Changeset 49056 in webkit for trunk/JavaScriptCore/wtf/RandomNumber.cpp

Timestamp:

Oct 2, 2009, 4:35:31 PM (16 years ago)

Author:

[email protected]

Message:

2009-10-02 Jonni Rainisto <​[email protected]>

Reviewed by Darin Adler.

Math.random() gives too low values on Win32 when _CRT_RAND_S is not defined
​https://bugs.webkit.org/show_bug.cgi?id=29956

• wtf/RandomNumber.cpp: (WTF::randomNumber): Added PLATFORM(WIN_OS) to handle 15bit rand()

File:

• trunk/JavaScriptCore/wtf/RandomNumber.cpp (modified) (1 diff)

trunk/JavaScriptCore/wtf/RandomNumber.cpp

@@ -83 +83 @@
 #elif PLATFORM(WINCE)
     return genrand_res53();
+#elif PLATFORM(WIN_OS)
+    uint32_t part1 = rand() & (RAND_MAX - 1);
+    uint32_t part2 = rand() & (RAND_MAX - 1);
+    uint32_t part3 = rand() & (RAND_MAX - 1);
+    uint32_t part4 = rand() & (RAND_MAX - 1);
+    // rand only provides 15 bits on Win32
+    uint64_t fullRandom = part1;
+    fullRandom <<= 15;
+    fullRandom |= part2;
+    fullRandom <<= 15;
+    fullRandom |= part3;
+    fullRandom <<= 15;
+    fullRandom |= part4;
+
+    // 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);