The Tor Browser: mobile/android/base/favicons/decoders/FaviconDecoder.java@b8a032363ba2 (annotated)

mobile/android/base/favicons/decoders/FaviconDecoder.java@b8a032363ba2 (annotated)

mobile/android/base/favicons/decoders/FaviconDecoder.java

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 package org.mozilla.gecko.favicons.decoders;
 import android.graphics.Bitmap;
 import android.util.Base64;
 import android.util.Log;
 import org.mozilla.gecko.gfx.BitmapUtils;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 /**
  * Class providing static utility methods for decoding favicons.
  */
 public class FaviconDecoder {
     private static final String LOG_TAG = "GeckoFaviconDecoder";
     static enum ImageMagicNumbers {
         // It is irritating that Java bytes are signed...
         PNG(new byte[] {(byte) (0x89 & 0xFF), 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a}),
         GIF(new byte[] {0x47, 0x49, 0x46, 0x38}),
         JPEG(new byte[] {-0x1, -0x28, -0x1, -0x20}),
         BMP(new byte[] {0x42, 0x4d}),
         WEB(new byte[] {0x57, 0x45, 0x42, 0x50, 0x0a});
         public byte[] value;
         private ImageMagicNumbers(byte[] value) {
             this.value = value;
         }
     }
     /**
      * Check for image format magic numbers of formats supported by Android.
      * @param buffer Byte buffer to check for magic numbers
      * @param offset Offset at which to look for magic numbers.
      * @return true if the buffer contains a bitmap decodable by Android (Or at least, a sequence
      *         starting with the magic numbers thereof). false otherwise.
      */
     private static boolean isDecodableByAndroid(byte[] buffer, int offset) {
         for (ImageMagicNumbers m : ImageMagicNumbers.values()) {
             if (bufferStartsWith(buffer, m.value, offset)) {
                 return true;
             }
         }
         return false;
     }
     /**
      * Utility function to check for the existence of a test byte sequence at a given offset in a
      * buffer.
      *
      * @param buffer Byte buffer to search.
      * @param test Byte sequence to search for.
      * @param bufferOffset Index in input buffer to expect test sequence.
      * @return true if buffer contains the byte sequence given in test at offset bufferOffset, false
      *         otherwise.
      */
     static boolean bufferStartsWith(byte[] buffer, byte[] test, int bufferOffset) {
         if (buffer.length < test.length) {
             return false;
         }
         for (int i = 0; i < test.length; ++i) {
             if (buffer[bufferOffset + i] != test[i]) {
                 return false;
             }
         }
         return true;
     }
     /**
      * Decode the favicon present in the region of the provided byte[] starting at offset and
      * proceeding for length bytes, if any. Returns either the resulting LoadFaviconResult or null if the
      * given range does not contain a bitmap we know how to decode.
      *
      * @param buffer Byte array containing the favicon to decode.
      * @param offset The index of the first byte in the array of the region of interest.
      * @param length The length of the region in the array to decode.
      * @return The decoded version of the bitmap in the described region, or null if none can be
      *         decoded.
      */
     public static LoadFaviconResult decodeFavicon(byte[] buffer, int offset, int length) {
         LoadFaviconResult result;
         if (isDecodableByAndroid(buffer, offset)) {
             result = new LoadFaviconResult();
             result.offset = offset;
             result.length = length;
             result.isICO = false;
             Bitmap decodedImage = BitmapUtils.decodeByteArray(buffer, offset, length);
             if (decodedImage == null) {
                 // What we got wasn't decodable after all. Probably corrupted image, or we got a muffled OOM.
                 return null;
             }
             // We assume here that decodeByteArray doesn't hold on to the entire supplied
             // buffer -- worst case, each of our buffers will be twice the necessary size.
             result.bitmapsDecoded = new SingleBitmapIterator(decodedImage);
             result.faviconBytes = buffer;
