if (len < UUID_STR_LEN + 1)

{

return false;

}

uint32_t ar[4];

for (uint8_t i = 0; i < 4; i++) {

ar[i] = mocpp_rng();

}

// Conforming to RFC 4122 Specification

// - byte 7: four most significant bits ==> 0100 --> always 4

// - byte 9: two most significant bits ==> 10 --> always {8, 9, A, B}.

//

// patch bits for version 1 and variant 4 here

ar[1] &= 0xFFF0FFFF; // remove 4 bits.

ar[1] |= 0x00040000; // variant 4

ar[2] &= 0xFFFFFFF3; // remove 2 bits

ar[2] |= 0x00000008; // version 1

// loop through the random 16 byte array

for (uint8_t i = 0, j = 0; i < 16; i++) {

// multiples of 4 between 8 and 20 get a -.

// note we are processing 2 digits in one loop.

if ((i & 0x1) == 0) {

if ((4 <= i) && (i <= 10)) {

uuidBuffer[j++] = '-';

}

}

// encode the byte as two hex characters

uint8_t nr = i / 4;

uint8_t xx = ar[nr];

uint8_t ch = xx & 0x0F;

uuidBuffer[j++] = (ch < 10)? '0' + ch : ('a' - 10) + ch;

ch = (xx >> 4) & 0x0F;

ar[nr] >>= 8;

uuidBuffer[j++] = (ch < 10)? '0' + ch : ('a' - 10) + ch;

}

uuidBuffer[UUID_STR_LEN] = 0;

return true;