How Can I Efficiently Embed Formatted std::strings into File Streams in Modern C ?

Embedding Formatted std::string in File Streams with sprintf

Modern C streamlines the integration of sprintf-formatted std::strings into file streams. Newer techniques offer significant improvements over legacy methods.

C 20

C 20 introduces std::format, enabling straightforward string formatting using python-like replacement fields:

#include <iostream>
#include <format>

int main() {
    std::cout <p><strong>C  11</strong></p>
<p>C  11's std::snprintf provides a safe and user-friendly option:</p>
<pre class="brush:php;toolbar:false">#include <memory>
#include <string>
#include <stdexcept>

template<typename ... args>
std::string string_format(const std::string& format, Args ... args) {
    int size_s = std::snprintf(nullptr, 0, format.c_str(), args ...) + 1;
    if (size_s (size_s);
    std::unique_ptr<char> buf(new char[size]);
    std::snprintf(buf.get(), size, format.c_str(), args ...);
    return std::string(buf.get(), buf.get() + size - 1);
}</char></typename></stdexcept></string></memory>

注意事项

• Use std::snprintf to determine the required buffer size before writing to the char[].
• Check for any formatting errors after using std::snprintf.
• Use a unique_ptr to manage the allocated character array's memory.

Additional Options

• std::snprintf is renamed to _snprintf in Microsoft compilers.
• For expanded functionality and security features, consider using the {fmt} library.

Conclusion

Modern C techniques vastly improve upon older approaches for incorporating formatted std::strings into file streams. Opting for C 20's std::format provides the most streamlined and secure solution. C 11's std::snprintf offers a solid alternative for backwards compatibility, while external libraries like {fmt} can further enhance functionality.

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