crypto: document rest of rand submodule (#8580)

vlib/crypto/rand/utils.v

@@ -7,6 +7,7 @@ module rand
 import math.bits
 import encoding.binary
 
+// int_u64 returns a random unsigned 64-bit integer `u64` read from a real OS source of entropy.
 pub fn int_u64(max u64) ?u64 {
 	bitlen := bits.len_64(max)
 	if bitlen == 0 {
@@ -19,8 +20,8 @@ pub fn int_u64(max u64) ?u64 {
 	}
 	mut n := u64(0)
 	for {
-		mut bytes := read(k)?
-		bytes[0] &= byte(int(u64(1)<<b) - 1)
+		mut bytes := read(k) ?
+		bytes[0] &= byte(int(u64(1) << b) - 1)
 		x := bytes_to_u64(bytes)
 		n = x[0]
 		// NOTE: maybe until we have bigint could do it another way?
@@ -35,20 +36,20 @@ pub fn int_u64(max u64) ?u64 {
 }
 
 fn bytes_to_u64(b []byte) []u64 {
-	ws := 64/8
-	mut z := []u64{len:((b.len + ws - 1) / ws)}
+	ws := 64 / 8
+	mut z := []u64{len: ((b.len + ws - 1) / ws)}
 	mut i := b.len
 	for k := 0; i >= ws; k++ {
-		z[k] = binary.big_endian_u64(b[i-ws..i])
+		z[k] = binary.big_endian_u64(b[i - ws..i])
 		i -= ws
 	}
 	if i > 0 {
 		mut d := u64(0)
 		for s := u64(0); i > 0; s += u64(8) {
-			d |= u64(b[i-1]) << s
+			d |= u64(b[i - 1]) << s
 			i--
 		}
-		z[z.len-1] = d
+		z[z.len - 1] = d
 	}
 	return z
 }