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      1 /* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* ***** BEGIN LICENSE BLOCK *****
      3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
      4  *
      5  * The contents of this file are subject to the Mozilla Public License Version
      6  * 1.1 (the "License"); you may not use this file except in compliance with
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      8  * http://www.mozilla.org/MPL/
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     10  * Software distributed under the License is distributed on an "AS IS" basis,
     11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
     12  * for the specific language governing rights and limitations under the
     13  * License.
     14  *
     15  * The Original Code is Mozilla Communicator client code.
     16  *
     17  * The Initial Developer of the Original Code is
     18  * Netscape Communications Corporation.
     19  * Portions created by the Initial Developer are Copyright (C) 1998
     20  * the Initial Developer. All Rights Reserved.
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     22  * Contributor(s):
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     25  * either the GNU General Public License Version 2 or later (the "GPL"), or
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     35  *
     36  * ***** END LICENSE BLOCK ***** */
     37 
     38 #ifndef GIFImageReader_h
     39 #define GIFImageReader_h
     40 
     41 // Define ourselves as the clientPtr.  Mozilla just hacked their C++ callback class into this old C decoder,
     42 // so we will too.
     43 #include "platform/SharedBuffer.h"
     44 #include "platform/image-decoders/gif/GIFImageDecoder.h"
     45 #include "wtf/Noncopyable.h"
     46 #include "wtf/OwnPtr.h"
     47 #include "wtf/PassOwnPtr.h"
     48 #include "wtf/Vector.h"
     49 
     50 #define MAX_DICTIONARY_ENTRY_BITS 12
     51 #define MAX_DICTIONARY_ENTRIES    4096 // 2^MAX_DICTIONARY_ENTRY_BITS
     52 #define MAX_COLORS                256
     53 #define BYTES_PER_COLORMAP_ENTRY  3
     54 
     55 const int cLoopCountNotSeen = -2;
     56 
     57 // List of possible parsing states.
     58 enum GIFState {
     59     GIFType,
     60     GIFGlobalHeader,
     61     GIFGlobalColormap,
     62     GIFImageStart,
     63     GIFImageHeader,
     64     GIFImageColormap,
     65     GIFImageBody,
     66     GIFLZWStart,
     67     GIFLZW,
     68     GIFSubBlock,
     69     GIFExtension,
     70     GIFControlExtension,
     71     GIFConsumeBlock,
     72     GIFSkipBlock,
     73     GIFDone,
     74     GIFCommentExtension,
     75     GIFApplicationExtension,
     76     GIFNetscapeExtensionBlock,
     77     GIFConsumeNetscapeExtension,
     78     GIFConsumeComment
     79 };
     80 
     81 struct GIFFrameContext;
     82 
     83 // LZW decoder state machine.
     84 class GIFLZWContext {
     85     WTF_MAKE_FAST_ALLOCATED;
     86 public:
     87     GIFLZWContext(WebCore::GIFImageDecoder* client, const GIFFrameContext* frameContext)
     88         : codesize(0)
     89         , codemask(0)
     90         , clearCode(0)
     91         , avail(0)
     92         , oldcode(0)
     93         , firstchar(0)
     94         , bits(0)
     95         , datum(0)
     96         , ipass(0)
     97         , irow(0)
     98         , rowsRemaining(0)
     99         , rowIter(0)
    100         , m_client(client)
    101         , m_frameContext(frameContext)
    102     { }
    103 
    104     bool prepareToDecode();
    105     bool outputRow(GIFRow::const_iterator rowBegin);
    106     bool doLZW(const unsigned char* block, size_t bytesInBlock);
    107     bool hasRemainingRows() { return rowsRemaining; }
    108 
    109 private:
    110     // LZW decoding states and output states.
    111     int codesize;
    112     int codemask;
    113     int clearCode; // Codeword used to trigger dictionary reset.
    114     int avail; // Index of next available slot in dictionary.
    115     int oldcode;
    116     unsigned char firstchar;
    117     int bits; // Number of unread bits in "datum".
    118     int datum; // 32-bit input buffer.
    119     int ipass; // Interlace pass; Ranges 1-4 if interlaced.
    120     size_t irow; // Current output row, starting at zero.
    121     size_t rowsRemaining; // Rows remaining to be output.
    122 
    123     unsigned short prefix[MAX_DICTIONARY_ENTRIES];
    124     unsigned char suffix[MAX_DICTIONARY_ENTRIES];
    125     unsigned short suffixLength[MAX_DICTIONARY_ENTRIES];
    126     GIFRow rowBuffer; // Single scanline temporary buffer.
    127     GIFRow::iterator rowIter;
    128 
    129     // Initialized during construction and read-only.
    130     WebCore::GIFImageDecoder* m_client;
    131     const GIFFrameContext* m_frameContext;
    132 };
    133 
    134 // Data structure for one LZW block.
