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    copied!<p>Declare the structure as a packed structure to avoid alignment issues;</p> <p>On windows use <code>#pragma pack (1)</code> (see <a href="http://msdn.microsoft.com/en-us/library/2e70t5y1%28v=vs.80%29.aspx" rel="nofollow">msdn</a>) </p> <p>On gcc use <code>__attribute__((packed))</code> </p> <p>to remove alignment problems. Actually gcc will support the windows style pragmas for compatibility. Have a look at:</p> <p><a href="http://gcc.gnu.org/onlinedocs/gcc/Structure_002dPacking-Pragmas.html" rel="nofollow">http://gcc.gnu.org/onlinedocs/gcc/Structure_002dPacking-Pragmas.html</a></p> <p>EDIT</p> <p>So example code below shows ONE packed structure inside another untouched structure:</p> <p>When compiled on x86_64-bit platform:</p> <pre><code>#include &lt;iostream&gt; #include &lt;stdint.h&gt; #include &lt;string.h&gt; using namespace std; uint8_t input[] = { 0x00, 0x03, 0x23, 0x00, 0x57, 0x6f, 0x57, 0x00, 0x01, 0x0c, 0x01, 0xf3, 0x16, 0x36, 0x38, 0x78, 0x00, 0x6e, 0x69, 0x57, 0x00, 0x42, 0x47, 0x6e, 0x65, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x01, 0x05, 0x41, 0x44, 0x4d, 0x49, 0x4e }; struct __attribute__((packed)) packet{ uint8_t cmd; uint8_t error; uint16_t pkt_size; uint32_t gamename; uint8_t version1; uint8_t version2; uint8_t version3; uint16_t build; uint32_t platform; uint32_t os; uint32_t country; uint32_t timezone_bias; uint8_t ip[4]; uint8_t srp_I_len; uint8_t srp_I[16]; }; struct data { long int foo; short a; uint8_t b; struct packet p; uint32_t bar; }; int main() { struct packet p; struct data d; cout &lt;&lt; "in: " &lt;&lt; sizeof(input) &lt;&lt; ", d: " &lt;&lt; sizeof (d) &lt;&lt; ", p: " &lt;&lt; sizeof(p) &lt;&lt; " d.p: " &lt;&lt; sizeof(d.p) &lt;&lt; endl; memset(&amp;p, 0, sizeof(p)); memcpy(&amp;p, input, sizeof(input)); cout &lt;&lt; (int) p.srp_I_len &lt;&lt; endl; cout &lt;&lt; p.srp_I &lt;&lt; endl; } $./foo in: 39, d: 72, p: 50 d.p: 50 5 ADMIN </code></pre>
 

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