How Can I Efficiently Read and Write Binary Files in C Avoiding Buffering Issues?

Reading and Writing Binary Files Effectively

Attempting to read and write binary files often poses challenges, such as when the resulting buffer only contains a fraction of the intended data. If you encounter this issue, this article provides two alternative approaches that address these limitations.

C -Specific Approach

The following C code uses the copy function and stream iterators to directly copy the file's contents without buffering:

#include <fstream>
#include <iterator>
#include <algorithm>

int main()
{
    std::ifstream input("C:\Final.gif", std::ios::binary);
    std::ofstream output("C:\myfile.gif", std::ios::binary);

    std::copy(
        std::istreambuf_iterator<char>(input),
        std::istreambuf_iterator<char>(),
        std::ostreambuf_iterator<char>(output));
}

This approach maintains the file's integrity and ensures accurate data transfer.

Buffering with a Vector

If you require the file's contents in a buffer for modifications, the following code uses a vector and stream iterators:

#include <fstream>
#include <iterator>
#include <vector>

int main()
{
    std::ifstream input("C:\Final.gif", std::ios::binary);

    // Copies all data into buffer
    std::vector<unsigned char> buffer(
        std::istreambuf_iterator<char>(input), {});
}

This solution allows you to manipulate the file's contents in-memory before writing them to the desired output file.

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