gs->is_local_colormap_defined = PR_TRUE;
PRStatus gif_write(gif_struct *gs, const PRUint8 *buf, PRUint32 len){  if (!gs)    return PR_FAILURE;  /* If we fail, some upstream data provider ignored the     zero return value from il_gif_write_ready() which says not to     send any more data to this stream until the delay timeout fires. */  if ((len != 0) && (gs->gathered >= MAX_READ_AHEAD))    return PR_FAILURE;  const PRUint8 *q, *p = buf, *ep = buf + len;  q = nsnull;                   /* Initialize to shut up gcc warnings */  while (p <= ep) {    switch (gs->state)    {    case gif_lzw:      if (do_lzw(gs, q) < 0) {        gs->state = gif_error;        break;      }      GETN(1, gif_sub_block);      break;    case gif_lzw_start:    {      /* Initialize LZW parser/decoder */      gs->datasize = *q;      if (gs->datasize > MAX_LZW_BITS) {        gs->state = gif_error;        break;      }      gs->clear_code = 1 << gs->datasize;      gs->avail = gs->clear_code + 2;      gs->oldcode = -1;      gs->codesize = gs->datasize + 1;      gs->codemask = (1 << gs->codesize) - 1;      gs->datum = gs->bits = 0;      if (!gs->prefix)        gs->prefix = (PRUint16 *)gif_calloc(sizeof(PRUint16), MAX_BITS);      if (!gs->suffix)        gs->suffix = ( PRUint8 *)gif_calloc(sizeof(PRUint8),  MAX_BITS);      if (!gs->stack)        gs->stack  = ( PRUint8 *)gif_calloc(sizeof(PRUint8),  MAX_BITS);      if (!gs->prefix || !gs->suffix || !gs->stack) {        /* complete from abort will free prefix & suffix */        gs->state = gif_oom;        break;      }      if (gs->clear_code >= MAX_BITS) {        gs->state = gif_error;        break;      }      /* init the tables */      for (int i = 0; i < gs->clear_code; i++)        gs->suffix[i] = i;      gs->stackp = gs->stack;      GETN(1, gif_sub_block);    }    break;    /* We're positioned at the very start of the file. */    case gif_init:    {      GETN(3, gif_type);      break;    }    /* All GIF files begin with "GIF87a" or "GIF89a" */    case gif_type:    {      if (strncmp((char*)q, "GIF", 3)) {        gs->state = gif_error;        break;      }      GETN(3, gif_version);    }    break;    case gif_version:    {      if (!strncmp((char*)q, "89a", 3)) {        gs->version = 89;      } else if (!strncmp((char*)q, "87a", 3)) {        gs->version = 87;      } else {        gs->state = gif_error;        break;      }      GETN(7, gif_global_header);    }    break;    case gif_global_header:    {      /* This is the height and width of the "screen" or       * frame into which images are rendered.  The       * individual images can be smaller than the       * screen size and located with an origin anywhere       * within the screen.       */      gs->screen_width = GETINT16(q);      gs->screen_height = GETINT16(q + 2);      gs->screen_bgcolor = q[5];      gs->global_colormap_size = 2<<(q[4]&0x07);      // XXX make callback      nsGIFDecoder2::BeginGIF(        gs->clientptr,        gs->screen_width,        gs->screen_height,        gs->screen_bgcolor);      if (q[4] & 0x80) /* global map */        /* 3 bytes for each entry in the global colormap */        GETN(gs->global_colormap_size*3, gif_global_colormap);      else        GETN(1, gif_image_start);      // q[6] = Pixel Aspect Ratio      //   Not used      //   float aspect = (float)((q[6] + 15) / 64.0);    }    break;    case gif_global_colormap:    {      PRUint8* map = (PRUint8*)PR_MALLOC(3 * gs->global_colormap_size);      if (!map) {        gs->state = gif_oom;        break;      }      gs->global_colormap = map;      memcpy(map, q, 3 * gs->global_colormap_size);      GETN(1, gif_image_start);    }    break;    case gif_image_start:    {      if (*q == ';') { /* terminator */        gs->state = gif_done;        break;      }      if (*q == '!') { /* extension */        GETN(2, gif_extension);        break;      }      /* If we get anything other than ',' (image separator), '!'       * (extension), or ';' (trailer), there is extraneous data       * between blocks. The GIF87a spec tells us to keep reading       * until we find an image separator, but GIF89a says such       * a file is corrupt. We follow GIF89a and bail out. */      if (*q != ',') {        if (gs->images_decoded > 0) {          /* The file is corrupt, but one or more images have           * been decoded correctly. In this case, we proceed           * as if the file were correctly terminated and set           * the state to gif_done, so the GIF will display.           */          gs->state = gif_done;        } else {          /* No images decoded, there is nothing to display. */          gs->state = gif_error;        }        break;      } else        GETN(9, gif_image_header);    }    break;    case gif_extension:    {      int len = gs->count = q[1];      gstate es = gif_skip_block;      switch (*q)      {      case 0xf9:        es = gif_control_extension;        break;      case 0x01:        // ignoring plain text extension        break;      case 0xff:        es = gif_application_extension;        break;      case 0xfe:        es = gif_consume_comment;        break;      }      if (len)        GETN(len, es);      else        GETN(1, gif_image_start);    }    break;    case gif_consume_block:      if (!