From f58941f2ac6b28131f5e83396f92ae77be427c3e Mon Sep 17 00:00:00 2001
From: Eli Collins <eli@apache.org>
Date: Mon, 20 Aug 2012 21:10:44 +0000
Subject: [PATCH] HADOOP-8614. IOUtils#skipFully hangs forever on EOF.
 Contributed by Colin Patrick McCabe

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1375216 13f79535-47bb-0310-9956-ffa450edef68
---
 .../hadoop-common/CHANGES.txt                 |  3 ++
 .../java/org/apache/hadoop/io/IOUtils.java    | 18 ++++++---
 .../org/apache/hadoop/io/TestIOUtils.java     | 39 +++++++++++++++++++
 3 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index b5163cc0c0c..ae1e22a1bb7 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -405,6 +405,9 @@ Branch-2 ( Unreleased changes )
     HADOOP-8654. TextInputFormat delimiter bug (Gelesh and Jason Lowe via
     bobby)
 
+    HADOOP-8614. IOUtils#skipFully hangs forever on EOF. 
+    (Colin Patrick McCabe via eli)
+
   BREAKDOWN OF HDFS-3042 SUBTASKS
 
     HADOOP-8220. ZKFailoverController doesn't handle failure to become active
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java
index 4f30483cd96..819f075812b 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java
@@ -206,12 +206,20 @@ public class IOUtils {
    * for any reason (including EOF)
    */
   public static void skipFully(InputStream in, long len) throws IOException {
-    while (len > 0) {
-      long ret = in.skip(len);
-      if (ret < 0) {
-        throw new IOException( "Premature EOF from inputStream");
+    long amt = len;
+    while (amt > 0) {
+      long ret = in.skip(amt);
+      if (ret == 0) {
+        // skip may return 0 even if we're not at EOF.  Luckily, we can 
+        // use the read() method to figure out if we're at the end.
+        int b = in.read();
+        if (b == -1) {
+          throw new EOFException( "Premature EOF from inputStream after " +
+              "skipping " + (len - amt) + " byte(s).");
+        }
+        ret = 1;
       }
-      len -= ret;
+      amt -= ret;
     }
   }
   
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java
index 6b7ffdfcf2b..b78b1ea9f31 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java
@@ -21,6 +21,8 @@ package org.apache.hadoop.io;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
+import java.io.ByteArrayInputStream;
+import java.io.EOFException;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
@@ -175,4 +177,41 @@ public class TestIOUtils {
           "Error while reading compressed data", ioe);
     }
   }
+  
+  @Test
+  public void testSkipFully() throws IOException {
+    byte inArray[] = new byte[] {0, 1, 2, 3, 4};
+    ByteArrayInputStream in = new ByteArrayInputStream(inArray);
+    try {
+      in.mark(inArray.length);
+      IOUtils.skipFully(in, 2);
+      IOUtils.skipFully(in, 2);
+      try {
+        IOUtils.skipFully(in, 2);
+        fail("expected to get a PrematureEOFException");
+      } catch (EOFException e) {
+        assertEquals(e.getMessage(), "Premature EOF from inputStream " +
+            "after skipping 1 byte(s).");
+      }
+      in.reset();
+      try {
+        IOUtils.skipFully(in, 20);
+        fail("expected to get a PrematureEOFException");
+      } catch (EOFException e) {
+        assertEquals(e.getMessage(), "Premature EOF from inputStream " +
+            "after skipping 5 byte(s).");
+      }
+      in.reset();
+      IOUtils.skipFully(in, 5);
+      try {
+        IOUtils.skipFully(in, 10);
+        fail("expected to get a PrematureEOFException");
+      } catch (EOFException e) {
+        assertEquals(e.getMessage(), "Premature EOF from inputStream " +
+            "after skipping 0 byte(s).");
+      }
+    } finally {
+      in.close();
+    }
+  }
 }