leddisplay/libraries/FastLED/bitswap.cpp

29 lines
939 B
C++
Raw Normal View History

2018-10-13 22:34:06 +02:00
#define FASTLED_INTERNAL
#include "FastLED.h"
/// Simplified form of bits rotating function. Based on code found here - http://www.hackersdelight.org/hdcodetxt/transpose8.c.txt - rotating
/// data into LSB for a faster write (the code using this data can happily walk the array backwards)
void transpose8x1_noinline(unsigned char *A, unsigned char *B) {
uint32_t x, y, t;
// Load the array and pack it into x and y.
y = *(unsigned int*)(A);
x = *(unsigned int*)(A+4);
// pre-transform x
t = (x ^ (x >> 7)) & 0x00AA00AA; x = x ^ t ^ (t << 7);
t = (x ^ (x >>14)) & 0x0000CCCC; x = x ^ t ^ (t <<14);
// pre-transform y
t = (y ^ (y >> 7)) & 0x00AA00AA; y = y ^ t ^ (t << 7);
t = (y ^ (y >>14)) & 0x0000CCCC; y = y ^ t ^ (t <<14);
// final transform
t = (x & 0xF0F0F0F0) | ((y >> 4) & 0x0F0F0F0F);
y = ((x << 4) & 0xF0F0F0F0) | (y & 0x0F0F0F0F);
x = t;
*((uint32_t*)B) = y;
*((uint32_t*)(B+4)) = x;
}