1 files changed, 98 insertions, 0 deletions
diff --git a/src/com/android/gallery3d/exif/ExifParser.java b/src/com/android/gallery3d/exif/ExifParser.java
new file mode 100644
index 000000000..534f2f6d9
--- /dev/null
+++ b/src/com/android/gallery3d/exif/ExifParser.java
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * 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.android.gallery3d.exif;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.ByteOrder;
+
+public class ExifParser {
+
+    private static final String TAG = "ExifParser";
+
+    private static final short SOI =  (short) 0xFFD8; // SOI marker of JPEG
+    private static final short APP1 = (short) 0xFFE1; // APP1 marker of JPEG
+
+    private static final int EXIF_HEADER = 0x45786966; // EXIF header "Exif"
+    private static final short EXIF_HEADER_TAIL = (short) 0x0000; // EXIF header in APP1
+
+    // TIFF header
+    private static final short LITTLE_ENDIAN_TAG = (short) 0x4949; // "II"
+    private static final short BIG_ENDIAN_TAG = (short) 0x4d4d; // "MM"
+    private static final short TIFF_HEADER_TAIL = 0x002A;
+
+    public IfdParser parse(InputStream inputStream) throws ExifInvalidFormatException, IOException{
+        if (!seekTiffData(inputStream)) {
+            return null;
+        }
+        TiffInputStream tiffStream = new TiffInputStream(inputStream);
+        parseTiffHeader(tiffStream);
+        long offset = tiffStream.readUnsignedInt();
+        if (offset > Integer.MAX_VALUE) {
+            throw new ExifInvalidFormatException("Offset value is larger than Integer.MAX_VALUE");
+        }
+        return new IfdParser(tiffStream, (int)offset);
+    }
+
+    private void parseTiffHeader(TiffInputStream tiffStream) throws IOException,
+            ExifInvalidFormatException {
+        short byteOrder = tiffStream.readShort();
+        ByteOrder order;
+        if (LITTLE_ENDIAN_TAG == byteOrder) {
+            tiffStream.setByteOrder(ByteOrder.LITTLE_ENDIAN);
+        } else if (BIG_ENDIAN_TAG == byteOrder) {
+            tiffStream.setByteOrder(ByteOrder.BIG_ENDIAN);
+        } else {
+            throw new ExifInvalidFormatException("Invalid TIFF header");
+        }
+
+        if (tiffStream.readShort() != TIFF_HEADER_TAIL) {
+            throw new ExifInvalidFormatException("Invalid TIFF header");
+        }
+    }
+
+    /**
+     * Try to seek the tiff data. If there is no tiff data, return false, else return true and
+     * the inputstream will be at the start of tiff data
+     */
+    private boolean seekTiffData(InputStream inputStream) throws IOException,
+            ExifInvalidFormatException {
+        DataInputStream dataStream = new DataInputStream(inputStream);
+
+        // SOI and APP1
+        if (dataStream.readShort() != SOI) {
+            throw new ExifInvalidFormatException("Invalid JPEG format");
+        }
+
+        if (dataStream.readShort() != APP1) {
+            return false;
+        }
+
+        // APP1 length, it's not used for us
+        dataStream.readShort();
+
+        // Exif header
+        if (dataStream.readInt() != EXIF_HEADER
+                || dataStream.readShort() != EXIF_HEADER_TAIL) {
+            // There is no EXIF data;
+            return false;
+        }
+
+        return true;
+    }
+}
+\ No newline at end of file