48.2. Byte order signatures and conversion blocks

Byte order signatures are known integer values that are available in the foreign system's byte oder. By examining these on a byte by byte basis, the byte ordering of the remote system can be determined. While typically systems have a consistent ordering of bytes in words and words in longwords, the library does not assume that.

A system that is supplying data to be converted with this library must provide a 16 bit and a 32 bit signature. These are the values 0x0102 and 0x01020304 repsectively written in that system's native byte ordering.

The function makecvtblock takes those signatures and delivers a DaqConversion block. The DaqConversion block is a data structure that provides conversion tables for foreign to host and host to foreign conversions.

Suppose you have data in a structure that contains these signatures as fields named s_ssig and s_lsig. The example below shows how to create a conversion block:

Example 48-4. Creating a DaqConversion

#include <cvt.h>
DaqConversion conversionBlock;
makecvtblock(data.s_lsig, data.s_ssig, &conversionBlock);

The DaqConversion block conversionBlock can be used in subsequent calls to do byte order conversions.