encode_rs.c

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/*
 * lib/reed_solomon/encode_rs.c
 *
 * Overview:
 *   Generic Reed Solomon encoder / decoder library
 *
 * Copyright 2002, Phil Karn, KA9Q
 * May be used under the terms of the GNU General Public License (GPL)
 *
 * Adaption to the kernel by Thomas Gleixner ([email protected])
 *
 * $Id: encode_rs.c,v 1.5 2005/11/07 11:14:59 gleixner Exp $
 *
 */

/* Generic data width independent code which is included by the
 * wrappers.
 * int encode_rsX (struct rs_control *rs, uintX_t *data, int len, uintY_t *par)
 */
{
    int i, j, pad;
    int nn = rs->nn;
    int nroots = rs->nroots;
    uint16_t *alpha_to = rs->alpha_to;
    uint16_t *index_of = rs->index_of;
    uint16_t *genpoly = rs->genpoly;
    uint16_t fb;
    uint16_t msk = (uint16_t) rs->nn;

    /* Check length parameter for validity */
    pad = nn - nroots - len;
    if (pad < 0 || pad >= nn)
        return -ERANGE;

    for (i = 0; i < len; i++) {
        fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]];
        /* feedback term is non-zero */
        if (fb != nn) {
            for (j = 1; j < nroots; j++) {
                par[j] ^= alpha_to[rs_modnn(rs, fb +
                             genpoly[nroots - j])];
            }
        }
        /* Shift */
        memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1));
        if (fb != nn) {
            par[nroots - 1] = alpha_to[rs_modnn(rs,
                                fb + genpoly[0])];
        } else {
            par[nroots - 1] = 0;
        }
    }
    return 0;
}