Beginnings of a rope text buffer implementation.

src/buffer.rs

@@ -1,4 +1,17 @@
 use std::mem;
+use std::fmt;
+
+
+fn newline_count(text: &str) -> uint {
+    let mut count = 0;
+    for c in text.chars() {
+        if c == '\n' {
+            count += 1;
+        }
+    }
+    return count;
+}
+
 
 /// A block of text, contiguous in memory
 pub struct TextBlock {
@@ -13,6 +26,19 @@ impl TextBlock {
         }
     }
     
+    /// Create a new text block with the contents of 'text'.
+    pub fn new_from_str(text: &str) -> TextBlock {
+        let mut tb = TextBlock {
+            data: Vec::<u8>::with_capacity(text.len())
+        };
+        
+        for b in text.bytes() {
+            tb.data.push(b);
+        }
+        
+        return tb;
+    }
+    
     /// Return the length of the text block in bytes.
     pub fn len(&self) -> uint {
         self.data.len()
@@ -85,16 +111,185 @@ impl TextBlock {
     }
 }
 
+impl fmt::Show for TextBlock {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.as_str())
+    }
+}
 
-// /// A rope text storage buffer, using TextBlocks for its underlying text
-// /// storage.
-// pub enum TextBuffer {
-//     Block(TextBlock),
-//     Node(Box<TextBuffer>, Box<TextBuffer>)
-// }
-// 
-// impl TextBuffer {
-//     pub fn new() -> TextBuffer {
-//         TextBuffer::Block(TextBlock::new())
-//     }
-// }
+
+
+
+/// A text rope node, using TextBlocks for its underlying text
+/// storage.
+// TODO: record number of graphines as well, to support utf8 properly
+pub struct TextNode {
+    pub data: TextNodeData,
+    pub newline_count: uint,
+    pub byte_count: uint,
+}
+
+pub enum TextNodeData {
+    Leaf(TextBlock),
+    Branch(Box<TextNode>, Box<TextNode>)
+}
+
+const MIN_LEAF_SIZE: uint = 512;
+const MAX_LEAF_SIZE: uint = MIN_LEAF_SIZE * 2;
+
+
+impl TextNode {
+    pub fn new() -> TextNode {
+        TextNode {
+            data: TextNodeData::Leaf(TextBlock::new()),
+            newline_count: 0,
+            byte_count: 0
+        }
+    }
+    
+    pub fn new_from_str(text: &str) -> TextNode {
+        TextNode {
+            data: TextNodeData::Leaf(TextBlock::new_from_str(text)),
+            newline_count: newline_count(text),
+            byte_count: text.len()
+        }
+    }
+
+    /// Splits a leaf node into equal-sized pieces until all children are
+    /// less than 'max_size'.
+    pub fn split(&mut self) {
+        if let TextNodeData::Branch(_, _) = self.data {
+            panic!("TextNode::split(): attempt to split a non-leaf node.");
+        }
+        
+        if self.byte_count > 1 {
+            // Split data into two new text blocks
+            let mut tn1 = box TextNode::new();
+            let mut tn2 = box TextNode::new();
+            if let TextNodeData::Leaf(ref mut tb) = self.data {
+                let pos = tb.len() / 2;
+                tn1 = box TextNode::new_from_str(tb.as_str().slice(0, pos));
+                tn2 = box TextNode::new_from_str(tb.as_str().slice(pos, tb.len()));
+            }
+            
+            // Swap the old and new data
+            let mut new_data = TextNodeData::Branch(tn1, tn2);
+            mem::swap(&mut self.data, &mut new_data);
+        }
+    }
+    
+    /// Merges the data of a non-leaf node to make it a leaf node    
+    pub fn merge(&mut self) {
+        if let TextNodeData::Branch(_, _) = self.data {
+            let mut s: String = String::from_str("");
+            
+            if let TextNodeData::Branch(ref mut left, ref mut right) = self.data {
+                // Merge left and right children first, to make sure we're dealing
+                // with leafs
+                if let TextNodeData::Branch(_, _) = left.data { left.merge(); }
+                if let TextNodeData::Branch(_, _) = right.data { right.merge(); }
+                
