Move random number generator from Math.random to jerry-libc, replace the logic with call to rand in Math.random.

JerryScript-DCO-1.0-Signed-off-by: Ruben Ayrapetyan r.ayrapetyan@samsung.com

jerry-libc/include/stdlib.h

@@ -25,4 +25,15 @@
 extern EXTERN_C void __attribute__ ((noreturn)) exit (int);
 extern EXTERN_C void __attribute__ ((noreturn)) abort (void);
 
+/**
+ * Maximum integer that could be returned by random number generator
+ *
+ * See also:
+ *          rand
+ */
+#define RAND_MAX (0x7fffffffu)
+
+extern EXTERN_C int rand (void);
+extern EXTERN_C void srand (unsigned int);
+
 #endif /* !JERRY_LIBC_STDLIB_H */

jerry-libc/jerry-libc.c

@@ -24,6 +24,11 @@
 
 #include "jerry-libc-defs.h"
 
+/**
+ * State of pseudo-random number generator
+ */
+static unsigned int libc_random_gen_state[4] = { 1455997910, 1999515274, 1234451287, 1949149569 };
+
 /**
  * Standard file descriptors
  */
@@ -326,3 +331,38 @@ isxdigit (int c)
 {
   return isdigit (c) || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F');
 }
+
+/**
+ * Generate pseudo-random integer
+ *
+ * Note:
+ *      The function implements George Marsaglia's XorShift random number generator
+ *
+ * @return integer in range [0; RAND_MAX]
+ */
+int
+rand (void)
+{
+  uint32_t intermediate = libc_random_gen_state[0] ^ (libc_random_gen_state[0] << 11);
+  intermediate ^= intermediate >> 8;
+
+  libc_random_gen_state[0] = libc_random_gen_state[1];
+  libc_random_gen_state[1] = libc_random_gen_state[2];
+  libc_random_gen_state[2] = libc_random_gen_state[3];
+
+  libc_random_gen_state[3] ^= libc_random_gen_state[3] >> 19;
+  libc_random_gen_state[3] ^= intermediate;
+
+  uint32_t ret = libc_random_gen_state[3] % (RAND_MAX + 1u);
+
+  return (int32_t) ret;
+} /* rand */
+
+/**
+ * Initialize pseudo-random number generator with the specified seed value
+ */
+void
+srand (unsigned int seed) /**< new seed */
+{
+  libc_random_gen_state[3] = seed;
+} /* srand */