mirror of https://github.com/gnss-sdr/gnss-sdr
120 lines
3.9 KiB
C++
120 lines
3.9 KiB
C++
/*!
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* \file unpack_2bit_samples.h
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*
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* \brief Unpacks 2 bit samples
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* samples may be packed in any of the following ways:
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* 1) Into bytes [ item == byte ]
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* 1a) Big endian ordering within the byte
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* 1b) Little endian ordering within the byte
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* 2) Into shorts [ item == short ]
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* 2a) Big endian ordering of bytes, big endian within the byte
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* 2b) Big endian ordering of bytes, little endian within the byte
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* 2c) Little endian ordering of bytes, big endian within the byte
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* 2d) Little endian ordering of bytes, little endian within the byte
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*
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* Within a byte the two possibilities look like this:
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* 7 6 5 4 3 2 1 0 : Bit number
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* x_n,1 x_n,0 x_n+1,1 x_n+1,0 x_n+2,1 x_n+2,0 x_n+3,1 x_n+3,0 : Little endian
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* x_n+3,1 x_n+3,0 x_n+2,1 x_n+2,0 x_n+1,0 x_n+1,0 x_n,1 x_n, 0 : Big Endian
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*
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* For a short (uint16_t) the bytes are either transmitted as follows:
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*
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* 1 0 : Byte number
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* Byte_n Byte_n+1 : Little endian
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* Byte_n+1 Byte_n : Bit endian
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*
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* The two bit values are assumed to have the following mapping:
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*
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* x_1 x_0 Value
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* 0 0 +1
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* 0 1 +3
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* 1 0 -3
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* 1 1 -1
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*
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* Letting x denote the two's complement interpretation of x_1 x_0, then:
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*
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* Value = 2*x + 1
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*
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* We want to output the data in the order:
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*
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* Value_0, Value_1, Value_2, ..., Value_n, Value_n+1, Value_n+2, ...
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*
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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) 2010-2018 (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 <https://www.gnu.org/licenses/>.
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*
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* -------------------------------------------------------------------------
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*/
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#ifndef GNSS_SDR_UNPACK_2BIT_SAMPLES_H
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#define GNSS_SDR_UNPACK_2BIT_SAMPLES_H
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#include <gnuradio/sync_interpolator.h>
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#include <cstdint>
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class unpack_2bit_samples;
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using unpack_2bit_samples_sptr = boost::shared_ptr<unpack_2bit_samples>;
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unpack_2bit_samples_sptr make_unpack_2bit_samples(
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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 = false);
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/*!
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* \brief This class takes 2 bit samples that have been packed into bytes or
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* shorts as input and generates a byte for each sample. It generates eight
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* times as much data as is input (every two bits become 16 bits)
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*/
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class unpack_2bit_samples : public gr::sync_interpolator
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{
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public:
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~unpack_2bit_samples();
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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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int 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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private:
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friend unpack_2bit_samples_sptr make_unpack_2bit_samples_sptr(
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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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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 swap_endian_items_;
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bool swap_endian_bytes_;
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bool reverse_interleaving_;
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std::vector<int8_t> work_buffer_;
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};
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#endif
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