Implemented rand() and srand()

photon/libc/include/stdlib.h

@@ -14,6 +14,9 @@ extern void *realloc(void *ptr, size_t sz);
 extern void *calloc(size_t n, size_t sz);
 extern void free(void *ptr);
 
+extern int rand(void);
+extern void srand(unsigned int seed);
+
 extern int atoi(const char *str);
 extern double atof(const char *str);
 extern long int strtol(const char *str, char **endptr, int base);

photon/libc/stdlib/rand.c

@@ -0,0 +1,31 @@
+#include <stddef.h>
+
+static unsigned int seed = 0;
+
+void srand(unsigned int _seed)
+{
+    seed = _seed;
+}
+
+int rand(void)
+{
+    int next = seed;
+    int result;
+
+    next *= 1103515245;
+    next += 12345;
+    result = (int)(next / 65536) % 2048;
+
+    next *= 1103515245;
+    next += 12345;
+    result <<= 10;
+    result ^= (int)(next / 65536) % 1024;
+
+    next *= 1103515245;
+    next += 12345;
+    result <<= 10;
+    result ^= (int)(next / 65536) % 1024;
+
+    seed = next;
+    return result;
+}