Bug 1271483 - p11. Implement comma-sep-string for-range iterator - r=cpearce draft
authorGerald Squelart <gsquelart@mozilla.com>
Thu, 26 May 2016 16:43:16 +1000
changeset 380484 af745ceacd4b194698b719ebe3f7b4ee07786565
parent 380483 59ae50f8545c8bc4e0c61a0d818651185c1b078c
child 380485 94381bb362bb4750b33519302de5d6062b782445
push id21230
push usergsquelart@mozilla.com
push dateWed, 22 Jun 2016 01:46:41 +0000
reviewerscpearce
bugs1271483
milestone50.0a1
Bug 1271483 - p11. Implement comma-sep-string for-range iterator - r=cpearce Utility class&function that creates an iteratable range from a comma-separated string, where each iteration will give a dependent substring (i.e., no string copy happening). This will help with going through lists of unplayable formats, to see if issues have been solved. If useful enough, this could later be published to a more public location (e.g. mfbt or xpcom). MozReview-Commit-ID: 3XP5PwQZFA1
dom/media/DecoderDoctorDiagnostics.cpp
--- a/dom/media/DecoderDoctorDiagnostics.cpp
+++ b/dom/media/DecoderDoctorDiagnostics.cpp
@@ -232,16 +232,129 @@ DecoderDoctorDocumentWatcher::EnsureTime
     if (NS_WARN_IF(NS_FAILED(
           mTimer->InitWithCallback(
             this, sAnalysisPeriod_ms, nsITimer::TYPE_ONE_SHOT)))) {
       mTimer = nullptr;
     }
   }
 }
 
+template <typename String>
+class StringListRange
+{
+  typedef typename String::char_type CharType;
+  typedef const CharType* Pointer;
+
+public:
+  // Iterator into range, trims items and skips empty items.
+  class Iterator
+  {
+  public:
+    bool operator!=(const Iterator& a) const
+    {
+      return mStart != a.mStart || mEnd != a.mEnd;
+    }
+    Iterator& operator++()
+    {
+      SearchItemAt(mComma + 1);
+      return *this;
+    }
+    typedef decltype(Substring(Pointer(), Pointer())) DereferencedType;
+    DereferencedType operator*()
+    {
+      return Substring(mStart, mEnd);
+    }
+  private:
+    friend class StringListRange;
+    Iterator(const CharType* aRangeStart, uint32_t aLength)
+      : mRangeEnd(aRangeStart + aLength)
+    {
+      SearchItemAt(aRangeStart);
+    }
+    void SearchItemAt(Pointer start)
+    {
+      // First, skip leading whitespace.
+      for (Pointer p = start; ; ++p) {
+        if (p >= mRangeEnd) {
+          mStart = mEnd = mComma = mRangeEnd;
+          return;
+        }
+        auto c = *p;
+        if (c == CharType(',')) {
+          // Comma -> Empty item -> Skip.
+        } else if (c != CharType(' ')) {
+          mStart = p;
+          break;
+        }
+      }
+      // Find comma, recording start of trailing space.
+      Pointer trailingWhitespace = nullptr;
+      for (Pointer p = mStart + 1; ; ++p) {
+        if (p >= mRangeEnd) {
+          mEnd = trailingWhitespace ? trailingWhitespace : p;
+          mComma = p;
+          return;
+        }
+        auto c = *p;
+        if (c == CharType(',')) {
+          mEnd = trailingWhitespace ? trailingWhitespace : p;
+          mComma = p;
+          return;
+        }
+        if (c == CharType(' ')) {
+          // Found a whitespace -> Record as trailing if not first one.
+          if (!trailingWhitespace) {
+            trailingWhitespace = p;
+          }
+        } else {
+          // Found a non-whitespace -> Reset trailing whitespace if needed.
+          if (trailingWhitespace) {
+            trailingWhitespace = nullptr;
+          }
+        }
+      }
+    }
+    const Pointer mRangeEnd;
+    Pointer mStart;
+    Pointer mEnd;
+    Pointer mComma;
+  };
+
+  explicit StringListRange(const String& aList) : mList(aList) {}
+  Iterator begin()
+  {
+    return Iterator(mList.Data(), mList.Length());
+  }
+  Iterator end()
+  {
+    return Iterator(mList.Data() + mList.Length(), 0);
+  }
+private:
+  const String& mList;
+};
+
+template <typename String>
+StringListRange<String>
+MakeStringListRange(const String& aList)
+{
+  return StringListRange<String>(aList);
+}
+
+template <typename ListString, typename ItemString>
+static bool
+StringListContains(const ListString& aList, const ItemString& aItem)
+{
+  for (const auto& listItem : MakeStringListRange(aList)) {
+    if (listItem.Equals(aItem)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 static void
 DispatchNotification(nsISupports* aSubject,
                      dom::DecoderDoctorNotificationType aNotificationType,
                      bool aIsSolved,
                      const char* aReportStringId,
                      const nsAString& aFormats)
 {
   if (!aSubject) {