HADOOP-7429. Add another IOUtils#copyBytes method. Contributed by Eli Collins

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1140442 13f79535-47bb-0310-9956-ffa450edef68

common/CHANGES.txt

@@ -237,6 +237,8 @@ Trunk (unreleased changes)
     HADOOP-310. Additional constructor requested in BytesWritable. (Brock
     Noland via atm)
 
+    HADOOP-7429. Add another IOUtils#copyBytes method. (eli)
+
   OPTIMIZATIONS
   
     HADOOP-7333. Performance improvement in PureJavaCrc32. (Eric Caspole

common/src/java/org/apache/hadoop/io/IOUtils.java

@@ -36,6 +36,7 @@ public class IOUtils {
 
   /**
    * Copies from one stream to another.
+   *
    * @param in InputStrem to read from
    * @param out OutputStream to write to
    * @param buffSize the size of the buffer 
@@ -44,7 +45,6 @@ public class IOUtils {
    */
   public static void copyBytes(InputStream in, OutputStream out, int buffSize, boolean close) 
     throws IOException {
-
     try {
       copyBytes(in, out, buffSize);
       if(close) {
@@ -70,7 +70,6 @@ public class IOUtils {
    */
   public static void copyBytes(InputStream in, OutputStream out, int buffSize) 
     throws IOException {
-
     PrintStream ps = out instanceof PrintStream ? (PrintStream)out : null;
     byte buf[] = new byte[buffSize];
     int bytesRead = in.read(buf);
@@ -82,9 +81,11 @@ public class IOUtils {
       bytesRead = in.read(buf);
     }
   }
+
   /**
    * Copies from one stream to another. <strong>closes the input and output streams 
    * at the end</strong>.
+   *
    * @param in InputStrem to read from
    * @param out OutputStream to write to
    * @param conf the Configuration object 
@@ -96,7 +97,8 @@ public class IOUtils {
   
   /**
    * Copies from one stream to another.
-   * @param in InputStrem to read from
+   *
+   * @param in InputStream to read from
    * @param out OutputStream to write to
    * @param conf the Configuration object
    * @param close whether or not close the InputStream and 
@@ -107,8 +109,37 @@ public class IOUtils {
     copyBytes(in, out, conf.getInt("io.file.buffer.size", 4096),  close);
   }
 
-  /** Reads len bytes in a loop.
+  /**
-   * @param in The InputStream to read from
+   * Copies count bytes from one stream to another.
+   *
+   * @param in InputStream to read from
+   * @param out OutputStream to write to
+   * @param count number of bytes to copy
+   * @throws IOException if bytes can not be read or written
+   */
+  public static void copyBytes(InputStream in, OutputStream out, long count)
+      throws IOException {
+    byte buf[] = new byte[4096];
+    long bytesRemaining = count;
+    int bytesRead;
+
+    while (bytesRemaining > 0) {
+      int bytesToRead = (int)
+        (bytesRemaining < buf.length ? bytesRemaining : buf.length);
+
+      bytesRead = in.read(buf, 0, bytesToRead);
+      if (bytesRead == -1)
+        break;
+
+      out.write(buf, 0, bytesRead);
+      bytesRemaining -= bytesRead;
+    }
+  }
+  
+  /**
+   * Reads len bytes in a loop.
+   *
+   * @param in InputStream to read from
    * @param buf The buffer to fill
    * @param off offset from the buffer
    * @param len the length of bytes to read
@@ -128,7 +159,8 @@ public class IOUtils {
     }
   }
   
-  /** Similar to readFully(). Skips bytes in a loop.
+  /**
+   * Similar to readFully(). Skips bytes in a loop.
    * @param in The InputStream to skip bytes from
    * @param len number of bytes to skip.
    * @throws IOException if it could not skip requested number of bytes 
@@ -147,6 +179,7 @@ public class IOUtils {
   /**
    * Close the Closeable objects and <b>ignore</b> any {@link IOException} or 
    * null pointers. Must only be used for cleanup in exception handlers.
+   *
    * @param log the log to record problems to at debug level. Can be null.
    * @param closeables the objects to close
    */
@@ -167,6 +200,7 @@ public class IOUtils {
   /**
    * Closes the stream ignoring {@link IOException}.
    * Must only be called in cleaning up from exception handlers.
+   *
    * @param stream the Stream to close
    */
   public static void closeStream(java.io.Closeable stream) {
@@ -175,10 +209,10 @@ public class IOUtils {
   
   /**
    * Closes the socket ignoring {@link IOException}
+   *
    * @param sock the Socket to close
    */
   public static void closeSocket(Socket sock) {
-    // avoids try { close() } dance
     if (sock != null) {
       try {
         sock.close();
@@ -187,7 +221,8 @@ public class IOUtils {
     }
   }
   
-  /** /dev/null of OutputStreams.
+  /**
+   * The /dev/null of OutputStreams.
    */
   public static class NullOutputStream extends OutputStream {
     public void write(byte[] b, int off, int len) throws IOException {