1/4 TIFF processing simplification by 'shifting' base of random access reader

Source/com/drew/imaging/jpeg/JpegMetadataReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -126,7 +126,7 @@ public static void process(@NotNull Metadata metadata, @NotNull InputStream inpu
         processJpegSegmentData(metadata, readers, segmentData);
     }
 
-    public static void processJpegSegmentData(Metadata metadata, Iterable<JpegSegmentMetadataReader> readers, JpegSegmentData segmentData)
+    public static void processJpegSegmentData(Metadata metadata, Iterable<JpegSegmentMetadataReader> readers, JpegSegmentData segmentData) throws IOException
     {
         // Pass the appropriate byte arrays to each reader.
         for (JpegSegmentMetadataReader reader : readers) {

Source/com/drew/imaging/jpeg/JpegSegmentMetadataReader.java

@@ -1,5 +1,27 @@
+/*
+ * Copyright 2002-2022 Drew Noakes and contributors
+ *
+ *    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.
+ *
+ * More information about this project is available at:
+ *
+ *    https://drewnoakes.com/code/exif/
+ *    https://github.com/drewnoakes/metadata-extractor
+ */
 package com.drew.imaging.jpeg;
 
+import java.io.IOException;
+
 import com.drew.lang.annotations.NotNull;
 import com.drew.metadata.Metadata;
 
@@ -21,6 +43,7 @@ public interface JpegSegmentMetadataReader
      *                 encountered in the original file.
      * @param metadata The {@link Metadata} object into which extracted values should be merged.
      * @param segmentType The {@link JpegSegmentType} being read.
+     * @throws IOException an error occurred while accessing the required data
      */
-    void readJpegSegments(@NotNull final Iterable<byte[]> segments, @NotNull final Metadata metadata, @NotNull final JpegSegmentType segmentType);
+    void readJpegSegments(@NotNull final Iterable<byte[]> segments, @NotNull final Metadata metadata, @NotNull final JpegSegmentType segmentType) throws IOException;
 }

Source/com/drew/imaging/png/PngMetadataReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -331,7 +331,7 @@ private static void processChunk(@NotNull Metadata metadata, @NotNull PngChunk c
         } else if (chunkType.equals(PngChunkType.eXIf)) {
             try {
                 ExifTiffHandler handler = new ExifTiffHandler(metadata, null, 0);
-                new TiffReader().processTiff(new ByteArrayReader(bytes), handler, 0);
+                new TiffReader().processTiff(new ByteArrayReader(bytes), handler);
             } catch (TiffProcessingException ex) {
                 PngDirectory directory = new PngDirectory(PngChunkType.eXIf);
                 directory.addError(ex.getMessage());

Source/com/drew/imaging/tiff/TiffHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -57,7 +57,6 @@ public interface TiffHandler
 
     boolean customProcessTag(int tagOffset,
                              @NotNull Set<Integer> processedIfdOffsets,
-                             int tiffHeaderOffset,
                              @NotNull RandomAccessReader reader,
                              int tagId,
                              int byteCount) throws IOException;

Source/com/drew/imaging/tiff/TiffMetadataReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -68,7 +68,7 @@ public static Metadata readMetadata(@NotNull RandomAccessReader reader) throws I
     {
         Metadata metadata = new Metadata();
         ExifTiffHandler handler = new ExifTiffHandler(metadata, null, 0);
-        new TiffReader().processTiff(reader, handler, 0);
+        new TiffReader().processTiff(reader, handler);
         return metadata;
     }
 }

Source/com/drew/imaging/tiff/TiffReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -40,17 +40,15 @@ public class TiffReader
      *
      * @param reader the {@link RandomAccessReader} from which the data should be read
      * @param handler the {@link TiffHandler} that will coordinate processing and accept read values
-     * @param tiffHeaderOffset the offset within <code>reader</code> at which the TIFF header starts
      * @throws TiffProcessingException if an error occurred during the processing of TIFF data that could not be
      *                                 ignored or recovered from
      * @throws IOException an error occurred while accessing the required data
      */
     public void processTiff(@NotNull final RandomAccessReader reader,
-                            @NotNull final TiffHandler handler,
-                            final int tiffHeaderOffset) throws TiffProcessingException, IOException
+                            @NotNull final TiffHandler handler) throws TiffProcessingException, IOException
     {
         // This must be either "MM" or "II".
-        short byteOrderIdentifier = reader.getInt16(tiffHeaderOffset);
+        short byteOrderIdentifier = reader.getInt16(0);
 
         if (byteOrderIdentifier == 0x4d4d) { // "MM"
             reader.setMotorolaByteOrder(true);
@@ -61,21 +59,21 @@ public void processTiff(@NotNull final RandomAccessReader reader,
         }
 
