/****************************************************************************

**

** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).

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** Contact: Nokia Corporation (qt-info@nokia.com)

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** This file is part of the plugins of the Qt Toolkit.

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** $QT_BEGIN_LICENSE:LGPL$

** No Commercial Usage

** This file contains pre-release code and may not be distributed.

** You may use this file in accordance with the terms and conditions

** contained in the Technology Preview License Agreement accompanying

** this package.

**

** GNU Lesser General Public License Usage

** Alternatively, this file may be used under the terms of the GNU Lesser

** General Public License version 2.1 as published by the Free Software

** Foundation and appearing in the file LICENSE.LGPL included in the

** packaging of this file.  Please review the following information to

** ensure the GNU Lesser General Public License version 2.1 requirements

** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

**

** In addition, as a special exception, Nokia gives you certain additional

** rights.  These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

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** If you have questions regarding the use of this file, please contact

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** $QT_END_LICENSE$

**

** WARNING:

**      A separate license from Unisys may be required to use the gif

**      reader. See http://www.unisys.com/about__unisys/lzw/

**      for information from Unisys

**

****************************************************************************/

#include "qgifhandler_p.h"

#include <qimage.h>

#include <qiodevice.h>

#include <qvariant.h>

QT_BEGIN_NAMESPACE

#define Q_TRANSPARENT 0x00ffffff

// avoid going through QImage::scanLine() which calls detach

#define FAST_SCAN_LINE(bits, bpl, y) (bits + (y) * bpl)

/*

  Incremental image decoder for GIF image format.

  This subclass of QImageFormat decodes GIF format images,

  including animated GIFs. Internally in

*/

class QGIFFormat {

public:

    QGIFFormat();

    ~QGIFFormat();

    int decode(QImage *image, const uchar* buffer, int length,

               int *nextFrameDelay, int *loopCount);

    static void scan(QIODevice *device, QVector<QSize> *imageSizes, int *loopCount);

    bool newFrame;

    bool partialNewFrame;

private:

    void fillRect(QImage *image, int x, int y, int w, int h, QRgb col);

    inline QRgb color(uchar index) const;

    // GIF specific stuff

    QRgb* globalcmap;

    QRgb* localcmap;

    QImage backingstore;

    unsigned char hold[16];

    bool gif89;

    int count;

    int ccount;

    int expectcount;

    enum State {

        Header,

        LogicalScreenDescriptor,

        GlobalColorMap,

        LocalColorMap,

        Introducer,

        ImageDescriptor,

        TableImageLZWSize,

        ImageDataBlockSize,

        ImageDataBlock,

        ExtensionLabel,

        GraphicControlExtension,

        ApplicationExtension,

        NetscapeExtensionBlockSize,

        NetscapeExtensionBlock,

        SkipBlockSize,

        SkipBlock,

        Done,

        Error

    } state;

    int gncols;

    int lncols;

    int ncols;

    int lzwsize;

    bool lcmap;

    int swidth, sheight;

    int width, height;

    int left, top, right, bottom;

    enum Disposal { NoDisposal, DoNotChange, RestoreBackground, RestoreImage };

    Disposal disposal;

    bool disposed;

    int trans_index;

    bool gcmap;

    int bgcol;

    int interlace;

    int accum;

    int bitcount;

    enum { max_lzw_bits=12 }; // (poor-compiler's static const int)

    int code_size, clear_code, end_code, max_code_size, max_code;

    int firstcode, oldcode, incode;

    short* table[2];

    short* stack;

    short *sp;

    bool needfirst;

    int x, y;

    int frame;

    bool out_of_bounds;

    bool digress;

    void nextY(unsigned char *bits, int bpl);

    void disposePrevious(QImage *image);

};

/*!

    Constructs a QGIFFormat.

