From 7d019ad5a16fa7d6ecfbf2fb096314013568eaf8 Mon Sep 17 00:00:00 2001
From: jules <jules@rawmaterialsoftware.com>
Date: Tue, 11 Dec 2012 22:05:57 +0000
Subject: [PATCH] Added ReadWriteLock::tryEnterRead()

---
 .../juce_core/threads/juce_ReadWriteLock.cpp  | 43 ++++++++++---------
 .../juce_core/threads/juce_ReadWriteLock.h    | 12 ++++++
 2 files changed, 35 insertions(+), 20 deletions(-)

diff --git a/modules/juce_core/threads/juce_ReadWriteLock.cpp b/modules/juce_core/threads/juce_ReadWriteLock.cpp
index 4e7ef20784..6aecf1868c 100644
--- a/modules/juce_core/threads/juce_ReadWriteLock.cpp
+++ b/modules/juce_core/threads/juce_ReadWriteLock.cpp
@@ -39,34 +39,37 @@ ReadWriteLock::~ReadWriteLock() noexcept
 
 //==============================================================================
 void ReadWriteLock::enterRead() const noexcept
+{
+    while (! tryEnterRead())
+        waitEvent.wait (100);
+}
+
+bool ReadWriteLock::tryEnterRead() const noexcept
 {
     const Thread::ThreadID threadId = Thread::getCurrentThreadId();
+
     const SpinLock::ScopedLockType sl (accessLock);
 
-    for (;;)
+    for (int i = 0; i < readerThreads.size(); ++i)
     {
-        for (int i = 0; i < readerThreads.size(); ++i)
+        ThreadRecursionCount& trc = readerThreads.getReference(i);
+
+        if (trc.threadID == threadId)
         {
-            ThreadRecursionCount& trc = readerThreads.getReference(i);
-
-            if (trc.threadID == threadId)
-            {
-                trc.count++;
-                return;
-            }
+            trc.count++;
+            return true;
         }
-
-        if (numWriters + numWaitingWriters == 0
-             || (threadId == writerThreadId && numWriters > 0))
-        {
-            ThreadRecursionCount trc = { threadId, 1 };
-            readerThreads.add (trc);
-            return;
-        }
-
-        const SpinLock::ScopedUnlockType ul (accessLock);
-        waitEvent.wait (100);
     }
+
+    if (numWriters + numWaitingWriters == 0
+         || (threadId == writerThreadId && numWriters > 0))
+    {
+        ThreadRecursionCount trc = { threadId, 1 };
+        readerThreads.add (trc);
+        return true;
+    }
+
+    return false;
 }
 
 void ReadWriteLock::exitRead() const noexcept
diff --git a/modules/juce_core/threads/juce_ReadWriteLock.h b/modules/juce_core/threads/juce_ReadWriteLock.h
index d74b8f76cf..b5a37c2d5d 100644
--- a/modules/juce_core/threads/juce_ReadWriteLock.h
+++ b/modules/juce_core/threads/juce_ReadWriteLock.h
@@ -79,6 +79,17 @@ public:
     */
     void enterRead() const noexcept;
 
+    /** Tries to lock this object for reading.
+
+        Multiple threads can simulaneously lock the object for reading, but if another
+        thread has it locked for writing, then this will block until it releases the
+        lock.
+
+        @returns true if the lock is successfully gained.
+        @see exitRead, ScopedReadLock
+    */
+    bool tryEnterRead() const noexcept;
+
     /** Releases the read-lock.
 
         If the caller thread hasn't got the lock, this can have unpredictable results.
@@ -106,6 +117,7 @@ public:
         This is like enterWrite(), but doesn't block - it returns true if it manages
         to obtain the lock.
 
+        @returns true if the lock is successfully gained.
         @see enterWrite
     */
     bool tryEnterWrite() const noexcept;