#5893: Fix an allocation problem after filling the continuous to the …

…last byte

libs/render/ContinuousBuffer.h

@@ -167,10 +167,11 @@ class ContinuousBuffer
     Handle getNextFreeSlotForSize(std::size_t requiredSize)
     {
         auto numSlots = _slots.size();
-        Handle rightmostFreeSlotIndex = 0;
+        Handle rightmostFreeSlotIndex = static_cast<Handle>(numSlots);
         std::size_t rightmostFreeOffset = 0;
+        Handle slotIndex = 0;
 
-        for (Handle slotIndex = 0; slotIndex < numSlots; ++slotIndex)
+        for (slotIndex = 0; slotIndex < numSlots; ++slotIndex)
         {
             auto& slot = _slots[slotIndex];
 
@@ -200,6 +201,16 @@ class ContinuousBuffer
         }
 
         // No space wherever, we need to expand the buffer
+
+        // Check if we have any free slots, otherwise allocate a new one
+        if (rightmostFreeSlotIndex == numSlots)
+        {
+            // Create a free slot with 0 size,
+            // rightMostFreeSlotIndex is now within the valid range
+            _slots.emplace_back(_buffer.size(), 0, false);
+        }
+
+        // Allocate more memory
         auto additionalSize = std::max(_buffer.size() * GrowthRate, requiredSize);
         _buffer.resize(_buffer.size() + additionalSize);
 

test/ContinuousBuffer.cpp

@@ -245,4 +245,27 @@ TEST(ContinuousBufferTest, GapMerging)
     EXPECT_TRUE(checkContinuousData(buffer, handle7, { sixteen }));
 }
 
+// Buffer will be tightly filled with no space left, allocation must succeed in this case
+TEST(ContinuousBufferTest, ExpandFullBuffer)
+{
+    auto eight = std::vector<int>({ 0,1,2,3,4,5,6,7 });
+    auto four = std::vector<int>({ 10,11,12,13 });
+
+    render::ContinuousBuffer<int> buffer(eight.size() + four.size()); // Allocate a buffer that matches exactly
+
+    auto handle1 = buffer.allocate(eight.size());
+    auto handle2 = buffer.allocate(four.size());
+
+    buffer.setData(handle1, eight);
+    buffer.setData(handle2, four);
+
+    EXPECT_TRUE(checkContinuousData(buffer, handle1, { eight, four}));
+
+    // Allocate another piece of memory
+    auto handle3 = buffer.allocate(eight.size());
+    buffer.setData(handle3, eight);
+
+    EXPECT_TRUE(checkContinuousData(buffer, handle1, { eight, four, eight }));
+}
+
 }