Modernize FX_Random further [pdfium : main]
0 views
Skip to first unread message
Lei Zhang (Gerrit)
Feb 20, 2026, 2:33:32 PM (2 days ago) Feb 20
to Andy Phan, Lei Zhang, Pdfium LUCI CQ, pdfium-...@googlegroups.com
Attention needed from Andy Phan
Lei Zhang added 2 comments![]( "Open in Gerrit")
File core/fxcrt/fx_random.cpp
Line 67, Patchset 1 (Latest):
if (!g_global_seed_initialized) {Lei Zhang . unresolved
Can get rid of `g_global_seed_initialized` with:
`static uint32_t global_seed = []() -> uint32_t { lambda_for_lines_68_to_74 }();`
Related details
Attention is currently required from:
- Andy Phan
Submit Requirements:
Code-Owners
Code-Review
No-Unresolved-Comments
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Lei Zhang (Gerrit)
Feb 20, 2026, 2:33:34 PM (2 days ago) Feb 20
to Andy Phan, Lei Zhang, Pdfium LUCI CQ, pdfium-...@googlegroups.com
Attention needed from Andy Phan
Lei Zhang voted Code-Review+1![]( "Open in Gerrit")
| Code-Review | +1 |
Related details
Attention is currently required from:
- Andy Phan
Submit Requirements:
Code-Owners
Code-Review
No-Unresolved-Comments
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Andy Phan (Gerrit)
Feb 20, 2026, 2:51:50 PM (2 days ago) Feb 20
to Lei Zhang, Pdfium LUCI CQ, pdfium-...@googlegroups.com
Andy Phan added 2 comments![]( "Open in Gerrit")
File core/fxcrt/fx_random.cpp
Can get rid of `g_global_seed_initialized` with:
`static uint32_t global_seed = []() -> uint32_t { lambda_for_lines_68_to_74 }();`
Code-Owners
Code-Review
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Andy Phan (Gerrit)
Feb 20, 2026, 5:20:51 PM (2 days ago) Feb 20
to Lei Zhang, Pdfium LUCI CQ, pdfium-...@googlegroups.com
Andy Phan voted Commit-Queue+2![]( "Open in Gerrit")
| Commit-Queue | +2 |
Related details
Attention set is empty
Submit Requirements:
Code-Owners
Code-Review
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Pdfium LUCI CQ (Gerrit)
Feb 20, 2026, 5:24:32 PM (2 days ago) Feb 20
to Andy Phan, Lei Zhang, pdfium-...@googlegroups.com
Pdfium LUCI CQ submitted the change with unreviewed changes![]( "Open in Gerrit")
Unreviewed changes
1 is the latest approved patch-set.
The change was submitted with unreviewed changes in the following files:
```
The name of the file: core/fxcrt/fx_random.h
Insertions: 2, Deletions: 2.
@@ -17,6 +17,8 @@
// A Mersenne Twister (MT) pseudo-random number generator.
class FX_Random {
public:
+ static constexpr size_t kStateSize = 848;
+
explicit FX_Random(uint32_t seed);
FX_Random(const FX_Random&) = delete;
@@ -32,8 +34,6 @@
uint32_t Generate();
private:
- static constexpr size_t kStateSize = 848;
-
uint32_t next_index_;
std::array<uint32_t, kStateSize> state_;
};
```
```
The name of the file: core/fxcrt/fx_random.cpp
Insertions: 34, Deletions: 32.
