Currently I read arrays in C++ with ifstream, read and reinterpret_cast by making a loop on values. Is it possible to load for example an unsigned int array from a binary file in one time without making a loop ?
Thank you very much
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1 Answer
Yes, simply pass the address of the first element of the array, and the size of the array in bytes:
// Allocate, for example, 47 ints
std::vector<int> numbers(47);
// Read in as many ints as 'numbers' has room for.
inFile.read(&numbers[0], numbers.size()*sizeof(numbers[0]));
Note: I almost never use raw arrays. If I need a sequence that looks like an array, I use std::vector. If you must use an array, the syntax is very similar.
The ability to read and write binary images is non-portable. You may not be able to re-read the data on another machine, or even on the same machine with a different compiler. But, you have that problem already, with the solution that you are using now.
3 Comments
CashCow
What you probably mean is that your code is not portable across different endian-ness or integral sizes, which leads to using a "one-at-a-time" conversion approach, however it is still faster even doing that than reading text format.
Vincent
What do you mean by not portable ? If you mean endianness and different size for int types, I try to write a class with template parameters to take that into account during reading. I can't use "text" files because I have already more than 1 Po of binary files on a supercomputer and I can't even imagine how much it would weight in "text" mode... So do you have a more portable version than raw binary files ?
Robᵩ
@Vincent - Yes, I mean endianess, size, and alignment. As I said, you must have solved those problems already.