2 files changed, 139 insertions, 0 deletions
diff --git a/core/java/android/os/FileUtils.java b/core/java/android/os/FileUtils.java
index b302f95..931cd3e 100644
--- a/core/java/android/os/FileUtils.java
+++ b/core/java/android/os/FileUtils.java
@@ -16,11 +16,13 @@
 
 package android.os;
 
+import android.provider.DocumentsContract.Document;
 import android.system.ErrnoException;
 import android.system.Os;
 import android.text.TextUtils;
 import android.util.Log;
 import android.util.Slog;
+import android.webkit.MimeTypeMap;
 
 import java.io.BufferedInputStream;
 import java.io.ByteArrayOutputStream;
@@ -34,6 +36,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
 import java.util.Comparator;
+import java.util.Objects;
 import java.util.regex.Pattern;
 import java.util.zip.CRC32;
 import java.util.zip.CheckedInputStream;
@@ -533,4 +536,76 @@ public class FileUtils {
         }
         return null;
     }
+
+    /**
+     * Generates a unique file name under the given parent directory. If the display name doesn't
+     * have an extension that matches the requested MIME type, the default extension for that MIME
+     * type is appended. If a file already exists, the name is appended with a numerical value to
+     * make it unique.
+     *
+     * For example, the display name 'example' with 'text/plain' MIME might produce
+     * 'example.txt' or 'example (1).txt', etc.
+     *
+     * @throws FileNotFoundException
+     */
+    public static File buildUniqueFile(File parent, String mimeType, String displayName)
+            throws FileNotFoundException {
+        String name;
+        String ext;
+
+        if (Document.MIME_TYPE_DIR.equals(mimeType)) {
+            name = displayName;
+            ext = null;
+        } else {
+            String mimeTypeFromExt;
+
+            // Extract requested extension from display name
+            final int lastDot = displayName.lastIndexOf('.');
+            if (lastDot >= 0) {
+                name = displayName.substring(0, lastDot);
+                ext = displayName.substring(lastDot + 1);
+                mimeTypeFromExt = MimeTypeMap.getSingleton().getMimeTypeFromExtension(
+                        ext.toLowerCase());
+            } else {
+                name = displayName;
+                ext = null;
+                mimeTypeFromExt = null;
+            }
+
+            if (mimeTypeFromExt == null) {
+                mimeTypeFromExt = "application/octet-stream";
+            }
+
+            final String extFromMimeType = MimeTypeMap.getSingleton().getExtensionFromMimeType(
+                    mimeType);
+            if (Objects.equals(mimeType, mimeTypeFromExt) || Objects.equals(ext, extFromMimeType)) {
+                // Extension maps back to requested MIME type; allow it
+            } else {
+                // No match; insist that create file matches requested MIME
+                name = displayName;
+                ext = extFromMimeType;
+            }
+        }
+
+        File file = buildFile(parent, name, ext);
+
+        // If conflicting file, try adding counter suffix
+        int n = 0;
+        while (file.exists()) {
+            if (n++ >= 32) {
+                throw new FileNotFoundException("Failed to create unique file");
+            }
+            file = buildFile(parent, name + " (" + n + ")", ext);
+        }
+
+        return file;
+    }
+
+    private static File buildFile(File parent, String name, String ext) {
+        if (TextUtils.isEmpty(ext)) {
+            return new File(parent, name);
+        } else {
+            return new File(parent, name + "." + ext);
+        }
+    }
 }
diff --git a/core/tests/coretests/src/android/os/FileUtilsTest.java b/core/tests/coretests/src/android/os/FileUtilsTest.java
index 5c9e813..ee9e2e4 100644
--- a/core/tests/coretests/src/android/os/FileUtilsTest.java
+++ b/core/tests/coretests/src/android/os/FileUtilsTest.java
@@ -21,6 +21,7 @@ import static android.text.format.DateUtils.HOUR_IN_MILLIS;
 import static android.text.format.DateUtils.WEEK_IN_MILLIS;
 
 import android.content.Context;
+import android.provider.DocumentsContract.Document;
 import android.test.AndroidTestCase;
 import android.test.suitebuilder.annotation.MediumTest;
 
@@ -43,6 +44,8 @@ public class FileUtilsTest extends AndroidTestCase {
     private File mDir;
     private File mTestFile;
     private File mCopyFile;
+    private File mTarget;
+
 
