How to convert different data-types to bytes in c++?

Question

I have a structure that looks like:

typedef struct{
  float distance;
  float reflectivity;      
}data_point;

typedef struct{
  int flag;
  float Azimuth;
  data_point points[32];
}data_block;

A data point is represented in the packet by three bytes - two bytes of distance and one byte of calibrated reflectivity. The distance is an unsigned integer. It has 2 mm granularity. Hence, a reported value of 51,154 represents 102,308 mm or 102.308 m. Calibrated reflectivity is reported on a scale of 0 to 255. The elevation angle (ω) is inferred based on the position of the data point within a data block.
flag from float to 2 bytes(constant 0xFFEE)
A two-byte azimuth value (α) appears after the flag bytes at the beginning of each data block. The azimuth is an unsigned integer. It represents an angle in hundredths of a degree. Therefore, a raw value of 27742 should be interpreted as 277.42°

How can I create a vector of 100 bytes of binary data? ( 2 + 2 + (32x3))?

You can't assume that the classes will have no padding, as your calculation implies. — Bathsheba
– Bathsheba, Commented Sep 9, 2019 at 12:10
One tedious option unaffected by compiler padding is to replace your structs with something that is exactly the size you desire (perhaps using a size setting constructor). Consider a std::vector<T>, where T might be uint8_t or char. Then add methods to read or write each field. When only a 'few' fields, this is not too bad, but it can grow quickly. A team I know used this approach when the 'other compiler' (sender vs receiver) was different, and either compiler padded differently. — 2785528
– 2785528, Commented Sep 9, 2019 at 12:34

Claudio · Accepted Answer · 2019-09-09 12:17:56Z

2

You can either:

Use a (custom) solution, as long as the compiler is instructed for not padding data
Rely on a serialization library. You could e.g. use SerializeToArray() provided by Google's protobuf library

answered Sep 9, 2019 at 12:17

Claudio

11k4 gold badges35 silver badges77 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Tom Trebicky Over a year ago

So many solutions, I would also offer Google's Flattbuffers and Boost Serialization.

Claudio Over a year ago

@tom Thank you for the contribution. If I'm not mistaking, flatbuffers are not by Google.

Tom Trebicky Over a year ago

I think they were written by Wouter van Oortmerssen while working at Fun Propulsion Labs, Google. I could be wrong though...

Collectives™ on Stack Overflow

How to convert different data-types to bytes in c++?

1 Answer 1

3 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Related