*/

QGIFFormat::QGIFFormat()

{

    globalcmap = 0;

    localcmap = 0;

    lncols = 0;

    gncols = 0;

    disposal = NoDisposal;

    out_of_bounds = false;

    disposed = true;

    frame = -1;

    state = Header;

    count = 0;

    lcmap = false;

    newFrame = false;

    partialNewFrame = false;

    table[0] = 0;

    table[1] = 0;

    stack = 0;

}

/*!

    Destroys a QGIFFormat.

*/

QGIFFormat::~QGIFFormat()

{

    if (globalcmap) delete[] globalcmap;

    if (localcmap) delete[] localcmap;

    delete [] stack;

}

void QGIFFormat::disposePrevious(QImage *image)

{

    if (out_of_bounds) {

        // flush anything that survived

        // ### Changed: QRect(0, 0, swidth, sheight)

    }

    // Handle disposal of previous image before processing next one

    if (disposed) return;

    int l = qMin(swidth-1,left);

    int r = qMin(swidth-1,right);

    int t = qMin(sheight-1,top);

    int b = qMin(sheight-1,bottom);

    switch (disposal) {

      case NoDisposal:

        break;

      case DoNotChange:

        break;

      case RestoreBackground:

        if (trans_index>=0) {

            // Easy:  we use the transparent color

            fillRect(image, l, t, r-l+1, b-t+1, Q_TRANSPARENT);

        } else if (bgcol>=0) {

            // Easy:  we use the bgcol given

            fillRect(image, l, t, r-l+1, b-t+1, color(bgcol));

        } else {

            // Impossible:  We don't know of a bgcol - use pixel 0

            QRgb *bits = (QRgb*)image->bits();

            fillRect(image, l, t, r-l+1, b-t+1, bits[0]);

        }

        // ### Changed: QRect(l, t, r-l+1, b-t+1)

        break;

      case RestoreImage: {

        if (frame >= 0) {

            for (int ln=t; ln<=b; ln++) {

                memcpy(image->scanLine(ln)+l,

                    backingstore.scanLine(ln-t),

                    (r-l+1)*sizeof(QRgb));

            }

            // ### Changed: QRect(l, t, r-l+1, b-t+1)

        }

      }

    }

    disposal = NoDisposal; // Until an extension says otherwise.

    disposed = true;

}

/*!

    This function decodes some data into image changes.

    Returns the number of bytes consumed.

*/

int QGIFFormat::decode(QImage *image, const uchar *buffer, int length,

                       int *nextFrameDelay, int *loopCount)

{

    // We are required to state that

    //    "The Graphics Interchange Format(c) is the Copyright property of

    //    CompuServe Incorporated. GIF(sm) is a Service Mark property of

    //    CompuServe Incorporated."

    if (!stack) {

        stack = new short[(1 << max_lzw_bits) * 4];

        table[0] = &stack[(1 << max_lzw_bits) * 2];

        table[1] = &stack[(1 << max_lzw_bits) * 3];

    }

    image->detach();

    int bpl = image->bytesPerLine();

    unsigned char *bits = image->bits();

#define LM(l, m) (((m)<<8)|l)

    digress = false;

    const int initial = length;

    while (!digress && length) {

        length--;

        unsigned char ch=*buffer++;

        switch (state) {

          case Header:

            hold[count++]=ch;

            if (count==6) {

                // Header

                gif89=(hold[3]!='8' || hold[4]!='7');

                state=LogicalScreenDescriptor;

                count=0;

            }

            break;

          case LogicalScreenDescriptor:

            hold[count++]=ch;

            if (count==7) {

                // Logical Screen Descriptor

                swidth=LM(hold[0], hold[1]);

                sheight=LM(hold[2], hold[3]);

                gcmap=!!(hold[4]&0x80);

                //UNUSED: bpchan=(((hold[4]&0x70)>>3)+1);

                //UNUSED: gcmsortflag=!!(hold[4]&0x08);

                gncols=2<<(hold[4]&0x7);

                bgcol=(gcmap) ? hold[5] : -1;

