From 086d2083e8ecf39edb4cc10b1e6a5dd93f2c949d Mon Sep 17 00:00:00 2001
From: peter <peter@jetbrains.com>
Date: Thu, 23 Oct 2014 11:40:23 +0200
Subject: [PATCH] don't expose whole document text through subsequences in
 document change events (IDEA-131780)

---
 .../openapi/editor/impl/DocumentImpl.java         | 15 +++++++++------
 .../src/com/intellij/util/text/ImmutableText.java | 11 +++++++++--
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/platform/core-impl/src/com/intellij/openapi/editor/impl/DocumentImpl.java b/platform/core-impl/src/com/intellij/openapi/editor/impl/DocumentImpl.java
index 918ebaa22425..34512a6fc714 100644
--- a/platform/core-impl/src/com/intellij/openapi/editor/impl/DocumentImpl.java
+++ b/platform/core-impl/src/com/intellij/openapi/editor/impl/DocumentImpl.java
@@ -493,7 +493,9 @@ public class DocumentImpl extends UserDataHolderBase implements DocumentEx {
       throwGuardedFragment(marker, offset, null, s.toString());
     }
 
-    updateText(myText.insert(offset, ImmutableText.valueOf(s)), offset, null, s, false, LocalTimeCounter.currentTime());
+    myText = myText.ensureChunked();
+    ImmutableText newText = myText.insert(offset, ImmutableText.valueOf(s));
+    updateText(newText, offset, null, newText.subtext(offset, offset + s.length()), false, LocalTimeCounter.currentTime());
     trimToSize();
   }
 
@@ -511,14 +513,13 @@ public class DocumentImpl extends UserDataHolderBase implements DocumentEx {
     if (!isWritable()) throw new ReadOnlyModificationException(this);
     if (startOffset == endOffset) return;
 
-    CharSequence sToDelete = myText.subSequence(startOffset, endOffset);
-
     RangeMarker marker = getRangeGuard(startOffset, endOffset);
     if (marker != null) {
-      throwGuardedFragment(marker, startOffset, sToDelete.toString(), null);
+      throwGuardedFragment(marker, startOffset, myText.subSequence(startOffset, endOffset).toString(), null);
     }
 
-    updateText(myText.delete(startOffset, endOffset), startOffset, sToDelete, null, false, LocalTimeCounter.currentTime());
+    myText = myText.ensureChunked();
+    updateText(myText.delete(startOffset, endOffset), startOffset, myText.subtext(startOffset, endOffset), null, false, LocalTimeCounter.currentTime());
   }
 
   @Override
@@ -582,7 +583,7 @@ public class DocumentImpl extends UserDataHolderBase implements DocumentEx {
     }
 
     CharSequence changedPart = s.subSequence(newStartInString, newEndInString);
-    CharSequence sToDelete = myText.subSequence(startOffset, endOffset);
+    CharSequence sToDelete = myText.subtext(startOffset, endOffset);
     RangeMarker guard = getRangeGuard(startOffset, endOffset);
     if (guard != null) {
       throwGuardedFragment(guard, startOffset, sToDelete.toString(), changedPart.toString());
@@ -593,7 +594,9 @@ public class DocumentImpl extends UserDataHolderBase implements DocumentEx {
       newText = (ImmutableText)s;
     }
     else {
+      myText = myText.ensureChunked();
       newText = myText.delete(startOffset, endOffset).insert(startOffset, changedPart);
+      changedPart = newText.subtext(startOffset, startOffset + changedPart.length());
     }
     updateText(newText, startOffset, sToDelete, changedPart, wholeTextReplaced, newModificationStamp);
     trimToSize();
diff --git a/platform/util/src/com/intellij/util/text/ImmutableText.java b/platform/util/src/com/intellij/util/text/ImmutableText.java
index 4ec4b93ec2b2..2dde3eb60293 100644
--- a/platform/util/src/com/intellij/util/text/ImmutableText.java
+++ b/platform/util/src/com/intellij/util/text/ImmutableText.java
@@ -96,7 +96,14 @@ public final class ImmutableText extends ImmutableCharSequence implements CharAr
     return new ImmutableText(new LeafNode(chars));
   }
 
-  private ImmutableText ensureChunked() {
+  /**
+   * When first loaded, ImmutableText contents are stored as a single large array. This saves memory but isn't
+   * modification-friendly as it disallows slightly changed texts to retain most of the internal structure of the
+   * original document. Whoever retains old non-chunked version will use more memory than really needed.
+   *
+   * @return a copy of this text better prepared for small modifications to fully enable structure-sharing capabilities
+   */
+  public ImmutableText ensureChunked() {
     if (length() > BLOCK_SIZE && myNode instanceof LeafNode) {
       return new ImmutableText(nodeOf(((LeafNode)myNode)._data, 0, length()));
     }
@@ -292,7 +299,7 @@ public final class ImmutableText extends ImmutableCharSequence implements CharAr
    * @throws IndexOutOfBoundsException if <code>(start < 0) || (end < 0) ||
    *         (start > end) || (end > this.length())</code>
    */
-  private ImmutableText subtext(int start, int end) {
+  public ImmutableText subtext(int start, int end) {
     if ((start < 0) || (start > end) || (end > length()))
       throw new IndexOutOfBoundsException();
     if ((start == 0) && (end == length()))