CODEWITHSUNDEEP
c++filevectorbinary
user13131159
user13131159

Reputation:

Reading from binary file to vector.c++

How to read from binary file (bytes, also known as unsigned charin C++) to vector skipping the first value which is number as unsigned int 32, because the first value is also the size of vector?

First value is also the size of the whole file.

Upvotes: 0

Views: 1701

Answers (1)

Thomas Matthews
Thomas Matthews

Reputation: 57678

You could try something like this: 

uint32_t data_size = 0;
data_file.read((char *) &data_size, sizeof(data_size));
std::vector<uint8_t> data(data_size);
data_file.read((char *) &data[0], data_size);

The above code fragment first reads the size or quantity of the data from the file.
A std::vector is created, using the quantity value that was read in.
Finally, the data is read into the vector.

Edit 1: Memory-mapped files
You may want to consider opening the data file as a memory mapped file. This is where the Operating System treats the file as memory. You don't have to store the data in memory nor read it in. Since memory mapped file APIs vary among operating systems, you'll have to search your Operating System API to find out how to use the feature.

Upvotes: 2

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