Arduino IDE: How to get PROGMEM const length? I have defined a byte array as a constant in the Atmel's flash memory:

const uint8_t eye [] PROGMEM = {
  0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
  0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff
};


How can I (repeatedly) read the length of this constant in the program? All the available functions in avr/pgmspace.h do not deliver the proper length, no matter how I use them. I tried strlen(eye), strlen_P(eye), strLen_PF(eye) and also sizeof(eye). I'm new to C, so I'm not sure about the whole pointer stuff.
Probably the best way would be to define below it 

const int eye_len = sizeof(eye)/sizeof(eye[0]);


If the linker does link time optimization, or if you only use it within the same file (and declare it static), it shouldn’t cost any memory, otherwise it will take up two bytes of ram.