Function VFormat

layers/utils/text_utils.cpp:25–50

namespace text {

std::string VFormat(const char* format, va_list argptr) {
    // Counts actual characters. Null terminator is accounted separately.
    const int initial_max_symbol_count = 1024;

    // Use vector as the output buffer for c-style formatting routines.
    // Do not write directly to std::string internal storage because its
    // structure and null terminator convention is not standardized.
    std::vector<char> buffer(initial_max_symbol_count + 1 /*null terminator*/);

    // The va_list will be modified by the call to vsnprintf. Use a copy in case we need to try again.
    va_list argptr2;
    va_copy(argptr2, argptr);
    const int symbol_count = vsnprintf(buffer.data(), buffer.size(), format, argptr2);
    va_end(argptr2);

    if (symbol_count < 0) {
        assert(false && "unexpected vsnprintf error");
        return {};
    }
    if (symbol_count > initial_max_symbol_count) {
        buffer.resize(symbol_count + 1 /*null terminator*/);
        vsnprintf(buffer.data(), buffer.size(), format, argptr);
    }
    std::string str(buffer.data());
    return str;
}

std::string Format(const char* format, ...) {
    va_list argptr;