         // Check the next two values for correctness.
-        final int tiffMarker = reader.getUInt16(2 + tiffHeaderOffset);
+        final int tiffMarker = reader.getUInt16(2);
         handler.setTiffMarker(tiffMarker);
 
-        int firstIfdOffset = reader.getInt32(4 + tiffHeaderOffset) + tiffHeaderOffset;
+        int firstIfdOffset = reader.getInt32(4);
 
         // David Ekholm sent a digital camera image that has this problem
         // TODO getLength should be avoided as it causes RandomAccessStreamReader to read to the end of the stream
         if (firstIfdOffset >= reader.getLength() - 1) {
             handler.warn("First IFD offset is beyond the end of the TIFF data segment -- trying default offset");
             // First directory normally starts immediately after the offset bytes, so try that
-            firstIfdOffset = tiffHeaderOffset + 2 + 2 + 4;
+            firstIfdOffset = 2 + 2 + 4;
         }
 
         Set<Integer> processedIfdOffsets = new HashSet<Integer>();
-        processIfd(handler, reader, processedIfdOffsets, firstIfdOffset, tiffHeaderOffset);
+        processIfd(handler, reader, processedIfdOffsets, firstIfdOffset);
     }
 
     /**
@@ -96,27 +94,28 @@ public void processTiff(@NotNull final RandomAccessReader reader,
      *
      * @param handler the {@link com.drew.imaging.tiff.TiffHandler} that will coordinate processing and accept read values
      * @param reader the {@link com.drew.lang.RandomAccessReader} from which the data should be read
-     * @param processedIfdOffsets the set of visited IFD offsets, to avoid revisiting the same IFD in an endless loop
+     * @param processedGlobalIfdOffsets the set of visited IFD offsets, to avoid revisiting the same IFD in an endless loop
      * @param ifdOffset the offset within <code>reader</code> at which the IFD data starts
-     * @param tiffHeaderOffset the offset within <code>reader</code> at which the TIFF header starts
      * @throws IOException an error occurred while accessing the required data
      */
     public static void processIfd(@NotNull final TiffHandler handler,
                                   @NotNull final RandomAccessReader reader,
-                                  @NotNull final Set<Integer> processedIfdOffsets,
-                                  final int ifdOffset,
-                                  final int tiffHeaderOffset) throws IOException
+                                  @NotNull final Set<Integer> processedGlobalIfdOffsets,
+                                  final int ifdOffset) throws IOException
     {
         Boolean resetByteOrder = null;
         try {
-            // check for directories we've already visited to avoid stack overflows when recursive/cyclic directory structures exist
-            if (processedIfdOffsets.contains(Integer.valueOf(ifdOffset))) {
+            // Check for directories we've already visited to avoid stack overflows when recursive/cyclic directory structures exist.
+            // Note that we track these offsets in the global frame, not the reader's local frame.
+            int globalIfdOffset = reader.toUnshiftedOffset(ifdOffset);
+            if (processedGlobalIfdOffsets.contains(Integer.valueOf(globalIfdOffset))) {
                 return;
             }
 
             // remember that we've visited this directory so that we don't visit it again later
-            processedIfdOffsets.add(ifdOffset);
+            processedGlobalIfdOffsets.add(globalIfdOffset);
 
+            // Validate IFD offset
             if (ifdOffset >= reader.getLength() || ifdOffset < 0) {
                 handler.error("Ignored IFD marked to start outside data segment");
                 return;
@@ -180,13 +179,12 @@ public static void processIfd(@NotNull final TiffHandler handler,
                 final long tagValueOffset;
                 if (byteCount > 4) {
                     // If it's bigger than 4 bytes, the dir entry contains an offset.
-                    final long offsetVal = reader.getUInt32(tagOffset + 8);
-                    if (offsetVal + byteCount > reader.getLength()) {
+                    tagValueOffset = reader.getUInt32(tagOffset + 8);
+                    if (tagValueOffset + byteCount > reader.getLength()) {
                         // Bogus pointer offset and / or byteCount value
                         handler.error("Illegal TIFF tag pointer offset");
                         continue;
                     }
-                    tagValueOffset = tiffHeaderOffset + offsetVal;
                 } else {
                     // 4 bytes or less and value is in the dir entry itself.
                     tagValueOffset = tagOffset + 8;
@@ -210,14 +208,14 @@ public static void processIfd(@NotNull final TiffHandler handler,
                     for (int i = 0; i < componentCount; i++) {
                         if (handler.tryEnterSubIfd(tagId)) {
                             isIfdPointer = true;
-                            int subDirOffset = tiffHeaderOffset + reader.getInt32((int) (tagValueOffset + i * 4));
-                            processIfd(handler, reader, processedIfdOffsets, subDirOffset, tiffHeaderOffset);
+                            long subDirOffset = reader.getUInt32((int) (tagValueOffset + i*4));
+                            processIfd(handler, reader, processedGlobalIfdOffsets, (int) subDirOffset);
                         }
                     }
                 }
 