*q)        GETN(1, gif_image_start);      else        GETN(*q, gif_skip_block);    break;    case gif_skip_block:      GETN(1, gif_consume_block);      break;    case gif_control_extension:    {      if (*q & 0x1) {        gs->tpixel = q[3];        gs->is_transparent = PR_TRUE;      } else {        gs->is_transparent = PR_FALSE;        // ignoring gfx control extension      }      gs->control_extension = PR_TRUE;      gs->disposal_method = (gdispose)(((*q) >> 2) & 0x7);      // Some specs say 3rd bit (value 4), other specs say value 3      // Let's choose 3 (the more popular)      if (gs->disposal_method == 4)        gs->disposal_method = (gdispose)3;      gs->delay_time = GETINT16(q + 1) * 10;      GETN(1, gif_consume_block);    }    break;    case gif_comment_extension:    {      gs->count = *q;      if (gs->count)        GETN(gs->count, gif_consume_comment);      else        GETN(1, gif_image_start);    }    break;    case gif_consume_comment:      GETN(1, gif_comment_extension);    break;    case gif_application_extension:      /* Check for netscape application extension */      if (!strncmp((char*)q, "NETSCAPE2.0", 11) ||        !strncmp((char*)q, "ANIMEXTS1.0", 11))        GETN(1, gif_netscape_extension_block);      else        GETN(1, gif_consume_block);    break;    /* Netscape-specific GIF extension: animation looping */    case gif_netscape_extension_block:      if (*q)        GETN(*q, gif_consume_netscape_extension);      else        GETN(1, gif_image_start);    break;    /* Parse netscape-specific application extensions */    case gif_consume_netscape_extension:    {      int netscape_extension = q[0] & 7;      /* Loop entire animation specified # of times.  Only read the         loop count during the first iteration. */      if (netscape_extension == 1) {        gs->loop_count = GETINT16(q + 1);        /* Zero loop count is infinite animation loop request */        if (gs->loop_count == 0)          gs->loop_count = -1;        GETN(1, gif_netscape_extension_block);      }      /* Wait for specified # of bytes to enter buffer */      else if (netscape_extension == 2) {        gs->requested_buffer_fullness = GETINT32(q + 1);        GETN(gs->requested_buffer_fullness, gif_wait_for_buffer_full);      } else        gs->state = gif_error; // 0,3-7 are yet to be defined netscape                               // extension codes      break;    }    case gif_wait_for_buffer_full:      gs->gathered = gs->requested_buffer_fullness;      GETN(1, gif_netscape_extension_block);      break;    case gif_image_header:    {      PRUintn height, width;      /* Get image offsets, with respect to the screen origin */      gs->x_offset = GETINT16(q);      gs->y_offset = GETINT16(q + 2);      /* Get image width and height. */      width  = GETINT16(q + 4);      height = GETINT16(q + 6);      /* Work around broken GIF files where the logical screen       * size has weird width or height.  We assume that GIF87a       * files don't contain animations.       */      if ((gs->images_decoded == 0) &&          ((gs->screen_height < height) || (gs->screen_width < width) ||           (gs->version == 87)))      {        gs->screen_height = height;        gs->screen_width = width;        gs->x_offset = 0;        gs->y_offset = 0;        nsGIFDecoder2::BeginGIF(gs->clientptr,                                gs->screen_width,                                gs->screen_height,                                gs->screen_bgcolor);      }      /* Work around more broken GIF files that have zero image         width or height */      if (!height || !width) {        height = gs->screen_height;        width = gs->screen_width;        if (!height || !width) {          gs->state = gif_error;          break;        }      }      gs->height = height;      gs->width = width;      nsGIFDecoder2::BeginImageFrame(gs->clientptr,                                     gs->images_decoded + 1,   /* Frame number, 1-n */                                     gs->x_offset,  /* X offset in logical screen */                                     gs->y_offset,  /* Y offset in logical screen */                                     width,                                     height);      /* This case will never be taken if this is the first image */      /* being decoded. If any of the later images are larger     */      /* than the screen size, we need to reallocate buffers.     */      if (gs->screen_width < width) {        /* XXX Deviant! */        gs->rowbuf = (PRUint8*)PR_REALLOC(gs->rowbuf, width);        if (!gs->rowbuf) {          gs->state = gif_oom;          break;        }        gs->screen_width = width;        if (gs->screen_height < gs->height)          gs->screen_height = gs->height;      }      else {        if (!gs->rowbuf)          gs->rowbuf = (PRUint8*)PR_MALLOC(gs->screen_width);      }      if (!gs->rowbuf) {          gs->state = gif_oom;          break;      }      if (q[8] & 0x40) {        gs->interlaced = PR_TRUE;        gs->ipass = 1;      } else {        gs->interlaced = PR_FALSE;        gs->ipass = 0;      }      if (gs->images_decoded == 0) {        gs->progressive_display = PR_TRUE;      } else {        /* Overlaying interlaced, transparent GIFs over           existing image data using the Haeberli display hack           requires saving the underlying image in order to           avoid jaggies at the transparency edges.  