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POData serialization in C?
 

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    <p>I have this structure which I want to write to a file:</p> <pre><code>typedef struct { char* egg; unsigned long sausage; long bacon; double spam; } order; </code></pre> <p>This file must be binary and must be readable by any machine that has a C99 compiler.</p> <p>I looked at various approaches to this matter such as ASN.1, XDR, XML, ProtocolBuffers and many others, but none of them fit my requirements:</p> <ul> <li>small</li> <li>simple</li> <li>written in <strong>C</strong></li> </ul> <p>I decided then to make my own data protocol. I could handle the following representations of <strong>integer</strong> types:</p> <ul> <li>unsigned</li> <li>signed in <em>one's complement</em></li> <li>signed in <em>two's complement</em></li> <li>signed in <em>sign and magnitude</em></li> </ul> <p>in a valid, simple and clean way (impressive, no?). However, the <strong>real</strong> types are being a pain now.</p> <p>How should I read <code>float</code> and <code>double</code> from a byte stream? The standard says that bitwise operators (at least <code>&amp;</code>, <code>|</code>, <code>&lt;&lt;</code> and <code>&gt;&gt;</code>) are for <strong>integer</strong> types only, which left me without hope. The only way I could think was:</p> <pre><code>int sign; int exponent; unsigned long mantissa; order my_order; sign = read_sign(); exponent = read_exponent(); mantissa = read_mantissa(); my_order.spam = sign * mantissa * pow(10, exponent); </code></pre> <p>but that doesn't seem really efficient. I also could not find a description of the representation of <code>double</code> and <code>float</code>. How should one proceed before this?</p>
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