Index: base/metrics/persistent_memory_allocator.h |
diff --git a/base/metrics/persistent_memory_allocator.h b/base/metrics/persistent_memory_allocator.h |
index f75b1c0bb69c8a2f94375d223b1624b699d9ef33..f6a4b01c9fd5e2ec766b04564f50255584e4bff2 100644 |
--- a/base/metrics/persistent_memory_allocator.h |
+++ b/base/metrics/persistent_memory_allocator.h |
@@ -49,22 +49,51 @@ class BASE_EXPORT PersistentMemoryAllocator { |
public: |
typedef uint32_t Reference; |
- // Internal state information when iterating over memory allocations. |
- class Iterator { |
+ // Iterator for going through all iterable memory records in an allocator. |
+ // Like the allocator itself, iterators are lock-free and thread-secure. |
+ // That means that multiple threads can share an iterator and the same |
+ // reference will not be returned twice. |
+ // |
+ // Iteration, in general, is tolerant of corrupted memory. It will return |
+ // what it can and stop only when corruption forces it to. Bad corruption |
+ // could cause the same object to be returned many times but it will |
+ // eventually quit. |
+ class BASE_EXPORT Iterator { |
public: |
- Iterator() : last(0) {} |
+ // Constructs an iterator on a given |allocator|, starting at the beginning. |
+ Iterator(const PersistentMemoryAllocator* allocator); |
Ilya Sherman
2016/03/24 02:03:58
nit: explicit
Ilya Sherman
2016/03/24 02:03:58
nit: Please document lifetime expectations for thi
bcwhite
2016/03/24 14:22:34
Done.
bcwhite
2016/03/24 14:22:34
Done.
|
+ |
+ // As above but resuming from the |starting_after| reference. The first call |
+ // to GetNext() will return the next object found after that reference. The |
+ // reference must be to an "iterable" object; references to non-iterable |
+ // objects (those that never had MakeIterable() called for them) will cause |
+ // a run-time error. |
+ Iterator(const PersistentMemoryAllocator* allocator, |
+ Reference starting_after); |
+ |
+ // Gets the next iterable, storing that type in |type_return|. The actual |
+ // return value is a reference to the allocation inside the allocator or |
+ // zero if there are no more. GetNext() may still be called again at a |
+ // later time to retrieve any new allocations that have been added. |
+ Reference GetNext(uint32_t* type_return); |
+ |
+ // Similar to above but gets the next iterable of a specific |type_match|. |
+ // This should not be mixed with calls to GetNext() because any allocations |
+ // skipped here due to a type mis-match will never be returned by later |
+ // calls to GetNext() meaning it's possible to completely miss entries. |
+ Reference GetNextOfType(uint32_t type_match); |
- bool operator==(const Iterator& rhs) const { return last == rhs.last; } |
- bool operator!=(const Iterator& rhs) const { return last != rhs.last; } |
+ private: |
+ // Weak-pointer to memory allocator being iterated over. |
+ const PersistentMemoryAllocator* allocator_; |
- void clear() { last = 0; } |
- bool is_clear() const { return last == 0; } |
+ // The last record that was returned. |
+ std::atomic<Reference> last_record_; |
- private: |
- friend class PersistentMemoryAllocator; |
+ // The number of records found; used for detecting loops. |
+ std::atomic<uint32_t> record_count_; |
- Reference last; |
- uint32_t niter; |
+ DISALLOW_COPY_AND_ASSIGN(Iterator); |
}; |
// Returned information about the internal state of the heap. |
@@ -211,17 +240,6 @@ class BASE_EXPORT PersistentMemoryAllocator { |
// also make the true amount less than what is reported. |
void GetMemoryInfo(MemoryInfo* meminfo) const; |
- // Iterating uses a |state| structure (initialized by CreateIterator) and |
- // returns both the reference to the object as well as the |type_id| of |
- // that object. A zero return value indicates there are currently no more |
- // objects to be found but future attempts can be made without having to |
- // reset the iterator to "first". Creating an iterator |starting_after| |
- // a known iterable object allows "resume" from that point with the next |
- // call to GetNextIterable returning the object after it. |
- void CreateIterator(Iterator* state) const { CreateIterator(state, 0); }; |
- void CreateIterator(Iterator* state, Reference starting_after) const; |
- Reference GetNextIterable(Iterator* state, uint32_t* type_id) const; |
- |
// If there is some indication that the memory has become corrupted, |
// calling this will attempt to prevent further damage by indicating to |
// all processes that something is not as expected. |