Merge pull request #9 from manosriram/feat/reader

add keyreader and keyvaluereader

examples/db.go

@@ -59,6 +59,16 @@ func main() {
 			fmt.Println(string(z))
 		} else if text == "sync" {
 			d.Sync()
+		} else if text == "keyreader" {
+			prefix := ""
+			d.KeyReader(prefix, func(k []byte) {
+				fmt.Printf("%s\n", string(k))
+			})
+		} else if text == "keyvaluereader" {
+			keyPrefix := ""
+			d.KeyValueReader(keyPrefix, func(k []byte, v []byte) {
+				fmt.Printf("%s %s\n", string(k), string(v))
+			})
 		}
 	}
 }

reader.go

@@ -0,0 +1,38 @@
+package nimbusdb
+
+import (
+	"strings"
+
+	"github.com/google/btree"
+)
+
+// KeyReader iterates through each key matching given prefix.
+// If prefix is an empty string, all keys are matched.
+// The second argument is a callback function which contains the key.
+func (db *Db) KeyReader(prefix string, handler func(k []byte)) {
+	db.keyDir.tree.Ascend(func(it btree.Item) bool {
+		key := it.(*item).key
+		if strings.HasPrefix(string(key), prefix) {
+			handler(key)
+		}
+		return true
+	})
+}
+
+// KeyValueReader iterates through each key-value pair matching given key's prefix.
+// If prefix is an empty string, all key-value pairs are matched.
+// The second argument is a callback function which contains key and the value.
+func (db *Db) KeyValueReader(keyPrefix string, handler func(k []byte, v []byte)) (bool, error) {
+	db.keyDir.tree.Ascend(func(it btree.Item) bool {
+		key := it.(*item).key
+		if strings.HasPrefix(string(key), keyPrefix) {
+			v, err := db.getKeyDir(key)
+			if err != nil {
+				return false
+			}
+			handler(it.(*item).key, v.v)
+		}
+		return true
+	})
+	return false, nil
+}