                 // If it wasn't an IFD pointer, allow custom tag processing to occur
-                if (!isIfdPointer && !handler.customProcessTag((int) tagValueOffset, processedIfdOffsets, tiffHeaderOffset, reader, tagId, (int) byteCount)) {
+                if (!isIfdPointer && !handler.customProcessTag((int) tagValueOffset, processedGlobalIfdOffsets, reader, tagId, (int) byteCount)) {
                     // If no custom processing occurred, process the tag in the standard fashion
                     processTag(handler, tagId, (int) tagValueOffset, (int) componentCount, formatCode, reader);
                 }
@@ -227,10 +225,8 @@ public static void processIfd(@NotNull final TiffHandler handler,
             final int finalTagOffset = calculateTagOffset(ifdOffset, dirTagCount);
             int nextIfdOffset = reader.getInt32(finalTagOffset);
             if (nextIfdOffset != 0) {
-                nextIfdOffset += tiffHeaderOffset;
                 if (nextIfdOffset >= reader.getLength()) {
                     // Last 4 bytes of IFD reference another IFD with an address that is out of bounds
-                    // Note this could have been caused by jhead 1.3 cropping too much
                     return;
                 } else if (nextIfdOffset < ifdOffset) {
                     // TODO is this a valid restriction?
@@ -239,7 +235,7 @@ public static void processIfd(@NotNull final TiffHandler handler,
                 }
 
                 if (handler.hasFollowerIfd()) {
-                    processIfd(handler, reader, processedIfdOffsets, nextIfdOffset, tiffHeaderOffset);
+                    processIfd(handler, reader, processedGlobalIfdOffsets, nextIfdOffset);
                 }
             }
         } finally {
@@ -326,7 +322,7 @@ private static void processTag(@NotNull final TiffHandler handler,
                 break;
             case TiffDataFormat.CODE_INT16_S:
                 if (componentCount == 1) {
-                    handler.setInt16s(tagId, (int)reader.getInt16(tagValueOffset));
+                    handler.setInt16s(tagId, reader.getInt16(tagValueOffset));
                 } else {
                     short[] array = new short[componentCount];
                     for (int i = 0; i < componentCount; i++)

Source/com/drew/lang/ByteArrayReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -60,6 +60,17 @@ public ByteArrayReader(@NotNull byte[] buffer, int baseOffset)
         _baseOffset = baseOffset;
     }
 
+    @Override
+    public RandomAccessReader withShiftedBaseOffset(int shift) throws IOException {
+        if (shift == 0) {
+            return this;
+        } else {
+            RandomAccessReader reader = new ByteArrayReader(_buffer, _baseOffset + shift);
+            reader.setMotorolaByteOrder(isMotorolaByteOrder());
+            return reader;
+        }
+    }
+
     @Override
     public int toUnshiftedOffset(int localOffset)
     {

Source/com/drew/lang/RandomAccessFileReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -60,6 +60,17 @@ public RandomAccessFileReader(@NotNull RandomAccessFile file, int baseOffset) th
         _length = _file.length();
     }
 
+    @Override
+    public RandomAccessReader withShiftedBaseOffset(int shift) throws IOException {
+        if (shift == 0) {
+            return this;
+        } else {
+            RandomAccessReader reader = new RandomAccessFileReader(_file, _baseOffset + shift);
+            reader.setMotorolaByteOrder(isMotorolaByteOrder());
+            return reader;
+        }
+    }
+
     @Override
     public int toUnshiftedOffset(int localOffset)
     {
@@ -69,7 +80,7 @@ public int toUnshiftedOffset(int localOffset)
     @Override
     public long getLength()
     {
-        return _length;
+        return _length - _baseOffset;
     }
 
     @Override
@@ -108,7 +119,7 @@ private void seek(final int index) throws IOException
         if (index == _currentIndex)
             return;
 
-        _file.seek(index);
+        _file.seek(index + _baseOffset);
         _currentIndex = index;
     }
 

Source/com/drew/lang/RandomAccessReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 Drew Noakes and contributors
+ * Copyright 2002-2022 Drew Noakes and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -47,6 +47,8 @@ public abstract class RandomAccessReader
 {
     private boolean _isMotorolaByteOrder = true;
 
+    public abstract RandomAccessReader withShiftedBaseOffset(int shift) throws IOException;
+
     public abstract int toUnshiftedOffset(int localOffset);
 
     /**