blockinputstream.html

来自「网络爬虫开源代码」· HTML 代码 · 共 226 行 · 第 1/2 页

<a name="105" href="#105">105</a>     <strong>private</strong> <strong>void</strong> ensureRawPosition() throws IOException {
<a name="106" href="#106">106</a>         <strong>if</strong> (raw.position() != expectedRawPosition) {
<a name="107" href="#107">107</a>             raw.position(expectedRawPosition);
<a name="108" href="#108">108</a>         }
<a name="109" href="#109">109</a>     }
<a name="110" href="#110">110</a>     
<a name="111" href="#111">111</a>     <strong>private</strong> <strong>boolean</strong> ensureBuffer() throws IOException {
<a name="112" href="#112">112</a>         <strong>if</strong> (block &lt; 0) {
<a name="113" href="#113">113</a>             <strong>return</strong> false;
<a name="114" href="#114">114</a>         }
<a name="115" href="#115">115</a>         ensureRawPosition();
<a name="116" href="#116">116</a>         <strong>if</strong> (blockBytesRead &lt; BLOCK_SIZE) {
<a name="117" href="#117">117</a>             <strong>return</strong> <strong>true</strong>;
<a name="118" href="#118">118</a>         }
<a name="119" href="#119">119</a>         block = bfs.getNextBlock(block);
<a name="120" href="#120">120</a>         <strong>if</strong> (block &lt; 0) {
<a name="121" href="#121">121</a>             <strong>return</strong> false;
<a name="122" href="#122">122</a>         }
<a name="123" href="#123">123</a>         seek(block, 0);
<a name="124" href="#124">124</a>         <strong>return</strong> <strong>true</strong>;
<a name="125" href="#125">125</a>     }
<a name="126" href="#126">126</a> 
<a name="127" href="#127">127</a>     
<a name="128" href="#128">128</a>     <strong>public</strong> <strong>long</strong> skip(<strong>long</strong> v) throws IOException {
<a name="129" href="#129">129</a>         <em class="comment">// FIXME</em>
<a name="130" href="#130">130</a>         <strong>int</strong> r = read();
<a name="131" href="#131">131</a>         <strong>return</strong> (r &lt; 0) ? 0 : 1;
<a name="132" href="#132">132</a>     }
<a name="133" href="#133">133</a> 
<a name="134" href="#134">134</a>     <strong>public</strong> <strong>int</strong> read() throws IOException {
<a name="135" href="#135">135</a>         <strong>if</strong> (!ensureBuffer()) {
<a name="136" href="#136">136</a>             <strong>return</strong> -1;
<a name="137" href="#137">137</a>         }
<a name="138" href="#138">138</a>         <strong>int</strong> r = raw.read();
<a name="139" href="#139">139</a>         position++;
<a name="140" href="#140">140</a>         expectedRawPosition++;
<a name="141" href="#141">141</a>         blockBytesRead++;
<a name="142" href="#142">142</a>         <strong>return</strong> r;
<a name="143" href="#143">143</a>     }
<a name="144" href="#144">144</a>     
<a name="145" href="#145">145</a>     
<a name="146" href="#146">146</a>     <strong>public</strong> <strong>int</strong> read(byte[] b, <strong>int</strong> ofs, <strong>int</strong> len) throws IOException {
<a name="147" href="#147">147</a>         <strong>if</strong> (!ensureBuffer()) {
<a name="148" href="#148">148</a>             <strong>return</strong> 0;
<a name="149" href="#149">149</a>         }
<a name="150" href="#150">150</a>         <strong>int</strong> rem = BLOCK_SIZE - (<strong>int</strong>)(position % BLOCK_SIZE);
<a name="151" href="#151">151</a>         len = Math.min(len, rem);
<a name="152" href="#152">152</a>         <strong>int</strong> c = raw.read(b, ofs, len);
<a name="153" href="#153">153</a>         position += c;
<a name="154" href="#154">154</a>         expectedRawPosition += c;
<a name="155" href="#155">155</a>         blockBytesRead++;
<a name="156" href="#156">156</a>         <strong>return</strong> len;
<a name="157" href="#157">157</a>     }
<a name="158" href="#158">158</a> 
