From 021c79f038c218a55b145fafcda5c59cf3a309d8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20Str=C3=B8mme?= <christian.stromme@digia.com>
Date: Fri, 11 Oct 2013 14:55:33 +0200
Subject: [PATCH] Android: Use java.util.Random in qrand()

Android does not provide rand_r(), so we would fall back to rand()
and srand() which means we where not keeping the promise of qrand
and qsrand being thread-safe. As a replacement we can use the Java
api and have one Random object for each thread.

Task-number: QTBUG-32814
Change-Id: Id46d195a0bb122bc7a5a8de43bdf088e11a9c42e
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
---
 src/corelib/global/qglobal.cpp | 36 ++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index ff2c4bbe5e1..1dd77c5859c 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -76,6 +76,10 @@
 #include <CoreServices/CoreServices.h>
 #endif
 
+#if defined(Q_OS_ANDROID)
+#include <private/qjni_p.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 #if !QT_DEPRECATED_SINCE(5, 0)
@@ -2335,6 +2339,9 @@ typedef uint SeedStorageType;
 typedef QThreadStorage<SeedStorageType *> SeedStorage;
 Q_GLOBAL_STATIC(SeedStorage, randTLS)  // Thread Local Storage for seed value
 
+#elif defined(Q_OS_ANDROID)
+typedef QThreadStorage<QJNIObjectPrivate> AndroidRandomStorage;
+Q_GLOBAL_STATIC(AndroidRandomStorage, randomTLS)
 #endif
 
 /*!
@@ -2368,6 +2375,16 @@ void qsrand(uint seed)
         //global static object, fallback to srand(seed)
         srand(seed);
     }
+#elif defined(Q_OS_ANDROID)
+    QJNIObjectPrivate random = QJNIObjectPrivate("java/util/Random",
+                                                 "(J)V",
+                                                 jlong(seed));
+    if (!random.isValid()) {
+        srand(seed);
+        return;
+    }
+
+    randomTLS->setLocalData(random);
 #else
     // On Windows srand() and rand() already use Thread-Local-Storage
     // to store the seed between calls
@@ -2409,6 +2426,25 @@ int qrand()
         //global static object, fallback to rand()
         return rand();
     }
+#elif defined(Q_OS_ANDROID)
+    AndroidRandomStorage *randomStorage = randomTLS();
+    if (!randomStorage)
+        return rand();
+
+    QJNIObjectPrivate random;
+    if (!randomStorage->hasLocalData()) {
+        random = QJNIObjectPrivate("java/util/Random",
+                                   "(J)V",
+                                   jlong(1));
+        if (!random.isValid())
+            return rand();
+
+        randomStorage->setLocalData(random);
+    } else {
+        random = randomStorage->localData();
+    }
+
+    return random.callMethod<jint>("nextInt", "(I)I", RAND_MAX);
 #else
     // On Windows srand() and rand() already use Thread-Local-Storage
     // to store the seed between calls