transpose8()

template<int m, int n>

FASTLED_FORCE_INLINE void transpose8	(	unsigned char *	A,
		unsigned char *	B )

Templated bit-rotating function.

Based on code found here: https://web.archive.org/web/20190108225554/http://www.hackersdelight.org/hdcodetxt/transpose8.c.txt

Definition at line 254 of file bitswap.h.

                                                                         {
  fl::u32 x, y, t;
 
  // Load the array and pack it into x and y.
  if(m == 1) {
    y = *(unsigned int*)(A);
    x = *(unsigned int*)(A+4);
  } else {
    x = (A[0]<<24)   | (A[m]<<16)   | (A[2*m]<<8) | A[3*m];
    y = (A[4*m]<<24) | (A[5*m]<<16) | (A[6*m]<<8) | A[7*m];
  }
 
  // 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;
 
  B[7*n] = y; y >>= 8;
  B[6*n] = y; y >>= 8;
  B[5*n] = y; y >>= 8;
  B[4*n] = y;
 
  B[3*n] = x; x >>= 8;
  B[2*n] = x; x >>= 8;
  B[n] = x; x >>= 8;
  B[0] = x;
  // B[0]=x>>24;    B[n]=x>>16;    B[2*n]=x>>8;  B[3*n]=x>>0;
  // B[4*n]=y>>24;  B[5*n]=y>>16;  B[6*n]=y>>8;  B[7*n]=y>>0;
}

References FASTLED_FORCE_INLINE, t, x, and y.