void SkRGB16_Black_Blitter::blitMask(const SkMask& mask,
                                     const SkIRect& clip) {
    if (mask.fFormat == SkMask::kBW_Format) {
        SkRGB16_Black_BlitBW(fDevice, mask, clip);
    } else {
        uint16_t* SK_RESTRICT device = fDevice.getAddr16(clip.fLeft, clip.fTop);
        const uint8_t* SK_RESTRICT alpha = mask.getAddr8(clip.fLeft, clip.fTop);
        unsigned width = clip.width();
        unsigned height = clip.height();
        size_t deviceRB = fDevice.rowBytes() - (width << 1);
        unsigned maskRB = mask.fRowBytes - width;

        SkASSERT((int)height > 0);
        SkASSERT((int)width > 0);
        SkASSERT((int)deviceRB >= 0);
        SkASSERT((int)maskRB >= 0);

        do {
            unsigned w = width;
            do {
                unsigned aa = *alpha++;
                *device = SkAlphaMulRGB16(*device, SkAlpha255To256(255 - aa));
                device += 1;
            } while (--w != 0);
            device = (uint16_t*)((char*)device + deviceRB);
            alpha += maskRB;
        } while (--height != 0);
    }
}
    virtual void filterSpan16(const uint16_t shader[], int count,
                              uint16_t result[]) {
        // all mul components are the same
        unsigned scale = SkAlpha255To256(SkColorGetR(fMul));

        if (count > 0) {
            do {
                *result++ = SkAlphaMulRGB16(*shader++, scale);
            } while (--count > 0);
        }
    }