update PieceTable::Iterator to allow empty pieces

src/core/PieceTable.cc

@@ -2,11 +2,13 @@
 
 PieceTable::PieceTable()
 {
-    start_piece = &m_pieces[PIECE_INDEX_START];
+    m_piece_index = 0u;
-    end_piece = &m_pieces[PIECE_INDEX_END];
+    start_piece = add_piece();
+    end_piece = add_piece();
+    start_piece->length = 0u;
+    end_piece->length = 0u;
     start_piece->next = end_piece;
     end_piece->prev = start_piece;
-    m_piece_index = 2u;
     tabstop = 4u;
     m_append_buffer_index = 0u;
     m_changes_index = 0u;
@@ -37,6 +39,10 @@ PieceTable::Iterator::Iterator(PieceTable * pt)
 {
     piece_table = pt;
     piece = pt->start_piece->next;
+    while ((piece->length == 0u) && (piece != piece_table->end_piece))
+    {
+        piece = piece->next;
+    }
     offset = 0u;
 }
 
@@ -54,31 +60,46 @@ uint8_t PieceTable::Iterator::num_bytes_in_code_point() const
 
 void PieceTable::Iterator::go_next_position()
 {
-    uint8_t code_point_size = num_bytes_in_code_point();
+    if (valid())
-    if ((offset + code_point_size) >= piece->length)
     {
-        go_next_piece();
+        uint8_t code_point_size = num_bytes_in_code_point();
-        return;
+        if ((offset + code_point_size) >= piece->length)
+        {
+            do
+            {
+                piece = piece->next;
+            } while ((piece != piece_table->end_piece) &&
+                     (piece->length == 0u));
+            offset = 0u;
+            return;
+        }
+        offset += code_point_size;
     }
-    offset += code_point_size;
 }
 
 void PieceTable::Iterator::go_prev_position()
 {
-    if (offset > 0)
+    if (piece != piece_table->start_piece)
     {
-        offset = Encoding::beginning_of_code_point(piece_table->encoding, &piece->start[offset - 1u]) - piece->start;
+        if (offset > 0)
-    }
-    else if (piece != piece_table->start_piece)
-    {
-        piece = piece->prev;
-        if (piece->length > 0u)
         {
-            offset = Encoding::beginning_of_code_point(piece_table->encoding, &piece->start[piece->length - 1u]) - piece->start;
+            offset = Encoding::beginning_of_code_point(piece_table->encoding, &piece->start[offset - 1u]) - piece->start;
         }
         else
         {
-            offset = 0u;
+            do
+            {
+                piece = piece->prev;
+            } while ((piece != piece_table->start_piece) &&
+                     (piece->length == 0u));
+            if (piece->length > 0u)
+            {
+                offset = Encoding::beginning_of_code_point(piece_table->encoding, &piece->start[piece->length - 1u]) - piece->start;
+            }
+            else
+            {
+                offset = 0u;
+            }
         }
     }
 }
@@ -99,7 +120,11 @@ void PieceTable::Iterator::go_next_piece()
 {
     if (piece != piece_table->end_piece)
     {
-        piece = piece->next;
+        do
+        {
+            piece = piece->next;
+        } while ((piece != piece_table->end_piece) &&
+                 (piece->length == 0u));
         offset = 0u;
     }
 }
@@ -108,7 +133,11 @@ void PieceTable::Iterator::go_prev_piece()
 {
     if (piece != piece_table->start_piece)
     {
-        piece = piece->prev;
+        do
+        {
+            piece = piece->prev;
+        } while ((piece != piece_table->start_piece) &&
+                 (piece->length == 0u));
         offset = 0u;
     }
 }

src/core/PieceTable.h

@@ -11,11 +11,6 @@
 class PieceTable
 {
 public:
-    enum
-    {
-        PIECE_INDEX_START = 0,
-        PIECE_INDEX_END = 1,
-    };
     enum
     {
         INTERNAL_EOL = '\n',