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<div class="title">Packing and Unpacking Data in Java </div> </div>
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<div class="textblock"><p>WiredTiger's data packing uses format strings similar to those specified in the Python struct module: <a href="http://docs.python.org/library/struct">http://docs.python.org/library/struct</a></p>
<p>The first character of the format string can be used to indicate the byte order, size and alignment of the packed data, according to the following table:</p>
<table class="doxtable">
<tr>
<th>Character</th><th>Byte order</th><th>Size</th><th>Alignment </th></tr>
<tr>
<td><code>.</code></td><td>big-endian</td><td>packed</td><td>none </td></tr>
<tr>
<td><code>></code></td><td>big-endian</td><td>standard</td><td>none </td></tr>
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<td><code><</code></td><td>little-endian</td><td>standard</td><td>none </td></tr>
<tr>
<td><code>@</code></td><td>native</td><td>native</td><td>native </td></tr>
</table>
<p>If the first character is not one of these, '.' (big-endian, packed) is assumed: it naturally sorts in lexicographic order, and the packed format uses variable-sized encoding of values to reduce the data size.</p>
<p>Note: <b> little-endian format</b> not yet supported in WiredTiger. Only the default big-endian, packed format is currently supported.</p>
<p>The remaining characters in the format string specify the type of each field to be packed into or unpacked from a byte array. See <a class="el" href="schema_lang_java.html#schema_column_types_lang_java">Column types</a> for the list of supported types.</p>
<p>In Java, data is packed and unpacked using cursor put* and get* operations, for example: </p><div class="fragment"><div class="line"> <span class="comment">/* Insert the records into the table. */</span></div><div class="line"> cursor = session.<a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#afb5b4a69c2c5cafe411b2b04fdc1c75d">open_cursor</a>(<span class="stringliteral">"table:poptable"</span>, null, <span class="stringliteral">"append"</span>);</div><div class="line"> <span class="keywordflow">for</span> (PopRecord p : popData) {</div><div class="line"> cursor.putValueString(p.country);</div><div class="line"> cursor.putValueShort(p.year);</div><div class="line"> cursor.putValueLong(p.population);</div><div class="line"> ret = cursor.insert();</div><div class="line"> }</div><div class="line"> ret = cursor.close();</div><div class="line"></div><div class="line"> <span class="comment">/* Update records in the table. */</span></div><div class="line"> cursor = session.<a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#afb5b4a69c2c5cafe411b2b04fdc1c75d">open_cursor</a>(<span class="stringliteral">"table:poptable"</span>, null, null);</div><div class="line"> <span class="keywordflow">while</span> ((ret = cursor.next()) == 0) {</div><div class="line"> recno = cursor.getKeyRecord();</div><div class="line"> country = cursor.getValueString();</div><div class="line"> year = cursor.getValueShort();</div><div class="line"> population = cursor.getValueLong();</div><div class="line"> cursor.putValueString(country);</div><div class="line"> cursor.putValueShort(year);</div><div class="line"> cursor.putValueLong(population + 1);</div><div class="line"> }</div><div class="line"> ret = cursor.close();</div><div class="line"></div><div class="line"> <span class="comment">/* List the records in the table. */</span></div><div class="line"> cursor = session.<a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#afb5b4a69c2c5cafe411b2b04fdc1c75d">open_cursor</a>(<span class="stringliteral">"table:poptable"</span>, null, null);</div><div class="line"> <span class="keywordflow">while</span> ((ret = cursor.next()) == 0) {</div><div class="line"> recno = cursor.getKeyRecord();</div><div class="line"> country = cursor.getValueString();</div><div class="line"> year = cursor.getValueShort();</div><div class="line"> population = cursor.getValueLong();</div><div class="line"> System.out.print(<span class="stringliteral">"ID "</span> + recno);</div><div class="line"> System.out.println(<span class="stringliteral">": country "</span> + country + <span class="stringliteral">", year "</span> + year +</div><div class="line"> <span class="stringliteral">", population "</span> + population);</div><div class="line"> }</div><div class="line"> ret = cursor.close();</div></div><!-- fragment --></div></div><!-- contents -->
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