                //aspect=hold[6] ? double(hold[6]+15)/64.0 : 1.0;

                trans_index = -1;

                count=0;

                ncols=gncols;

                if (gcmap) {

                    ccount=0;

                    state=GlobalColorMap;

                    globalcmap = new QRgb[gncols+1]; // +1 for trans_index

                    globalcmap[gncols] = Q_TRANSPARENT;

                } else {

                    state=Introducer;

                }

            }

            break;

          case GlobalColorMap: case LocalColorMap:

            hold[count++]=ch;

            if (count==3) {

                QRgb rgb = qRgb(hold[0], hold[1], hold[2]);

                if (state == LocalColorMap) {

                    if (ccount < lncols)

                        localcmap[ccount] =  rgb;

                } else {

                    globalcmap[ccount] = rgb;

                }

                if (++ccount >= ncols) {

                    if (state == LocalColorMap)

                        state=TableImageLZWSize;

                    else

                        state=Introducer;

                }

                count=0;

            }

            break;

          case Introducer:

            hold[count++]=ch;

            switch (ch) {

              case ',':

                state=ImageDescriptor;

                break;

              case '!':

                state=ExtensionLabel;

                break;

              case ';':

                  // ### Changed: QRect(0, 0, swidth, sheight)

                state=Done;

                break;

              default:

                digress=true;

                // Unexpected Introducer - ignore block

                state=Error;

            }

            break;

          case ImageDescriptor:

            hold[count++]=ch;

            if (count==10) {

                int newleft=LM(hold[1], hold[2]);

                int newtop=LM(hold[3], hold[4]);

                int newwidth=LM(hold[5], hold[6]);

                int newheight=LM(hold[7], hold[8]);

                // disbelieve ridiculous logical screen sizes,

                // unless the image frames are also large.

                if (swidth/10 > qMax(newwidth,200))

                    swidth = -1;

                if (sheight/10 > qMax(newheight,200))

                    sheight = -1;

                if (swidth <= 0)

                    swidth = newleft + newwidth;

                if (sheight <= 0)

                    sheight = newtop + newheight;

                QImage::Format format = trans_index >= 0 ? QImage::Format_ARGB32 : QImage::Format_RGB32;

                if (image->isNull()) {

                    (*image) = QImage(swidth, sheight, format);

                    bpl = image->bytesPerLine();

                    bits = image->bits();

                    memset(bits, 0, image->byteCount());

                }

                disposePrevious(image);

                disposed = false;

                left = newleft;

                top = newtop;

                width = newwidth;

                height = newheight;

                right=qMax(0, qMin(left+width, swidth)-1);

                bottom=qMax(0, qMin(top+height, sheight)-1);

                lcmap=!!(hold[9]&0x80);

                interlace=!!(hold[9]&0x40);

                //bool lcmsortflag=!!(hold[9]&0x20);

                lncols=lcmap ? (2<<(hold[9]&0x7)) : 0;

                if (lncols) {

                    if (localcmap)

                        delete [] localcmap;

                    localcmap = new QRgb[lncols+1];

                    localcmap[lncols] = Q_TRANSPARENT;

                    ncols = lncols;

                } else {

                    ncols = gncols;

                }

                frame++;

                if (frame == 0) {

                    if (left || top || width<swidth || height<sheight) {

                        // Not full-size image - erase with bg or transparent

                        if (trans_index >= 0) {

                            fillRect(image, 0, 0, swidth, sheight, color(trans_index));

                            // ### Changed: QRect(0, 0, swidth, sheight)

                        } else if (bgcol>=0) {

                            fillRect(image, 0, 0, swidth, sheight, color(bgcol));

                            // ### Changed: QRect(0, 0, swidth, sheight)

