The Tor Browser: mobile/android/base/favicons/decoders/IconDirectoryEntry.java@fc2d59ddac77 (annotated)

mobile/android/base/favicons/decoders/IconDirectoryEntry.java@fc2d59ddac77 (annotated)

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

Wed, 31 Dec 2014 07:22:50 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 07:22:50 +0100
branch: TOR_BUG_3246
changeset 4: fc2d59ddac77
permissions: -rw-r--r--

Correct previous dual key logic pending first delivery installment.

 /* 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;
 /**
  * Representation of an ICO file ICONDIRENTRY structure.
  */
 public class IconDirectoryEntry implements Comparable<IconDirectoryEntry> {
     public static int maxBPP;
     int width;
     int height;
     int paletteSize;
     int bitsPerPixel;
     int payloadSize;
     int payloadOffset;
     boolean payloadIsPNG;
     // Tracks the index in the Icon Directory of this entry. Useful only for pruning.
     int index;
     boolean isErroneous;
     public IconDirectoryEntry(int width, int height, int paletteSize, int bitsPerPixel, int payloadSize, int payloadOffset, boolean payloadIsPNG) {
         this.width = width;
         this.height = height;
         this.paletteSize = paletteSize;
         this.bitsPerPixel = bitsPerPixel;
         this.payloadSize = payloadSize;
         this.payloadOffset = payloadOffset;
         this.payloadIsPNG = payloadIsPNG;
     }
     /**
      * Method to get a dummy Icon Directory Entry with the Erroneous bit set.
      *
      * @return An erroneous placeholder Icon Directory Entry.
      */
     public static IconDirectoryEntry getErroneousEntry() {
         IconDirectoryEntry ret = new IconDirectoryEntry(-1, -1, -1, -1, -1, -1, false);
         ret.isErroneous = true;
         return ret;
     }
     /**
      * Create an IconDirectoryEntry object from a byte[]. Interprets the buffer starting at the given
      * offset as an IconDirectoryEntry and returns the result.
      *
      * @param buffer Byte array containing the icon directory entry to decode.
      * @param regionOffset Offset into the byte array of the valid region of the buffer.
      * @param regionLength Length of the valid region in the buffer.
      * @param entryOffset Offset of the icon directory entry to decode within the buffer.
      * @return An IconDirectoryEntry object representing the entry specified, or null if the entry
      *         is obviously invalid.
      */
     public static IconDirectoryEntry createFromBuffer(byte[] buffer, int regionOffset, int regionLength, int entryOffset) {
         // Verify that the reserved field is really zero.
         if (buffer[entryOffset + 3] != 0) {
             return getErroneousEntry();
         }
         // Verify that the entry points to a region that actually exists in the buffer, else bin it.
         int fieldPtr = entryOffset + 8;
         int entryLength = (buffer[fieldPtr] & 0xFF) |
                           (buffer[fieldPtr + 1] & 0xFF) << 8 |
                           (buffer[fieldPtr + 2] & 0xFF) << 16 |
                           (buffer[fieldPtr + 3] & 0xFF) << 24;
         // Advance to the offset field.
         fieldPtr += 4;
         int payloadOffset = (buffer[fieldPtr] & 0xFF) |
                             (buffer[fieldPtr + 1] & 0xFF) << 8 |
                             (buffer[fieldPtr + 2] & 0xFF) << 16 |
                             (buffer[fieldPtr + 3] & 0xFF) << 24;
         // Fail if the entry describes a region outside the buffer.
         if (payloadOffset < 0 || entryLength < 0 || payloadOffset + entryLength > regionOffset + regionLength) {
             return getErroneousEntry();
         }
         // Extract the image dimensions.
         int imageWidth = buffer[entryOffset] & 0xFF;
         int imageHeight = buffer[entryOffset+1] & 0xFF;
         // Because Microsoft, a size value of zero represents an image size of 256.
         if (imageWidth == 0) {
             imageWidth = 256;
         }
         if (imageHeight == 0) {
             imageHeight = 256;
         }
         // If the image uses a colour palette, this is the number of colours, otherwise this is zero.
         int paletteSize = buffer[entryOffset + 2] & 0xFF;
         // The plane count - usually 0 or 1. When > 1, taken as multiplier on bitsPerPixel.
         int colorPlanes = buffer[entryOffset + 4] & 0xFF;
         int bitsPerPixel = (buffer[entryOffset + 6] & 0xFF) |
                            (buffer[entryOffset + 7] & 0xFF) << 8;
         if (colorPlanes > 1) {
             bitsPerPixel *= colorPlanes;
         }
         // Look for PNG magic numbers at the start of the payload.
         boolean payloadIsPNG = FaviconDecoder.bufferStartsWith(buffer, FaviconDecoder.ImageMagicNumbers.PNG.value, regionOffset + payloadOffset);
         return new IconDirectoryEntry(imageWidth, imageHeight, paletteSize, bitsPerPixel, entryLength, payloadOffset, payloadIsPNG);
     }
     /**
      * Get the number of bytes from the start of the ICO file to the beginning of this entry.
      */
     public int getOffset() {
         return ICODecoder.ICO_HEADER_LENGTH_BYTES + (index * ICODecoder.ICO_ICONDIRENTRY_LENGTH_BYTES);
     }
     @Override
     public int compareTo(IconDirectoryEntry another) {
         if (width > another.width) {
             return 1;
         }
         if (width < another.width) {
             return -1;
         }
         // Where both images exceed the max BPP, take the smaller of the two BPP values.
         if (bitsPerPixel >= maxBPP && another.bitsPerPixel >= maxBPP) {
             if (bitsPerPixel < another.bitsPerPixel) {
                 return 1;
             }
             if (bitsPerPixel > another.bitsPerPixel) {
                 return -1;
             }
         }
         // Otherwise, take the larger of the BPP values.
         if (bitsPerPixel > another.bitsPerPixel) {
             return 1;
         }
         if (bitsPerPixel < another.bitsPerPixel) {
             return -1;
         }
         // Prefer large palettes.
         if (paletteSize > another.paletteSize) {
             return 1;
         }
         if (paletteSize < another.paletteSize) {
             return -1;
         }
         // Prefer smaller payloads.
         if (payloadSize < another.payloadSize) {
             return 1;
         }
         if (payloadSize > another.payloadSize) {
             return -1;
         }
         // If all else fails, prefer PNGs over BMPs. They tend to be smaller.
         if (payloadIsPNG && !another.payloadIsPNG) {
             return 1;
         }
         if (!payloadIsPNG && another.payloadIsPNG) {
             return -1;
         }
         return 0;
     }
     public static void setMaxBPP(int maxBPP) {
         IconDirectoryEntry.maxBPP = maxBPP;
     }
     @Override
     public String toString() {
         return "IconDirectoryEntry{" +
                 "\nwidth=" + width +
                 ", \nheight=" + height +
                 ", \npaletteSize=" + paletteSize +
                 ", \nbitsPerPixel=" + bitsPerPixel +
                 ", \npayloadSize=" + payloadSize +
                 ", \npayloadOffset=" + payloadOffset +
                 ", \npayloadIsPNG=" + payloadIsPNG +
                 ", \nindex=" + index +
                 '}';
     }
 }

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mobile/android/base/favicons/decoders/IconDirectoryEntry.java@fc2d59ddac77 (annotated)

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