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/*
* Copyright 2004,2006 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* GNU Radio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <pager_flex_deinterleave.h>
#include <pageri_bch3221.h>
#include <pageri_util.h>
#include <gr_io_signature.h>
pager_flex_deinterleave_sptr pager_make_flex_deinterleave()
{
return pager_flex_deinterleave_sptr(new pager_flex_deinterleave());
}
pager_flex_deinterleave::pager_flex_deinterleave() :
gr_sync_decimator("flex_deinterleave",
gr_make_io_signature(1, 1, sizeof(unsigned char)),
gr_make_io_signature(1, 1, sizeof(gr_int32)), 32)
{
set_output_multiple(8); // One FLEX block at a time
}
int pager_flex_deinterleave::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const unsigned char *in = (const unsigned char *)input_items[0];
gr_int32 *out = (gr_int32 *)output_items[0];
// FLEX codewords are interleaved in blocks of 256 bits or 8, 32 bit
// codes. To deinterleave we parcel each incoming bit into the MSB
// of each codeword, then switch to MSB-1, etc. This is done by shifting
// in the bits from the right on each codeword as the bits come in.
// When we are done we have a FLEX block of eight codewords, ready for
// conversion to data words.
//
// FLEX data words are recovered by reversing the bit order of the code
// word, masking off the (reversed) ECC, and inverting the remainder of
// the bits (!).
//
// The data portion of a FLEX frame consists of 11 of these deinterleaved
// and converted blocks.
//
// set_output_multiple garauntees we have output space for at least
// eight data words, and 256 bits are supplied on input
int i, j;
for (i = 0; i < 32; i++) {
for (j = 0; j < 8; j++) {
d_codewords[j] <<= 1;
d_codewords[j] |= *in++;
}
}
// Now convert code words into data words
for (j = 0; j < 8; j++) {
gr_int32 codeword = d_codewords[j];
// Apply BCH 32,21 error correction
// TODO: mark dataword when codeword fails ECC
pageri_bch3221(codeword);
// Reverse bit order
codeword = pageri_reverse_bits32(codeword);
// Mask off ECC then invert lower 21 bits
codeword = (codeword & 0x001FFFFF)^0x001FFFFF;
*out++ = codeword;
}
return j;
}
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