Cursor.Get is now Cursor.Seek, and returns the first possible key.

This makes range and prefix queries possible.

Closes: #44

cursor.go

@@ -48,32 +48,28 @@ func (c *Cursor) Next() (key []byte, value []byte) {
 	return c.keyValue()
 }
 
-// Get moves the cursor to a given key and returns its value.
-// If the key does not exist then the cursor is left at the closest key and a nil value is returned.
-func (c *Cursor) Get(key []byte) (value []byte) {
+// Seek moves the cursor to a given key and returns it.
+// If the key does not exist then the next key is used. If no keys
+// follow, a nil value is returned.
+func (c *Cursor) Seek(seek []byte) (key []byte, value []byte) {
 	// Start from root page and traverse to correct page.
 	c.stack = c.stack[:0]
-	c.search(key, c.transaction.page(c.root))
+	c.search(seek, c.transaction.page(c.root))
 	p, index := c.top()
 
 	// If the cursor is pointing to the end of page then return nil.
 	if index == p.count {
-		return nil
+		return nil, nil
 	}
 
-	// If our target node isn't the same key as what's passed in then return nil.
-	if !bytes.Equal(key, c.element().key()) {
-		return nil
-	}
-
-	return c.element().value()
+	return c.element().key(), c.element().value()
 }
 
 // first moves the cursor to the first leaf element under the last page in the stack.
 func (c *Cursor) first() {
 	p := c.stack[len(c.stack)-1].page
 	for {
-		// Exit when we hit a leaf page. 
+		// Exit when we hit a leaf page.
 		if (p.flags & leafPageFlag) != 0 {
 			break
 		}

rwtransaction.go

@@ -20,7 +20,7 @@ func (t *RWTransaction) init(db *DB) {
 	t.Transaction.init(db)
 	t.pages = make(map[pgid]*page)
 
-	// Increment the transaction id. 
+	// Increment the transaction id.
 	t.meta.txnid += txnid(1)
 }
 
@@ -114,7 +114,7 @@ func (t *RWTransaction) Put(name string, key []byte, value []byte) error {
 
 	// Move cursor to correct position.
 	c := b.cursor()
-	c.Get(key)
+	c.Seek(key)
 
 	// Insert the key/value.
 	c.node(t).put(key, key, value, 0)
@@ -133,7 +133,7 @@ func (t *RWTransaction) Delete(name string, key []byte) error {
 
 	// Move cursor to correct position.
 	c := b.cursor()
-	c.Get(key)
+	c.Seek(key)
 
 	// Delete the node if we have a matching key.
 	c.node(t).del(key)

transaction.go

@@ -1,5 +1,9 @@
 package bolt
 
+import (
+	"bytes"
+)
+
 // Transaction represents a read-only transaction on the database.
 // It can be used for retrieving values for keys as well as creating cursors for
 // iterating over the data.
@@ -90,7 +94,12 @@ func (t *Transaction) Get(name string, key []byte) (value []byte, err error) {
 	if err != nil {
 		return nil, err
 	}
-	return c.Get(key), nil
+	k, v := c.Seek(key)
+	// If our target node isn't the same key as what's passed in then return nil.
+	if !bytes.Equal(key, k) {
+		return nil, nil
+	}
+	return v, nil
 }
 
 // ForEach executes a function for each key/value pair in a bucket.