mirror of
https://github.com/gnss-sdr/gnss-sdr
synced 2024-06-28 16:03:15 +00:00
226 lines
7.8 KiB
C++
226 lines
7.8 KiB
C++
/*!
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* \file unpack_2bit_samples.cc
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*
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* \brief Unpacks 2 bit samples that have been packed into bytes or shorts
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* \author Cillian O'Driscoll cillian.odriscoll (at) gmail.com
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2015 (see AUTHORS file for a list of contributors)
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*
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* GNSS-SDR is a software defined Global Navigation
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* Satellite Systems receiver
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*
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* This file is part of GNSS-SDR.
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*
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* GNSS-SDR is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GNSS-SDR is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
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*
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* -------------------------------------------------------------------------
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*/
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#include "unpack_2bit_samples.h"
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#include <gnuradio/io_signature.h>
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struct byte_2bit_struct
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{
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signed sample_0:2; // <- 2 bits wide only
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signed sample_1:2; // <- 2 bits wide only
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signed sample_2:2; // <- 2 bits wide only
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signed sample_3:2; // <- 2 bits wide only
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};
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union byte_and_samples
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{
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int8_t byte;
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byte_2bit_struct samples;
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};
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bool systemIsBigEndian()
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{
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union
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{
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uint32_t i;
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char c[4];
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} test_int = {0x01020304};
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return test_int.c[0] == 1;
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}
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bool systemBytesAreBigEndian()
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{
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byte_and_samples b;
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b.byte = static_cast<int8_t>(0x01);
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if(*(char *)&b.byte == 1) return false;
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else return true;
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}
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void swapEndianness( int8_t const *in, std::vector< int8_t > &out, size_t item_size, unsigned int ninput_items )
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{
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unsigned int i;
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unsigned int j = 0;
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int k = 0;
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int l = 0;
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size_t skip = item_size - 1;
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for( i = 0; i < ninput_items; ++i )
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{
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k = j + skip;
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l = j;
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while( k >= l )
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{
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out[j++] = in[k--];
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}
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}
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}
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unpack_2bit_samples_sptr make_unpack_2bit_samples( bool big_endian_bytes,
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size_t item_size,
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bool big_endian_items,
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bool reverse_interleaving )
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{
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return unpack_2bit_samples_sptr(
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new unpack_2bit_samples( big_endian_bytes,
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item_size,
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big_endian_items,
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reverse_interleaving )
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);
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}
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unpack_2bit_samples::unpack_2bit_samples( bool big_endian_bytes,
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size_t item_size,
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bool big_endian_items,
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bool reverse_interleaving )
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: sync_interpolator("unpack_2bit_samples",
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gr::io_signature::make(1, 1, item_size),
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gr::io_signature::make(1, 1, sizeof(char)),
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4*item_size ), // we make 4 bytes out for every byte in
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big_endian_bytes_(big_endian_bytes),
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item_size_(item_size),
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big_endian_items_(big_endian_items),
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swap_endian_items_(false),
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reverse_interleaving_(reverse_interleaving)
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{
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bool big_endian_system = systemIsBigEndian();
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// Only swap the item bytes if the item size > 1 byte and the system
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// endianess is not the same as the item endianness:
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swap_endian_items_ = ( item_size_ > 1 ) &&
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( big_endian_system != big_endian_items);
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bool big_endian_bytes_system = systemBytesAreBigEndian();
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swap_endian_bytes_ = ( big_endian_bytes_system != big_endian_bytes_ );
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}
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unpack_2bit_samples::~unpack_2bit_samples()
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{}
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int unpack_2bit_samples::work(int noutput_items,
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gr_vector_const_void_star &input_items,
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gr_vector_void_star &output_items)
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{
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signed char const *in = reinterpret_cast<signed char const *>(input_items[0]);
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int8_t *out = reinterpret_cast<int8_t*>(output_items[0]);
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size_t ninput_bytes = noutput_items/4;
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size_t ninput_items = ninput_bytes/item_size_;
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// Handle endian swap if needed
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if( swap_endian_items_ )
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{
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work_buffer_.reserve( ninput_bytes );
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swapEndianness( in, work_buffer_, item_size_, ninput_items );
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in = const_cast< signed char const *> ( &work_buffer_[0] );
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}
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// Here the in pointer can be interpreted as a stream of bytes to be
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// converted. But we now have two possibilities:
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// 1) The samples in a byte are in big endian order
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// 2) The samples in a byte are in little endian order
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byte_and_samples raw_byte;
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int n = 0;
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if( !reverse_interleaving_ )
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{
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if( swap_endian_bytes_ )
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{
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for(unsigned int i = 0; i < ninput_bytes; ++i)
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{
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// Read packed input sample (1 byte = 4 samples)
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raw_byte.byte = in[i];
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_3 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_2 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_1 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_0 + 1 );
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}
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}
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else
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{
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for(unsigned int i = 0; i < ninput_bytes; ++i )
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{
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// Read packed input sample (1 byte = 4 samples)
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raw_byte.byte = in[i];
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_0 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_1 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_2 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_3 + 1 );
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}
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}
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}
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else
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{
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if( swap_endian_bytes_ )
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{
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for(unsigned int i = 0; i < ninput_bytes; ++i)
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{
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// Read packed input sample (1 byte = 4 samples)
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raw_byte.byte = in[i];
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_2 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_3 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_0 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_1 + 1 );
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}
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}
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else
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{
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for(unsigned int i = 0; i < ninput_bytes; ++i )
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{
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// Read packed input sample (1 byte = 4 samples)
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raw_byte.byte = in[i];
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_1 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_0 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_3 + 1 );
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out[n++] = static_cast<int8_t>( 2*raw_byte.samples.sample_2 + 1 );
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}
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}
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}
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return noutput_items;
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}
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