From 85969fb913c06e08e6481ebce55b1eba5a9f3292 Mon Sep 17 00:00:00 2001
From: Eric House <xwords@eehouse.org>
Date: Sun, 6 Sep 2020 15:55:56 -0700
Subject: [PATCH] seed random at start of jni, not of first game opened

Noticed the same emulator would always generate the same MQTT id, even
after a factory reset. That's because I was seeding rand() in that
jni *game* init code, not the (called-earlier) init of the whole jni
world. MQTT id generation happens on app launch before any game can be
opened so was using an unseeded rand().
---
 .../java/org/eehouse/android/xw4/jni/XwJNI.java   | 13 ++++++++-----
 xwords4/android/jni/xwjni.c                       | 15 ++++++++-------
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/xwords4/android/app/src/main/java/org/eehouse/android/xw4/jni/XwJNI.java b/xwords4/android/app/src/main/java/org/eehouse/android/xw4/jni/XwJNI.java
index 00a95a2bf..b7ddf995a 100644
--- a/xwords4/android/app/src/main/java/org/eehouse/android/xw4/jni/XwJNI.java
+++ b/xwords4/android/app/src/main/java/org/eehouse/android/xw4/jni/XwJNI.java
@@ -121,7 +121,11 @@ public class XwJNI {
     private long m_ptrGlobals;
     private XwJNI()
     {
-        m_ptrGlobals = initGlobals( new DUtilCtxt(), JNIUtilsImpl.get() );
+        long seed = Utils.nextRandomInt();
+        seed <<= 32;
+        seed |= Utils.nextRandomInt();
+        seed ^= System.currentTimeMillis();
+        m_ptrGlobals = globalsInit( new DUtilCtxt(), JNIUtilsImpl.get(), seed );
     }
 
     public static void cleanGlobalsEmu()
@@ -217,8 +221,7 @@ public class XwJNI {
     // Game methods
     private static GamePtr initGameJNI( long rowid )
     {
-        int seed = Utils.nextRandomInt();
-        long ptr = initGameJNI( getJNI().m_ptrGlobals, seed );
+        long ptr = gameJNIInit( getJNI().m_ptrGlobals );
         GamePtr result = 0 == ptr ? null : new GamePtr( ptr, rowid );
         return result;
     }
@@ -659,7 +662,7 @@ public class XwJNI {
     private static native int[] di_getIndices( long closure );
 
     // Private methods -- called only here
-    private static native long initGlobals( DUtilCtxt dutil, JNIUtils jniu );
+    private static native long globalsInit( DUtilCtxt dutil, JNIUtils jniu, long seed );
     private static native String dvc_getMQTTDevID( long jniState, String[] topic );
     private static native byte[] dvc_makeMQTTInvite( long jniState, NetLaunchInfo nli,
                                                      String[] addrToTopic );
@@ -675,7 +678,7 @@ public class XwJNI {
                                                byte[] stream );
     private static native byte[] nli_to_stream( long jniState, NetLaunchInfo nli );
     private static native NetLaunchInfo nli_from_stream( long jniState, byte[] stream );
-    private static native long initGameJNI( long jniState, int seed );
+    private static native long gameJNIInit( long jniState );
     private static native void envDone( long globals );
     private static native long dict_make( long jniState, byte[] dict, String name, String path );
     private static native void dict_ref( long dictPtr );
diff --git a/xwords4/android/jni/xwjni.c b/xwords4/android/jni/xwjni.c
index d10c84eb2..51a9f01ca 100644
--- a/xwords4/android/jni/xwjni.c
+++ b/xwords4/android/jni/xwjni.c
@@ -367,13 +367,17 @@ getState( JNIEnv* env, GamePtrType gamePtr, const char* func )
 #endif
 
 JNIEXPORT jlong JNICALL
-Java_org_eehouse_android_xw4_jni_XwJNI_initGlobals
-( JNIEnv* env, jclass C, jobject jdutil, jobject jniu )
+Java_org_eehouse_android_xw4_jni_XwJNI_globalsInit
+( JNIEnv* env, jclass C, jobject jdutil, jobject jniu, jlong jseed )
 {
 #ifdef MEM_DEBUG
     MemPoolCtx* mpool = mpool_make( NULL );
     XP_LOGF( "%s(): ptr size: %zu", __func__, sizeof(mpool) );
 #endif
+    int seed = (int)jseed;
+    XP_LOGFF( "calling srandom(seed %d)", seed );
+    srandom( seed );
+
     JNIGlobalState* globalState = (JNIGlobalState*)XP_CALLOC( mpool,
                                                               sizeof(*globalState) );
     map_init( MPPARM(mpool) &globalState->ti, env );
@@ -1227,8 +1231,8 @@ struct _JNIState {
     }                                                 \
 
 JNIEXPORT jlong JNICALL
-Java_org_eehouse_android_xw4_jni_XwJNI_initGameJNI
-( JNIEnv* env, jclass C, jlong jniGlobalPtr, jint seed )
+Java_org_eehouse_android_xw4_jni_XwJNI_gameJNIInit
+( JNIEnv* env, jclass C, jlong jniGlobalPtr )
 {
 #ifdef MEM_DEBUG
     MemPoolCtx* mpool = ((JNIGlobalState*)jniGlobalPtr)->mpool;
@@ -1245,9 +1249,6 @@ Java_org_eehouse_android_xw4_jni_XwJNI_initGameJNI
     MPASSIGN( state->mpool, mpool );
     globals->vtMgr = make_vtablemgr(MPPARM_NOCOMMA(mpool));
 
-    /* XP_LOGF( "%s: initing srand with %d", __func__, seed ); */
-    srandom( seed );
-
     /* LOG_RETURNF( "%p", state ); */
     return (jlong) state;
 }