<a name="159" href="#159">159</a> 
<a name="160" href="#160">160</a>     <strong>public</strong> <strong>int</strong> read(byte[] b) throws IOException {
<a name="161" href="#161">161</a>         <strong>return</strong> read(b, 0, b.length);
<a name="162" href="#162">162</a>     }
<a name="163" href="#163">163</a> 
<a name="164" href="#164">164</a> 
<a name="165" href="#165">165</a>     <strong>public</strong> <strong>long</strong> position() {
<a name="166" href="#166">166</a>         <strong>return</strong> position;
<a name="167" href="#167">167</a>     }
<a name="168" href="#168">168</a> 
<a name="169" href="#169">169</a> 
<a name="170" href="#170">170</a>     <strong>public</strong> <strong>void</strong> position(<strong>long</strong> v) throws IOException {
<a name="171" href="#171">171</a>         ensureRawPosition();
<a name="172" href="#172">172</a>         <strong>if</strong> (v == position) {
<a name="173" href="#173">173</a>             <strong>return</strong>;
<a name="174" href="#174">174</a>         }
<a name="175" href="#175">175</a>         
<a name="176" href="#176">176</a>         <em class="comment">// If new position is in same block, just seek.</em>
<a name="177" href="#177">177</a>         <strong>if</strong> (v / BLOCK_SIZE == position / BLOCK_SIZE) {
<a name="178" href="#178">178</a>             <strong>long</strong> rem = v % BLOCK_SIZE;
<a name="179" href="#179">179</a>             seek(block, rem);
<a name="180" href="#180">180</a>             position = v;
<a name="181" href="#181">181</a>             <strong>return</strong>;
<a name="182" href="#182">182</a>         }
<a name="183" href="#183">183</a>         
<a name="184" href="#184">184</a>         <strong>if</strong> (v > position) {
<a name="185" href="#185">185</a>             seekAfter(v);
<a name="186" href="#186">186</a>         } <strong>else</strong> {
<a name="187" href="#187">187</a>             seekBefore(v);
<a name="188" href="#188">188</a>         }
<a name="189" href="#189">189</a>     }
<a name="190" href="#190">190</a> 
<a name="191" href="#191">191</a>     
<a name="192" href="#192">192</a>     <strong>private</strong> <strong>void</strong> seekAfter(<strong>long</strong> v) throws IOException {
<a name="193" href="#193">193</a>         <strong>long</strong> currentBlock = position / BLOCK_SIZE;
<a name="194" href="#194">194</a>         <strong>long</strong> destBlock = v / BLOCK_SIZE;
<a name="195" href="#195">195</a>         <strong>long</strong> blockAdvance = destBlock - currentBlock;
<a name="196" href="#196">196</a>         <strong>for</strong> (<strong>int</strong> i = 0; i &lt; blockAdvance; i++) {
<a name="197" href="#197">197</a>             block = bfs.getNextBlock(block);
<a name="198" href="#198">198</a>         }
<a name="199" href="#199">199</a>         seek(block, v % BLOCK_SIZE);
<a name="200" href="#200">200</a>         position = v;
<a name="201" href="#201">201</a>     }
<a name="202" href="#202">202</a> 
<a name="203" href="#203">203</a>     
<a name="204" href="#204">204</a>     <strong>private</strong> <strong>void</strong> seekBefore(<strong>long</strong> v) throws IOException {
<a name="205" href="#205">205</a>         <strong>long</strong> blockAdvance = (v - 1) / BLOCK_SIZE;
<a name="206" href="#206">206</a>         block = start;
<a name="207" href="#207">207</a>         <strong>for</strong> (<strong>int</strong> i = 0; i &lt; blockAdvance; i++) {
<a name="208" href="#208">208</a>             block = bfs.getNextBlock(block);
<a name="209" href="#209">209</a>         }
<a name="210" href="#210">210</a>         seek(block, v % BLOCK_SIZE);
<a name="211" href="#211">211</a>     }
<a name="212" href="#212">212</a> }
</pre>
<hr/><div id="footer">This page was automatically generated by <a href="http://maven.apache.org/">Maven</a></div></body>
</html>