diff -r 000000000000 -r 6474c204b198 mobile/android/base/favicons/decoders/ICODecoder.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/favicons/decoders/ICODecoder.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,377 @@
+/* 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 org.mozilla.gecko.favicons.Favicons;
+import org.mozilla.gecko.gfx.BitmapUtils;
+
+import android.util.SparseArray;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * Utility class for determining the region of a provided array which contains the largest bitmap,
+ * assuming the provided array is a valid ICO and the bitmap desired is square, and for pruning
+ * unwanted entries from ICO files, if desired.
+ *
+ * An ICO file is a container format that may hold up to 255 images in either BMP or PNG format.
+ * A mixture of image types may not exist.
+ *
+ * The format consists of a header specifying the number, n,  of images, followed by the Icon Directory.
+ *
+ * The Icon Directory consists of n Icon Directory Entries, each 16 bytes in length, specifying, for
+ * the corresponding image, the dimensions, colour information, payload size, and location in the file.
+ *
+ * All numerical fields follow a little-endian byte ordering.
+ *
+ * Header format:
+ *
+ *  0               1               2               3
+ *  0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |  Reserved field. Must be zero |  Type (1 for ICO, 2 for CUR)  |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |         Image count (n)       |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * The type field is expected to always be 1. CUR format images should not be used for Favicons.
+ *
+ *
+ * Icon Directory Entry format:
+ *
+ *  0               1               2               3
+ *  0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |  Image width  | Image height  | Palette size  | Reserved (0)  |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |       Colour plane count      |         Bits per pixel        |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                   Size of image data, in bytes                |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |      Start of image data, as an offset from start of file     |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * Image dimensions of zero are to be interpreted as image dimensions of 256.
+ *
+ * The palette size field records the number of colours in the stored BMP, if a palette is used. Zero
+ * if the payload is a PNG or no palette is in use.
+ *
+ * The number of colour planes is, usually, 0 (Not in use) or 1. Values greater than 1 are to be
+ * interpreted not as a colour plane count, but as a multiplying factor on the bits per pixel field.
+ * (Apparently 65535 was not deemed a sufficiently large maximum value of bits per pixel.)
+ *
+ *
+ * The Icon Directory consists of n-many Icon Directory Entries in sequence, with no gaps.
+ *
+ * This class is not thread safe.
+ */
+public class ICODecoder implements Iterable<Bitmap> {
+    // The number of bytes that compacting will save for us to bother doing it.
+    public static final int COMPACT_THRESHOLD = 4000;
+
+    // Some geometry of an ICO file.
+    public static final int ICO_HEADER_LENGTH_BYTES = 6;
+    public static final int ICO_ICONDIRENTRY_LENGTH_BYTES = 16;
+
+    // The buffer containing bytes to attempt to decode.
+    private byte[] decodand;
+
+    // The region of the decodand to decode.
+    private int offset;
+    private int len;
+
+    private IconDirectoryEntry[] iconDirectory;
+    private boolean isValid;
+    private boolean hasDecoded;
+
+    public ICODecoder(byte[] decodand, int offset, int len) {
+        this.decodand = decodand;
+        this.offset = offset;
+        this.len = len;
+    }
+
+    /**
+     * Decode the Icon Directory for this ICO and store the result in iconDirectory.
+     *
+     * @return true if ICO decoding was considered to probably be a success, false if it certainly
+     *         was a failure.
+     */
+    private boolean decodeIconDirectoryAndPossiblyPrune() {
+        hasDecoded = true;
+
+        // Fail if the end of the described range is out of bounds.
+        if (offset + len > decodand.length) {
+            return false;
+        }
+
+        // Fail if we don't have enough space for the header.
+        if (len < ICO_HEADER_LENGTH_BYTES) {
+            return false;
+        }
+
+        // Check that the reserved fields in the header are indeed zero, and that the type field
+        // specifies ICO. If not, we've probably been given something that isn't really an ICO.
+        if (decodand[offset] != 0 ||
+            decodand[offset + 1] != 0 ||
+            decodand[offset + 2] != 1 ||
+            decodand[offset + 3] != 0) {
+            return false;
+        }
+
+        // Here, and in many other places, byte values are ANDed with 0xFF. This is because Java
+        // bytes are signed - to obtain a numerical value of a longer type which holds the unsigned
+        // interpretation of the byte of interest, we do this.
+        int numEncodedImages = (decodand[offset + 4] & 0xFF) |
+                               (decodand[offset + 5] & 0xFF) << 8;
+
+
+        // Fail if there are no images or the field is corrupt.
+        if (numEncodedImages <= 0) {
+            return false;
+        }
+
+        final int headerAndDirectorySize = ICO_HEADER_LENGTH_BYTES + (numEncodedImages * ICO_ICONDIRENTRY_LENGTH_BYTES);
+
+        // Fail if there is not enough space in the buffer for the stated number of icondir entries,
+        // let alone the data.
