[AGENT++] Bug in asn1.cpp on 64-bit architecture

[Alex Agranov]

I ported my application that uses SNMP++/AGENT++ stacks to the 64-bit SPARC Solaris box and discovered that it fails to parse incoming SNMP messages. I localized the bug and fixed it, so that now my application runs just fine.

The patch is a one-liner fix in asn_parse_length() function in asn1.cpp module.
It is related to the fact that on 64-bit architecture (both Solaris and Linux) sizeof(int)==4 but sizeof(long)==8, while on 32-bit architecture both types are 4 bytes long.

# diff -C2 asn1.cpp asn1.orig
*** asn1.cpp    Wed Feb  4 15:44:28 2009
--- asn1.orig   Wed Feb  4 15:53:48 2009
***************
*** 544,548 ****
      memcpy((char *)length, (char *)data + 1, (int)lengthbyte);
      *length = ntohl(*length);
!     *length >>= (8 * ((sizeof(unsigned long)) - lengthbyte));
      // check for length greater than 2^31
      if (*length > 0x80000000ul) {
--- 544,548 ----
      memcpy((char *)length, (char *)data + 1, (int)lengthbyte);
      *length = ntohl(*length);
!     *length >>= (8 * ((sizeof(int)) - lengthbyte));
      // check for length greater than 2^31
      if (*length > 0x80000000ul) {

I already reported before (about half a year ago) that SNMP++/AGENT++ sometimes uses 64-bit data types (long) instead of 32-bit data types (int) on 64-bit architectures. However now I can confirm that besides the minor bug described above, the ASN parser and the rest of the stack seem to  work just fine (of course we waste some memory, but it's not a big deal for me)...

Regards,
   Alex Agranov

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