Copy RNG from Glulxe, add support for native RNG too

config.h

@@ -19,6 +19,9 @@
 // Define this if we can use the "inline" keyword.
 // #define USE_INLINE
 
+// Define this to use a function native_random() to get random numbers.
+// #define USE_NATIVE_RANDOM
+
 // Define this to memory-map the game file to speed up loading. (Unix-specific)
 // #define USE_MMAP
 

git.h

@@ -120,8 +120,7 @@ extern git_sint32* gStackPointer;
 
 extern enum IOMode gIoMode;
 
-extern glui32 lo_random ();
-extern void lo_seed_random (glui32 seed);
+extern glui32 native_random ();
 
 extern void startProgram (size_t cacheSize);
 

git_unix.c

@@ -104,3 +104,12 @@ void glk_main ()
 }
 
 #endif // USE_MMAP
+
+#ifdef USE_NATIVE_RANDOM
+
+glui32 native_random()
+{
+    return arc4random();
+}
+
+#endif // USE_NATIVE_RANDOM

git_windows.c

@@ -1,5 +1,9 @@
 // Startup code for Windows Git
 
+#ifdef _MSC_VER // For Visual C++, get rand_s()
+#define _CRT_RAND_S
+#endif
+
 #include "glk.h"
 #include "WinGlk.h"
 #include "git.h"
@@ -101,3 +105,13 @@ void glk_main()
         CloseHandle(file);
 }
 
+glui32 native_random()
+{
+#ifdef _MSC_VER
+    unsigned int value;
+    rand_s(&value);
+    return value;
+#else
+    return xo_random();
+#endif
+}

glkop.c

@@ -100,7 +100,6 @@
 
 #define glulx_malloc malloc
 #define glulx_free free
-#define glulx_random lo_random
 
 #ifndef TRUE
 #define TRUE 1
@@ -109,6 +108,7 @@
 #define FALSE 0
 #endif
 
+#include <time.h>
 #include "glk.h"
 #include "git.h"
 #include "gi_dispa.h"
@@ -270,7 +270,8 @@ static maybe_unused char *get_game_id(void);
 int git_init_dispatch()
 {
   int ix;
-
+  int randish;
+
   /* What with one thing and another, this *could* be called more than
      once. We only need to allocate the tables once. */
   if (git_classes)
@@ -289,8 +290,9 @@ int git_init_dispatch()
   if (!git_classes)
     return FALSE;
 
+  randish = time(NULL) % 101;
   for (ix=0; ix<num_classes; ix++) {
-    git_classes[ix] = new_classtable((glulx_random() % (glui32)(101)) + 1);
+    git_classes[ix] = new_classtable(1+120*ix+randish);
     if (!git_classes[ix])
       return FALSE;
   }

terp.c

@@ -35,38 +35,85 @@ enum IOMode gIoMode = IO_NULL;
 // -------------------------------------------------------------
 // Random number generator, from Glulxe
 
-static glui32 rand_table[55]; /* State for the RNG. */
-static int rand_index1, rand_index2;
+static glui32 xo_random(void);
+static void xo_seed_random(glui32 seed);
 
-glui32 lo_random()
+static int rand_use_native = 1;
+
+/* Set the random-number seed, and also select which RNG to use.
+*/
+void git_seed_random(glui32 seed)
 {
-  rand_index1 = (rand_index1 + 1) % 55;
-  rand_index2 = (rand_index2 + 1) % 55;
-  rand_table[rand_index1] = rand_table[rand_index1] - rand_table[rand_index2];
-  return rand_table[rand_index1];
+  if (seed == 0)
+  {
+    rand_use_native = 1;
+    xo_seed_random(time(NULL));
+  }
+  else
+  {
+    rand_use_native = 0;
+    xo_seed_random(seed);
+  }
 }
 
