diff options
| -rw-r--r-- | absl/strings/internal/cord_internal.h | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h index 8d9836ba..20dd008c 100644 --- a/absl/strings/internal/cord_internal.h +++ b/absl/strings/internal/cord_internal.h @@ -157,20 +157,19 @@ class RefcountAndFlags { // false will be visible to a thread that just observed this method returning // false. Always returns false when the immortal bit is set. inline bool Decrement() { - int32_t refcount = count_.load(std::memory_order_acquire) & kRefcountMask; - assert(refcount > 0 || refcount & kImmortalFlag); + int32_t refcount = count_.load(std::memory_order_acquire); + assert((refcount & kRefcountMask) > 0 || refcount & kImmortalFlag); return refcount != kRefIncrement && (count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel) & - kRefcountMask) != kRefIncrement; + kHighRefcountMask) != 0; } // Same as Decrement but expect that refcount is greater than 1. inline bool DecrementExpectHighRefcount() { int32_t refcount = - count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel) & - kRefcountMask; - assert(refcount > 0 || refcount & kImmortalFlag); - return refcount != kRefIncrement; + count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel); + assert((refcount & kRefcountMask) > 0 || refcount & kImmortalFlag); + return (refcount & kHighRefcountMask) != 0; } // Returns the current reference count using acquire semantics. @@ -214,6 +213,15 @@ class RefcountAndFlags { // purposes of equality. (A refcount of 0 or 1 does not count as 0 or 1 // if the immortal bit is set.) kRefcountMask = ~kReservedFlag, + + // Bitmask to use when checking if refcount is equal to 1 and not + // immortal when decrementing the refcount. This masks out kRefIncrement and + // all flags except kImmortalFlag. If the masked RefcountAndFlags is 0, we + // assume the refcount is equal to 1, since we know it's not immortal and + // not greater than 1. If the masked RefcountAndFlags is not 0, we can + // assume the refcount is not equal to 1 since either a higher bit in the + // refcount is set, or kImmortal is set. + kHighRefcountMask = kRefcountMask & ~kRefIncrement, }; std::atomic<int32_t> count_; |