/* -*- c++ -*- */
/*
 * Copyright 2018 Free Software Foundation, Inc.
 *
 * This file is part of VOLK
 *
 * SPDX-License-Identifier: LGPL-3.0-or-later
 */

/*!
 * \page volk_32u_reverse_32u
 *
 * \b bit reversal of the input 32 bit word

 * <b>Dispatcher Prototype</b>
 * \code volk_32u_reverse_32u(uint32_t *outputVector, uint32_t *inputVector; unsigned int
 num_points);
 * \endcode
 *
 * \b Inputs
 * \li inputVector: The input vector
 * \li num_points The number of data points.
 *
 * \b Outputs
 * \li outputVector: The vector where the results will be stored, which is the
 bit-reversed input
 *
 * \endcode
 */
#ifndef INCLUDED_VOLK_32u_REVERSE_32u_U_H
struct dword_split {
    int b00 : 1;
    int b01 : 1;
    int b02 : 1;
    int b03 : 1;
    int b04 : 1;
    int b05 : 1;
    int b06 : 1;
    int b07 : 1;
    int b08 : 1;
    int b09 : 1;
    int b10 : 1;
    int b11 : 1;
    int b12 : 1;
    int b13 : 1;
    int b14 : 1;
    int b15 : 1;
    int b16 : 1;
    int b17 : 1;
    int b18 : 1;
    int b19 : 1;
    int b20 : 1;
    int b21 : 1;
    int b22 : 1;
    int b23 : 1;
    int b24 : 1;
    int b25 : 1;
    int b26 : 1;
    int b27 : 1;
    int b28 : 1;
    int b29 : 1;
    int b30 : 1;
    int b31 : 1;
};
struct char_split {
    uint8_t b00 : 1;
    uint8_t b01 : 1;
    uint8_t b02 : 1;
    uint8_t b03 : 1;
    uint8_t b04 : 1;
    uint8_t b05 : 1;
    uint8_t b06 : 1;
    uint8_t b07 : 1;
};

// Idea from "Bit Twiddling Hacks", which dedicates this method to public domain
// http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
static const unsigned char BitReverseTable256[] = {
    0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, 0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0,
    0x70, 0xF0, 0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8, 0x18, 0x98, 0x58, 0xD8,
    0x38, 0xB8, 0x78, 0xF8, 0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4, 0x14, 0x94,
    0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4, 0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
    0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC, 0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2,
    0x62, 0xE2, 0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2, 0x0A, 0x8A, 0x4A, 0xCA,
    0x2A, 0xAA, 0x6A, 0xEA, 0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA, 0x06, 0x86,
    0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6, 0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
    0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, 0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE,
    0x7E, 0xFE, 0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1, 0x11, 0x91, 0x51, 0xD1,
    0x31, 0xB1, 0x71, 0xF1, 0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, 0x19, 0x99,
    0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9, 0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
    0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5, 0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD,
    0x6D, 0xED, 0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD, 0x03, 0x83, 0x43, 0xC3,
    0x23, 0xA3, 0x63, 0xE3, 0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3, 0x0B, 0x8B,
    0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, 0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
    0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7, 0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7,
    0x77, 0xF7, 0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 0x1F, 0x9F, 0x5F, 0xDF,
    0x3F, 0xBF, 0x7F, 0xFF
};
#ifdef LV_HAVE_GENERIC
static inline void volk_32u_reverse_32u_dword_shuffle(uint32_t* out,
                                                      const uint32_t* in,
                                                      unsigned int num_points)
{
    const struct dword_split* in_ptr = (const struct dword_split*)in;
    struct dword_split* out_ptr = (struct dword_split*)out;
    unsigned int number = 0;
    for (; number < num_points; ++number) {
        out_ptr->b00 = in_ptr->b31;
        out_ptr->b01 = in_ptr->b30;
        out_ptr->b02 = in_ptr->b29;
        out_ptr->b03 = in_ptr->b28;
        out_ptr->b04 = in_ptr->b27;
        out_ptr->b05 = in_ptr->b26;
        out_ptr->b06 = in_ptr->b25;
        out_ptr->b07 = in_ptr->b24;
        out_ptr->b08 = in_ptr->b23;
        out_ptr->b09 = in_ptr->b22;
        out_ptr->b10 = in_ptr->b21;
        out_ptr->b11 = in_ptr->b20;
        out_ptr->b12 = in_ptr->b19;
        out_ptr->b13 = in_ptr->b18;
        out_ptr->b14 = in_ptr->b17;
        out_ptr->b15 = in_ptr->b16;
        out_ptr->b16 = in_ptr->b15;
        out_ptr->b17 = in_ptr->b14;
        out_ptr->b18 = in_ptr->b13;
        out_ptr->b19 = in_ptr->b12;
        out_ptr->b20 = in_ptr->b11;
        out_ptr->b21 = in_ptr->b10;
        out_ptr->b22 = in_ptr->b09;
        out_ptr->b23 = in_ptr->b08;
        out_ptr->b24 = in_ptr->b07;
        out_ptr->b25 = in_ptr->b06;
        out_ptr->b26 = in_ptr->b05;
        out_ptr->b27 = in_ptr->b04;
        out_ptr->b28 = in_ptr->b03;
        out_ptr->b29 = in_ptr->b02;
        out_ptr->b30 = in_ptr->b01;
        out_ptr->b31 = in_ptr->b00;
        ++in_ptr;
        ++out_ptr;
    }
}
#endif /* LV_HAVE_GENERIC */

