NIO CountBytes example

gcloud-java-examples/README.md

@@ -37,8 +37,8 @@ To run examples from your command line:
 
 2. Set your current project using `gcloud config set project PROJECT_ID`. This step is not necessary for `ResourceManagerExample`.
 
-3. Compile using Maven: `mvn install -DskipTests -Dmaven.javadoc.skip=true -Dmaven.source.skip=true` in command line from your base project directory
-   then `cd gcloud-java-examples` and finally `mvn package appassembler:assemble -DskipTests -Dmaven.javadoc.skip=true -Dmaven.source.skip=true`.
+3. Compile using Maven: `mvn install -DskipTests` in command line from your base project directory
+   then `cd gcloud-java-examples` and finally `mvn package appassembler:assemble -DskipTests`.
 
 4. Run an example from the command line using the Maven-generated scripts.
 

gcloud-java-examples/pom.xml

@@ -63,6 +63,10 @@
               <mainClass>com.google.cloud.examples.nio.Stat</mainClass>
               <name>Stat</name>
             </program>
+            <program>
+              <mainClass>com.google.cloud.examples.nio.CountBytes</mainClass>
+              <name>CountBytes</name>
+            </program>
             <program>
               <mainClass>
                 com.google.cloud.examples.resourcemanager.ResourceManagerExample

gcloud-java-examples/src/main/java/com/google/cloud/examples/nio/CountBytes.java

@@ -0,0 +1,82 @@
+package com.google.cloud.examples.nio;
+
+import com.google.common.base.Stopwatch;
+
+import java.io.IOException;
+import java.net.URI;
+import java.nio.ByteBuffer;
+import java.nio.channels.SeekableByteChannel;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * CountBytes will read through the whole file given as input.
+ *
+ * <p>It's meant for testing that NIO correctly saturates your network link.
+ *
+ * <p>See the README for compilation instructions. Run this code with
+ * {@code target/appassembler/bin/CountBytes <file>}
+ */
+public class CountBytes {
+
+  /**
+   * See the class documentation.
+   */
+  public static void main(String[] args) throws IOException {
+    if (args.length == 0 || args[0].equals("--help")) {
+      help();
+      return;
+    }
+    for (String a : args) {
+      countFile(a);
+    }
+  }
+
+  /**
+   * Print the length of the indicated file.
+   *
+   * <p>This uses the normal Java NIO Api, so it can take advantage of any installed
+   * NIO Filesystem provider without any extra effort.
+   */
+  private static void countFile(String fname) {
+    // large buffers pay off
+    final int bufSize = 50 * 1024 * 1024;
+    try {
+      Path path = Paths.get(new URI(fname));
+      long size = Files.size(path);
+      System.out.println(fname + ": " + size + " bytes.");
+      ByteBuffer buf = ByteBuffer.allocate(bufSize);
+      System.out.println("Reading the whole file...");
+      Stopwatch sw = Stopwatch.createStarted();
+      SeekableByteChannel chan = Files.newByteChannel(path);
+      long total = 0;
+      int readCalls = 0;
+      for (int read = 1; read > 0; ) {
+        readCalls ++;
+        read = chan.read(buf);
+        buf.flip();
+        total += read;
+      }
+      long elapsed = sw.elapsed(TimeUnit.SECONDS);
+      System.out.println("Read all " + total + " bytes in " + elapsed + "s. (" + readCalls +" calls to chan.read)");
+      if (total != size) {
+        System.out.println("Wait, this doesn't match! We saw " + total + " bytes, yet the file size is listed at " + size + " bytes.");
+      }
+    } catch (Exception ex) {
+      System.out.println(fname + ": " + ex.toString());
+    }
+  }
+
+  private static void help() {
+    String[] help =
+        {"The argument is a <path>",
+         "and we show the length of that file.",
+        };
+    for (String s : help) {
+      System.out.println(s);
+    }
+  }
+
+}