PeerStreamer

/*

 * GIF decoder

 * Copyright (c) 2003 Fabrice Bellard.

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "avformat.h"

int gif_write(ByteIOContext *pb, AVImageInfo *info);

//#define DEBUG

#define MAXBITS                 12

#define         SIZTABLE        (1<<MAXBITS)

#define GCE_DISPOSAL_NONE       0

#define GCE_DISPOSAL_INPLACE    1

#define GCE_DISPOSAL_BACKGROUND 2

#define GCE_DISPOSAL_RESTORE    3

typedef struct GifState {

    int screen_width;

    int screen_height;

    int bits_per_pixel;

    int background_color_index;

    int transparent_color_index;

    int color_resolution;

    uint8_t *image_buf;

    int image_linesize;

    uint32_t *image_palette;

    int pix_fmt;

    /* after the frame is displayed, the disposal method is used */

    int gce_disposal;

    /* delay during which the frame is shown */

    int gce_delay;

    /* LZW compatible decoder */

    ByteIOContext *f;

    int eob_reached;

    uint8_t *pbuf, *ebuf;

    int bbits;

    unsigned int bbuf;

    int cursize;                /* The current code size */

    int curmask;

    int codesize;

    int clear_code;

    int end_code;

    int newcodes;               /* First available code */

    int top_slot;               /* Highest code for current size */

    int slot;                   /* Last read code */

    int fc, oc;

    uint8_t *sp;

    uint8_t stack[SIZTABLE];

    uint8_t suffix[SIZTABLE];

    uint16_t prefix[SIZTABLE];

    /* aux buffers */

    uint8_t global_palette[256 * 3];

    uint8_t local_palette[256 * 3];

    uint8_t buf[256];

} GifState;

static const uint8_t gif87a_sig[6] = "GIF87a";

static const uint8_t gif89a_sig[6] = "GIF89a";

static const uint16_t mask[17] =

{

    0x0000, 0x0001, 0x0003, 0x0007,

    0x000F, 0x001F, 0x003F, 0x007F,

    0x00FF, 0x01FF, 0x03FF, 0x07FF,

    0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF

};

/* Probe gif video format or gif image format. The current heuristic

   supposes the gif87a is always a single image. For gif89a, we

   consider it as a video only if a GCE extension is present in the

   first kilobyte. */

static int gif_video_probe(AVProbeData * pd)

{

    const uint8_t *p, *p_end;

    int bits_per_pixel, has_global_palette, ext_code, ext_len;

    int gce_flags, gce_disposal;

    if (pd->buf_size < 24 ||

        memcmp(pd->buf, gif89a_sig, 6) != 0)

        return 0;

    p_end = pd->buf + pd->buf_size;

    p = pd->buf + 6;

    bits_per_pixel = (p[4] & 0x07) + 1;

    has_global_palette = (p[4] & 0x80);

    p += 7;

    if (has_global_palette)

        p += (1 << bits_per_pixel) * 3;

    for(;;) {

        if (p >= p_end)

            return 0;

        if (*p != '!')

            break;

        p++;

        if (p >= p_end)

            return 0;

        ext_code = *p++;

        if (p >= p_end)

            return 0;

        ext_len = *p++;

        if (ext_code == 0xf9) {

            if (p >= p_end)

                return 0;

            /* if GCE extension found with gce_disposal != 0: it is

               likely to be an animation */

            gce_flags = *p++;

            gce_disposal = (gce_flags >> 2) & 0x7;

            if (gce_disposal != 0)

                return AVPROBE_SCORE_MAX;

            else

                return 0;

        }

        for(;;) {

            if (ext_len == 0)

                break;

            p += ext_len;

            if (p >= p_end)

                return 0;

            ext_len = *p++;

        }

    }

    return 0;

}

static int gif_image_probe(AVProbeData * pd)

{

    if (pd->buf_size >= 24 &&

        (memcmp(pd->buf, gif87a_sig, 6) == 0 ||

         memcmp(pd->buf, gif89a_sig, 6) == 0))

        return AVPROBE_SCORE_MAX - 1;

    else

        return 0;

}

static void GLZWDecodeInit(GifState * s, int csize)

{

    /* read buffer */

    s->eob_reached = 0;

    s->pbuf = s->buf;

    s->ebuf = s->buf;

    s->bbuf = 0;

    s->bbits = 0;