#ifdef LV_HAVE_GENERIC
static inline void volk_32u_reverse_32u_byte_shuffle(uint32_t* out,
                                                     const uint32_t* in,
                                                     unsigned int num_points)
{
    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;
    unsigned int number = 0;
    for (; number < num_points; ++number) {
        const struct char_split* in8 = (const struct char_split*)in_ptr;
        struct char_split* out8 = (struct char_split*)out_ptr;

        out8[3].b00 = in8[0].b07;
        out8[3].b01 = in8[0].b06;
        out8[3].b02 = in8[0].b05;
        out8[3].b03 = in8[0].b04;
        out8[3].b04 = in8[0].b03;
        out8[3].b05 = in8[0].b02;
        out8[3].b06 = in8[0].b01;
        out8[3].b07 = in8[0].b00;

        out8[2].b00 = in8[1].b07;
        out8[2].b01 = in8[1].b06;
        out8[2].b02 = in8[1].b05;
        out8[2].b03 = in8[1].b04;
        out8[2].b04 = in8[1].b03;
        out8[2].b05 = in8[1].b02;
        out8[2].b06 = in8[1].b01;
        out8[2].b07 = in8[1].b00;

        out8[1].b00 = in8[2].b07;
        out8[1].b01 = in8[2].b06;
        out8[1].b02 = in8[2].b05;
        out8[1].b03 = in8[2].b04;
        out8[1].b04 = in8[2].b03;
        out8[1].b05 = in8[2].b02;
        out8[1].b06 = in8[2].b01;
        out8[1].b07 = in8[2].b00;

        out8[0].b00 = in8[3].b07;
        out8[0].b01 = in8[3].b06;
        out8[0].b02 = in8[3].b05;
        out8[0].b03 = in8[3].b04;
        out8[0].b04 = in8[3].b03;
        out8[0].b05 = in8[3].b02;
        out8[0].b06 = in8[3].b01;
        out8[0].b07 = in8[3].b00;
        ++in_ptr;
        ++out_ptr;
    }
}
#endif /* LV_HAVE_GENERIC */

// Idea from "Bit Twiddling Hacks", which dedicates this method to public domain
// http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
#ifdef LV_HAVE_GENERIC
static inline void
volk_32u_reverse_32u_lut(uint32_t* out, const uint32_t* in, unsigned int num_points)
{
    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;
    unsigned int number = 0;
    for (; number < num_points; ++number) {
        *out_ptr = (BitReverseTable256[*in_ptr & 0xff] << 24) |
                   (BitReverseTable256[(*in_ptr >> 8) & 0xff] << 16) |
                   (BitReverseTable256[(*in_ptr >> 16) & 0xff] << 8) |
                   (BitReverseTable256[(*in_ptr >> 24) & 0xff]);
        ++in_ptr;
        ++out_ptr;
    }
}
#endif /* LV_HAVE_GENERIC */

