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diff --git a/src/photos/PhotoFileSniffer.vala b/src/photos/PhotoFileSniffer.vala
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+/* Copyright 2010-2014 Yorba Foundation
+ *
+ * This software is licensed under the GNU LGPL (version 2.1 or later).
+ * See the COPYING file in this distribution.
+ */
+
+public class DetectedPhotoInformation {
+    public PhotoFileFormat file_format = PhotoFileFormat.UNKNOWN;
+    public PhotoMetadata? metadata = null;
+    public string? md5 = null;
+    public string? exif_md5 = null;
+    public string? thumbnail_md5 = null;
+    public string? format_name = null;
+    public Dimensions image_dim = Dimensions();
+    public Gdk.Colorspace colorspace = Gdk.Colorspace.RGB;
+    public int channels = 0;
+    public int bits_per_channel = 0;
+}
+
+//
+// A PhotoFileSniffer is expected to examine the supplied file as efficiently as humanly possible
+// to detect (a) if it is of a file format supported by the particular sniffer, and (b) fill out
+// a DetectedPhotoInformation record and return it to the caller.
+//
+// The PhotoFileSniffer is not expected to cache information.  It should return a fresh
+// DetectedPhotoInformation record each time.
+//
+// PhotoFileSniffer must be thread-safe.  Like PhotoFileAdapters, it is not expected to guarantee
+// atomicity with respect to the filesystem.
+//
+
+public abstract class PhotoFileSniffer {
+    public enum Options {
+        GET_ALL =       0x00000000,
+        NO_MD5 =        0x00000001
+    }
+    
+    protected File file;
+    protected Options options;
+    protected bool calc_md5;
+    
+    public PhotoFileSniffer(File file, Options options) {
+        this.file = file;
+        this.options = options;
+        
+        calc_md5 = (options & Options.NO_MD5) == 0;
+    }
+    
+    public abstract DetectedPhotoInformation? sniff(out bool is_corrupted) throws Error;
+}
+
+//
+// PhotoFileInterrogator
+//
+// A PhotoFileInterrogator is merely an aggregator of PhotoFileSniffers.  It will create sniffers
+// for each supported PhotoFileFormat and see if they recognize the file.
+//
+// The PhotoFileInterrogator is not thread-safe.
+//
+
+public class PhotoFileInterrogator {
+    private File file;
+    private PhotoFileSniffer.Options options;
+    private DetectedPhotoInformation? detected = null;
+    private bool is_photo_corrupted = false;
+    
+    public PhotoFileInterrogator(File file,
+        PhotoFileSniffer.Options options = PhotoFileSniffer.Options.GET_ALL) {
+        this.file = file;
+        this.options = options;
+    }
+    
+    // This should only be called after interrogate().  Will return null every time, otherwise.
+    // If called after interrogate and returns null, that indicates the file is not an image file.
+    public DetectedPhotoInformation? get_detected_photo_information() {
+        return detected;
+    }
+    
+    // Call after interrogate().
+    public bool get_is_photo_corrupted() {
+        return is_photo_corrupted;
+    }
+    
+    public void interrogate() throws Error {
+        foreach (PhotoFileFormat file_format in PhotoFileFormat.get_supported()) {
+            PhotoFileSniffer sniffer = file_format.create_sniffer(file, options);
+            
+            bool is_corrupted;
+            detected = sniffer.sniff(out is_corrupted);
+            if (detected != null && !is_corrupted) {
+                assert(detected.file_format == file_format);
+                
+                break;
+            } else if (is_corrupted) {
+                message("Sniffing halted for %s: potentially corrupted image file", file.get_path());
+                is_photo_corrupted = true;
+                detected = null;
+                
+                break;
+            }
+        }
+    }
+}
+