Fix bad cast in CIndexBuffer. Modify IIndexBuffer interface for cleanup and safety.

CIndexBuffer::setType could end up casting a temporary u16 variable to u32& (reference!).
Probably never noticed as this tended to mostly works (guess next byte on stack often 0?).
To prevent this from happening again I modifed IIndexBuffer::push_back to work with copies instead of references.
While breaking the interface anyway I also deprecated pointer() which is just identical to getData() anyway.
I get the idea of staying similar to core::array interface, but it's just confusing (and not same due to lack of types anyway).
Also added a const version for getData()

On a side-note - same setType bug still in CVertexBuffer, but a bit harder to fix there. So will be an new patch.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6357 dfc29bdd-3216-0410-991c-e03cc46cb475

changes.txt

@@ -1,6 +1,9 @@
 --------------------------
 Changes in 1.9 (not yet released)
 
+- IIndexBuffer has some interface changes: pointer() deprecated (was same as getData()). Adding a const version of getData(). 
+  Also some functions no longer use references but copy by value which shouldn't be slower for this and is safer to use.
+- Fix CIndexBuffer::setType going from 16 to 32 bit. This had some casts which simply could mess up the results.
 - Fix OSX nor resizing properly. Thanks @torleif, Jordach and sfan5 for patch and report: https://irrlicht.sourceforge.io/forum/viewtopic.php?f=2&t=52819
 - X meshloader fixes bug with uninitialized normals. Thanks @sfan5 for patch: https://irrlicht.sourceforge.io/forum/viewtopic.php?f=2&t=52819
 - stl meshloader now faster, especially with text format

include/CIndexBuffer.h

@@ -14,7 +14,7 @@ namespace scene
 
 	class CIndexBuffer : public IIndexBuffer
 	{
-
+		// Virtual function wrapper around irr::core::array
 		class IIndexList
 		{
 		public:
@@ -22,7 +22,7 @@ namespace scene
 
 			virtual u32 stride() const =0;
 			virtual u32 size() const =0;
-			virtual void push_back(const u32 &element) =0;
+			virtual void push_back(u32 value) =0;
 			virtual u32 operator [](u32 index) const =0;
 			virtual u32 getLast() =0;
 			virtual void setValue(u32 index, u32 value) =0;
@@ -30,6 +30,7 @@ namespace scene
 			virtual void reallocate(u32 new_size, bool canShrink=true) =0;
 			virtual u32 allocated_size() const =0;
 			virtual void* pointer() =0;
+			virtual const void* const_pointer() const =0;
 			virtual video::E_INDEX_TYPE getType() const =0;
 		};
 
@@ -43,10 +44,9 @@ namespace scene
 
 			virtual u32 size() const IRR_OVERRIDE {return Indices.size();}
 
-			virtual void push_back(const u32 &element) IRR_OVERRIDE
+			virtual void push_back(u32 value) IRR_OVERRIDE
 			{
-				// push const ref due to compiler problem with gcc 4.6, big endian
-				Indices.push_back((const T&)element);
+				Indices.push_back((T)value);
 			}
 
 			virtual u32 operator [](u32 index) const IRR_OVERRIDE
@@ -76,7 +76,8 @@ namespace scene
 				return Indices.allocated_size();
 			}
 
-			virtual void* pointer() IRR_OVERRIDE  {return Indices.pointer();}
+			virtual void* pointer() IRR_OVERRIDE  { return Indices.pointer(); }
+			virtual const void* const_pointer() const IRR_OVERRIDE  { return Indices.const_pointer(); }
 
 			virtual video::E_INDEX_TYPE getType() const IRR_OVERRIDE
 			{
@@ -109,7 +110,6 @@ namespace scene
 			delete Indices;
 		}
 
-		//virtual void setType(video::E_INDEX_TYPE IndexType);
 		virtual void setType(video::E_INDEX_TYPE indexType) IRR_OVERRIDE
 		{
 			if ( Indices && Indices->getType() == indexType )
@@ -145,6 +145,7 @@ namespace scene
 		}
 
 		virtual void* getData() IRR_OVERRIDE {return Indices->pointer();}
+		virtual const void* getData() const IRR_OVERRIDE { return Indices->const_pointer(); }
 
 		virtual video::E_INDEX_TYPE getType() const IRR_OVERRIDE {return Indices->getType();}
 
@@ -155,9 +156,9 @@ namespace scene
 			return Indices->size();
 		}
 
-		virtual void push_back(const u32 &element) IRR_OVERRIDE
+		virtual void push_back(u32 value) IRR_OVERRIDE
 		{
-			Indices->push_back(element);
+			Indices->push_back(value);
 		}
 
 		virtual u32 operator [](u32 index) const IRR_OVERRIDE
@@ -190,11 +191,6 @@ namespace scene
 			return Indices->allocated_size();
 		}
 
-		virtual void* pointer() IRR_OVERRIDE
-		{
-			return Indices->pointer();
-		}
-
 		//! get the current hardware mapping hint
 		virtual E_HARDWARE_MAPPING getHardwareMappingHint() const IRR_OVERRIDE
 		{

include/IIndexBuffer.h

@@ -23,10 +23,18 @@ namespace scene
 		//! Pointer to first element
 		virtual void* getData() =0;
 
-		//! Same as getData()
-		virtual void* pointer() =0;
+		//! Const pointer to first element
+		virtual const void* getData() const =0;
+
+		//! Deprecated: Was same as getData(), just closer to core::array interface
+		IRR_DEPRECATED void* pointer() { return getData(); }
 
 		virtual video::E_INDEX_TYPE getType() const =0;
+
+		//! Change between 16 and 32 bit indices.
+		/** This copies all indices to a new buffer of corresponding type.
+		Be careful - going from 32 to 16 bit will only  work correctly 
+		if none of your indices is larger than 16 bit. */
 		virtual void setType(video::E_INDEX_TYPE IndexType) =0;
 
 		//! Number of bytes per element
@@ -35,14 +43,17 @@ namespace scene
 		//! Number of elements
 		virtual u32 size() const =0;
 
-		virtual void push_back (const u32 &element) =0;
+		//! Add value to end. Note that for 16 bit index types values shouldn't be larger than u16
+		virtual void push_back(u32 value) =0;
 
-		//! Set value at index. 
+		//! Set value at index. Note that for 16 bit index types values shouldn't be larger than u16
 		/** Buffer must be already large enough. This is basically the non const version of operator [] */
 		virtual void setValue(u32 index, u32 value) =0;
 
+		//! Access element value at given index
 		virtual u32 operator [](u32 index) const =0;
 		virtual u32 getLast() =0;
+
 		virtual void set_used(u32 usedNow) =0;
 		virtual void reallocate(u32 new_size, bool canShrink=true) =0;
 		virtual u32 allocated_size() const=0;