             return result;
         }
         // If it's not decodable by Android, it might be an ICO. Let's try.
         ICODecoder decoder = new ICODecoder(buffer, offset, length);
         result = decoder.decode();
         if (result == null) {
             return null;
         }
         return result;
     }
     public static LoadFaviconResult decodeDataURI(String uri) {
         if (uri == null) {
             Log.w(LOG_TAG, "Can't decode null data: URI.");
             return null;
         }
         if (!uri.startsWith("data:image/")) {
             Log.w(LOG_TAG, "Can't decode non-image data: URI.");
             return null;
         }
         // Otherwise, let's attack this blindly. Strictly we should be parsing.
         int offset = uri.indexOf(',') + 1;
         if (offset == 0) {
             Log.w(LOG_TAG, "No ',' in data: URI; malformed?");
             return null;
         }
         try {
             String base64 = uri.substring(offset);
             byte[] raw = Base64.decode(base64, Base64.DEFAULT);
             return decodeFavicon(raw);
         } catch (Exception e) {
             Log.w(LOG_TAG, "Couldn't decode data: URI.", e);
             return null;
         }
     }
     public static LoadFaviconResult decodeFavicon(byte[] buffer) {
         return decodeFavicon(buffer, 0, buffer.length);
     }
     /**
      * Returns the smallest bitmap in the icon represented by the provided
      * data: URI that's larger than the desired width, or the largest if
      * there is no larger icon.
      *
      * Returns null if no bitmap could be extracted.
      *
      * Bug 961600: we shouldn't be doing all of this work. The favicon cache
      * should be used, and will give us the right size icon.
      */
     public static Bitmap getMostSuitableBitmapFromDataURI(String iconURI, int desiredWidth) {
         LoadFaviconResult result = FaviconDecoder.decodeDataURI(iconURI);
         if (result == null) {
             // Nothing we can do.
             Log.w(LOG_TAG, "Unable to decode icon URI.");
             return null;
         }
         final Iterator<Bitmap> bitmaps = result.getBitmaps();
         if (!bitmaps.hasNext()) {
             Log.w(LOG_TAG, "No bitmaps in decoded icon.");
             return null;
         }
         Bitmap bitmap = bitmaps.next();
         if (!bitmaps.hasNext()) {
             // We're done! There was only one, so this is as big as it gets.
             return bitmap;
         }
         // Find a bitmap of the most suitable size.
         int currentWidth = bitmap.getWidth();
         while ((currentWidth < desiredWidth) &&
                bitmaps.hasNext()) {
             final Bitmap b = bitmaps.next();
             if (b.getWidth() > currentWidth) {
                 currentWidth = b.getWidth();
                 bitmap = b;
             }
         }
         return bitmap;
     }
     /**
      * Iterator to hold a single bitmap.
      */
     static class SingleBitmapIterator implements Iterator<Bitmap> {
         private Bitmap bitmap;
         public SingleBitmapIterator(Bitmap b) {
             bitmap = b;
         }
         /**
          * Slightly cheating here - this iterator supports peeking (Handy in a couple of obscure
          * places where the runtime type of the Iterator under consideration is known and
          * destruction of it is discouraged.
          *
          * @return The bitmap carried by this SingleBitmapIterator.
          */
         public Bitmap peek() {
             return bitmap;
         }
         @Override
         public boolean hasNext() {
             return bitmap != null;
         }
         @Override
         public Bitmap next() {
             if (bitmap == null) {
                 throw new NoSuchElementException("Element already returned from SingleBitmapIterator.");
             }
             Bitmap ret = bitmap;
             bitmap = null;
             return ret;
         }
         @Override
         public void remove() {
             throw new UnsupportedOperationException("remove() not supported on SingleBitmapIterator.");
         }
     }
 }

The Tor Browser / annotate

mobile/android/base/favicons/decoders/FaviconDecoder.java@b8a032363ba2 (annotated)

mobile/android/base/favicons/decoders/FaviconDecoder.java