We are           unprepared to deal with that, so don't display such           images progressively */        gs->progressive_display = PR_FALSE;      }      /* Clear state from last image */      gs->requested_buffer_fullness = 0;      gs->irow = 0;      gs->rows_remaining = gs->height;      gs->rowend = gs->rowbuf + gs->width;      gs->rowp = gs->rowbuf;      /* bits per pixel is 1<<((q[8]&0x07) + 1); */      if (q[8] & 0x80) /* has a local colormap? */      {        int num_colors = 2 << (q[8] & 0x7);        if (num_colors > gs->local_colormap_size)          PR_FREEIF(gs->local_colormap);        gs->local_colormap_size = num_colors;        /* Switch to the new local palette after it loads */        gs->is_local_colormap_defined = PR_TRUE;        GETN(gs->local_colormap_size * 3, gif_image_colormap);      } else {        /* Switch back to the global palette */        gs->is_local_colormap_defined = PR_FALSE;        GETN(1, gif_lzw_start);      }    }    break;    case gif_image_colormap:    {      PRUint8 *map = gs->local_colormap;      if (!map) {        map = gs->local_colormap = (PRUint8*)PR_MALLOC(3 * gs->local_colormap_size);        if (!map) {          gs->state = gif_oom;          break;        }      }      memcpy(map, q, 3 * gs->local_colormap_size);      GETN(1, gif_lzw_start);    }    break;    case gif_sub_block:    {      if ((gs->count = *q) != 0)      /* Still working on the same image: Process next LZW data block */      {        /* Make sure there are still rows left. If the GIF data */        /* is corrupt, we may not get an explicit terminator.   */        if (gs->rows_remaining == 0) {          /* This is an illegal GIF, but we remain tolerant. */#ifdef DONT_TOLERATE_BROKEN_GIFS          gs->state = gif_error;          break;#else          GETN(1, gif_sub_block);#endif        }        GETN(gs->count, gif_lzw);      }      else      /* See if there are any more images in this sequence. */      {        gs->images_decoded++;        nsGIFDecoder2::EndImageFrame(gs->clientptr,                                     gs->images_decoded,                                     gs->delay_time);        /* Clear state from this image */        gs->control_extension = PR_FALSE;        gs->is_transparent = PR_FALSE;        /* An image can specify a delay time before which to display           subsequent images. */        if (gs->delay_time < MINIMUM_DELAY_TIME)          gs->delay_time = MINIMUM_DELAY_TIME;        GETN(1, gif_image_start);      }    }    break;    case gif_done:      nsGIFDecoder2::EndGIF(gs->clientptr, gs->loop_count);      return PR_SUCCESS;      break;    case gif_delay:    case gif_gather:    {      PRInt32 gather_remaining;      PRInt32 request_size = gs->gather_request_size;      {        gather_remaining = request_size - gs->gathered;        /* Do we already have enough data in the accumulation           buffer to satisfy the request ?  (This can happen           after we transition from the gif_delay state.) */        if (gather_remaining <= 0) {          gs->gathered -= request_size;          q = gs->gather_head;          gs->gather_head += request_size;          gs->state = gs->post_gather_state;          break;        }        /* Shift remaining data to the head of the buffer */        if (gs->gathered && (gs->gather_head != gs->hold)) {          memmove(gs->hold, gs->gather_head, gs->gathered);          gs->gather_head = gs->hold;        }        /* If we add the data just handed to us by the netlib           to what we've already gathered, is there enough to satisfy           the current request ? */        if ((ep - p) >= gather_remaining) {          if (gs->gathered) { /* finish a prior gather */            char *hold = (char*)gs->hold;            BlockAllocCat(hold, gs->gathered, (char*)p, gather_remaining);            gs->hold = (PRUint8*)hold;            q = gs->gather_head = gs->hold;            gs->gathered = 0;          } else            q = p;          p += gather_remaining;          gs->state = gs->post_gather_state;        } else {          char *hold = (char*)gs->hold;          BlockAllocCat(hold, gs->gathered, (char*)p, ep - p);          gs->hold = (PRUint8*)hold;          gs->gather_head = gs->hold;          gs->gathered += ep-p;          return PR_SUCCESS;        }      }    }    break;    // Handle out of memory errors    case gif_oom:      return PR_FAILURE;    // Handle general errors    case gif_error:      nsGIFDecoder2::EndGIF(gs->clientptr, gs->loop_count);      return PR_FAILURE;    case gif_stop_animating:      return PR_SUCCESS;    // We shouldn't ever get here.    default:      break;    }  }  return PR_SUCCESS;}