1 files changed, 84 insertions, 0 deletions
diff --git a/src/repl/scala/tools/nsc/interpreter/session/FileBackedHistory.scala b/src/repl/scala/tools/nsc/interpreter/session/FileBackedHistory.scala
new file mode 100644
index 0000000000..dddfb1b8f6
--- /dev/null
+++ b/src/repl/scala/tools/nsc/interpreter/session/FileBackedHistory.scala
@@ -0,0 +1,84 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2013 LAMP/EPFL
+ * @author Paul Phillips
+ */
+
+package scala.tools.nsc
+package interpreter
+package session
+
+import scala.tools.nsc.io._
+import FileBackedHistory._
+
+/** TODO: file locking.
+ */
+trait FileBackedHistory extends JLineHistory with JPersistentHistory {
+  def maxSize: Int
+  protected lazy val historyFile: File = defaultFile
+  private var isPersistent = true
+
+  locally {
+    load()
+  }
+
+  def withoutSaving[T](op: => T): T = {
+    val saved = isPersistent
+    isPersistent = false
+    try op
+    finally isPersistent = saved
+  }
+  def addLineToFile(item: CharSequence): Unit = {
+    if (isPersistent)
+      append(item + "\n")
+  }
+
+  /** Overwrites the history file with the current memory. */
+  protected def sync(): Unit = {
+    val lines = asStrings map (_ + "\n")
+    historyFile.writeAll(lines: _*)
+  }
+  /** Append one or more lines to the history file. */
+  protected def append(lines: String*): Unit = {
+    historyFile.appendAll(lines: _*)
+  }
+
+  def load(): Unit = {
+    if (!historyFile.canRead)
+      historyFile.createFile()
+
+    val lines: IndexedSeq[String] = {
+      try historyFile.lines().toIndexedSeq
+      catch {
+        // It seems that control characters in the history file combined
+        // with the default codec can lead to nio spewing exceptions.  Rather
+        // than abandon hope we'll try to read it as ISO-8859-1
+        case _: Exception =>
+          try historyFile.lines("ISO-8859-1").toIndexedSeq
+          catch { case _: Exception => Vector() }
+      }
+    }
+
+    repldbg("Loading " + lines.size + " into history.")
+
+    // avoid writing to the history file
+    withoutSaving(lines takeRight maxSize foreach add)
+    // truncate the history file if it's too big.
+    if (lines.size > maxSize) {
+      repldbg("File exceeds maximum size: truncating to " + maxSize + " entries.")
+      sync()
+    }
+    moveToEnd()
+  }
+
+  def flush(): Unit = ()
+  def purge(): Unit = historyFile.truncate()
+}
+
+object FileBackedHistory {
+  //   val ContinuationChar = '\003'
+  //   val ContinuationNL: String = Array('\003', '\n').mkString
+  import Properties.userHome
+
+  def defaultFileName = ".scala_history"
+  def defaultFile: File = File(Path(userHome) / defaultFileName)
+}