+                // Push data into a string
+                if let TextNodeData::Leaf(ref tb) = left.data {
+                    s.push_str(tb.as_str());
+                }
+                if let TextNodeData::Leaf(ref tb) = right.data {
+                    s.push_str(tb.as_str());
+                }
+            }
+        
+            self.data = TextNodeData::Leaf(TextBlock::new_from_str(s.as_slice()));
+        }
+    }
+    
+    /// Insert 'text' at position 'pos'.
+    pub fn insert_text(&mut self, text: &str, pos: uint) {
+        if pos > self.byte_count {
+            panic!("TextNode::insert_text(): attempt to insert text after end of node text.");
+        }
+        
+        match self.data {
+            TextNodeData::Leaf(_) => {
+                if let TextNodeData::Leaf(ref mut tb) = self.data {
+                    tb.insert_text(text, pos);
+                }
+                self.newline_count += newline_count(text);
+                self.byte_count += text.len();
+                
+                if self.byte_count > MAX_LEAF_SIZE {
+                    self.split();
+                }
+            },
+            
+            TextNodeData::Branch(ref mut left, ref mut right) => {
+                if pos <= left.byte_count {
+                    left.insert_text(text, pos);
+                }
+                else {
+                    right.insert_text(text, pos - left.byte_count);
+                }
+                
+                self.newline_count = left.newline_count + right.newline_count;
+                self.byte_count = left.byte_count + right.byte_count;
+            }
+        }
+    }
+}
+
+impl fmt::Show for TextNode {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self.data {
+            TextNodeData::Leaf(ref tb) => {
+                tb.fmt(f)
+            },
+            
+            TextNodeData::Branch(ref left, ref right) => {
+                try!(left.fmt(f));
+                right.fmt(f)
+            }
+        }
+    }
+}
+
+
+
+
+/// A text buffer
+pub struct TextBuffer {
+    root: TextNode
+}
+
+impl TextBuffer {
+    pub fn new() -> TextBuffer {
+        TextBuffer {
+            root: TextNode::new()
+        }
+    }
+    
+    pub fn len(&self) -> uint {
+        self.root.byte_count
+    }
+    
+    /// Insert 'text' at byte position 'pos'.
+    pub fn insert_text(&mut self, text: &str, pos: uint) {
+        self.root.insert_text(text, pos);
+    }
+    
+    /// Remove the text between byte positions 'pos_a' and 'pos_b'.
+    pub fn remove_text(&mut self, pos_a: uint, pos_b: uint) {
+        match self.root.data {
+            TextNodeData::Leaf(ref mut tb) => {
+                tb.remove_text(pos_a, pos_b);
+                self.root.byte_count = tb.len();
+            },
+            
+            TextNodeData::Branch(_, _) => {}
+        }
+    }
+}
+
+impl fmt::Show for TextBuffer {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.root.fmt(f)
+    }
+}

src/main.rs

@@ -3,7 +3,7 @@ extern crate docopt;
 extern crate serialize;
 
 use docopt::Docopt;
-use buffer::TextBlock; 
+use buffer::TextBuffer; 
 
 mod buffer;
 
@@ -30,16 +30,14 @@ fn main() {
     // Get command-line arguments
     let args: Args = Docopt::new(USAGE).and_then(|d| d.decode()).unwrap_or_else(|e| e.exit());
     
-    let mut tb = TextBlock::new();
+    let mut tb = TextBuffer::new();
 
-    for _ in range(0i, 1000) {
-        tb.insert_text("Hello", 0);
-        tb.insert_text("Goodbye", 0);
+    for _ in range(0i, 100) {
         tb.insert_text(args.arg_file.as_slice(), 0);
-        if tb.len() > 1024 {
-            tb.remove_text(0, 12 + args.arg_file.len());
-        }
+        //if tb.len() > 1024 {
+        //    tb.remove_text(0, args.arg_file.len());
+        //}
     }
     
-    println!("{}", tb.as_str());
+    println!("{}", tb);
 }