gzipheader.html

用JAVA编写的,在做实验的时候留下来的,本来想删的,但是传上来,大家分享吧

<a name="171" href="#171">171</a>         <strong>final</strong> <strong>int</strong> FLG_FHCRC  = 2;
<a name="172" href="#172">172</a>         <strong>if</strong> ((<strong>this</strong>.flg &amp; FLG_FHCRC) == FLG_FHCRC) {
<a name="173" href="#173">173</a>             <strong>int</strong> calcCrc = (<strong>int</strong>)(crc.getValue() &amp; 0xffff);
<a name="174" href="#174">174</a>             <strong>if</strong> (readShort(in, crc) != calcCrc) {
<a name="175" href="#175">175</a>                 <strong>throw</strong> <strong>new</strong> IOException(<span class="string">"Bad header CRC"</span>);
<a name="176" href="#176">176</a>             }
<a name="177" href="#177">177</a>             <strong>this</strong>.length += 2;
<a name="178" href="#178">178</a>         }
<a name="179" href="#179">179</a>     }
<a name="180" href="#180">180</a>     
<a name="181" href="#181">181</a>     <em>/**<em>*</em></em>
<a name="182" href="#182">182</a> <em>     * Test gzip magic is next in the stream.</em>
<a name="183" href="#183">183</a> <em>     * Reads two bytes.  Caller needs to manage resetting stream.</em>
<a name="184" href="#184">184</a> <em>     * @param in InputStream to read.</em>
<a name="185" href="#185">185</a> <em>     * @return true if found gzip magic.  False otherwise</em>
<a name="186" href="#186">186</a> <em>     * or an IOException (including EOFException).</em>
<a name="187" href="#187">187</a> <em>     * @throws IOException</em>
<a name="188" href="#188">188</a> <em>     */</em>
<a name="189" href="#189">189</a>     <strong>public</strong> <strong>boolean</strong> testGzipMagic(InputStream in) throws IOException {
<a name="190" href="#190">190</a>         <strong>return</strong> testGzipMagic(in, <strong>null</strong>);
<a name="191" href="#191">191</a>     }
<a name="192" href="#192">192</a>     
<a name="193" href="#193">193</a>     <em>/**<em>*</em></em>
<a name="194" href="#194">194</a> <em>     * Test gzip magic is next in the stream.</em>
<a name="195" href="#195">195</a> <em>     * Reads two bytes.  Caller needs to manage resetting stream.</em>
<a name="196" href="#196">196</a> <em>     * @param in InputStream to read.</em>
<a name="197" href="#197">197</a> <em>     * @param crc CRC to update.</em>
<a name="198" href="#198">198</a> <em>     * @return true if found gzip magic.  False otherwise</em>
<a name="199" href="#199">199</a> <em>     * or an IOException (including EOFException).</em>
<a name="200" href="#200">200</a> <em>     * @throws IOException</em>
<a name="201" href="#201">201</a> <em>     */</em>
<a name="202" href="#202">202</a>     <strong>public</strong> <strong>boolean</strong> testGzipMagic(InputStream in, CRC32 crc)
<a name="203" href="#203">203</a>             throws IOException {
<a name="204" href="#204">204</a>         <strong>return</strong> readShort(in, crc) == GZIPInputStream.GZIP_MAGIC;
<a name="205" href="#205">205</a>     }
<a name="206" href="#206">206</a>     
<a name="207" href="#207">207</a>     <em>/**<em>*</em></em>
<a name="208" href="#208">208</a> <em>     * Read an int. </em>
<a name="209" href="#209">209</a> <em>     * </em>
<a name="210" href="#210">210</a> <em>     * We do not expect to get a -1 reading.  If we do, we throw exception.</em>
<a name="211" href="#211">211</a> <em>     * Update the crc as we go.</em>
<a name="212" href="#212">212</a> <em>     * </em>
<a name="213" href="#213">213</a> <em>     * @param in InputStream to read.</em>
<a name="214" href="#214">214</a> <em>     * @param crc CRC to update.</em>
<a name="215" href="#215">215</a> <em>     * @return int read.</em>
<a name="216" href="#216">216</a> <em>     * </em>
<a name="217" href="#217">217</a> <em>     * @throws IOException</em>
<a name="218" href="#218">218</a> <em>     */</em>
<a name="219" href="#219">219</a>     <strong>private</strong> <strong>int</strong> readInt(InputStream in, CRC32 crc) throws IOException {
<a name="220" href="#220">220</a>         <strong>int</strong> s = readShort(in, crc);
<a name="221" href="#221">221</a>         <strong>return</strong> ((readShort(in, crc) &lt;&lt; 16) &amp; 0xffff0000) | s;
<a name="222" href="#222">222</a>     }
<a name="223" href="#223">223</a>     
