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POJava: how many bytes needed to transmit double data type array containing nulls?
 

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  1. POJava: how many bytes needed to transmit double data type array containing nulls?
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    <p>If I pass an array of data type double having 100 elements (for example) from an application server's (Linux CentOS) Java (1.6) method to a client using a binary transfer (e.g. <a href="http://en.wikipedia.org/wiki/Action_Message_Format" rel="nofollow">AMF protocol</a>), how many bytes are transmitted? </p> <p>For example, if it were an array of double floating-point numbers, each number occupies 8 bytes. So, if the array is 100 elements long, and each element were null, would an array size of 800 bytes be transmitted? That is, does each element still occupy 8 bytes if it is null? </p> <p>UPDATE:</p> <p>Ultimately what I'm getting at with the above question, is I have a (x,y) data set on a server that represents a plot. The y data is unique, but the x-data is equally spaced. So, I can avoid transmitting the x-data from the server to the client (instead transmitting the x-interval and let the client re-create the predictable x-axis values). However, the array being passed from the server to the client appears as:</p> <pre><code>myArray[0].x = null myArray[0].y = 1e-302 myArray[1].x = null myArray[1].y = 1.42e-202 ... myArray[99].x = null myArray[99].y = 2.3234e-3 </code></pre> <p>and I'm wondering if those <code>null</code> values are going to each be 8 bytes long or if I'll get some memory savings because they are <code>null</code>.</p> <p>UPDATE 2:</p> <p>PDF page 82 here for the BlazeDS (e.g. LCDS) <a href="http://help.adobe.com/en_US/LiveCycleDataServicesES/3.1/Developing/lcds31_using.pdf" rel="nofollow">documentation</a> describes conversion from Java to ActionScript AMF3 (used by BlazeDS and LCDS). On PDF page 83 the table shows Java type <code>null</code> maps to ActionScript AMF3 type <code>null</code>. </p>
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    1. COThis is highly context-dependent.
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    2. COthat is 100% up to the protocol. is it actually AMF or is that just an example?
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    3. COAMF seems to encode nulls with one byte (0x01, the type byte) and doubles with nine bytes (the type byte followed by the 8-byte double). In that case, you will save a lot by encoding nulls instead of regular data values.
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