How to Effectively Read Binary Files into a Vector of Unsigned Chars?

Reading Binary Files into a Vector of Unsigned Chars

When tasked with reading a binary file into a vector of unsigned chars, several options present themselves.

Option 1: Explicit Cast to char*

This approach reads the data into a vector using an explicit cast to char*:

<code class="cpp">std::vector<BYTE> readFile(const char* filename) {
    // ...
    file.read((char*) &fileData[0], fileSize);
    return fileData;
}</code>

While functional, it requires an explicit cast, which can be a source of unease.

Option 2: istreambuf_iterator with char

Using std::istreambuf_iterator with char as the template argument simplifies the code:

<code class="cpp">std::vector<BYTE> readFile(const char* filename) {
    // ...
    return std::vector<BYTE>(std::istreambuf_iterator<char>(file),
                            std::istreambuf_iterator<char>());
}</code>

However, it still uses char in the iterator, even though the vector contains unsigned char.

Option 3: basic_ifstream with BYTE

This option explicitly declares the input file stream to use BYTE as the type, providing clarity of intent:

<code class="cpp">std::vector<BYTE> readFile(const char* filename) {
    // ...
    std::basic_ifstream<BYTE> file(filename, std::ios::binary);
    return std::vector<BYTE>(std::istreambuf_iterator<BYTE>(file),
                            std::istreambuf_iterator<BYTE>());
}</code>

The suitability of basic_ifstream depends on the specific use case.

istreambuf_iterator: Simplicity vs Efficiency

std::istreambuf_iterator offers simplicity but may not be the most efficient option for binary data. It uses >> to interpret data, potentially introducing unnecessary overhead. Consider alternative approaches like std::copy.

Additional Considerations

• Ensure the file stream is open.
• Test the performance of different options with binary data.
• Set std::ios::skipws to false for binary files to avoid skipping newlines.

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