Rename FilesystemUtils to NativePosixFiles.

This helps avoid confusion with File*S*ystemUtils, which differs in only the case of a character but is a completely different class.

--
MOS_MIGRATED_REVID=113054116
diff --git a/src/test/java/com/google/devtools/build/lib/unix/NativePosixFilesTest.java b/src/test/java/com/google/devtools/build/lib/unix/NativePosixFilesTest.java
new file mode 100644
index 0000000..46522a7
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/unix/NativePosixFilesTest.java
@@ -0,0 +1,112 @@
+// Copyright 2014 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.unix;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.hash.HashCode;
+import com.google.devtools.build.lib.testutil.TestUtils;
+import com.google.devtools.build.lib.vfs.FileSystem;
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
+import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.UnixFileSystem;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+
+/**
+ * This class tests the FilesystemUtils class.
+ */
+@RunWith(JUnit4.class)
+public class NativePosixFilesTest {
+  private FileSystem testFS;
+  private Path workingDir;
+  private Path testFile;
+
+  @Before
+  public final void createFileSystem() throws Exception  {
+    testFS = new UnixFileSystem();
+    workingDir = testFS.getPath(new File(TestUtils.tmpDir()).getCanonicalPath());
+    testFile = workingDir.getRelative("test");
+  }
+
+  /**
+   * This test validates that the md5sum() method returns hashes that match the official test
+   * vectors specified in RFC 1321, The MD5 Message-Digest Algorithm.
+   *
+   * @throws Exception
+   */
+  @Test
+  public void testValidateMd5Sum() throws Exception {
+    ImmutableMap<String, String> testVectors = ImmutableMap.<String, String>builder()
+        .put("", "d41d8cd98f00b204e9800998ecf8427e")
+        .put("a", "0cc175b9c0f1b6a831c399e269772661")
+        .put("abc", "900150983cd24fb0d6963f7d28e17f72")
+        .put("message digest", "f96b697d7cb7938d525a2f31aaf161d0")
+        .put("abcdefghijklmnopqrstuvwxyz", "c3fcd3d76192e4007dfb496cca67e13b")
+        .put("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
+        "d174ab98d277d9f5a5611c2c9f419d9f")
+        .put(
+        "12345678901234567890123456789012345678901234567890123456789012345678901234567890",
+        "57edf4a22be3c955ac49da2e2107b67a")
+        .build();
+
+    for (String testInput : testVectors.keySet()) {
+      FileSystemUtils.writeContentAsLatin1(testFile, testInput);
+      HashCode result = NativePosixFiles.md5sum(testFile.getPathString());
+      assertThat(testVectors).containsEntry(testInput, result.toString());
+    }
+  }
+
+  @Test
+  public void throwsFileAccessException() throws Exception {
+    FileSystemUtils.createEmptyFile(testFile);
+    NativePosixFiles.chmod(testFile.getPathString(), 0200);
+
+    try {
+      NativePosixFiles.md5sum(testFile.getPathString());
+      fail("Expected FileAccessException, but wasn't thrown.");
+    } catch (FileAccessException e) {
+      assertThat(e).hasMessage(testFile + " (Permission denied)");
+    }
+  }
+
+  @Test
+  public void throwsFileNotFoundException() throws Exception {
+    try {
+      NativePosixFiles.md5sum(testFile.getPathString());
+      fail("Expected FileNotFoundException, but wasn't thrown.");
+    } catch (FileNotFoundException e) {
+      assertThat(e).hasMessage(testFile + " (No such file or directory)");
+    }
+  }
+
+  @Test
+  public void throwsFilePermissionException() throws Exception {
+    File foo = new File("/bin");
+    try {
+      NativePosixFiles.setWritable(foo);
+      fail("Expected FilePermissionException, but wasn't thrown.");
+    } catch (FilePermissionException e) {
+      assertThat(e).hasMessage(foo + " (Operation not permitted)");
+    }
+  }
+}