[FastTextAutosizer] Keep m_blocksForFingerprint and m_fingerprints in sync

Source/core/rendering/FastTextAutosizer.cpp

Index: Source/core/rendering/FastTextAutosizer.cpp
diff --git a/Source/core/rendering/FastTextAutosizer.cpp b/Source/core/rendering/FastTextAutosizer.cpp
index bd0810acda0e91a23b4cad15404c8a0c8b1f1cbf..b3ea134bb848d728a439af8c5e36eb9c14903908 100644
--- a/Source/core/rendering/FastTextAutosizer.cpp
+++ b/Source/core/rendering/FastTextAutosizer.cpp
@@ -659,9 +659,38 @@ FastTextAutosizer::Cluster* FastTextAutosizer::currentCluster() const
     return m_clusterStack.last().get();
 }
 
+#ifndef NDEBUG
+bool FastTextAutosizer::FingerprintMapper::mapsAreConsistent()
+{
+    // For each fingerprint -> block mapping in m_blocksForFingerprint we should have an associated
+    // map from block -> fingerprint in m_fingerprints.
+    ReverseFingerprintMap::iterator end = m_blocksForFingerprint.end();
+    for (ReverseFingerprintMap::iterator fingerprintIt = m_blocksForFingerprint.begin(); fingerprintIt != end; ++fingerprintIt) {
+        Fingerprint fingerprint = fingerprintIt->key;
+        BlockSet* blocks = fingerprintIt->value.get();
+        for (BlockSet::iterator blockIt = blocks->begin(); blockIt != blocks->end(); ++blockIt) {
+            const RenderBlock* block = (*blockIt);
+            ASSERT(m_fingerprints.get(block) == fingerprint);
+        }
+    }
+
+    return true;

[skobes, 2014/03/05 04:12:22]

It's a bit silly to have a return value that is always true - just return void
and call it assertMapsAreConsistent.

[pdr., 2014/03/05 04:20:31]

Fair point. I was jumping through silly hoops to avoid #ifndef NDEBUG checks.

Fixed.

+}
+#endif
+
 void FastTextAutosizer::FingerprintMapper::add(const RenderObject* renderer, Fingerprint fingerprint)
 {
+    // Make sure to remove any existing fingerprint mapping for this renderer.
+    Fingerprint oldFingerprint = m_fingerprints.get(renderer);
+    if (oldFingerprint && renderer->isRenderBlock()) {
+        ReverseFingerprintMap::iterator blocksIter = m_blocksForFingerprint.find(oldFingerprint);
+        if (blocksIter != m_blocksForFingerprint.end())
+            blocksIter->value->remove(toRenderBlock(renderer));

[skobes, 2014/03/05 04:12:22]

I think I liked it better when this just called FingerprintMapper::remove.

If blocksIter->value is empty after this call, don't we want to remove it from
m_blocksForFingerprint?

[pdr., 2014/03/05 04:20:31]

Yeah, I agree. This will have one unnecessary hash lookup (we remove an entry
from m_fingerprints and immediately set it below) but I think it's worth it for
code maintainability.

Done.

+    }
+
     m_fingerprints.set(renderer, fingerprint);
+
+    ASSERT(mapsAreConsistent());
 }
 
 void FastTextAutosizer::FingerprintMapper::addTentativeClusterRoot(const RenderBlock* block, Fingerprint fingerprint)
@@ -672,6 +701,7 @@ void FastTextAutosizer::FingerprintMapper::addTentativeClusterRoot(const RenderB
     if (addResult.isNewEntry)
         addResult.storedValue->value = adoptPtr(new BlockSet);
     addResult.storedValue->value->add(block);
+    ASSERT(mapsAreConsistent());
 }
 
 void FastTextAutosizer::FingerprintMapper::remove(const RenderObject* renderer)
@@ -688,6 +718,7 @@ void FastTextAutosizer::FingerprintMapper::remove(const RenderObject* renderer)
     blocks.remove(toRenderBlock(renderer));
     if (blocks.isEmpty())
         m_blocksForFingerprint.remove(blocksIter);
+    ASSERT(mapsAreConsistent());
 }
 
 FastTextAutosizer::Fingerprint FastTextAutosizer::FingerprintMapper::get(const RenderObject* renderer)