Add local pseudo-RNG to randLIB

Rather than using system rand(), provide our own pseudo-RNG.

Generator used is "xoroshiro128+", which has 16 bytes of state and
2^128-1 period.

Main advantage is that we can now seed with up to 128 bits of entropy,
rather than the 32 bits srand() limited us to. We also can be assured of
the quality of the algorithm.

As the core generator is 64-bit, we now provide a get 64-bit function,
and others are based on this.

Incorporate Linux's /dev/urandom use into the main source file.

Author: kjbracey

mbed-client-randlib/platform/arm_hal_random.h

@@ -25,6 +25,10 @@ extern "C" {
 extern void arm_random_module_init(void);
 /**
  * \brief Get random library seed value.
+ *
+ * This function should return as random a value as possible, using
+ * hardware sources. Repeated calls should return different values if
+ * at all possible.
  */
 extern uint32_t arm_random_seed_get(void);
 #ifdef __cplusplus

mbed-client-randlib/randLIB.h

@@ -48,11 +48,23 @@ extern "C" {
 /**
   * \brief Init seed for Pseudo Random.
   *
+  * Makes call(s) to the platform's arm_random_seed_get() to seed the
+  * pseudo-random generator.
+  *
   * \return None
   *
   */
 extern void randLIB_seed_random(void);
 
+/**
+ * \brief Update seed for pseudo-random generator
+ *
+ * Adds seed information to existing generator, to perturb the
+ * sequence.
+ * \param seed 64 bits of data to add to the seed.
+ */
+extern void randLIB_add_seed(uint64_t seed);
+
 /**
   * \brief Generate 8-bit random number.
   *
@@ -75,21 +87,29 @@ extern uint16_t randLIB_get_16bit(void);
   * \brief Generate 32-bit random number.
   *
   * \param None
-  * \return 16-bit random number
+  * \return 32-bit random number
   *
   */
 extern uint32_t randLIB_get_32bit(void);
 
+/**
+  * \brief Generate 64-bit random number.
+  *
+  * \param None
+  * \return 64-bit random number
+  *
+  */
+extern uint64_t randLIB_get_64bit(void);
+
 /**
   * \brief Generate n-bytes random numbers.
   *
   * \param data_ptr pointer where random will be stored
-  * \param eight_bit_boundary how many bytes need random
-  * \return 0 process valid
-  * \return -1 Unsupported Parameters
+  * \param count how many bytes need random
   *
+  * \return data_ptr
   */
-extern int8_t randLIB_get_n_bytes_random(uint8_t *data_ptr, uint8_t eight_bit_boundary);
+extern void *randLIB_get_n_bytes_random(void *data_ptr, uint8_t count);
 
 /**
   * \brief Generate a random number within a range.
@@ -117,6 +137,12 @@ uint16_t randLIB_get_random_in_range(uint16_t min, uint16_t max);
   */
 uint32_t randLIB_randomise_base(uint32_t base, uint16_t min_factor, uint16_t max_factor);
 
+#ifdef RANDLIB_PRNG
+/* \internal Reset the PRNG state to zero (invalid) */
+void randLIB_reset(void);
+#endif
+
+
 #ifdef __cplusplus
 }
 #endif