michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.favicons.decoders;
michael@0: 
michael@0: /**
michael@0:  * Representation of an ICO file ICONDIRENTRY structure.
michael@0:  */
michael@0: public class IconDirectoryEntry implements Comparable<IconDirectoryEntry> {
michael@0: 
michael@0:     public static int maxBPP;
michael@0: 
michael@0:     int width;
michael@0:     int height;
michael@0:     int paletteSize;
michael@0:     int bitsPerPixel;
michael@0:     int payloadSize;
michael@0:     int payloadOffset;
michael@0:     boolean payloadIsPNG;
michael@0: 
michael@0:     // Tracks the index in the Icon Directory of this entry. Useful only for pruning.
michael@0:     int index;
michael@0:     boolean isErroneous;
michael@0: 
michael@0:     public IconDirectoryEntry(int width, int height, int paletteSize, int bitsPerPixel, int payloadSize, int payloadOffset, boolean payloadIsPNG) {
michael@0:         this.width = width;
michael@0:         this.height = height;
michael@0:         this.paletteSize = paletteSize;
michael@0:         this.bitsPerPixel = bitsPerPixel;
michael@0:         this.payloadSize = payloadSize;
michael@0:         this.payloadOffset = payloadOffset;
michael@0:         this.payloadIsPNG = payloadIsPNG;
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Method to get a dummy Icon Directory Entry with the Erroneous bit set.
michael@0:      *
michael@0:      * @return An erroneous placeholder Icon Directory Entry.
michael@0:      */
michael@0:     public static IconDirectoryEntry getErroneousEntry() {
michael@0:         IconDirectoryEntry ret = new IconDirectoryEntry(-1, -1, -1, -1, -1, -1, false);
michael@0:         ret.isErroneous = true;
michael@0: 
michael@0:         return ret;
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Create an IconDirectoryEntry object from a byte[]. Interprets the buffer starting at the given
michael@0:      * offset as an IconDirectoryEntry and returns the result.
michael@0:      *
michael@0:      * @param buffer Byte array containing the icon directory entry to decode.
michael@0:      * @param regionOffset Offset into the byte array of the valid region of the buffer.
michael@0:      * @param regionLength Length of the valid region in the buffer.
michael@0:      * @param entryOffset Offset of the icon directory entry to decode within the buffer.
michael@0:      * @return An IconDirectoryEntry object representing the entry specified, or null if the entry
michael@0:      *         is obviously invalid.
michael@0:      */
michael@0:     public static IconDirectoryEntry createFromBuffer(byte[] buffer, int regionOffset, int regionLength, int entryOffset) {
michael@0:         // Verify that the reserved field is really zero.
michael@0:         if (buffer[entryOffset + 3] != 0) {
michael@0:             return getErroneousEntry();
michael@0:         }
michael@0: 
michael@0:         // Verify that the entry points to a region that actually exists in the buffer, else bin it.
michael@0:         int fieldPtr = entryOffset + 8;
michael@0:         int entryLength = (buffer[fieldPtr] & 0xFF) |
michael@0:                           (buffer[fieldPtr + 1] & 0xFF) << 8 |
michael@0:                           (buffer[fieldPtr + 2] & 0xFF) << 16 |
michael@0:                           (buffer[fieldPtr + 3] & 0xFF) << 24;
michael@0: 
michael@0:         // Advance to the offset field.
michael@0:         fieldPtr += 4;
michael@0: 
michael@0:         int payloadOffset = (buffer[fieldPtr] & 0xFF) |
michael@0:                             (buffer[fieldPtr + 1] & 0xFF) << 8 |
michael@0:                             (buffer[fieldPtr + 2] & 0xFF) << 16 |
michael@0:                             (buffer[fieldPtr + 3] & 0xFF) << 24;
michael@0: 
michael@0:         // Fail if the entry describes a region outside the buffer.
michael@0:         if (payloadOffset < 0 || entryLength < 0 || payloadOffset + entryLength > regionOffset + regionLength) {
michael@0:             return getErroneousEntry();
michael@0:         }
michael@0: 
michael@0:         // Extract the image dimensions.
michael@0:         int imageWidth = buffer[entryOffset] & 0xFF;
michael@0:         int imageHeight = buffer[entryOffset+1] & 0xFF;
michael@0: 
michael@0:         // Because Microsoft, a size value of zero represents an image size of 256.
michael@0:         if (imageWidth == 0) {
michael@0:             imageWidth = 256;
michael@0:         }
michael@0: 
michael@0:         if (imageHeight == 0) {
michael@0:             imageHeight = 256;
michael@0:         }
michael@0: 
michael@0:         // If the image uses a colour palette, this is the number of colours, otherwise this is zero.
