nsTArray<T>
is a typesafe array for holding various objects, similar to std::vector<T>
. (note that
nsTArray<T>
is dynamically-sized, unlike std::array<T>
) Here's an
incomplete list of mappings between the two:
std::vector<T> | nsTArray<T> |
---|---|
size() |
Length() |
empty() |
IsEmpty() |
resize() |
SetLength() or SetLengthAndRetainStorage() |
capacity() |
Capacity() |
reserve() |
SetCapacity() |
push_back() |
AppendElement() |
insert() |
AppendElements() |
emplace_back() |
EmplaceBack() |
clear() |
Clear() or ClearAndRetainStorage() |
data() |
Elements() |
at() |
ElementAt() |
back() |
LastElement() |
When the thin_vec
crate is built in Gecko, thin_vec::ThinVec<T>
is
guaranteed to have the same memory layout and allocation strategy as
nsTArray
, meaning that the two types may be used interchangeably across
FFI boundaries. The type is not safe to pass by-value over FFI
boundaries, due to Rust and C++ differing in when they run destructors.
The element type T
must be memory-compatible with both Rust and C++ code
to use over FFI.
These types are the recommended interface for writing new XPCOM hashmaps and hashsets in XPCOM code.
The following types are supported as the key parameter to nsTHashMap
and
nsTHashSet
.
Type | Hash Key |
---|---|
T* |
nsPtrHashKey<T> |
T* |
nsPtrHashKey<T> |
nsCString |
nsCStringHashKey |
nsString |
nsStringHashKey |
uint32_t |
nsUint32HashKey |
uint64_t |
nsUint64HashKey |
intptr_t |
IntPtrHashKey |
nsCOMPtr<nsISupports> |
nsISupportsHashKey |
RefPtr<T> |
nsRefPtrHashKey<T> |
nsID |
nsIDHashKey |
Any key not in this list must inherit from the PLDHashEntryHdr
class to
implement manual hashing behaviour.
Note
The nsTHashMap
and nsTHashSet
types are not declared exactly like
this in code. This is intended largely as a practical reference.
.. cpp:class:: template<K, V> nsTHashMap<K, V> The ``nsTHashMap<K, V>`` class is currently defined as a thin type alias around ``nsBaseHashtable``. See the methods defined on that class for more detailed documentation. https://searchfox.org/mozilla-central/source/xpcom/ds/nsBaseHashtable.h .. cpp:function:: uint32_t Count() const .. cpp:function:: bool IsEmpty() const .. cpp:function:: bool Get(KeyType aKey, V* aData) const Get the value, returning a flag indicating the presence of the entry in the table. .. cpp:function:: V Get(KeyType aKey) const Get the value, returning a default-initialized object if the entry is not present in the table. .. cpp:function:: Maybe<V> MaybeGet(KeyType aKey) const Get the value, returning Nothing if the entry is not present in the table. .. cpp:function:: V& LookupOrInsert(KeyType aKey, Args&&... aArgs) const .. cpp:function:: V& LookupOrInsertWith(KeyType aKey, F&& aFunc) const
.. cpp:class:: template<K> nsTHashSet<K> The ``nsTHashSet<K>`` class is currently defined as a thin type alias around ``nsTBaseHashSet``. See the methods defined on that class for more detailed documentation. https://searchfox.org/mozilla-central/source/xpcom/ds/nsTHashSet.h