<a name="224" href="#224">224</a>     <em>/**<em>*</em></em>
<a name="225" href="#225">225</a> <em>     * Read a short. </em>
<a name="226" href="#226">226</a> <em>     * </em>
<a name="227" href="#227">227</a> <em>     * We do not expect to get a -1 reading.  If we do, we throw exception.</em>
<a name="228" href="#228">228</a> <em>     * Update the crc as we go.</em>
<a name="229" href="#229">229</a> <em>     * </em>
<a name="230" href="#230">230</a> <em>     * @param in InputStream to read.</em>
<a name="231" href="#231">231</a> <em>     * @param crc CRC to update.</em>
<a name="232" href="#232">232</a> <em>     * @return Short read.</em>
<a name="233" href="#233">233</a> <em>     * </em>
<a name="234" href="#234">234</a> <em>     * @throws IOException</em>
<a name="235" href="#235">235</a> <em>     */</em>
<a name="236" href="#236">236</a>     <strong>private</strong> <strong>int</strong> readShort(InputStream in, CRC32 crc) throws IOException {
<a name="237" href="#237">237</a>         <strong>int</strong> b = readByte(in, crc);
<a name="238" href="#238">238</a>         <strong>return</strong> ((readByte(in, crc) &lt;&lt; 8) &amp; 0x00ff00) | b;
<a name="239" href="#239">239</a>     }
<a name="240" href="#240">240</a>     
<a name="241" href="#241">241</a>     <em>/**<em>*</em></em>
<a name="242" href="#242">242</a> <em>     * Read a byte. </em>
<a name="243" href="#243">243</a> <em>     * </em>
<a name="244" href="#244">244</a> <em>     * We do not expect to get a -1 reading.  If we do, we throw exception.</em>
<a name="245" href="#245">245</a> <em>     * Update the crc as we go.</em>
<a name="246" href="#246">246</a> <em>     * </em>
<a name="247" href="#247">247</a> <em>     * @param in InputStream to read.</em>
<a name="248" href="#248">248</a> <em>     * @return Byte read.</em>
<a name="249" href="#249">249</a> <em>     * </em>
<a name="250" href="#250">250</a> <em>     * @throws IOException</em>
<a name="251" href="#251">251</a> <em>     */</em>
<a name="252" href="#252">252</a>     <strong>protected</strong> <strong>int</strong> readByte(InputStream in) throws IOException {
<a name="253" href="#253">253</a>             <strong>return</strong> readByte(in, <strong>null</strong>);
<a name="254" href="#254">254</a>     }
<a name="255" href="#255">255</a>     
<a name="256" href="#256">256</a>     <em>/**<em>*</em></em>
<a name="257" href="#257">257</a> <em>     * Read a byte. </em>
<a name="258" href="#258">258</a> <em>     * </em>
<a name="259" href="#259">259</a> <em>     * We do not expect to get a -1 reading.  If we do, we throw exception.</em>
<a name="260" href="#260">260</a> <em>     * Update the crc as we go.</em>
<a name="261" href="#261">261</a> <em>     * </em>
<a name="262" href="#262">262</a> <em>     * @param in InputStream to read.</em>
<a name="263" href="#263">263</a> <em>     * @param crc CRC to update.</em>
<a name="264" href="#264">264</a> <em>     * @return Byte read.</em>
<a name="265" href="#265">265</a> <em>     * </em>
<a name="266" href="#266">266</a> <em>     * @throws IOException</em>
<a name="267" href="#267">267</a> <em>     */</em>
<a name="268" href="#268">268</a>     <strong>protected</strong> <strong>int</strong> readByte(InputStream in, CRC32 crc) throws IOException {
<a name="269" href="#269">269</a>         <strong>int</strong> b = in.read();
<a name="270" href="#270">270</a>         <strong>if</strong> (b == -1) {
<a name="271" href="#271">271</a>             <strong>throw</strong> <strong>new</strong> EOFException();
<a name="272" href="#272">272</a>         }
<a name="273" href="#273">273</a>         <strong>if</strong> (crc != <strong>null</strong>) {
<a name="274" href="#274">274</a>             crc.update(b);
<a name="275" href="#275">275</a>         }
<a name="276" href="#276">276</a>         <strong>return</strong> b &amp; 0xff;
<a name="277" href="#277">277</a>     }
<a name="278" href="#278">278</a>     
<a name="279" href="#279">279</a>     <em>/**<em>*</em></em>
<a name="280" href="#280">280</a> <em>     * Read a byte. </em>
<a name="281" href="#281">281</a> <em>     * </em>
<a name="282" href="#282">282</a> <em>     * We do not expect to get a -1 reading.  If we do, we throw exception.</em>
