Function string_printf

src/butil/string_printf.cpp:80–99

}  // end anonymous namespace

std::string string_printf(const char* format, ...) {
    // snprintf will tell us how large the output buffer should be, but
    // we then have to call it a second time, which is costly. By
    // guestimating the final size, we avoid the double snprintf in many
    // cases, resulting in a performance win. We use this constructor
    // of std::string to avoid a double allocation, though it does pad
    // the resulting string with nul bytes. Our guestimation is twice
    // the format string size, or 32 bytes, whichever is larger.  This
    // is a heuristic that doesn't affect correctness but attempts to be
    // reasonably fast for the most common cases.
    std::string ret;
    va_list ap;
    va_start(ap, format);
    if (string_printf_impl(ret, std::max(32UL, strlen(format) * 2),
                           format, ap) != 0) {
        ret.clear();
    }
    va_end(ap);
    return ret;
}

std::string string_printf(size_t hint_size, const char* format, ...) {
    // snprintf will tell us how large the output buffer should be, but