+        if (len < headerAndDirectorySize) {
+            return false;
+        }
+
+        // Put the pointer on the first byte of the first Icon Directory Entry.
+        int bufferIndex = offset + ICO_HEADER_LENGTH_BYTES;
+
+        // We now iterate over the Icon Directory, decoding each entry as we go. We also need to
+        // discard all entries except one >= the maximum interesting size.
+
+        // Size of the smallest image larger than the limit encountered.
+        int minimumMaximum = Integer.MAX_VALUE;
+
+        // Used to track the best entry for each size. The entries we want to keep.
+        SparseArray<IconDirectoryEntry> preferenceArray = new SparseArray<IconDirectoryEntry>();
+
+        for (int i = 0; i < numEncodedImages; i++, bufferIndex += ICO_ICONDIRENTRY_LENGTH_BYTES) {
+            // Decode the Icon Directory Entry at this offset.
+            IconDirectoryEntry newEntry = IconDirectoryEntry.createFromBuffer(decodand, offset, len, bufferIndex);
+            newEntry.index = i;
+
+            if (newEntry.isErroneous) {
+                continue;
+            }
+
+            if (newEntry.width > Favicons.largestFaviconSize) {
+                // If we already have a smaller image larger than the maximum size of interest, we
+                // don't care about the new one which is larger than the smallest image larger than
+                // the maximum size.
+                if (newEntry.width >= minimumMaximum) {
+                    continue;
+                }
+
+                // Remove the previous minimum-maximum.
+                preferenceArray.delete(minimumMaximum);
+
+                minimumMaximum = newEntry.width;
+            }
+
+            IconDirectoryEntry oldEntry = preferenceArray.get(newEntry.width);
+            if (oldEntry == null) {
+                preferenceArray.put(newEntry.width, newEntry);
+                continue;
+            }
+
+            if (oldEntry.compareTo(newEntry) < 0) {
+                preferenceArray.put(newEntry.width, newEntry);
+            }
+        }
+
+        final int count = preferenceArray.size();
+
+        // Abort if no entries are desired (Perhaps all are corrupt?)
+        if (count == 0) {
+            return false;
+        }
+
+        // Allocate space for the icon directory entries in the decoded directory.
+        iconDirectory = new IconDirectoryEntry[count];
+
+        // The size of the data in the buffer that we find useful.
+        int retainedSpace = ICO_HEADER_LENGTH_BYTES;
+
+        for (int i = 0; i < count; i++) {
+            IconDirectoryEntry e = preferenceArray.valueAt(i);
+            retainedSpace += ICO_ICONDIRENTRY_LENGTH_BYTES + e.payloadSize;
+            iconDirectory[i] = e;
+        }
+
+        isValid = true;
+
+        // Set the number of images field in the buffer to reflect the number of retained entries.
+        decodand[offset + 4] = (byte) iconDirectory.length;
+        decodand[offset + 5] = (byte) (iconDirectory.length >>> 8);
+
+        if ((len - retainedSpace) > COMPACT_THRESHOLD) {
+            compactingCopy(retainedSpace);
+        }
+
+        return true;
+    }
+
+    /**
+     * Copy the buffer into a new array of exactly the required size, omitting any unwanted data.
+     */
+    private void compactingCopy(int spaceRetained) {
+        byte[] buf = new byte[spaceRetained];
+
+        // Copy the header.
+        System.arraycopy(decodand, offset, buf, 0, ICO_HEADER_LENGTH_BYTES);
+
+        int headerPtr = ICO_HEADER_LENGTH_BYTES;
+
+        int payloadPtr = ICO_HEADER_LENGTH_BYTES + (iconDirectory.length * ICO_ICONDIRENTRY_LENGTH_BYTES);
+
+        int ind = 0;
+        for (IconDirectoryEntry entry : iconDirectory) {
+            // Copy this entry.
+            System.arraycopy(decodand, offset + entry.getOffset(), buf, headerPtr, ICO_ICONDIRENTRY_LENGTH_BYTES);
+
+            // Copy its payload.
+            System.arraycopy(decodand, offset + entry.payloadOffset, buf, payloadPtr, entry.payloadSize);
+
+            // Update the offset field.
+            buf[headerPtr + 12] = (byte) payloadPtr;
+            buf[headerPtr + 13] = (byte) (payloadPtr >>> 8);
+            buf[headerPtr + 14] = (byte) (payloadPtr >>> 16);
+            buf[headerPtr + 15] = (byte) (payloadPtr >>> 24);
+
+            entry.payloadOffset = payloadPtr;
+            entry.index = ind;
+
+            payloadPtr += entry.payloadSize;
+            headerPtr += ICO_ICONDIRENTRY_LENGTH_BYTES;
+            ind++;
+        }
+
+        decodand = buf;
+        offset = 0;
+        len = spaceRetained;
+    }
+
+    /**
+     * Decode and return the bitmap represented by the given index in the Icon Directory, if valid.
