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POHow to append binary data to a buffer in node.js
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  1. POHow to append binary data to a buffer in node.js
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    copied!<p>I have a buffer with some binary data:</p> <pre><code>var b = new Buffer ([0x00, 0x01, 0x02]); </code></pre> <p>and I want to append <code>0x03</code>.</p> <p>How can I append more binary data? I'm searching in the documentation but for appending data it must be a string, if not, an error occurs (<em>TypeError: Argument must be a string</em>):</p> <pre><code>var b = new Buffer (256); b.write ("hola"); console.log (b.toString ("utf8", 0, 4)); //hola b.write (", adios", 4); console.log (b.toString ("utf8", 0, 11)); //hola, adios </code></pre> <p>Then, the only solution I can see here is to create a new buffer for every appended binary data and copy it to the major buffer with the correct offset:</p> <pre><code>var b = new Buffer (4); //4 for having a nice printed buffer, but the size will be 16KB new Buffer ([0x00, 0x01, 0x02]).copy (b); console.log (b); //&lt;Buffer 00 01 02 00&gt; new Buffer ([0x03]).copy (b, 3); console.log (b); //&lt;Buffer 00 01 02 03&gt; </code></pre> <p>But this seems a bit inefficient because I have to instantiate a new buffer for every append.</p> <p>Do you know a better way for appending binary data?</p> <p><strong>EDIT</strong></p> <p>I've written a <a href="https://github.com/Gagle/Node-BufferedWriter" rel="nofollow noreferrer">BufferedWriter</a> that writes bytes to a file using internal buffers. Same as <a href="https://github.com/Gagle/Node-BufferedReader" rel="nofollow noreferrer">BufferedReader</a> but for writing.</p> <p>A quick example:</p> <pre><code>//The BufferedWriter truncates the file because append == false new BufferedWriter ("file") .on ("error", function (error){ console.log (error); }) //From the beginning of the file: .write ([0x00, 0x01, 0x02], 0, 3) //Writes 0x00, 0x01, 0x02 .write (new Buffer ([0x03, 0x04]), 1, 1) //Writes 0x04 .write (0x05) //Writes 0x05 .close (); //Closes the writer. A flush is implicitly done. //The BufferedWriter appends content to the end of the file because append == true new BufferedWriter ("file", true) .on ("error", function (error){ console.log (error); }) //From the end of the file: .write (0xFF) //Writes 0xFF .close (); //Closes the writer. A flush is implicitly done. //The file contains: 0x00, 0x01, 0x02, 0x04, 0x05, 0xFF </code></pre> <p><strong>LAST UPDATE</strong></p> <p>Use <a href="http://nodejs.org/api/buffer.html#buffer_class_method_buffer_concat_list_totallength" rel="nofollow noreferrer">concat</a>.</p>
 

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