JavaScriptCore-521.tar.gz

[apple/javascriptcore.git] / wtf / RandomNumber.cpp

diff --git a/wtf/RandomNumber.cpp b/wtf/RandomNumber.cpp
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+/*
+ * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
+ *           (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "RandomNumber.h"
+
+#include "RandomNumberSeed.h"
+
+#include <limits>
+#include <limits.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+namespace WTF {
+
+double weakRandomNumber()
+{
+#if COMPILER(MSVC) && defined(_CRT_RAND_S)
+    // rand_s is incredibly slow on windows so we fall back on rand for Math.random
+    return (rand() + (rand() / (RAND_MAX + 1.0))) / (RAND_MAX + 1.0);
+#else
+    return randomNumber();
+#endif
+}
+
+double randomNumber()
+{
+#if !ENABLE(JSC_MULTIPLE_THREADS)
+    static bool s_initialized = false;
+    if (!s_initialized) {
+        initializeRandomNumberGenerator();
+        s_initialized = true;
+    }
+#endif
+    
+#if COMPILER(MSVC) && defined(_CRT_RAND_S)
+    uint32_t bits;
+    rand_s(&bits);
+    return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
+#elif PLATFORM(DARWIN)
+    uint32_t bits = arc4random();
+    return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
+#elif PLATFORM(UNIX)
+    uint32_t part1 = random() & (RAND_MAX - 1);
+    uint32_t part2 = random() & (RAND_MAX - 1);
+    // random only provides 31 bits
+    uint64_t fullRandom = part1;
+    fullRandom <<= 31;
+    fullRandom |= part2;
+
+    // Mask off the low 53bits
+    fullRandom &= (1LL << 53) - 1;
+    return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
+#else
+    uint32_t part1 = rand() & (RAND_MAX - 1);
+    uint32_t part2 = rand() & (RAND_MAX - 1);
+    // rand only provides 31 bits, and the low order bits of that aren't very random
+    // so we take the high 26 bits of part 1, and the high 27 bits of part2.
+    part1 >>= 5; // drop the low 5 bits
+    part2 >>= 4; // drop the low 4 bits
+    uint64_t fullRandom = part1;
+    fullRandom <<= 27;
+    fullRandom |= part2;
+
+    // Mask off the low 53bits
+    fullRandom &= (1LL << 53) - 1;
+    return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
+#endif
+}
+
+}