    135 struct GIFLZWBlock {
    136     WTF_MAKE_FAST_ALLOCATED;
    137 public:
    138     GIFLZWBlock(size_t position, size_t size)
    139         : blockPosition(position)
    140         , blockSize(size)
    141     {
    142     }
    143 
    144     size_t blockPosition;
    145     size_t blockSize;
    146 };
    147 
    148 class GIFColorMap {
    149     WTF_MAKE_FAST_ALLOCATED;
    150 public:
    151     typedef Vector<WebCore::ImageFrame::PixelData> Table;
    152 
    153     GIFColorMap()
    154         : m_isDefined(false)
    155         , m_position(0)
    156         , m_colors(0)
    157     {
    158     }
    159 
    160     // Set position and number of colors for the RGB table in the data stream.
    161     void setTablePositionAndSize(size_t position, size_t colors)
    162     {
    163         m_position = position;
    164         m_colors = colors;
    165     }
    166     void setDefined() { m_isDefined = true; }
    167     bool isDefined() const { return m_isDefined; }
    168 
    169     // Build RGBA table using the data stream.
    170     void buildTable(const unsigned char* data, size_t length);
    171     const Table& table() const { return m_table; }
    172 
    173 private:
    174     bool m_isDefined;
    175     size_t m_position;
    176     size_t m_colors;
    177     Table m_table;
    178 };
    179 
    180 // Frame output state machine.
    181 struct GIFFrameContext {
    182     WTF_MAKE_FAST_ALLOCATED; WTF_MAKE_NONCOPYABLE(GIFFrameContext);
    183 public:
    184     GIFFrameContext(int id)
    185         : m_frameId(id)
    186         , m_xOffset(0)
    187         , m_yOffset(0)
    188         , m_width(0)
    189         , m_height(0)
    190         , m_transparentPixel(kNotFound)
    191         , m_disposalMethod(WebCore::ImageFrame::DisposeNotSpecified)
    192         , m_dataSize(0)
    193         , m_progressiveDisplay(false)
    194         , m_interlaced(false)
    195         , m_delayTime(0)
    196         , m_currentLzwBlock(0)
    197         , m_isComplete(false)
    198         , m_isHeaderDefined(false)
    199         , m_isDataSizeDefined(false)
    200     {
    201     }
    202 
    203     ~GIFFrameContext()
    204     {
    205     }
    206 
    207     void addLzwBlock(size_t position, size_t size)
    208     {
    209         m_lzwBlocks.append(GIFLZWBlock(position, size));
    210     }
    211 
    212     bool decode(const unsigned char* data, size_t length, WebCore::GIFImageDecoder* client, bool* frameDecoded);
    213 
    214     int frameId() const { return m_frameId; }
    215     void setRect(unsigned x, unsigned y, unsigned width, unsigned height)
    216     {
    217         m_xOffset = x;
    218         m_yOffset = y;
    219         m_width = width;
    220         m_height = height;
    221     }
    222     WebCore::IntRect frameRect() const { return WebCore::IntRect(m_xOffset, m_yOffset, m_width, m_height); }
    223     unsigned xOffset() const { return m_xOffset; }
    224     unsigned yOffset() const { return m_yOffset; }
    225     unsigned width() const { return m_width; }
    226     unsigned height() const { return m_height; }
    227     size_t transparentPixel() const { return m_transparentPixel; }
    228     void setTransparentPixel(size_t pixel) { m_transparentPixel = pixel; }
    229     WebCore::ImageFrame::DisposalMethod disposalMethod() const { return m_disposalMethod; }
    230     void setDisposalMethod(WebCore::ImageFrame::DisposalMethod disposalMethod) { m_disposalMethod = disposalMethod; }
    231     unsigned delayTime() const { return m_delayTime; }
    232     void setDelayTime(unsigned delay) { m_delayTime = delay; }
    233     bool isComplete() const { return m_isComplete; }
    234     void setComplete() { m_isComplete = true; }
    235     bool isHeaderDefined() const { return m_isHeaderDefined; }
    236     void setHeaderDefined() { m_isHeaderDefined = true; }
    237     bool isDataSizeDefined() const { return m_isDataSizeDefined; }
    238     int dataSize() const { return m_dataSize; }
    239     void setDataSize(int size)
    240     {
    241         m_dataSize = size;
    242         m_isDataSizeDefined = true;
    243     }
    244     bool progressiveDisplay() const { return m_progressiveDisplay; }
    245     void setProgressiveDisplay(bool progressiveDisplay) { m_progressiveDisplay = progressiveDisplay; }
    246     bool interlaced() const { return m_interlaced; }
    247     void setInterlaced(bool interlaced) { m_interlaced = interlaced; }
    248 
    249     void clearDecodeState() { m_lzwContext.clear(); }
    250     const GIFColorMap& localColorMap() const { return m_localColorMap; }
    251     GIFColorMap& localColorMap() { return m_localColorMap; }
    252 
    253 private:
    254     int m_frameId;
    255     unsigned m_xOffset;
    256     unsigned m_yOffset; // With respect to "screen" origin.