-void lo_seed_random(glui32 seed)
+/* Return a random number in the range 0 to 2^32-1. */
+glui32 git_random()
 {
-  glui32 k = 1;
-  int i, loop;
-
-  rand_table[54] = seed;
-  rand_index1 = 0;
-  rand_index2 = 31;
-
-  for (i = 0; i < 55; i++) {
-    int ii = (21 * i) % 55;
-    rand_table[ii] = k;
-    k = seed - k;
-    seed = rand_table[ii];
-  }
-  for (loop = 0; loop < 4; loop++) {
-    for (i = 0; i < 55; i++)
-      rand_table[i] = rand_table[i] - rand_table[ (1 + i + 30) % 55];
+#ifdef USE_NATIVE_RANDOM
+  if (rand_use_native)
+    return native_random();
+#endif
+  return xo_random();
+}
+
+/* This is the "xoshiro128**" random-number generator and seed function.
+Adapted from: https://prng.di.unimi.it/xoshiro128starstar.c
+About this algorithm: https://prng.di.unimi.it/
+*/
+static uint32_t xo_table[4];
+
+static void xo_seed_random(glui32 seed)
+{
+  int ix;
+  /* Set up the 128-bit state from a single 32-bit integer. We rely
+  on a different RNG, SplitMix32. This isn't high-quality, but we
+  just need to get a bunch of bits into xo_table. */
+  for (ix=0; ix<4; ix++) {
+    seed += 0x9E3779B9;
+    glui32 s = seed;
+    s ^= s >> 15;
+    s *= 0x85EBCA6B;
+    s ^= s >> 13;
+    s *= 0xC2B2AE35;
+    s ^= s >> 16;
+    xo_table[ix] = s;
   }
 }
 
+static glui32 xo_random(void)
+{
+  /* I've inlined the utility function:
+  rotl(x, k) => (x << k) | (x >> (32 - k))
+  */
+
+  const uint32_t t1x5 = xo_table[1] * 5;
+  const uint32_t result = ((t1x5 << 7) | (t1x5 >> (32-7))) * 9;
+
+  const uint32_t t1s9 = xo_table[1] << 9;
+
+  xo_table[2] ^= xo_table[0];
+  xo_table[3] ^= xo_table[1];
+  xo_table[1] ^= xo_table[2];
+  xo_table[0] ^= xo_table[3];
+
+  xo_table[2] ^= t1s9;
+
+  const uint32_t t3 = xo_table[3];
+  xo_table[3] =  ((t3 << 11) | (t3 >> (32-11)));
+
+  return result;
+}
+
 // -------------------------------------------------------------
 // Floating point support
 
@@ -202,7 +249,7 @@ void startProgram (size_t cacheSize)
     initCompiler (cacheSize);
 
     // Initialise the random number generator.
-    lo_seed_random (time(NULL));
+    git_seed_random (0);
 
     // Set up the stack.
 
@@ -1271,17 +1318,17 @@ do_S1_addr8:  memWrite8 (READ_PC, S1); NEXT;
 
     do_random:
         if (L1 > 0)
-            S1 = lo_random () % L1;
+            S1 = git_random () % L1;
         else if (L1 < 0)
-            S1 = -(lo_random () % -L1);
+            S1 = -(git_random () % -L1);
         else
         {
-            S1 = lo_random ();
+            S1 = git_random ();
         }
         NEXT;
 
     do_setrandom:
-        lo_seed_random (L1 ? L1 : time(NULL));
+        git_seed_random (L1);
         NEXT;
 
     do_glk:

win/Git.vcxproj

@@ -50,7 +50,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <AdditionalIncludeDirectories>WindowsGlk/include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>USE_INLINE;USE_DIRECT_THREADING;WIN32;_DEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>USE_NATIVE_RANDOM;USE_INLINE;USE_DIRECT_THREADING;WIN32;_DEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <Optimization>Disabled</Optimization>
@@ -74,7 +74,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
       <AdditionalIncludeDirectories>WindowsGlk/include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>USE_INLINE;USE_DIRECT_THREADING;WIN32;NDEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>USE_NATIVE_RANDOM;USE_INLINE;USE_DIRECT_THREADING;WIN32;NDEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <AdditionalOptions>-Wno-unused-function %(AdditionalOptions)</AdditionalOptions>
@@ -147,4 +147,4 @@ copy help\Git.chm $(OutDir)</Command>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>