// Single-Byte code from "Bit Twiddling Hacks", which dedicates this method to public
// domain http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith64Bits
#ifdef LV_HAVE_GENERIC
static inline void
volk_32u_reverse_32u_2001magic(uint32_t* out, const uint32_t* in, unsigned int num_points)
{
    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;
    const uint8_t* in8;
    uint8_t* out8;
    unsigned int number = 0;
    for (; number < num_points; ++number) {
        in8 = (const uint8_t*)in_ptr;
        out8 = (uint8_t*)out_ptr;
        out8[3] = ((in8[0] * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
        out8[2] = ((in8[1] * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
        out8[1] = ((in8[2] * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
        out8[0] = ((in8[3] * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
        ++in_ptr;
        ++out_ptr;
    }
}
#endif /* LV_HAVE_GENERIC */

#ifdef LV_HAVE_GENERIC
// Current gr-pager implementation
static inline void
volk_32u_reverse_32u_1972magic(uint32_t* out, const uint32_t* in, unsigned int num_points)
{
    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;
    const uint8_t* in8;
    uint8_t* out8;
    unsigned int number = 0;
    for (; number < num_points; ++number) {
        in8 = (const uint8_t*)in_ptr;
        out8 = (uint8_t*)out_ptr;
        out8[3] = (in8[0] * 0x0202020202ULL & 0x010884422010ULL) % 1023;
        out8[2] = (in8[1] * 0x0202020202ULL & 0x010884422010ULL) % 1023;
        out8[1] = (in8[2] * 0x0202020202ULL & 0x010884422010ULL) % 1023;
        out8[0] = (in8[3] * 0x0202020202ULL & 0x010884422010ULL) % 1023;
        ++in_ptr;
        ++out_ptr;
    }
}
#endif /* LV_HAVE_GENERIC */

// After lengthy thought and quite a bit of whiteboarding:
#ifdef LV_HAVE_GENERIC
static inline void volk_32u_reverse_32u_bintree_permute_top_down(uint32_t* out,
                                                                 const uint32_t* in,
                                                                 unsigned int num_points)
{
    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;
    unsigned int number = 0;
    for (; number < num_points; ++number) {
        uint32_t tmp = *in_ptr;
        /* permute uint16:
           The idea is to simply shift the lower 16 bit up, and the upper 16 bit down.
         */
        tmp = (tmp << 16) | (tmp >> 16);
        /* permute bytes:
           shift up by 1 B first, then only consider even bytes, and OR with the unshifted
           even bytes
         */
        tmp = ((tmp & (0xFF | 0xFF << 16)) << 8) | ((tmp >> 8) & (0xFF | 0xFF << 16));
        /* permute 4bit tuples:
           Same idea, but the "consideration" mask expression becomes unwieldy
         */
        tmp = ((tmp & (0xF | 0xF << 8 | 0xF << 16 | 0xF << 24)) << 4) |
              ((tmp >> 4) & (0xF | 0xF << 8 | 0xF << 16 | 0xF << 24));
        /* permute 2bit tuples:
           Here, we collapsed the "consideration" mask to a simple hexmask: 0b0011 =
           3; we need those every 4b, which coincides with a hex digit!
        */
        tmp = ((tmp & (0x33333333)) << 2) | ((tmp >> 2) & (0x33333333));
        /* permute odd/even:
           0x01 = 0x1;  we need these every 2b, which works out: 0x01 | (0x01 << 2) =
           0x05!
         */
        tmp = ((tmp & (0x55555555)) << 1) | ((tmp >> 1) & (0x55555555));

