c2p_core.h

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/*
 *  Fast C2P (Chunky-to-Planar) Conversion
 *
 *  Copyright (C) 2003-2008 Geert Uytterhoeven
 *
 *  NOTES:
 *    - This code was inspired by Scout's C2P tutorial
 *    - It assumes to run on a big endian system
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License. See the file COPYING in the main directory of this archive
 *  for more details.
 */


    /*
     *  Basic transpose step
     */

static inline void _transp(u32 d[], unsigned int i1, unsigned int i2,
               unsigned int shift, u32 mask)
{
    u32 t = (d[i1] ^ (d[i2] >> shift)) & mask;

    d[i1] ^= t;
    d[i2] ^= t << shift;
}


extern void c2p_unsupported(void);

static inline u32 get_mask(unsigned int n)
{
    switch (n) {
    case 1:
        return 0x55555555;

    case 2:
        return 0x33333333;

    case 4:
        return 0x0f0f0f0f;

    case 8:
        return 0x00ff00ff;

    case 16:
        return 0x0000ffff;
    }

    c2p_unsupported();
    return 0;
}


    /*
     *  Transpose operations on 8 32-bit words
     */

static inline void transp8(u32 d[], unsigned int n, unsigned int m)
{
    u32 mask = get_mask(n);

    switch (m) {
    case 1:
        /* First n x 1 block */
        _transp(d, 0, 1, n, mask);
        /* Second n x 1 block */
        _transp(d, 2, 3, n, mask);
        /* Third n x 1 block */
        _transp(d, 4, 5, n, mask);
        /* Fourth n x 1 block */
        _transp(d, 6, 7, n, mask);
        return;

    case 2:
        /* First n x 2 block */
        _transp(d, 0, 2, n, mask);
        _transp(d, 1, 3, n, mask);
        /* Second n x 2 block */
        _transp(d, 4, 6, n, mask);
        _transp(d, 5, 7, n, mask);
        return;

    case 4:
        /* Single n x 4 block */
        _transp(d, 0, 4, n, mask);
        _transp(d, 1, 5, n, mask);
        _transp(d, 2, 6, n, mask);
        _transp(d, 3, 7, n, mask);
        return;
    }

    c2p_unsupported();
}


    /*
     *  Transpose operations on 4 32-bit words
     */

static inline void transp4(u32 d[], unsigned int n, unsigned int m)
{
    u32 mask = get_mask(n);

    switch (m) {
    case 1:
        /* First n x 1 block */
        _transp(d, 0, 1, n, mask);
        /* Second n x 1 block */
        _transp(d, 2, 3, n, mask);
        return;

    case 2:
        /* Single n x 2 block */
        _transp(d, 0, 2, n, mask);
        _transp(d, 1, 3, n, mask);
        return;
    }

    c2p_unsupported();
}


    /*
     *  Transpose operations on 4 32-bit words (reverse order)
     */

static inline void transp4x(u32 d[], unsigned int n, unsigned int m)
{
    u32 mask = get_mask(n);

    switch (m) {
    case 2:
        /* Single n x 2 block */
        _transp(d, 2, 0, n, mask);
        _transp(d, 3, 1, n, mask);
        return;
    }

    c2p_unsupported();
}


    /*
     *  Compose two values, using a bitmask as decision value
     *  This is equivalent to (a & mask) | (b & ~mask)
     */

static inline u32 comp(u32 a, u32 b, u32 mask)
{
    return ((a ^ b) & mask) ^ b;
}