    /* decoder */

    s->codesize = csize;

    s->cursize = s->codesize + 1;

    s->curmask = mask[s->cursize];

    s->top_slot = 1 << s->cursize;

    s->clear_code = 1 << s->codesize;

    s->end_code = s->clear_code + 1;

    s->slot = s->newcodes = s->clear_code + 2;

    s->oc = s->fc = 0;

    s->sp = s->stack;

}

/* XXX: optimize */

static inline int GetCode(GifState * s)

{

    int c, sizbuf;

    uint8_t *ptr;

    while (s->bbits < s->cursize) {

        ptr = s->pbuf;

        if (ptr >= s->ebuf) {

            if (!s->eob_reached) {

                sizbuf = get_byte(s->f);

                s->ebuf = s->buf + sizbuf;

                s->pbuf = s->buf;

                if (sizbuf > 0) {

                    get_buffer(s->f, s->buf, sizbuf);

                } else {

                    s->eob_reached = 1;

                }

            }

            ptr = s->pbuf;

        }

        s->bbuf |= ptr[0] << s->bbits;

        ptr++;

        s->pbuf = ptr;

        s->bbits += 8;

    }

    c = s->bbuf & s->curmask;

    s->bbuf >>= s->cursize;

    s->bbits -= s->cursize;

    return c;

}

/* NOTE: the algorithm here is inspired from the LZW GIF decoder

   written by Steven A. Bennett in 1987. */

/* return the number of byte decoded */

static int GLZWDecode(GifState * s, uint8_t * buf, int len)

{

    int l, c, code, oc, fc;

    uint8_t *sp;

    if (s->end_code < 0)

        return 0;

    l = len;

    sp = s->sp;

    oc = s->oc;

    fc = s->fc;

    while (sp > s->stack) {

        *buf++ = *(--sp);

        if ((--l) == 0)

            goto the_end;

    }

    for (;;) {

        c = GetCode(s);

        if (c == s->end_code) {

            s->end_code = -1;

            break;

        } else if (c == s->clear_code) {

            s->cursize = s->codesize + 1;

            s->curmask = mask[s->cursize];

            s->slot = s->newcodes;

            s->top_slot = 1 << s->cursize;

            while ((c = GetCode(s)) == s->clear_code);

            if (c == s->end_code) {

                s->end_code = -1;

                break;

            }

            /* test error */

            if (c >= s->slot)

                c = 0;

            fc = oc = c;

            *buf++ = c;

            if ((--l) == 0)

                break;

        } else {

            code = c;

            if (code >= s->slot) {

                *sp++ = fc;

                code = oc;

            }

            while (code >= s->newcodes) {

                *sp++ = s->suffix[code];

                code = s->prefix[code];

            }

            *sp++ = code;

            if (s->slot < s->top_slot) {

                s->suffix[s->slot] = fc = code;

                s->prefix[s->slot++] = oc;

                oc = c;

            }

            if (s->slot >= s->top_slot) {

                if (s->cursize < MAXBITS) {

                    s->top_slot <<= 1;

                    s->curmask = mask[++s->cursize];

                }

            }

            while (sp > s->stack) {

                *buf++ = *(--sp);

                if ((--l) == 0)

                    goto the_end;

            }

        }

    }

  the_end:

    s->sp = sp;

    s->oc = oc;

    s->fc = fc;

    return len - l;

}

static int gif_read_image(GifState *s)

{

    ByteIOContext *f = s->f;

    int left, top, width, height, bits_per_pixel, code_size, flags;

    int is_interleaved, has_local_palette, y, x, pass, y1, linesize, n, i;

    uint8_t *ptr, *line, *d, *spal, *palette, *sptr, *ptr1;

    left = get_le16(f);

    top = get_le16(f);

    width = get_le16(f);

    height = get_le16(f);

    flags = get_byte(f);

    is_interleaved = flags & 0x40;

    has_local_palette = flags & 0x80;

    bits_per_pixel = (flags & 0x07) + 1;

#ifdef DEBUG

    printf("gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);

#endif

    if (has_local_palette) {

        get_buffer(f, s->local_palette, 3 * (1 << bits_per_pixel));

        palette = s->local_palette;

    } else {

        palette = s->global_palette;

        bits_per_pixel = s->bits_per_pixel;

    }

    /* verify that all the image is inside the screen dimensions */

    if (left + width > s->screen_width ||

        top + height > s->screen_height)

        return -EINVAL;