        *out_ptr = tmp;
        ++in_ptr;
        ++out_ptr;
    }
}
#endif /* LV_HAVE_GENERIC */
#ifdef LV_HAVE_GENERIC
static inline void volk_32u_reverse_32u_bintree_permute_bottom_up(uint32_t* out,
                                                                  const uint32_t* in,
                                                                  unsigned int num_points)
{
    // same stuff as top_down, inverted order (permutation matrices don't care, you know!)
    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;
    unsigned int number = 0;
    for (; number < num_points; ++number) {
        uint32_t tmp = *in_ptr;
        tmp = ((tmp & (0x55555555)) << 1) | ((tmp >> 1) & (0x55555555));
        tmp = ((tmp & (0x33333333)) << 2) | ((tmp >> 2) & (0x33333333));
        tmp = ((tmp & (0xF | 0xF << 8 | 0xF << 16 | 0xF << 24)) << 4) |
              ((tmp >> 4) & (0xF | 0xF << 8 | 0xF << 16 | 0xF << 24));
        tmp = ((tmp & (0xFF | 0xFF << 16)) << 8) | ((tmp >> 8) & (0xFF | 0xFF << 16));
        tmp = (tmp << 16) | (tmp >> 16);

        *out_ptr = tmp;
        ++in_ptr;
        ++out_ptr;
    }
}
#endif /* LV_HAVE_GENERIC */

#ifdef LV_HAVE_NEONV8
#include <arm_neon.h>

static inline void
volk_32u_reverse_32u_neonv8(uint32_t* out, const uint32_t* in, unsigned int num_points)
{
    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;

    const uint8x16_t idx = { 3, 2, 1, 0, 7, 6, 5, 4, 11, 10, 9, 8, 15, 14, 13, 12 };

    const unsigned int quarterPoints = num_points / 4;
    unsigned int number = 0;
    for (; number < quarterPoints; ++number) {
        __VOLK_PREFETCH(in_ptr + 4);
        uint32x4_t x = vld1q_u32(in_ptr);
        uint32x4_t z =
            vreinterpretq_u32_u8(vqtbl1q_u8(vrbitq_u8(vreinterpretq_u8_u32(x)), idx));
        vst1q_u32(out_ptr, z);
        in_ptr += 4;
        out_ptr += 4;
    }
    number = quarterPoints * 4;
    for (; number < num_points; ++number) {
        *out_ptr = (BitReverseTable256[*in_ptr & 0xff] << 24) |
                   (BitReverseTable256[(*in_ptr >> 8) & 0xff] << 16) |
                   (BitReverseTable256[(*in_ptr >> 16) & 0xff] << 8) |
                   (BitReverseTable256[(*in_ptr >> 24) & 0xff]);
        ++in_ptr;
        ++out_ptr;
    }
}

#else
#ifdef LV_HAVE_NEON
#include <arm_neon.h>

#define DO_RBIT                           \
    __VOLK_ASM("rbit %[result], %[value]" \
               : [result] "=r"(*out_ptr)  \
               : [value] "r"(*in_ptr)     \
               :);                        \
    in_ptr++;                             \
    out_ptr++;

static inline void
volk_32u_reverse_32u_arm(uint32_t* out, const uint32_t* in, unsigned int num_points)
{

    const uint32_t* in_ptr = in;
    uint32_t* out_ptr = out;
    const unsigned int eighthPoints = num_points / 8;
    unsigned int number = 0;
    for (; number < eighthPoints; ++number) {
        __VOLK_PREFETCH(in_ptr + 8);
        DO_RBIT;
        DO_RBIT;
        DO_RBIT;
        DO_RBIT;
        DO_RBIT;
        DO_RBIT;
        DO_RBIT;
        DO_RBIT;
    }
    number = eighthPoints * 8;
    for (; number < num_points; ++number) {
        DO_RBIT;
    }
}
#undef DO_RBIT
#endif /* LV_HAVE_NEON */
#endif /* LV_HAVE_NEONV8 */


#endif /* INCLUDED_volk_32u_reverse_32u_u_H */
