[C++] Converting Binary Data to Types

[Schmacker]

Hi there,

I'm trying to teach myself some things about random file I/O with binary, and have come across a task that I am unsure I know how to approach.

Currently I write out a bunch of variable length structs to a binary file. They look something like this

struct testStruct
{
   std::string term;
   unsigned long termCount;
};
 

When writing out I am writing the length of the string before I write the string, as an unsigned long, so that I can know how long the string will be. After writing out 10 of theses to disk, I then read all 10 back in as a single chunk of binary data, using ifstream.read(), and store it in a char array.

What I want to do is then go through this array and, for want of a better term, extract the actual types and data out of the array. I have tried casting, but that just truncates, and I have tried bit shifts, but I think that I don't understand those well enough to actually make it work.

Can someone suggest a way to do this? Is bit shifting a good approach? Is there something that I haven't mentioned that could be used? It would be much appreciated.

Thanks,
Dylan Jenkinson

[Schmacker]

Never mind, I figured out what I was doing wrong.

Thanks

[sicarie]

Care to post what it was in case someone runs into a similar issue?

[weaknessforcats]

Most likely the data was written out in constant sized blocks. There's no random access of variable sized blocks.