Mono.CSharp.Switch.TableSwitchEmit C# (CSharp) Method

		void TableSwitchEmit (EmitContext ec, Expression val)
		{
			int element_count = Elements.Count;
			object [] element_keys = new object [element_count];
			Elements.Keys.CopyTo (element_keys, 0);
			Array.Sort (element_keys);

			// initialize the block list with one element per key
			var key_blocks = new List<KeyBlock> (element_count);
			foreach (object key in element_keys)
				key_blocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));

			KeyBlock current_kb;
			// iteratively merge the blocks while they are at least half full
			// there's probably a really cool way to do this with a tree...
			while (key_blocks.Count > 1)
			{
				var key_blocks_new = new List<KeyBlock> ();
				current_kb = (KeyBlock) key_blocks [0];
				for (int ikb = 1; ikb < key_blocks.Count; ikb++)
				{
					KeyBlock kb = (KeyBlock) key_blocks [ikb];
					if ((current_kb.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (current_kb, kb))
					{
						// merge blocks
						current_kb.last = kb.last;
						current_kb.Size += kb.Size;
					}
					else
					{
						// start a new block
						key_blocks_new.Add (current_kb);
						current_kb = kb;
					}
				}
				key_blocks_new.Add (current_kb);
				if (key_blocks.Count == key_blocks_new.Count)
					break;
				key_blocks = key_blocks_new;
			}

			// initialize the key lists
			foreach (KeyBlock kb in key_blocks)
				kb.element_keys = new List<object> ();

			// fill the key lists
			int iBlockCurr = 0;
			if (key_blocks.Count > 0) {
				current_kb = (KeyBlock) key_blocks [0];
				foreach (object key in element_keys)
				{
					bool next_block = (key is UInt64) ? (ulong) key > (ulong) current_kb.last :
						System.Convert.ToInt64 (key) > current_kb.last;
					if (next_block)
						current_kb = (KeyBlock) key_blocks [++iBlockCurr];
					current_kb.element_keys.Add (key);
				}
			}

			// sort the blocks so we can tackle the largest ones first
			key_blocks.Sort ();

			// okay now we can start...
			Label lbl_end = ec.DefineLabel ();	// at the end ;-)
			Label lbl_default = default_target;

			Type type_keys = null;
			if (element_keys.Length > 0)
				type_keys = element_keys [0].GetType ();	// used for conversions

			TypeSpec compare_type;
			
			if (TypeManager.IsEnumType (SwitchType))
				compare_type = EnumSpec.GetUnderlyingType (SwitchType);
			else
				compare_type = SwitchType;
			
			for (int iBlock = key_blocks.Count - 1; iBlock >= 0; --iBlock)
			{
				KeyBlock kb = ((KeyBlock) key_blocks [iBlock]);
				lbl_default = (iBlock == 0) ? default_target : ec.DefineLabel ();
				if (kb.Length <= 2)
				{
					foreach (object key in kb.element_keys) {
						SwitchLabel sl = (SwitchLabel) Elements [key];
						if (key is int && (int) key == 0) {
							val.EmitBranchable (ec, sl.GetILLabel (ec), false);
						} else {
							val.Emit (ec);
							EmitObjectInteger (ec, key);
							ec.Emit (OpCodes.Beq, sl.GetILLabel (ec));
						}
					}
				}
				else
				{
					// TODO: if all the keys in the block are the same and there are
					//       no gaps/defaults then just use a range-check.
					if (compare_type == TypeManager.int64_type ||
						compare_type == TypeManager.uint64_type)
					{
						// TODO: optimize constant/I4 cases

						// check block range (could be > 2^31)
						val.Emit (ec);
						EmitObjectInteger (ec, System.Convert.ChangeType (kb.first, type_keys));
						ec.Emit (OpCodes.Blt, lbl_default);
						val.Emit (ec);
						EmitObjectInteger (ec, System.Convert.ChangeType (kb.last, type_keys));
						ec.Emit (OpCodes.Bgt, lbl_default);

						// normalize range
						val.Emit (ec);
						if (kb.first != 0)
						{
							EmitObjectInteger (ec, System.Convert.ChangeType (kb.first, type_keys));
							ec.Emit (OpCodes.Sub);
						}
						ec.Emit (OpCodes.Conv_I4);	// assumes < 2^31 labels!
					}
					else
					{
						// normalize range
						val.Emit (ec);
						int first = (int) kb.first;
						if (first > 0)
						{
							ec.EmitInt (first);
							ec.Emit (OpCodes.Sub);
						}
						else if (first < 0)
						{
							ec.EmitInt (-first);
							ec.Emit (OpCodes.Add);
						}
					}

					// first, build the list of labels for the switch
					int iKey = 0;
					int cJumps = kb.Length;
					Label [] switch_labels = new Label [cJumps];
					for (int iJump = 0; iJump < cJumps; iJump++)
					{
						object key = kb.element_keys [iKey];
						if (System.Convert.ToInt64 (key) == kb.first + iJump)
						{
							SwitchLabel sl = (SwitchLabel) Elements [key];
							switch_labels [iJump] = sl.GetILLabel (ec);
							iKey++;
						}
						else
							switch_labels [iJump] = lbl_default;
					}
					// emit the switch opcode
					ec.Emit (OpCodes.Switch, switch_labels);
				}

				// mark the default for this block
				if (iBlock != 0)
					ec.MarkLabel (lbl_default);
			}

			// TODO: find the default case and emit it here,
			//       to prevent having to do the following jump.
			//       make sure to mark other labels in the default section

			// the last default just goes to the end
			if (element_keys.Length > 0)
				ec.Emit (OpCodes.Br, lbl_default);

			// now emit the code for the sections
			bool found_default = false;

			foreach (SwitchSection ss in Sections) {
				foreach (SwitchLabel sl in ss.Labels) {
					if (sl.Converted == SwitchLabel.NullStringCase) {
						ec.MarkLabel (null_target);
					} else if (sl.Label == null) {
						ec.MarkLabel (lbl_default);
						found_default = true;
						if (!has_null_case)
							ec.MarkLabel (null_target);
					}
					ec.MarkLabel (sl.GetILLabel (ec));
					ec.MarkLabel (sl.GetILLabelCode (ec));
				}
				ss.Block.Emit (ec);
			}
			
			if (!found_default) {
				ec.MarkLabel (lbl_default);
				if (!has_null_case) {
					ec.MarkLabel (null_target);
				}
			}
			
			ec.MarkLabel (lbl_end);
		}