a> <em>     */</em>
<a name="334" href="#334">334</a>     <strong>protected</strong> <strong>void</strong> readHeader() throws IOException {
<a name="335" href="#335">335</a>         <strong>new</strong> <a href="../../../org/archive/io/GzipHeader.html">GzipHeader</a>(<strong>this</strong>.in);
<a name="336" href="#336">336</a>         <em class="comment">// Reset the crc for subsequent reads.</em>
<a name="337" href="#337">337</a>         <strong>this</strong>.crc.reset();
<a name="338" href="#338">338</a>     }
<a name="339" href="#339">339</a> 
<a name="340" href="#340">340</a>     <em>/**<em>*</em></em>
<a name="341" href="#341">341</a> <em>     * Seek to passed offset.</em>
<a name="342" href="#342">342</a> <em>     * </em>
<a name="343" href="#343">343</a> <em>     * After positioning the stream, it resets the inflater.</em>
<a name="344" href="#344">344</a> <em>     * Assumption is that public use of this method is only</em>
<a name="345" href="#345">345</a> <em>     * to position stream at start of a gzip member.</em>
<a name="346" href="#346">346</a> <em>     * </em>
<a name="347" href="#347">347</a> <em>     * @param position Absolute position of a gzip member start.</em>
<a name="348" href="#348">348</a> <em>     * @throws IOException</em>
<a name="349" href="#349">349</a> <em>     */</em>
<a name="350" href="#350">350</a>     <strong>public</strong> <strong>void</strong> position(<strong>long</strong> position) throws IOException {
<a name="351" href="#351">351</a>         ((RepositionableStream)<strong>this</strong>.in).position(position);
<a name="352" href="#352">352</a>         resetInflater();
<a name="353" href="#353">353</a>     }
<a name="354" href="#354">354</a> 
<a name="355" href="#355">355</a>     <strong>public</strong> <strong>long</strong> position() throws IOException {
<a name="356" href="#356">356</a>        <strong>return</strong>  ((RepositionableStream)<strong>this</strong>.in).position();
<a name="357" href="#357">357</a>     }
<a name="358" href="#358">358</a>     
<a name="359" href="#359">359</a>     <em>/**<em>*</em></em>
<a name="360" href="#360">360</a> <em>     * Seek to a gzip member.</em>
<a name="361" href="#361">361</a> <em>     * </em>
<a name="362" href="#362">362</a> <em>     * Moves stream to new position, resets inflater and reads in the gzip</em>
<a name="363" href="#363">363</a> <em>     * header ready for subsequent calls to read.</em>
<a name="364" href="#364">364</a> <em>     * </em>
<a name="365" href="#365">365</a> <em>     * @param position Absolute position of a gzip member start.</em>
<a name="366" href="#366">366</a> <em>     * @throws IOException</em>
<a name="367" href="#367">367</a> <em>     */</em>
<a name="368" href="#368">368</a>     <strong>public</strong> <strong>void</strong> gzipMemberSeek(<strong>long</strong> position) throws IOException {
<a name="369" href="#369">369</a>         position(position);
<a name="370" href="#370">370</a>         readHeader();
<a name="371" href="#371">371</a>     }
<a name="372" href="#372">372</a>     
<a name="373" href="#373">373</a>     <strong>public</strong> <strong>void</strong> gzipMemberSeek() throws IOException {
<a name="374" href="#374">374</a>         gzipMemberSeek(position());
<a name="375" href="#375">375</a>     }
<a name="376" href="#376">376</a>     
<a name="377" href="#377">377</a>     <em>/**<em>*</em></em>
<a name="378" href="#378">378</a> <em>     * Gzip passed bytes.</em>
<a name="379" href="#379">379</a> <em>     * Use only when bytes is small.</em>
<a name="380" href="#380">380</a> <em>     * @param bytes What to gzip.</em>
<a name="381" href="#381">381</a> <em>     * @return A gzip member of bytes.</em>
