Tidied up ReadWriteLock a bit, and optimised Array to reduce allocation frequency when working with small numbers of items.

modules/juce_core/containers/juce_Array.h

@@ -679,30 +679,23 @@ public:
                             // avoids getting warning messages about the parameter being unused
 
         const ScopedLockType lock (getLock());
-        int start = 0;
-        int end_ = numUsed;
 
-        for (;;)
+        for (int s = 0, e = numUsed;;)
         {
-            if (start >= end_)
-            {
+            if (s >= e)
                 return -1;
-            }
-            else if (comparator.compareElements (elementToLookFor, data.elements [start]) == 0)
-            {
-                return start;
-            }
-            else
-            {
-                const int halfway = (start + end_) >> 1;
 
-                if (halfway == start)
-                    return -1;
-                else if (comparator.compareElements (elementToLookFor, data.elements [halfway]) >= 0)
-                    start = halfway;
-                else
-                    end_ = halfway;
-            }
+            if (comparator.compareElements (elementToLookFor, data.elements [s]) == 0)
+                return s;
+
+            const int halfway = (s + e) / 2;
+            if (halfway == s)
+                return -1;
+
+            if (comparator.compareElements (elementToLookFor, data.elements [halfway]) >= 0)
+                s = halfway;
+            else
+                e = halfway;
         }
     }
 
@@ -733,9 +726,7 @@ public:
             if (numberToShift > 0)
                 memmove (e, e + 1, ((size_t) numberToShift) * sizeof (ElementType));
 
-            if ((numUsed << 1) < data.numAllocated)
-                minimiseStorageOverheads();
-
+            minimiseStorageAfterRemoval();
             return removed;
         }
         else
@@ -798,9 +789,7 @@ public:
                 memmove (e, e + numberToRemove, ((size_t) numToShift) * sizeof (ElementType));
 
             numUsed -= numberToRemove;
-
-            if ((numUsed << 1) < data.numAllocated)
-                minimiseStorageOverheads();
+            minimiseStorageAfterRemoval();
         }
     }
 
@@ -820,9 +809,7 @@ public:
             data.elements [numUsed - i].~ElementType();
 
         numUsed -= howManyToRemove;
-
-        if ((numUsed << 1) < data.numAllocated)
-            minimiseStorageOverheads();
+        minimiseStorageAfterRemoval();
     }
 
     /** Removes any elements which are also in another array.
@@ -1029,6 +1016,12 @@ private:
         for (int i = 0; i < numUsed; ++i)
             data.elements[i].~ElementType();
     }
+
+    void minimiseStorageAfterRemoval()
+    {
+        if (data.numAllocated > numUsed * 2)
+            data.shrinkToNoMoreThan (jmax (numUsed, 64 / (int) sizeof (ElementType)));
+    }
 };
 
 

modules/juce_core/threads/juce_ReadWriteLock.cpp

@@ -45,27 +45,22 @@ void ReadWriteLock::enterRead() const noexcept
 
     for (;;)
     {
-        jassert (readerThreads.size() % 2 == 0);
-
-        int i;
-        for (i = 0; i < readerThreads.size(); i += 2)
-            if (readerThreads.getUnchecked(i) == threadId)
-                break;
-
-        if (i < readerThreads.size()
-              || numWriters + numWaitingWriters == 0
-              || (threadId == writerThreadId && numWriters > 0))
+        for (int i = 0; i < readerThreads.size(); ++i)
         {
-            if (i < readerThreads.size())
-            {
-                readerThreads.set (i + 1, (Thread::ThreadID) (1 + (pointer_sized_int) readerThreads.getUnchecked (i + 1)));
-            }
-            else
+            ThreadRecursionCount& trc = readerThreads.getReference(i);
+
+            if (trc.threadID == threadId)
             {
-                readerThreads.add (threadId);
-                readerThreads.add ((Thread::ThreadID) 1);
+                trc.count++;
+                return;
             }
+        }
 
+        if (numWriters + numWaitingWriters == 0
+             || (threadId == writerThreadId && numWriters > 0))
+        {
+            ThreadRecursionCount trc = { threadId, 1 };
+            readerThreads.add (trc);
             return;
         }
 
@@ -79,21 +74,17 @@ void ReadWriteLock::exitRead() const noexcept
     const Thread::ThreadID threadId = Thread::getCurrentThreadId();
     const SpinLock::ScopedLockType sl (accessLock);
 
-    for (int i = 0; i < readerThreads.size(); i += 2)
+    for (int i = 0; i < readerThreads.size(); ++i)
     {
-        if (readerThreads.getUnchecked(i) == threadId)
-        {
-            const pointer_sized_int newCount = ((pointer_sized_int) readerThreads.getUnchecked (i + 1)) - 1;
+        ThreadRecursionCount& trc = readerThreads.getReference(i);
 
-            if (newCount == 0)
+        if (trc.threadID == threadId)
+        {
+            if (--(trc.count) == 0)
             {
-                readerThreads.removeRange (i, 2);
+                readerThreads.remove (i);
                 waitEvent.signal();
             }
-            else
-            {
-                readerThreads.set (i + 1, (Thread::ThreadID) newCount);
-            }
 
             return;
         }
@@ -112,8 +103,8 @@ void ReadWriteLock::enterWrite() const noexcept
     {
         if (readerThreads.size() + numWriters == 0
              || threadId == writerThreadId
-             || (readerThreads.size() == 2
-                  && readerThreads.getUnchecked(0) == threadId))
+             || (readerThreads.size() == 1
+                  && readerThreads.getReference(0).threadID == threadId))
         {
             writerThreadId = threadId;
             ++numWriters;
@@ -135,8 +126,8 @@ bool ReadWriteLock::tryEnterWrite() const noexcept
 
     if (readerThreads.size() + numWriters == 0
          || threadId == writerThreadId
-         || (readerThreads.size() == 2
-              && readerThreads.getUnchecked(0) == threadId))
+         || (readerThreads.size() == 1
+              && readerThreads.getReference(0).threadID == threadId))
     {
         writerThreadId = threadId;
         ++numWriters;

modules/juce_core/threads/juce_ReadWriteLock.h

@@ -129,7 +129,14 @@ private:
     WaitableEvent waitEvent;
     mutable int numWaitingWriters, numWriters;
     mutable Thread::ThreadID writerThreadId;
-    mutable Array <Thread::ThreadID> readerThreads;
+
+    struct ThreadRecursionCount
+    {
+        Thread::ThreadID threadID;
+        int count;
+    };
+
+    mutable Array <ThreadRecursionCount> readerThreads;
 
     JUCE_DECLARE_NON_COPYABLE (ReadWriteLock);
 };