Question

This might already have been discussed, but I couldn’t find any related topic.

I want to read short values from a file and store them in a buffer of int values using fread. So basically I want to do this:

  int *data; //int buffer
  data = (int *) malloc(1000 * sizeof(int));
  fread(data, sizeof(short), 1000, infile); //infile is organized in 2-byte chunks

Data are stored in a file in 2-byte chunks (short). But when I read those data, I want to put them into an int buffer. How can I do that without copying from a short buffer to an int buffer? fread gets void pointer, so it doesn’t care about the type of buffer.

Answer 1

The fread function doesn’t know about types, that’s correct. That’s why it cant read raw bytes and convert them, it just puts them as-is into the provided buffer. And as you know, a short on most platforms is two bytes while int is four. So that will not work as fread has not idea about that.

You either read one short at a time, putting it into the int buffer, or read into a temporary short buffer then loop and copy value by value into the int buffer.