qsub8()

LIB8STATIC_ALWAYS_INLINE uint8_t qsub8	(	uint8_t	i,
		uint8_t	j )

Subtract one byte from another, saturating at 0x00.

Parameters

i	byte to subtract from
j	byte to subtract

Returns

i - j with a floor of 0

Examples

Fire2012.ino, Fire2012WithPalette.ino, NoisePlusPalette.ino, and TwinkleFox.ino.

Definition at line 103 of file math8.h.

                                                             {
#if QSUB8_C == 1
    int t = i - j;
    if (t < 0)
        t = 0;
    return t;
#elif QSUB8_AVRASM == 1
 
    asm volatile(
        /* First, subtract j from i, conditioning the C flag */
        "sub %0, %1    \n\t"
 
        /* Now test the C flag.
        If C is clear, we branch around a load of 0x00 into i.
        If C is set, we go ahead and load 0x00 into i.
        */
        "brcc L_%=     \n\t"
        "ldi %0, 0x00  \n\t"
        "L_%=: "
        : "+d"(i) // r16-r31, restricted by ldi
        : "r"(j));
    return i;
#else
#error "No implementation for qsub8 available."
#endif
}

References LIB8STATIC_ALWAYS_INLINE.

Referenced by coolLikeIncandescent(), fl::TwinkleFox::coolLikeIncandescentFunction(), fl::Fire2012::draw(), fillnoise8(), fl::NoisePalette::fillnoise8(), Fire2012(), Fire2012WithPalette(), getPaletteIndex(), getPaletteIndex(), operator-(), CRGB::operator-=(), rgb2hsv_approximate(), and CRGB::subtractFromRGB().

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