What is the fastest way to deconstruct a fixed length binary/alpha message?

Question

What would you suggest as the fastest or best way to parse a fixed length message in c++ which has fields defined like

field = 'type', length = 2, type = 'alphanumeric'

field = 'length', length = 2, type = 'binary' (edit:length = 2 means 16 bit)
...
...

and so on

I read about making a struct and then using reinterpret_cast but im not sure how to use that or if there is any better method.

By parsing, i mean extracting human readable format like 'Type = X', 'Length = 15' etc

If possible, try using a look-up table loaded into memory. Simple comparisons are much faster than decoding. — Breakthrough
– Breakthrough, Commented Dec 8, 2009 at 14:29
What are the semantics of the binary type? Does length=2 mean any 16-bit quantity or 00-99? — Greg Bacon
– Greg Bacon, Commented Dec 8, 2009 at 14:32

2 revs · Accepted Answer · 2009-12-08 14:56:38Z

2

Is this what you mean?

char* binaryMessage; //From somewhere
struct Fields {
    short type; // 2 bytes
    short length; // 2 bytes
};
Fields* fields = reinterpret_cast<Fields*>(binaryMessage);
std::cout << "Type = " << fields->type;
std::cout << "Length = " << fields->length;

A safer alternative is boost::basic_bufferstream:

basic_bufferstream<char> stream(binaryMessage, lengthOfMessage, std::ios_base::in);
Fields fields;
stream >> fields.type;
stream >> fields.length;

edited Dec 8, 2009 at 14:56

community wiki

2 revs
Andreas Brinck

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1 Comment

randomThought Over a year ago

This is one way though but is it really safe since reinterpret_cast is considered pretty dangerous to use

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