From cf71d6bd2c370c069c03d8d80a021fa471447812 Mon Sep 17 00:00:00 2001
From: "Maxim.Mossienko" <Maxim.Mossienko@jetbrains.com>
Date: Tue, 10 Dec 2013 16:11:34 +0100
Subject: [PATCH] avoid allocating sun.nio.cs.US_ASCII$Decoder when converting
 byte[] to String

: 1,267,720,880 (3%) bytes in 31,693,022 (3%) objects (avg size 40 bytes)
                 	sun.nio.cs.US_ASCII.newDecoder: 1,267,720,880 (100%) bytes in 31,693,022 (100%) objects
                 		java.lang.String.<init>: 1,267,673,560 (99%) bytes in 31,691,839 (99%) objects
                 			com.intellij.util.io.IOUtil.readUTFFast: 1,267,673,480 (99%) bytes in 31,691,837 (99%) objects
---
 platform/util/src/com/intellij/util/io/IOUtil.java | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/platform/util/src/com/intellij/util/io/IOUtil.java b/platform/util/src/com/intellij/util/io/IOUtil.java
index c10f04a78dba..625b1e693b10 100644
--- a/platform/util/src/com/intellij/util/io/IOUtil.java
+++ b/platform/util/src/com/intellij/util/io/IOUtil.java
@@ -18,6 +18,7 @@ package com.intellij.util.io;
 import com.intellij.openapi.util.ThrowableComputable;
 import com.intellij.openapi.util.io.FileUtil;
 import com.intellij.openapi.vfs.CharsetToolkit;
+import com.intellij.reference.SoftReference;
 import com.intellij.util.SystemProperties;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
@@ -113,6 +114,8 @@ public class IOUtil {
   }
 
   public static final Charset US_ASCII = Charset.forName("US-ASCII");
+  private static final ThreadLocal<SoftReference<char[]>> spareBufferLocal = new ThreadLocal<SoftReference<char[]>>();
+
   public static String readUTFFast(@NotNull byte[] buffer, @NotNull DataInput storage) throws IOException {
     int len = 0xFF & (int)storage.readByte();
     if (len == 0xFF) {
@@ -126,7 +129,15 @@ public class IOUtil {
 
     if (len == 0) return "";
     storage.readFully(buffer, 0, len);
-    return new String(buffer, 0, len, US_ASCII);
+
+    SoftReference<char[]> reference = spareBufferLocal.get();
+    char[] chars = reference != null ? reference.get() : null;
+    if (chars == null) {
+      chars = new char[STRING_LENGTH_THRESHOLD];
+      spareBufferLocal.set(new SoftReference<char[]>(chars));
+    }
+    for(int i = 0; i < len; ++i) chars[i] = (char)(buffer[i] &0xFF);
+    return new String(chars, 0, len);
   }
 
   public static boolean isAscii(@NotNull String str) {