<a name="283" href="#283">283</a> <em>     * Update the crc as we go.</em>
<a name="284" href="#284">284</a> <em>     * </em>
<a name="285" href="#285">285</a> <em>     * @param in InputStream to read.</em>
<a name="286" href="#286">286</a> <em>     * @param crc CRC to update.</em>
<a name="287" href="#287">287</a> <em>     * @param buffer Buffer to read into.</em>
<a name="288" href="#288">288</a> <em>     * @param offset Offset to start filling buffer at.</em>
<a name="289" href="#289">289</a> <em>     * @param length How much to read.</em>
<a name="290" href="#290">290</a> <em>     * @return Bytes read.</em>
<a name="291" href="#291">291</a> <em>     * </em>
<a name="292" href="#292">292</a> <em>     * @throws IOException</em>
<a name="293" href="#293">293</a> <em>     */</em>
<a name="294" href="#294">294</a>     <strong>protected</strong> <strong>int</strong> readByte(InputStream in, CRC32 crc, byte [] buffer,
<a name="295" href="#295">295</a>                 <strong>int</strong> offset, <strong>int</strong> length)
<a name="296" href="#296">296</a>             throws IOException {
<a name="297" href="#297">297</a>         <strong>for</strong> (<strong>int</strong> i = offset; i &lt; length; i++) {
<a name="298" href="#298">298</a>             buffer[offset + i] = (byte)readByte(in, crc);   
<a name="299" href="#299">299</a>         }
<a name="300" href="#300">300</a>         <strong>return</strong> length;
<a name="301" href="#301">301</a>     }
<a name="302" href="#302">302</a>     
<a name="303" href="#303">303</a>     <em>/**<em>*</em></em>
<a name="304" href="#304">304</a> <em>     * @return Returns the fextra.</em>
<a name="305" href="#305">305</a> <em>     */</em>
<a name="306" href="#306">306</a>     <strong>public</strong> byte[] getFextra() {
<a name="307" href="#307">307</a>         <strong>return</strong> <strong>this</strong>.fextra;
<a name="308" href="#308">308</a>     }
<a name="309" href="#309">309</a>     
<a name="310" href="#310">310</a>     <em>/**<em>*</em></em>
<a name="311" href="#311">311</a> <em>     * @return Returns the flg.</em>
<a name="312" href="#312">312</a> <em>     */</em>
<a name="313" href="#313">313</a>     <strong>public</strong> <strong>int</strong> getFlg() {
<a name="314" href="#314">314</a>         <strong>return</strong> <strong>this</strong>.flg;
<a name="315" href="#315">315</a>     }
<a name="316" href="#316">316</a>     
<a name="317" href="#317">317</a>     <em>/**<em>*</em></em>
<a name="318" href="#318">318</a> <em>     * @return Returns the os.</em>
<a name="319" href="#319">319</a> <em>     */</em>
<a name="320" href="#320">320</a>     <strong>public</strong> <strong>int</strong> getOs() {
<a name="321" href="#321">321</a>         <strong>return</strong> <strong>this</strong>.os;
<a name="322" href="#322">322</a>     }
<a name="323" href="#323">323</a>     
<a name="324" href="#324">324</a>     <em>/**<em>*</em></em>
<a name="325" href="#325">325</a> <em>     * @return Returns the xfl.</em>
<a name="326" href="#326">326</a> <em>     */</em>
<a name="327" href="#327">327</a>     <strong>public</strong> <strong>int</strong> getXfl() {
<a name="328" href="#328">328</a>         <strong>return</strong> <strong>this</strong>.xfl;
<a name="329" href="#329">329</a>     }
<a name="330" href="#330">330</a>     
<a name="331" href="#331">331</a>     <em>/**<em>*</em></em>
<a name="332" href="#332">332</a> <em>     * @return Returns the mtime.</em>
<a name="333" href="#333">333</a> <em>     */</em>
<a name="334" href="#334">334</a>     <strong>public</strong> <strong>int</strong> getMtime() {
<a name="335" href="#335">335</a>         <strong>return</strong> <strong>this</strong>.mtime;
<a name="336" href="#336">336</a>     }
<a name="337" href="#337">337</a>     
<a name="338" href="#338">338</a>     <em>/**<em>*</em></em>
<a name="339" href="#339">339</a> <em>     * @return Returns the length.</em>
<a name="340" href="#340">340</a> <em>     */</em>
<a name="341" href="#341">341</a>     <strong>public</strong> <strong>int</strong> getLength() {
<a name="342" href="#342">342</a>         <strong>return</strong> length;
<a name="343" href="#343">343</a>     }
<a name="344" href="#344">344</a> }
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