    /* build the palette */

    if (s->pix_fmt == PIX_FMT_RGB24) {

        line = av_malloc(width);

        if (!line)

            return -ENOMEM;

    } else {

        n = (1 << bits_per_pixel);

        spal = palette;

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

            s->image_palette[i] = (0xff << 24) |

                (spal[0] << 16) | (spal[1] << 8) | (spal[2]);

            spal += 3;

        }

        for(; i < 256; i++)

            s->image_palette[i] = (0xff << 24);

        /* handle transparency */

        if (s->transparent_color_index >= 0)

            s->image_palette[s->transparent_color_index] = 0;

        line = NULL;

    }

    /* now get the image data */

    s->f = f;

    code_size = get_byte(f);

    GLZWDecodeInit(s, code_size);

    /* read all the image */

    linesize = s->image_linesize;

    ptr1 = s->image_buf + top * linesize + (left * 3);

    ptr = ptr1;

    pass = 0;

    y1 = 0;

    for (y = 0; y < height; y++) {

        if (s->pix_fmt == PIX_FMT_RGB24) {

            /* transcode to RGB24 */

            GLZWDecode(s, line, width);

            d = ptr;

            sptr = line;

            for(x = 0; x < width; x++) {

                spal = palette + sptr[0] * 3;

                d[0] = spal[0];

                d[1] = spal[1];

                d[2] = spal[2];

                d += 3;

                sptr++;

            }

        } else {

            GLZWDecode(s, ptr, width);

        }

        if (is_interleaved) {

            switch(pass) {

            default:

            case 0:

            case 1:

                y1 += 8;

                ptr += linesize * 8;

                if (y1 >= height) {

                    y1 = 4;

                    if (pass == 0)

                        ptr = ptr1 + linesize * 4;

                    else

                        ptr = ptr1 + linesize * 2;

                    pass++;

                }

                break;

            case 2:

                y1 += 4;

                ptr += linesize * 4;

                if (y1 >= height) {

                    y1 = 1;

                    ptr = ptr1 + linesize;

                    pass++;

                }

                break;

            case 3:

                y1 += 2;

                ptr += linesize * 2;

                break;

            }

        } else {

            ptr += linesize;

        }

    }

    av_free(line);

    /* read the garbage data until end marker is found */

    while (!s->eob_reached)

        GetCode(s);

    return 0;

}

static int gif_read_extension(GifState *s)

{

    ByteIOContext *f = s->f;

    int ext_code, ext_len, i, gce_flags, gce_transparent_index;

    /* extension */

    ext_code = get_byte(f);

    ext_len = get_byte(f);

#ifdef DEBUG

    printf("gif: ext_code=0x%x len=%d\n", ext_code, ext_len);

#endif

    switch(ext_code) {

    case 0xf9:

        if (ext_len != 4)

            goto discard_ext;

        s->transparent_color_index = -1;

        gce_flags = get_byte(f);

        s->gce_delay = get_le16(f);

        gce_transparent_index = get_byte(f);

        if (gce_flags & 0x01)

            s->transparent_color_index = gce_transparent_index;

        else

            s->transparent_color_index = -1;

        s->gce_disposal = (gce_flags >> 2) & 0x7;

#ifdef DEBUG

        printf("gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",

               gce_flags, s->gce_delay,

               s->transparent_color_index, s->gce_disposal);

#endif

        ext_len = get_byte(f);

        break;

    }

    /* NOTE: many extension blocks can come after */

 discard_ext:

    while (ext_len != 0) {

        for (i = 0; i < ext_len; i++)

            get_byte(f);

        ext_len = get_byte(f);

#ifdef DEBUG

        printf("gif: ext_len1=%d\n", ext_len);

#endif

    }

    return 0;

}

static int gif_read_header1(GifState *s)

{

    ByteIOContext *f = s->f;

    uint8_t sig[6];

    int ret, v, n;

    int has_global_palette;

    /* read gif signature */

    ret = get_buffer(f, sig, 6);

    if (ret != 6)

        return -1;

    if (memcmp(sig, gif87a_sig, 6) != 0 &&

        memcmp(sig, gif89a_sig, 6) != 0)

        return -1;

    /* read screen header */

    s->transparent_color_index = -1;

    s->screen_width = get_le16(f);

    s->screen_height = get_le16(f);

    if(   (unsigned)s->screen_width  > 32767

       || (unsigned)s->screen_height > 32767){

        av_log(NULL, AV_LOG_ERROR, "picture size too large\n");

        return -1;

