HADOOP-11039. ByteBufferReadable API doc is inconsistent with the implementations. (Yi Liu via Colin P. McCabe)

(cherry picked from commit 249cc905017948d64aab3d14d7a64df3b7b35a13)

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -307,6 +307,9 @@ Release 2.7.0 - UNRELEASED
 
     HADOOP-11448. Fix findbugs warnings in FileBasedIPList. (ozawa)
 
+    HADOOP-11039. ByteBufferReadable API doc is inconsistent with the
+    implementations. (Yi Liu via Colin P. McCabe)
+
 Release 2.6.0 - 2014-11-18
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/ByteBufferReadable.java

@@ -29,9 +29,8 @@ public interface ByteBufferReadable {
    * Reads up to buf.remaining() bytes into buf. Callers should use
    * buf.limit(..) to control the size of the desired read.
    * <p/>
-   * After a successful call, buf.position() and buf.limit() should be
-   * unchanged, and therefore any data can be immediately read from buf.
-   * buf.mark() may be cleared or updated.
+   * After a successful call, buf.position() will be advanced by the number 
+   * of bytes read and buf.limit() should be unchanged.
    * <p/>
    * In the case of an exception, the values of buf.position() and buf.limit()
    * are undefined, and callers should be prepared to recover from this
@@ -45,9 +44,9 @@ public interface ByteBufferReadable {
    * signal an error upon their receipt.
    *
    * @param buf
-   *          the ByteBuffer to receive the results of the read operation. Up to
-   *          buf.limit() - buf.position() bytes may be read.
-   * @return the number of bytes available to read from buf
+   *          the ByteBuffer to receive the results of the read operation.
+   * @return the number of bytes read, possibly zero, or -1 if 
+   *         reach end-of-stream
    * @throws IOException
    *           if there is some error performing the read
    */