scale8_LEAVING_R1_DIRTY()

LIB8STATIC_ALWAYS_INLINE uint8_t scale8_LEAVING_R1_DIRTY	(	uint8_t	i,
		fract8	scale )

This version of scale8() does not clean up the R1 register on AVR.

If you are doing several "scale8()'s" in a row, use this, and then explicitly call cleanup_R1().

Warning

You MUST call cleanup_R1() after using this function!

Parameters

i	input value to scale
scale	scale factor, in n/256 units

Returns

scaled value

See also

scale8()

Definition at line 170 of file scale8.h.

                                                                       {
#if SCALE8_C == 1
#if (FASTLED_SCALE8_FIXED == 1)
    return (((uint16_t)i) * ((uint16_t)(scale) + 1)) >> 8;
#else
    return ((int)i * (int)(scale)) >> 8;
#endif
#elif SCALE8_AVRASM == 1
    asm volatile(
#if (FASTLED_SCALE8_FIXED == 1)
        // Multiply 8-bit i * 8-bit scale, giving 16-bit r1,r0
        "mul %0, %1          \n\t"
        // Add i to r0, possibly setting the carry flag
        "add r0, %0         \n\t"
        // load the immediate 0 into i (note, this does _not_ touch any flags)
        "ldi %0, 0x00       \n\t"
        // walk and chew gum at the same time
        "adc %0, r1          \n\t"
#else
        /* Multiply 8-bit i * 8-bit scale, giving 16-bit r1,r0 */
        "mul %0, %1    \n\t"
        /* Move the high 8-bits of the product (r1) back to i */
        "mov %0, r1    \n\t"
#endif
        /* R1 IS LEFT DIRTY HERE; YOU MUST ZERO IT OUT YOURSELF  */
        /* "clr __zero_reg__    \n\t" */
        : "+d"(i)    /* writes to i; r16-r31, restricted by ldi */
        : "r"(scale) /* uses scale */
        : "r0", "r1" /* clobbers r0, r1 */
    );
    // Return the result
    return i;
#else
#error "No implementation for scale8_LEAVING_R1_DIRTY available."
#endif
}

References LIB8STATIC_ALWAYS_INLINE, and scale.

Referenced by blend8(), ColorFromPalette(), ColorFromPalette(), ColorFromPalette(), ColorFromPalette(), ColorFromPalette(), ColorFromPalette(), ColorFromPaletteExtended(), ColorFromPaletteExtended(), ColorFromPaletteExtended(), ease8InOutCubic(), fadeUsingColor(), CRGB::getAverageLight(), CRGB::getLuma(), hsv2rgb_rainbow(), MyColorFromPaletteExtended(), nblend(), nblend(), nscale8x2(), and nscale8x3().

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