                        }

                    }

                }

                if (disposal == RestoreImage) {

                    int l = qMin(swidth-1,left);

                    int r = qMin(swidth-1,right);

                    int t = qMin(sheight-1,top);

                    int b = qMin(sheight-1,bottom);

                    int w = r-l+1;

                    int h = b-t+1;

                    if (backingstore.width() < w

                        || backingstore.height() < h) {

                        // We just use the backing store as a byte array

                        backingstore = QImage(qMax(backingstore.width(), w),

                                              qMax(backingstore.height(), h),

                                              QImage::Format_RGB32);

                        memset(bits, 0, image->byteCount());

                    }

                    const int dest_bpl = backingstore.bytesPerLine();

                    unsigned char *dest_data = backingstore.bits();

                    for (int ln=0; ln<h; ln++) {

                        memcpy(FAST_SCAN_LINE(dest_data, dest_bpl, ln),

                               FAST_SCAN_LINE(bits, bpl, t+ln) + l, w*sizeof(QRgb));

                    }

                }

                count=0;

                if (lcmap) {

                    ccount=0;

                    state=LocalColorMap;

                } else {

                    state=TableImageLZWSize;

                }

                x = left;

                y = top;

                accum = 0;

                bitcount = 0;

                sp = stack;

                firstcode = oldcode = 0;

                needfirst = true;

                out_of_bounds = left>=swidth || y>=sheight;

            }

            break;

          case TableImageLZWSize: {

            lzwsize=ch;

            if (lzwsize > max_lzw_bits) {

                state=Error;

            } else {

                code_size=lzwsize+1;

                clear_code=1<<lzwsize;

                end_code=clear_code+1;

                max_code_size=2*clear_code;

                max_code=clear_code+2;

                int i;

                for (i=0; i<clear_code; i++) {

                    table[0][i]=0;

                    table[1][i]=i;

                }

                state=ImageDataBlockSize;

            }

            count=0;

            break;

          } case ImageDataBlockSize:

            expectcount=ch;

            if (expectcount) {

                state=ImageDataBlock;

            } else {

                state=Introducer;

                digress = true;

                newFrame = true;

            }

            break;

          case ImageDataBlock:

            count++;

            accum|=(ch<<bitcount);

            bitcount+=8;

            while (bitcount>=code_size && state==ImageDataBlock) {

                int code=accum&((1<<code_size)-1);

                bitcount-=code_size;

                accum>>=code_size;

                if (code==clear_code) {

                    if (!needfirst) {

                        code_size=lzwsize+1;

                        max_code_size=2*clear_code;

                        max_code=clear_code+2;

                    }

                    needfirst=true;

                } else if (code==end_code) {

                    bitcount = -32768;

                    // Left the block end arrive

                } else {

                    if (needfirst) {

                        firstcode=oldcode=code;

                        if (!out_of_bounds && image->height() > y && firstcode!=trans_index)

                            ((QRgb*)FAST_SCAN_LINE(bits, bpl, y))[x] = color(firstcode);

                        x++;

                        if (x>=swidth) out_of_bounds = true;

                        needfirst=false;

                        if (x>=left+width) {

                            x=left;

                            out_of_bounds = left>=swidth || y>=sheight;

                            nextY(bits, bpl);

                        }

                    } else {

                        incode=code;

                        if (code>=max_code) {

                            *sp++=firstcode;

                            code=oldcode;

                        }

                        while (code>=clear_code+2) {

                            *sp++=table[1][code];

                            if (code==table[0][code]) {

                                state=Error;

                                break;

                            }

                            if (sp-stack>=(1<<(max_lzw_bits))*2) {

                                state=Error;

                                break;

                            }

                            code=table[0][code];

                        }

                        *sp++=firstcode=table[1][code];

                        code=max_code;

                        if (code<(1<<max_lzw_bits)) {

                            table[0][code]=oldcode;

                            table[1][code]=firstcode;

                            max_code++;

                            if ((max_code>=max_code_size)

                             && (max_code_size<(1<<max_lzw_bits)))

                            {

                                max_code_size*=2;