nscale8_video_LEAVING_R1_DIRTY()

LIB8STATIC_ALWAYS_INLINE void nscale8_video_LEAVING_R1_DIRTY	(	uint8_t &	i,
		fract8	scale )

In place modifying version of scale8_video() that does not clean up the R1 register on AVR.

If you are doing several "scale8_video()'s" in a row, use this, and then explicitly call cleanup_R1().

Warning

You MUST call cleanup_R1() after using this function!

Warning

This function always modifies its arguments in place!

Parameters

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

See also

scale8_video()

Definition at line 321 of file scale8.h.

                                                                           {
#if SCALE8_C == 1 || defined(LIB8_ATTINY)
    i = (((int)i * (int)scale) >> 8) + ((i && scale) ? 1 : 0);
#elif SCALE8_AVRASM == 1
    asm volatile("  tst %[i]\n\t"
                 "  breq L_%=\n\t"
                 "  mul %[i], %[scale]\n\t"
                 "  mov %[i], r1\n\t"
                 "  breq L_%=\n\t"
                 "  subi %[i], 0xFF\n\t"
                 "L_%=: \n\t"
                 : [i] "+d"(i) // r16-r31, restricted by subi
                 : [scale] "r"(scale)
                 : "r0", "r1");
#else
#error "No implementation for scale8_video_LEAVING_R1_DIRTY available."
#endif
}

References LIB8STATIC_ALWAYS_INLINE, and scale.

Referenced by nscale8x2_video(), and nscale8x3_video().

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