X-Git-Url: http://git.webkit.org/?p=WebKit-https.git;a=blobdiff_plain;f=JavaScriptCore%2Fwtf%2FRandomNumber.cpp;h=e5692271ecc220910b71e090548bffc388fb206e;hp=cbf46f1c44dce53b2cb059e5aa418cb3794f954c;hb=2c77d737a1423b1bc44cfbe9642043f9b5c05a05;hpb=d61fab1f86e5e56ceb3a6fd4d476833305f94336

diff --git a/JavaScriptCore/wtf/RandomNumber.cpp b/JavaScriptCore/wtf/RandomNumber.cpp
index cbf46f1..e569227 100644
--- a/JavaScriptCore/wtf/RandomNumber.cpp
+++ b/JavaScriptCore/wtf/RandomNumber.cpp
@@ -29,7 +29,9 @@
 
 #include "RandomNumberSeed.h"
 
+#include <limits>
 #include <limits.h>
+#include <stdint.h>
 #include <stdlib.h>
 
 namespace WTF {
@@ -43,17 +45,43 @@ double randomNumber()
         s_initialized = true;
     }
 #endif
-
+    
+    uint32_t part1;
+    uint32_t part2;
+    uint64_t fullRandom;
 #if COMPILER(MSVC) && defined(_CRT_RAND_S)
-    unsigned u;
-    rand_s(&u);
-
-    return static_cast<double>(u) / (static_cast<double>(UINT_MAX) + 1.0);
+    rand_s(&part1);
+    rand_s(&part2);
+    fullRandom = part1;
+    fullRandom <<= 32;
+    fullRandom |= part2;
 #elif PLATFORM(DARWIN)
-    return static_cast<double>(random()) / (static_cast<double>(RAND_MAX) + 1.0);
+    part1 = arc4random();
+    part2 = arc4random();
+    fullRandom = part1;
+    fullRandom <<= 32;
+    fullRandom |= part2;
+#elif PLATFORM(UNIX)
+    part1 = random() & (RAND_MAX - 1);
+    part2 = random() & (RAND_MAX - 1);
+    // random only provides 31 bits
+    fullRandom = part1;
+    fullRandom <<= 31;
+    fullRandom |= part2;
 #else
-    return static_cast<double>(rand()) / (static_cast<double>(RAND_MAX) + 1.0);
+    part1 = rand() & (RAND_MAX - 1);
+    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
+    fullRandom = part1;
+    fullRandom <<= 27;
+    fullRandom |= part2;
 #endif
+    // Mask off the low 53bits
+    fullRandom &= (1LL << 53) - 1;
+    return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
 }
 
 }