Revision: 8490
Author: [email protected]
Date: Thu Jun 30 06:07:43 2011
Log: Improve pseudorandom number generation and move the PNG state to
Isolate.
Review URL: http://codereview.chromium.org/7248060
http://code.google.com/p/v8/source/detail?r=8490
Modified:
/branches/bleeding_edge/src/isolate.h
/branches/bleeding_edge/src/v8.cc
=======================================
--- /branches/bleeding_edge/src/isolate.h Wed Jun 29 07:56:08 2011
+++ /branches/bleeding_edge/src/isolate.h Thu Jun 30 06:07:43 2011
@@ -332,6 +332,8 @@
V(int, bad_char_shift_table,
kUC16AlphabetSize) \
V(int, good_suffix_shift_table, (kBMMaxShift +
1)) \
V(int, suffix_table, (kBMMaxShift +
1)) \
+ V(uint32_t, random_seed,
4) \
+ V(uint32_t, private_random_seed,
4) \
ISOLATE_INIT_DEBUG_ARRAY_LIST(V)
typedef List<HeapObject*, PreallocatedStorage> DebugObjectCache;
=======================================
--- /branches/bleeding_edge/src/v8.cc Tue Apr 12 12:15:53 2011
+++ /branches/bleeding_edge/src/v8.cc Thu Jun 30 06:07:43 2011
@@ -100,42 +100,36 @@
}
-static uint32_t random_seed() {
- if (FLAG_random_seed == 0) {
- return random();
- }
- return FLAG_random_seed;
+static void seed_random(uint32_t* state) {
+ for (int i = 0; i < 4; ++i) {
+ state[i] = FLAG_random_seed;
+ while (state[i] == 0) {
+ state[i] = random();
+ }
+ }
}
-typedef struct {
- uint32_t hi;
- uint32_t lo;
-} random_state;
-
-
// Random number generator using George Marsaglia's MWC algorithm.
-static uint32_t random_base(random_state *state) {
- // Initialize seed using the system random(). If one of the seeds
- // should ever become zero again, or if random() returns zero, we
- // avoid getting stuck with zero bits in hi or lo by re-initializing
- // them on demand.
- if (state->hi == 0) state->hi = random_seed();
- if (state->lo == 0) state->lo = random_seed();
-
- // Mix the bits.
- state->hi = 36969 * (state->hi & 0xFFFF) + (state->hi >> 16);
- state->lo = 18273 * (state->lo & 0xFFFF) + (state->lo >> 16);
- return (state->hi << 16) + (state->lo & 0xFFFF);
+static uint32_t random_base(uint32_t* state) {
+ // Initialize seed using the system random().
+ // No non-zero seed will ever become zero again.
+ if (state[0] == 0) seed_random(state);
+
+ // Mix the bits. Never replaces state[i] with 0 if it is nonzero.
+ state[0] = 18273 * (state[0] & 0xFFFF) + (state[0] >> 16);
+ state[1] = 36969 * (state[1] & 0xFFFF) + (state[1] >> 16);
+ state[2] = 23208 * (state[2] & 0xFFFF) + (state[2] >> 16);
+ state[3] = 27753 * (state[3] & 0xFFFF) + (state[3] >> 16);
+
+ return ((state[2] ^ state[3]) << 16) + ((state[0] ^ state[1]) & 0xFFFF);
}
// Used by JavaScript APIs
uint32_t V8::Random(Isolate* isolate) {
ASSERT(isolate == Isolate::Current());
- // TODO(isolates): move lo and hi to isolate
- static random_state state = {0, 0};
- return random_base(&state);
+ return random_base(isolate->random_seed());
}
@@ -144,9 +138,7 @@
// leaks that could be used in an exploit.
uint32_t V8::RandomPrivate(Isolate* isolate) {
ASSERT(isolate == Isolate::Current());
- // TODO(isolates): move lo and hi to isolate
- static random_state state = {0, 0};
- return random_base(&state);
+ return random_base(isolate->private_random_seed());
}
--
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