wave8_transpose_4_bf1()

FASTLED_FORCE_INLINE FL_IRAM FL_OPTIMIZE_FUNCTION void fl::detail::wave8_transpose_4_bf1	(	const u8	lanes[4],
		u8	W0,
		u8	W1,
		u8	output[4 *sizeof(Wave8Byte)] )

BF1 for 4-lane Wave8.

Output: 8 symbols × 4 bytes = 32 bytes. Each byte packs 2 pulses × 4 lanes — high nibble = earlier pulse, low nibble = later pulse; within each nibble, lanes 0..3 in bits 0..3.

Definition at line 370 of file wave8.hpp.

                                                             {
    u8 d_mask[8];
    u8 m0_mask[8];
    const u8 D_byte = W0 ^ W1;
    for (int p = 0; p < 8; ++p) {
        const int shift = 7 - p;
        d_mask[p] = ((D_byte >> shift) & 1) ? 0xFFu : 0x00u;
        m0_mask[p] = ((W0 >> shift) & 1) ? 0xFFu : 0x00u;
    }
    // Bit transpose: cols[s] (low nibble) = bit(7-s) of lanes 0..3.
    // spreadA(lanes[L]) puts the 4 high-nibble bits of lanes[L] into bit 0 of
    // 4 separate bytes; OR'd across lanes with shifts gives 4 bytes (cols[0..3]).
    const u32 aLo = spreadA(lanes[0]) | (spreadA(lanes[1]) << 1)
                  | (spreadA(lanes[2]) << 2) | (spreadA(lanes[3]) << 3);
    const u32 bLo = spreadB(lanes[0]) | (spreadB(lanes[1]) << 1)
                  | (spreadB(lanes[2]) << 2) | (spreadB(lanes[3]) << 3);
    u8 cols[8];
    cols[0] = static_cast<u8>(aLo);
    cols[1] = static_cast<u8>(aLo >> 8);
    cols[2] = static_cast<u8>(aLo >> 16);
    cols[3] = static_cast<u8>(aLo >> 24);
    cols[4] = static_cast<u8>(bLo);
    cols[5] = static_cast<u8>(bLo >> 8);
    cols[6] = static_cast<u8>(bLo >> 16);
    cols[7] = static_cast<u8>(bLo >> 24);
    for (int s = 0; s < 8; ++s) {
        const u8 col = cols[s];  // bits 0..3 = lanes 0..3
        for (int k = 0; k < 4; ++k) {
            const int p_hi = 2 * k;
            const int p_lo = 2 * k + 1;
            const u8 hi = static_cast<u8>((m0_mask[p_hi] & 0xF0u) ^ ((col << 4) & d_mask[p_hi]));
            const u8 lo = static_cast<u8>((m0_mask[p_lo] & 0x0Fu) ^ (col & d_mask[p_lo]));
            output[s * 4 + k] = static_cast<u8>(hi | lo);
        }
    }
}

References spreadA(), spreadB(), fl::W0, and fl::W1.

Referenced by fl::wave8Transpose_4_bf1().

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