+     *
+     * @param index The index into the Icon Directory of the image of interest.
+     * @return The decoded Bitmap object for this image, or null if the entry is invalid or decoding
+     *         fails.
+     */
+    public Bitmap decodeBitmapAtIndex(int index) {
+        final IconDirectoryEntry iconDirEntry = iconDirectory[index];
+
+        if (iconDirEntry.payloadIsPNG) {
+            // PNG payload. Simply extract it and decode it.
+            return BitmapUtils.decodeByteArray(decodand, offset + iconDirEntry.payloadOffset, iconDirEntry.payloadSize);
+        }
+
+        // The payload is a BMP, so we need to do some magic to get the decoder to do what we want.
+        // We construct an ICO containing just the image we want, and let Android do the rest.
+        byte[] decodeTarget = new byte[ICO_HEADER_LENGTH_BYTES + ICO_ICONDIRENTRY_LENGTH_BYTES + iconDirEntry.payloadSize];
+
+        // Set the type field in the ICO header.
+        decodeTarget[2] = 1;
+
+        // Set the num-images field in the header to 1.
+        decodeTarget[4] = 1;
+
+        // Copy the ICONDIRENTRY we need into the new buffer.
+        System.arraycopy(decodand, offset + iconDirEntry.getOffset(), decodeTarget, ICO_HEADER_LENGTH_BYTES, ICO_ICONDIRENTRY_LENGTH_BYTES);
+
+        // Copy the payload into the new buffer.
+        final int singlePayloadOffset =  ICO_HEADER_LENGTH_BYTES + ICO_ICONDIRENTRY_LENGTH_BYTES;
+        System.arraycopy(decodand, offset + iconDirEntry.payloadOffset, decodeTarget, singlePayloadOffset, iconDirEntry.payloadSize);
+
+        // Update the offset field of the ICONDIRENTRY to make the new ICO valid.
+        decodeTarget[ICO_HEADER_LENGTH_BYTES + 12] = (byte) singlePayloadOffset;
+        decodeTarget[ICO_HEADER_LENGTH_BYTES + 13] = (byte) (singlePayloadOffset >>> 8);
+        decodeTarget[ICO_HEADER_LENGTH_BYTES + 14] = (byte) (singlePayloadOffset >>> 16);
+        decodeTarget[ICO_HEADER_LENGTH_BYTES + 15] = (byte) (singlePayloadOffset >>> 24);
+
+        // Decode the newly-constructed singleton-ICO.
+        return BitmapUtils.decodeByteArray(decodeTarget);
+    }
+
+    /**
+     * Fetch an iterator over the images in this ICO, or null if this ICO seems to be invalid.
+     *
+     * @return An iterator over the Bitmaps stored in this ICO, or null if decoding fails.
+     */
+    @Override
+    public ICOIterator iterator() {
+        // If a previous call to decode concluded this ICO is invalid, abort.
+        if (hasDecoded && !isValid) {
+            return null;
+        }
+
+        // If we've not been decoded before, but now fail to make any sense of the ICO, abort.
+        if (!hasDecoded) {
+            if (!decodeIconDirectoryAndPossiblyPrune()) {
+                return null;
+            }
+        }
+
+        // If decoding was a success, return an iterator over the images in this ICO.
+        return new ICOIterator();
+    }
+
+    /**
+     * Decode this ICO and return the result as a LoadFaviconResult.
+     * @return A LoadFaviconResult representing the decoded ICO.
+     */
+    public LoadFaviconResult decode() {
+        // The call to iterator returns null if decoding fails.
+        Iterator<Bitmap> bitmaps = iterator();
+        if (bitmaps == null) {
+            return null;
+        }
+
+        LoadFaviconResult result = new LoadFaviconResult();
+
+        result.bitmapsDecoded = bitmaps;
+        result.faviconBytes = decodand;
+        result.offset = offset;
+        result.length = len;
+        result.isICO = true;
+
+        return result;
+    }
+
+    /**
+     * Inner class to iterate over the elements in the ICO represented by the enclosing instance.
+     */
+    private class ICOIterator implements Iterator<Bitmap> {
+        private int mIndex = 0;
+
+        @Override
+        public boolean hasNext() {
+            return mIndex < iconDirectory.length;
+        }
+
+        @Override
+        public Bitmap next() {
+            if (mIndex > iconDirectory.length) {
+                throw new NoSuchElementException("No more elements in this ICO.");
+            }
+            return decodeBitmapAtIndex(mIndex++);
+        }
+
+        @Override
+        public void remove() {
+            if (iconDirectory[mIndex] == null) {
+                throw new IllegalStateException("Remove already called for element " + mIndex);
+            }
+            iconDirectory[mIndex] = null;
+        }
+    }
+}