     @Override
     protected void setUp() throws Exception {
@@ -50,11 +53,15 @@ public class FileUtilsTest extends AndroidTestCase {
         mDir = getContext().getDir("testing", Context.MODE_PRIVATE);
         mTestFile = new File(mDir, "test.file");
         mCopyFile = new File(mDir, "copy.file");
+
+        mTarget = getContext().getFilesDir();
+        FileUtils.deleteContents(mTarget);
     }
 
     @Override
     protected void tearDown() throws Exception {
         IoUtils.deleteContents(mDir);
+        FileUtils.deleteContents(mTarget);
     }
 
     // TODO: test setPermissions(), getPermissions()
@@ -225,6 +232,63 @@ public class FileUtilsTest extends AndroidTestCase {
         assertEquals("foo_bar__baz", FileUtils.buildValidFatFilename("foo?bar**baz"));
     }
 
+    public void testBuildUniqueFile_normal() throws Exception {
+        assertNameEquals("test.jpg", FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test"));
+        assertNameEquals("test.jpg", FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test.jpg"));
+        assertNameEquals("test.jpeg", FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test.jpeg"));
+        assertNameEquals("TEst.JPeg", FileUtils.buildUniqueFile(mTarget, "image/jpeg", "TEst.JPeg"));
+        assertNameEquals("test.png.jpg",
+                FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test.png.jpg"));
+        assertNameEquals("test.png.jpg",
+                FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test.png"));
+
+        assertNameEquals("test.flac", FileUtils.buildUniqueFile(mTarget, "audio/flac", "test"));
+        assertNameEquals("test.flac", FileUtils.buildUniqueFile(mTarget, "audio/flac", "test.flac"));
+        assertNameEquals("test.flac",
+                FileUtils.buildUniqueFile(mTarget, "application/x-flac", "test"));
+        assertNameEquals("test.flac",
+                FileUtils.buildUniqueFile(mTarget, "application/x-flac", "test.flac"));
+    }
+
+    public void testBuildUniqueFile_unknown() throws Exception {
+        assertNameEquals("test",
+                FileUtils.buildUniqueFile(mTarget, "application/octet-stream", "test"));
+        assertNameEquals("test.jpg",
+                FileUtils.buildUniqueFile(mTarget, "application/octet-stream", "test.jpg"));
+        assertNameEquals(".test",
+                FileUtils.buildUniqueFile(mTarget, "application/octet-stream", ".test"));
+
+        assertNameEquals("test", FileUtils.buildUniqueFile(mTarget, "lolz/lolz", "test"));
+        assertNameEquals("test.lolz", FileUtils.buildUniqueFile(mTarget, "lolz/lolz", "test.lolz"));
+    }
+
+    public void testBuildUniqueFile_dir() throws Exception {
+        assertNameEquals("test", FileUtils.buildUniqueFile(mTarget, Document.MIME_TYPE_DIR, "test"));
+        new File(mTarget, "test").mkdir();
+        assertNameEquals("test (1)",
+                FileUtils.buildUniqueFile(mTarget, Document.MIME_TYPE_DIR, "test"));
+
+        assertNameEquals("test.jpg",
+                FileUtils.buildUniqueFile(mTarget, Document.MIME_TYPE_DIR, "test.jpg"));
+        new File(mTarget, "test.jpg").mkdir();
+        assertNameEquals("test.jpg (1)",
+                FileUtils.buildUniqueFile(mTarget, Document.MIME_TYPE_DIR, "test.jpg"));
+    }
+
+    public void testBuildUniqueFile_increment() throws Exception {
+        assertNameEquals("test.jpg", FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test.jpg"));
+        new File(mTarget, "test.jpg").createNewFile();
+        assertNameEquals("test (1).jpg",
+                FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test.jpg"));
+        new File(mTarget, "test (1).jpg").createNewFile();
+        assertNameEquals("test (2).jpg",
+                FileUtils.buildUniqueFile(mTarget, "image/jpeg", "test.jpg"));
+    }
+
+    private static void assertNameEquals(String expected, File actual) {
+        assertEquals(expected, actual.getName());
+    }
+
     private void touch(String name, long age) throws Exception {
         final File file = new File(mDir, name);
         file.createNewFile();