Merge pull request #110 from fa93hws/file-channel

use file channel to improve content hash efficiency

Author: tinder-maxwellelliott

src/main/java/com/bazel_diff/BazelClient.java

@@ -2,8 +2,6 @@
 
 import com.google.devtools.build.lib.query2.proto.proto2api.Build;
 
-import com.google.common.collect.Iterables;
-
 import java.io.*;
 import java.nio.charset.StandardCharsets;
 import java.io.IOException;
@@ -93,7 +91,8 @@ private Map<String, BazelSourceFileTarget> processBazelSourcefileTargets(List<Bu
                 BazelSourceFileTargetImpl sourceFileTarget = new BazelSourceFileTargetImpl(
                         sourceFile.getName(),
                         digest.digest().clone(),
-                        readSourcefileTargets ? workingDirectory : null
+                        readSourcefileTargets ? workingDirectory : null,
+                        verbose
                 );
                 sourceTargets.put(sourceFileTarget.getName(), sourceFileTarget);
             }

src/main/java/com/bazel_diff/BazelSourceFileTarget.java

@@ -1,11 +1,11 @@
 package com.bazel_diff;
 
-import java.io.ByteArrayOutputStream;
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.IOException;
-import java.nio.file.Files;
+import java.io.*;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
 import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.io.IOException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 
@@ -18,21 +18,44 @@ class BazelSourceFileTargetImpl implements BazelSourceFileTarget {
     private String name;
     private byte[] digest;
 
-    BazelSourceFileTargetImpl(String name, byte[] digest, Path workingDirectory)
+    private void digestLargeFile(MessageDigest finalDigest, FileChannel inChannel) throws IOException {
+        int bufferSize = 10240; // 10kb
+        ByteBuffer buffer = ByteBuffer.allocate(bufferSize);
+        while (inChannel.read(buffer) != -1) {
+            buffer.flip();
+            finalDigest.update(buffer);
+            buffer.clear();
+        }
+    }
+
+    private void digestSmallFile(MessageDigest finalDigest, FileChannel inChannel) throws IOException {
+        long fileSize = inChannel.size();
+        ByteBuffer buffer = ByteBuffer.allocate((int) fileSize);
+        inChannel.read(buffer);
+        buffer.flip();
+        finalDigest.update(buffer);
+    }
+
+    BazelSourceFileTargetImpl(String name, byte[] digest, Path workingDirectory, Boolean verbose)
         throws IOException, NoSuchAlgorithmException {
         this.name = name;
         MessageDigest finalDigest = MessageDigest.getInstance("SHA-256");
         if (workingDirectory != null && name.startsWith("//")) {
             String filenameSubstring = name.substring(2);
             String filenamePath = filenameSubstring.replaceFirst(":", "/");
-            File sourceFile = new File(workingDirectory.toString(), filenamePath);
-            if (sourceFile.isFile() && sourceFile.canRead()) {
-                byte[] buffer = new byte[16384];
-                FileInputStream in = new FileInputStream(sourceFile);
-                int rc = in.read(buffer);
-                while (rc != -1) {
-                    finalDigest.update(buffer, 0, rc);
-                    rc = in.read(buffer);
+            Path absoluteFilePath = Paths.get(workingDirectory.toString(), filenamePath);
+            try (RandomAccessFile sourceFile = new RandomAccessFile(absoluteFilePath.toString(), "r")) {
+                FileChannel inChannel = sourceFile.getChannel();
+                if (inChannel.size() > 1048576) { // 1mb
+                    digestLargeFile(finalDigest, inChannel);
+                } else {
+                    digestSmallFile(finalDigest, inChannel);
+                }
+                sourceFile.close();
+                inChannel.close();
+            } catch (FileNotFoundException e) {
+                if (verbose) {
+                    System.out.printf("BazelDiff: [Warning] file %s not found%n", absoluteFilePath);
                 }
             }
         }