return syscall.SetNonblock(fd.Sysfd, false)
}

// Darwin and FreeBSD can't read or write 2GB+ files at a time,
// even on 64-bit systems.
// The same is true of socket implementations on many systems.
// See golang.org/issue/7812 and golang.org/issue/16266.
// Use 1GB instead of, say, 2GB-1, to keep subsequent reads aligned.
const maxRW = 1 << 30

// Read implements io.Reader.

  // There is a limit of 2GB for a flatbuffer.
  bool flatbuffer_limit_exceeded = builder_.GetSize() > flatbuffer_size_max;
  if (flatbuffer_limit_exceeded && require_use_buffer_offset_ == false) {
    require_use_buffer_offset_ = true;
    return std::nullopt;
  }
  if (flatbuffer_limit_exceeded) {
    LOG(ERROR) << "Model structure size is bigger than 2gb";
    return std::nullopt;
  }

	// exceed Go's 48 bit limit, it's extremely unlikely in
	// practice.
	//
	// On 32-bit platforms, we accept the full 32-bit address
	// space because doing so is cheap.
	// mips32 only has access to the low 2GB of virtual memory, so
	// we further limit it to 31 bits.
	//
	// On ios/arm64, although 64-bit pointers are presumably
	// available, pointers are truncated to 33 bits in iOS <14.

				// the base address for the executable.
				o -= PEBASE
			}

			// On amd64, 4-byte offsets will be sign-extended, so it is impossible to
			// access more than 2GB of static data; fail at link time is better than
			// fail at runtime. See https://golang.org/issue/7980.
			// Instead of special casing only amd64, we treat this as an error on all

    * when converter flag "_experimenal_use_buffer_offset" is enabled, additional metadata is automatically excluded from the generated model. The behaviour is the same as "exclude_conversion_metadata" is set
    * If the model is larger than 2GB, then we also require "exclude_conversion_metadata" flag to be set

### Major Features and Improvements