Question

I’m working on a project with a “customer made” database. He developed a C++/CLI application that stores and retrieves his data from a binary file using the BinaryWriter.Write(String) and BinaryReader.ReadString() methods.

I’m no C++/CLI expert but from what I understand these methods use a 7-bits encoding of the first bytes to determine the String length.

I need to access his data from a rail application, anyone’s got an idea of how to do the same think in ruby?

Answer 1

If you’re dealing with raw binary data, you’ll probably need to spend some time familiarizing yourself with the pack and unpack methods and their various options. Maybe what you’re describing is a “Pascal string” where the length is encoded up front, or a variation on that.

For example:

length = data.unpack("C")[0]
string = data.unpack("Ca#{length}")[0]

The double-unpack is required because you don’t know the length of the string to unpack until you do the first step. You could probably do this using a substring as well, like data[1,length] if you’re reasonably certain you’re not dealing with UTF-8 data.