    }

    v = get_byte(f);

    s->color_resolution = ((v & 0x70) >> 4) + 1;

    has_global_palette = (v & 0x80);

    s->bits_per_pixel = (v & 0x07) + 1;

    s->background_color_index = get_byte(f);

    get_byte(f);                /* ignored */

#ifdef DEBUG

    printf("gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",

           s->screen_width, s->screen_height, s->bits_per_pixel,

           has_global_palette);

#endif

    if (has_global_palette) {

        n = 1 << s->bits_per_pixel;

        get_buffer(f, s->global_palette, n * 3);

    }

    return 0;

}

static int gif_parse_next_image(GifState *s)

{

    ByteIOContext *f = s->f;

    int ret, code;

    for (;;) {

        code = url_fgetc(f);

#ifdef DEBUG

        printf("gif: code=%02x '%c'\n", code, code);

#endif

        switch (code) {

        case ',':

            if (gif_read_image(s) < 0)

                return AVERROR_IO;

            ret = 0;

            goto the_end;

        case ';':

            /* end of image */

            ret = AVERROR_IO;

            goto the_end;

        case '!':

            if (gif_read_extension(s) < 0)

                return AVERROR_IO;

            break;

        case EOF:

        default:

            /* error or errneous EOF */

            ret = AVERROR_IO;

            goto the_end;

        }

    }

  the_end:

    return ret;

}

static int gif_read_header(AVFormatContext * s1,

                           AVFormatParameters * ap)

{

    GifState *s = s1->priv_data;

    ByteIOContext *f = &s1->pb;

    AVStream *st;

    s->f = f;

    if (gif_read_header1(s) < 0)

        return -1;

    /* allocate image buffer */

    s->image_linesize = s->screen_width * 3;

    s->image_buf = av_malloc(s->screen_height * s->image_linesize);

    if (!s->image_buf)

        return -ENOMEM;

    s->pix_fmt = PIX_FMT_RGB24;

    /* now we are ready: build format streams */

    st = av_new_stream(s1, 0);

    if (!st)

        return -1;

    st->codec->codec_type = CODEC_TYPE_VIDEO;

    st->codec->codec_id = CODEC_ID_RAWVIDEO;

    st->codec->time_base.den = 5;

    st->codec->time_base.num = 1;

    /* XXX: check if screen size is always valid */

    st->codec->width = s->screen_width;

    st->codec->height = s->screen_height;

    st->codec->pix_fmt = PIX_FMT_RGB24;

    return 0;

}

static int gif_read_packet(AVFormatContext * s1,

                           AVPacket * pkt)

{

    GifState *s = s1->priv_data;

    int ret;

    ret = gif_parse_next_image(s);

    if (ret < 0)

        return ret;

    /* XXX: avoid copying */

    if (av_new_packet(pkt, s->screen_width * s->screen_height * 3)) {

        return AVERROR_IO;

    }

    pkt->stream_index = 0;

    memcpy(pkt->data, s->image_buf, s->screen_width * s->screen_height * 3);

    return 0;

}

static int gif_read_close(AVFormatContext *s1)

{

    GifState *s = s1->priv_data;

    av_free(s->image_buf);

    return 0;

}

/* read gif as image */

static int gif_read(ByteIOContext *f,

                    int (*alloc_cb)(void *opaque, AVImageInfo *info), void *opaque)

{

    GifState s1, *s = &s1;

    AVImageInfo info1, *info = &info1;

    int ret;

    memset(s, 0, sizeof(GifState));

    s->f = f;

    if (gif_read_header1(s) < 0)

        return -1;

    info->width = s->screen_width;

    info->height = s->screen_height;

    info->pix_fmt = PIX_FMT_PAL8;

    ret = alloc_cb(opaque, info);

    if (ret)

        return ret;

    s->image_buf = info->pict.data[0];

    s->image_linesize = info->pict.linesize[0];

    s->image_palette = (uint32_t *)info->pict.data[1];

    if (gif_parse_next_image(s) < 0)

        return -1;

    return 0;

}

AVInputFormat gif_iformat =

{

    "gif",

    "gif format",

    sizeof(GifState),

    gif_video_probe,

    gif_read_header,

    gif_read_packet,

    gif_read_close,

};

AVImageFormat gif_image_format = {

    "gif",

    "gif",

    gif_image_probe,

    gif_read,

    (1 << PIX_FMT_PAL8),

    gif_write,

};