Function is_integer

libraries/lib-string-utils/3party/fast_float.h:479–479

Next function can be micro-optimized, but compilers are entirely able to optimize it well.

// Next function can be micro-optimized, but compilers are entirely
// able to optimize it well.
fastfloat_really_inline bool is_integer(char c)  noexcept  { return c >= '0' && c <= '9'; }

fastfloat_really_inline uint64_t byteswap(uint64_t val) {
  return (val & 0xFF00000000000000) >> 56