@@ -27,9 +27,6 @@
constexpr uint32_t kUpperMask = 0x80000000;
constexpr uint32_t kLowerMask = 0x7fffffff;
-bool g_global_seed_initialized = false;
-uint32_t g_global_seed = 0;
-
#if BUILDFLAG(IS_WIN)
bool GenerateSeedFromCryptoRandom(uint32_t* seed) {
HCRYPTPROV hCP = 0;
@@ -64,29 +61,34 @@
}
uint32_t GetNextGlobalSeed() {
- if (!g_global_seed_initialized) {
+ static uint32_t global_seed = []() -> uint32_t {
+ uint32_t initial_seed;
#if BUILDFLAG(IS_WIN)
- if (!GenerateSeedFromCryptoRandom(&g_global_seed)) {
- g_global_seed = GenerateSeedFromEnvironment();
+ if (!GenerateSeedFromCryptoRandom(&initial_seed)) {
+ initial_seed = GenerateSeedFromEnvironment();
}
#else
- g_global_seed = GenerateSeedFromEnvironment();
+ initial_seed = GenerateSeedFromEnvironment();
#endif
- g_global_seed_initialized = true;
+ return initial_seed;
+ }();
+ return ++global_seed;
+}
+
+std::array<uint32_t, FX_Random::kStateSize> InitState(uint32_t seed) {
+ std::array<uint32_t, FX_Random::kStateSize> state;
+ state[0] = seed;
+ for (uint32_t i = 1; i < FX_Random::kStateSize; i++) {
+ const uint32_t prev = state[i - 1];
+ state[i] = (1812433253UL * (prev ^ (prev >> 30)) + i);
}
- return ++g_global_seed;
+ return state;
}
} // namespace
-FX_Random::FX_Random(uint32_t seed) {
- state_[0] = seed;
- for (uint32_t i = 1; i < kStateSize; ++i) {
- const uint32_t prev = state_[i - 1];
- state_[i] = (1812433253UL * (prev ^ (prev >> 30)) + i);
- }
- next_index_ = kStateSize;
-}
+FX_Random::FX_Random(uint32_t seed)
+ : next_index_(kStateSize), state_(InitState(seed)) {}
FX_Random::~FX_Random() = default;
@@ -99,31 +101,31 @@
}
uint32_t FX_Random::Generate() {
- uint32_t bits;
+ uint32_t result;
if (next_index_ >= kStateSize) {
static constexpr std::array<uint32_t, 2> kMatrixATable = {{0, 0x9908b0df}};
uint32_t i;
for (i = 0; i < kStateSize - kTwistOffset; ++i) {
- bits = (state_[i] & kUpperMask) | (state_[i + 1] & kLowerMask);
+ result = (state_[i] & kUpperMask) | (state_[i + 1] & kLowerMask);
state_[i] =
- state_[i + kTwistOffset] ^ (bits >> 1) ^ kMatrixATable[bits & 1];
+ state_[i + kTwistOffset] ^ (result >> 1) ^ kMatrixATable[result & 1];
}
for (; i < kStateSize - 1; ++i) {
- bits = (state_[i] & kUpperMask) | (state_[i + 1] & kLowerMask);
- // `kTwistOffset` - `kStateSize` underflows, but this is safe because
+ result = (state_[i] & kUpperMask) | (state_[i + 1] & kLowerMask);
+ // `kTwistOffset - kStateSize` underflows, but this is safe because
// unsigned underflow is well-defined.
- state_[i] = state_[i + (kTwistOffset - kStateSize)] ^ (bits >> 1) ^
- kMatrixATable[bits & 1];
+ state_[i] = state_[i + (kTwistOffset - kStateSize)] ^ (result >> 1) ^
+ kMatrixATable[result & 1];
}
- bits = (state_[kStateSize - 1] & kUpperMask) | (state_[0] & kLowerMask);
+ result = (state_[kStateSize - 1] & kUpperMask) | (state_[0] & kLowerMask);
state_[kStateSize - 1] =
- state_[kTwistOffset - 1] ^ (bits >> 1) ^ kMatrixATable[bits & 1];
+ state_[kTwistOffset - 1] ^ (result >> 1) ^ kMatrixATable[result & 1];
next_index_ = 0;
}
- bits = state_[next_index_++];
- bits ^= (bits >> 11);
- bits ^= (bits << 7) & 0x9d2c5680UL;
- bits ^= (bits << 15) & 0xefc60000UL;
- bits ^= (bits >> 18);
- return bits;
+ result = state_[next_index_++];
+ result ^= (result >> 11);
+ result ^= (result << 7) & 0x9d2c5680UL;
+ result ^= (result << 15) & 0xefc60000UL;
+ result ^= (result >> 18);
+ return result;
}
```
Change information
Commit message:
Modernize FX_Random further
Modernize FX_Random by:
1. Renaming all abbreviated variables to more human-readable names.
2. Updating naming style to modern convention.
3. Changing macros to constants.
4. Replace global variables by using static variables and lambdas.
Change-Id: I23bddecd739a980e2ec3101de85f2fded8c73721
Reviewed-by: Lei Zhang <the...@chromium.org>
Commit-Queue: Andy Phan <andy...@chromium.org>
Files:
- M core/fxcrt/fx_random.cpp
- M core/fxcrt/fx_random.h
Change size: M
Delta: 2 files changed, 56 insertions(+), 55 deletions(-)
Branch: refs/heads/main
Submit Requirements:
Code-Review: +1 by Lei Zhang
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Reply all
Reply to author
Forward
0 new messages