<a name="382" href="#382">382</a> <em>     * @throws IOException</em>
<a name="383" href="#383">383</a> <em>     */</em>
<a name="384" href="#384">384</a>     <strong>public</strong> <strong>static</strong> byte [] gzip(byte [] bytes) throws IOException {
<a name="385" href="#385">385</a>         ByteArrayOutputStream baos = <strong>new</strong> ByteArrayOutputStream();
<a name="386" href="#386">386</a>         GZIPOutputStream gzipOS = <strong>new</strong> GZIPOutputStream(baos);
<a name="387" href="#387">387</a>         gzipOS.write(bytes, 0, bytes.length);
<a name="388" href="#388">388</a>         gzipOS.close();
<a name="389" href="#389">389</a>         <strong>return</strong> baos.toByteArray();
<a name="390" href="#390">390</a>     }
<a name="391" href="#391">391</a>     
<a name="392" href="#392">392</a>     <em>/**<em>*</em></em>
<a name="393" href="#393">393</a> <em>     * Tests passed stream is GZIP stream by reading in the HEAD.</em>
<a name="394" href="#394">394</a> <em>     * Does reposition of stream when done.</em>
<a name="395" href="#395">395</a> <em>     * @param rs An InputStream that is Repositionable.</em>
<a name="396" href="#396">396</a> <em>     * @return True if compressed stream.</em>
<a name="397" href="#397">397</a> <em>     * @throws IOException</em>
<a name="398" href="#398">398</a> <em>     */</em>
<a name="399" href="#399">399</a>     <strong>public</strong> <strong>static</strong> <strong>boolean</strong> isCompressedRepositionableStream(
<a name="400" href="#400">400</a>             <strong>final</strong> RepositionableStream rs)
<a name="401" href="#401">401</a>     throws IOException {
<a name="402" href="#402">402</a>         <strong>boolean</strong> result = false;
<a name="403" href="#403">403</a>         <strong>long</strong> p = rs.position();
<a name="404" href="#404">404</a>         <strong>try</strong> {
<a name="405" href="#405">405</a>             result = isCompressedStream((InputStream)rs);
<a name="406" href="#406">406</a>         } <strong>finally</strong> {
<a name="407" href="#407">407</a>             rs.position(p);
<a name="408" href="#408">408</a>         }
<a name="409" href="#409">409</a>         <strong>return</strong> result; 
<a name="410" href="#410">410</a>     }
<a name="411" href="#411">411</a>     
<a name="412" href="#412">412</a>     <em>/**<em>*</em></em>
<a name="413" href="#413">413</a> <em>     * Tests passed stream is gzip stream by reading in the HEAD.</em>
<a name="414" href="#414">414</a> <em>     * Does not reposition stream when done.</em>
<a name="415" href="#415">415</a> <em>     * @param is An InputStream.</em>
<a name="416" href="#416">416</a> <em>     * @return True if compressed stream.</em>
<a name="417" href="#417">417</a> <em>     * @throws IOException</em>
<a name="418" href="#418">418</a> <em>     */</em>
<a name="419" href="#419">419</a>     <strong>public</strong> <strong>static</strong> <strong>boolean</strong> isCompressedStream(<strong>final</strong> InputStream is)
<a name="420" href="#420">420</a>     throws IOException {
<a name="421" href="#421">421</a>         <strong>try</strong> {
<a name="422" href="#422">422</a>             <strong>new</strong> <a href="../../../org/archive/io/GzipHeader.html">GzipHeader</a>(is);
<a name="423" href="#423">423</a>         } <strong>catch</strong> (NoGzipMagicException e) {
<a name="424" href="#424">424</a>             <strong>return</strong> false;
<a name="425" href="#425">425</a>         }
<a name="426" href="#426">426</a>         <strong>return</strong> <strong>true</strong>;
<a name="427" href="#427">427</a>     }
<a name="428" href="#428">428</a> }
</pre>
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