michael@0:         int paletteSize = buffer[entryOffset + 2] & 0xFF;
michael@0: 
michael@0:         // The plane count - usually 0 or 1. When > 1, taken as multiplier on bitsPerPixel.
michael@0:         int colorPlanes = buffer[entryOffset + 4] & 0xFF;
michael@0: 
michael@0:         int bitsPerPixel = (buffer[entryOffset + 6] & 0xFF) |
michael@0:                            (buffer[entryOffset + 7] & 0xFF) << 8;
michael@0: 
michael@0:         if (colorPlanes > 1) {
michael@0:             bitsPerPixel *= colorPlanes;
michael@0:         }
michael@0: 
michael@0:         // Look for PNG magic numbers at the start of the payload.
michael@0:         boolean payloadIsPNG = FaviconDecoder.bufferStartsWith(buffer, FaviconDecoder.ImageMagicNumbers.PNG.value, regionOffset + payloadOffset);
michael@0: 
michael@0:         return new IconDirectoryEntry(imageWidth, imageHeight, paletteSize, bitsPerPixel, entryLength, payloadOffset, payloadIsPNG);
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Get the number of bytes from the start of the ICO file to the beginning of this entry.
michael@0:      */
michael@0:     public int getOffset() {
michael@0:         return ICODecoder.ICO_HEADER_LENGTH_BYTES + (index * ICODecoder.ICO_ICONDIRENTRY_LENGTH_BYTES);
michael@0:     }
michael@0: 
michael@0:     @Override
michael@0:     public int compareTo(IconDirectoryEntry another) {
michael@0:         if (width > another.width) {
michael@0:             return 1;
michael@0:         }
michael@0: 
michael@0:         if (width < another.width) {
michael@0:             return -1;
michael@0:         }
michael@0: 
michael@0:         // Where both images exceed the max BPP, take the smaller of the two BPP values.
michael@0:         if (bitsPerPixel >= maxBPP && another.bitsPerPixel >= maxBPP) {
michael@0:             if (bitsPerPixel < another.bitsPerPixel) {
michael@0:                 return 1;
michael@0:             }
michael@0: 
michael@0:             if (bitsPerPixel > another.bitsPerPixel) {
michael@0:                 return -1;
michael@0:             }
michael@0:         }
michael@0: 
michael@0:         // Otherwise, take the larger of the BPP values.
michael@0:         if (bitsPerPixel > another.bitsPerPixel) {
michael@0:             return 1;
michael@0:         }
michael@0: 
michael@0:         if (bitsPerPixel < another.bitsPerPixel) {
michael@0:             return -1;
michael@0:         }
michael@0: 
michael@0:         // Prefer large palettes.
michael@0:         if (paletteSize > another.paletteSize) {
michael@0:             return 1;
michael@0:         }
michael@0: 
michael@0:         if (paletteSize < another.paletteSize) {
michael@0:             return -1;
michael@0:         }
michael@0: 
michael@0:         // Prefer smaller payloads.
michael@0:         if (payloadSize < another.payloadSize) {
michael@0:             return 1;
michael@0:         }
michael@0: 
michael@0:         if (payloadSize > another.payloadSize) {
michael@0:             return -1;
michael@0:         }
michael@0: 
michael@0:         // If all else fails, prefer PNGs over BMPs. They tend to be smaller.
michael@0:         if (payloadIsPNG && !another.payloadIsPNG) {
michael@0:             return 1;
michael@0:         }
michael@0: 
michael@0:         if (!payloadIsPNG && another.payloadIsPNG) {
michael@0:             return -1;
michael@0:         }
michael@0: 
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     public static void setMaxBPP(int maxBPP) {
michael@0:         IconDirectoryEntry.maxBPP = maxBPP;
michael@0:     }
michael@0: 
michael@0:     @Override
michael@0:     public String toString() {
michael@0:         return "IconDirectoryEntry{" +
michael@0:                 "\nwidth=" + width +
michael@0:                 ", \nheight=" + height +
michael@0:                 ", \npaletteSize=" + paletteSize +
michael@0:                 ", \nbitsPerPixel=" + bitsPerPixel +
michael@0:                 ", \npayloadSize=" + payloadSize +
michael@0:                 ", \npayloadOffset=" + payloadOffset +
michael@0:                 ", \npayloadIsPNG=" + payloadIsPNG +
michael@0:                 ", \nindex=" + index +
michael@0:                 '}';
michael@0:     }
michael@0: }