Bug 1620113 - part1 : support `contain` and `length` for LinkedList. r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D66854

--HG--
extra : moz-landing-system : lando

mfbt/LinkedList.h

@@ -402,6 +402,12 @@ class LinkedList {
     Type mCurrent;
 
    public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = T;
+    using difference_type = std::ptrdiff_t;
+    using pointer = T*;
+    using reference = T&;
+
     explicit Iterator(Type aCurrent) : mCurrent(aCurrent) {}
 
     Type operator*() const { return mCurrent; }
@@ -488,6 +494,13 @@ class LinkedList {
    */
   bool isEmpty() const { return !sentinel.isInList(); }
 
+  /**
+   * Returns whether the given element is in the list.
+   */
+  bool contains(ConstRawType aElm) const {
+    return std::find(begin(), end(), aElm) != end();
+  }
+
   /*
    * Remove all the elements from the list.
    *
@@ -499,6 +512,19 @@ class LinkedList {
     }
   }
 
+  /**
+   * Return the length of elements in the list.
+   */
+  size_t length() const {
+    size_t length = 0;
+    ConstRawType element = getFirst();
+    while (element) {
+      length++;
+      element = element->getNext();
+    }
+    return length;
+  }
+
   /*
    * Allow range-based iteration:
    *

mfbt/tests/TestLinkedList.cpp

@@ -33,6 +33,7 @@ static void TestList() {
   SomeClass one(1), two(2), three(3);
 
   MOZ_RELEASE_ASSERT(list.isEmpty());
+  MOZ_RELEASE_ASSERT(list.length() == 0);
   MOZ_RELEASE_ASSERT(!list.getFirst());
   MOZ_RELEASE_ASSERT(!list.getLast());
   MOZ_RELEASE_ASSERT(!list.popFirst());
@@ -53,7 +54,12 @@ static void TestList() {
   MOZ_RELEASE_ASSERT(!two.isInList());
   MOZ_RELEASE_ASSERT(!three.isInList());
 
+  MOZ_RELEASE_ASSERT(list.contains(&one));
+  MOZ_RELEASE_ASSERT(!list.contains(&two));
+  MOZ_RELEASE_ASSERT(!list.contains(&three));
+
   MOZ_RELEASE_ASSERT(!list.isEmpty());
+  MOZ_RELEASE_ASSERT(list.length() == 1);
   MOZ_RELEASE_ASSERT(list.getFirst()->mValue == 1);
   MOZ_RELEASE_ASSERT(list.getLast()->mValue == 1);
 
@@ -63,6 +69,7 @@ static void TestList() {
     CheckListValues(list, check);
   }
 
+  MOZ_RELEASE_ASSERT(list.length() == 2);
   MOZ_RELEASE_ASSERT(list.getFirst()->mValue == 2);
   MOZ_RELEASE_ASSERT(list.getLast()->mValue == 1);
 
@@ -72,6 +79,7 @@ static void TestList() {
     CheckListValues(list, check);
   }
 
+  MOZ_RELEASE_ASSERT(list.length() == 3);
   MOZ_RELEASE_ASSERT(list.getFirst()->mValue == 2);
   MOZ_RELEASE_ASSERT(list.getLast()->mValue == 3);
 
@@ -153,6 +161,7 @@ static void TestList() {
     x->incr();
   }
 
+  MOZ_RELEASE_ASSERT(list.length() == 2);
   MOZ_RELEASE_ASSERT(list.getFirst() == &two);
   MOZ_RELEASE_ASSERT(list.getLast() == &three);
   MOZ_RELEASE_ASSERT(list.getFirst()->mValue == 3);