    257     unsigned m_width;
    258     unsigned m_height;
    259     size_t m_transparentPixel; // Index of transparent pixel. Value is kNotFound if there is no transparent pixel.
    260     WebCore::ImageFrame::DisposalMethod m_disposalMethod; // Restore to background, leave in place, etc.
    261     int m_dataSize;
    262 
    263     bool m_progressiveDisplay; // If true, do Haeberli interlace hack.
    264     bool m_interlaced; // True, if scanlines arrive interlaced order.
    265 
    266     unsigned m_delayTime; // Display time, in milliseconds, for this image in a multi-image GIF.
    267 
    268     OwnPtr<GIFLZWContext> m_lzwContext;
    269     Vector<GIFLZWBlock> m_lzwBlocks; // LZW blocks for this frame.
    270     GIFColorMap m_localColorMap;
    271 
    272     size_t m_currentLzwBlock;
    273     bool m_isComplete;
    274     bool m_isHeaderDefined;
    275     bool m_isDataSizeDefined;
    276 };
    277 
    278 class PLATFORM_EXPORT GIFImageReader {
    279     WTF_MAKE_FAST_ALLOCATED; WTF_MAKE_NONCOPYABLE(GIFImageReader);
    280 public:
    281     GIFImageReader(WebCore::GIFImageDecoder* client = 0)
    282         : m_client(client)
    283         , m_state(GIFType)
    284         , m_bytesToConsume(6) // Number of bytes for GIF type, either "GIF87a" or "GIF89a".
    285         , m_bytesRead(0)
    286         , m_version(0)
    287         , m_screenWidth(0)
    288         , m_screenHeight(0)
    289         , m_loopCount(cLoopCountNotSeen)
    290         , m_parseCompleted(false)
    291     {
    292     }
    293 
    294     ~GIFImageReader()
    295     {
    296     }
    297 
    298     void setData(PassRefPtr<WebCore::SharedBuffer> data) { m_data = data; }
    299     bool parse(WebCore::GIFImageDecoder::GIFParseQuery);
    300     bool decode(size_t frameIndex);
    301 
    302     size_t imagesCount() const
    303     {
    304         if (m_frames.isEmpty())
    305             return 0;
    306 
    307         // This avoids counting an empty frame when the file is truncated right after
    308         // GIFControlExtension but before GIFImageHeader.
    309         // FIXME: This extra complexity is not necessary and we should just report m_frames.size().
    310         return m_frames.last()->isHeaderDefined() ? m_frames.size() : m_frames.size() - 1;
    311     }
    312     int loopCount() const { return m_loopCount; }
    313 
    314     const GIFColorMap& globalColorMap() const
    315     {
    316         return m_globalColorMap;
    317     }
    318 
    319     const GIFFrameContext* frameContext(size_t index) const
    320     {
    321         return index < m_frames.size() ? m_frames[index].get() : 0;
    322     }
    323 
    324     bool parseCompleted() const { return m_parseCompleted; }
    325 
    326     void clearDecodeState(size_t index) { m_frames[index]->clearDecodeState(); }
    327 
    328 private:
    329     bool parseData(size_t dataPosition, size_t len, WebCore::GIFImageDecoder::GIFParseQuery);
    330     void setRemainingBytes(size_t);
    331 
    332     const unsigned char* data(size_t dataPosition) const
    333     {
    334         return reinterpret_cast<const unsigned char*>(m_data->data()) + dataPosition;
    335     }
    336 
    337     void addFrameIfNecessary();
    338     bool currentFrameIsFirstFrame() const
    339     {
    340         return m_frames.isEmpty() || (m_frames.size() == 1u && !m_frames[0]->isComplete());
    341     }
    342 
    343     WebCore::GIFImageDecoder* m_client;
    344 
    345     // Parsing state machine.
    346     GIFState m_state; // Current decoder master state.
    347     size_t m_bytesToConsume; // Number of bytes to consume for next stage of parsing.
    348     size_t m_bytesRead; // Number of bytes processed.
    349 
    350     // Global (multi-image) state.
    351     int m_version; // Either 89 for GIF89 or 87 for GIF87.
    352     unsigned m_screenWidth; // Logical screen width & height.
    353     unsigned m_screenHeight;
    354     GIFColorMap m_globalColorMap;
    355     int m_loopCount; // Netscape specific extension block to control the number of animation loops a GIF renders.
    356 
    357     Vector<OwnPtr<GIFFrameContext> > m_frames;
    358 
    359     RefPtr<WebCore::SharedBuffer> m_data;
    360     bool m_parseCompleted;
    361 };
    362 
    363 #endif
    364