void JBIG2Stream::readHalftoneRegionSeg(Guint segNum, GBool imm,
					GBool lossless, Guint length,
					Guint *refSegs, Guint nRefSegs) {
  JBIG2Bitmap *bitmap;
  JBIG2Segment *seg;
  JBIG2PatternDict *patternDict;
  JBIG2Bitmap *skipBitmap;
  Guint *grayImg;
  JBIG2Bitmap *grayBitmap;
  JBIG2Bitmap *patternBitmap;
  Guint w, h, x, y, segInfoFlags, extCombOp;
  Guint flags, mmr, templ, enableSkip, combOp;
  Guint gridW, gridH, stepX, stepY, patW, patH;
  int atx[4], aty[4];
  int gridX, gridY, xx, yy, bit, j;
  Guint bpp, m, n, i;

  if (!readULong(&w) || !readULong(&h) ||
      !readULong(&x) || !readULong(&y) ||
      !readUByte(&segInfoFlags)) {
    goto eofError;
  }
  extCombOp = segInfoFlags & 7;

  if (!readUByte(&flags)) {
    goto eofError;
  }
  mmr = flags & 1;
  templ = (flags >> 1) & 3;
  enableSkip = (flags >> 3) & 1;
  combOp = (flags >> 4) & 7;
  if (!readULong(&gridW) || !readULong(&gridH) ||
      !readLong(&gridX) || !readLong(&gridY) ||
      !readUWord(&stepX) || !readUWord(&stepY)) {
    goto eofError;
  }
  if (w == 0 || h == 0 || w >= INT_MAX / h) {
    error(errSyntaxError, curStr->getPos(), "Bad bitmap size in JBIG2 halftone segment");
    return;
  }
  if (gridH == 0 || gridW >= INT_MAX / gridH) {
    error(errSyntaxError, curStr->getPos(), "Bad grid size in JBIG2 halftone segment");
    return;
  }

  if (nRefSegs != 1) {
    error(errSyntaxError, curStr->getPos(), "Bad symbol dictionary reference in JBIG2 halftone segment");
    return;
  }
  seg = findSegment(refSegs[0]);
  if (seg == NULL || seg->getType() != jbig2SegPatternDict) {
    error(errSyntaxError, curStr->getPos(), "Bad symbol dictionary reference in JBIG2 halftone segment");
    return;
  }

  patternDict = (JBIG2PatternDict *)seg;
  i = patternDict->getSize();
  if (i <= 1) {
    bpp = 0;
  } else {
    --i;
    bpp = 0;
    while (i > 0) {
      ++bpp;
      i >>= 1;
    }
  }
  patW = patternDict->getBitmap(0)->getWidth();
  patH = patternDict->getBitmap(0)->getHeight();

  if (!mmr) {
    resetGenericStats(templ, NULL);
    arithDecoder->start();
  }

  bitmap = new JBIG2Bitmap(segNum, w, h);
  if (flags & 0x80) { // HDEFPIXEL
    bitmap->clearToOne();
  } else {
    bitmap->clearToZero();
  }

  skipBitmap = NULL;
  if (enableSkip) {
    skipBitmap = new JBIG2Bitmap(0, gridW, gridH);
    skipBitmap->clearToZero();
    for (m = 0; m < gridH; ++m) {
      for (n = 0; n < gridW; ++n) {
	xx = gridX + m * stepY + n * stepX;
	yy = gridY + m * stepX - n * stepY;
	if (((xx + (int)patW) >> 8) <= 0 || (xx >> 8) >= (int)w ||
	    ((yy + (int)patH) >> 8) <= 0 || (yy >> 8) >= (int)h) {
	  skipBitmap->setPixel(n, m);
	}
      }
    }
  }

  grayImg = (Guint *)gmallocn(gridW * gridH, sizeof(Guint));
  memset(grayImg, 0, gridW * gridH * sizeof(Guint));
  atx[0] = templ <= 1 ? 3 : 2;  aty[0] = -1;
  atx[1] = -3;                  aty[1] = -1;
  atx[2] =  2;                  aty[2] = -2;
  atx[3] = -2;                  aty[3] = -2;
  for (j = bpp - 1; j >= 0; --j) {
    grayBitmap = readGenericBitmap(mmr, gridW, gridH, templ, gFalse,
				   enableSkip, skipBitmap, atx, aty, -1);
    i = 0;
    for (m = 0; m < gridH; ++m) {
      for (n = 0; n < gridW; ++n) {
	bit = grayBitmap->getPixel(n, m) ^ (grayImg[i] & 1);
	grayImg[i] = (grayImg[i] << 1) | bit;
	++i;
      }
    }
    delete grayBitmap;
  }

  i = 0;
  for (m = 0; m < gridH; ++m) {
    xx = gridX + m * stepY;
    yy = gridY + m * stepX;
    for (n = 0; n < gridW; ++n) {
      if (!(enableSkip && skipBitmap->getPixel(n, m))) {
	patternBitmap = patternDict->getBitmap(grayImg[i]);
	if (unlikely(patternBitmap == NULL)) {
	  error(errSyntaxError, curStr->getPos(), "Bad pattern bitmap");
	  return;
	}
	bitmap->combine(patternBitmap, xx >> 8, yy >> 8, combOp);
      }
      xx += stepX;
      yy -= stepY;
      ++i;
    }
  }

  gfree(grayImg);
  if (skipBitmap) {
    delete skipBitmap;
  }

  if (imm) {
    if (pageH == 0xffffffff && y + h > curPageH) {
      pageBitmap->expand(y + h, pageDefPixel);
    }
    pageBitmap->combine(bitmap, x, y, extCombOp);
    delete bitmap;

  } else {
    segments->append(bitmap);
  }

  return;

 eofError:
  error(errSyntaxError, curStr->getPos(), "Unexpected EOF in JBIG2 stream");
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.