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73 lines
1.8 KiB
C++
73 lines
1.8 KiB
C++
//
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// TapePRG.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 14/08/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "TapePRG.hpp"
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#include <sys/stat.h>
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using namespace Storage;
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TapePRG::TapePRG(const char *file_name) : _file(nullptr), _bitPhase(3)
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{
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struct stat file_stats;
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stat(file_name, &file_stats);
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// There's really no way to validate other than that if this file is larger than 64kb,
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// of if load address + length > 65536 then it's broken.
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if(file_stats.st_size >= 65538 || file_stats.st_size < 3)
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throw ErrorBadFormat;
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_file = fopen(file_name, "rb");
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if(!_file) throw ErrorBadFormat;
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_load_address = (uint16_t)fgetc(_file);
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_load_address |= (uint16_t)fgetc(_file) << 8;
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if (_load_address + file_stats.st_size >= 65536)
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throw ErrorBadFormat;
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}
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TapePRG::~TapePRG()
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{
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if(_file) fclose(_file);
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}
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Tape::Pulse TapePRG::get_next_pulse()
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{
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static const unsigned int leader_zero_length = 179;
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static const unsigned int zero_length = 169;
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static const unsigned int one_length = 247;
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static const unsigned int word_marker_length = 328;
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_bitPhase = (_bitPhase+1)&3;
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if(!_bitPhase) get_next_output_token();
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Tape::Pulse pulse;
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switch(_outputToken)
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{
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case Leader: pulse.length.length = leader_zero_length; break;
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case Zero: pulse.length.length = (_bitPhase&2) ? one_length : zero_length; break;
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case One: pulse.length.length = (_bitPhase&2) ? zero_length : one_length; break;
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case WordMarker: pulse.length.length = (_bitPhase&2) ? one_length : word_marker_length; break;
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}
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pulse.length.clock_rate = 1000000;
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pulse.type = (_bitPhase&1) ? Pulse::Low : Pulse::High;
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return pulse;
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}
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void TapePRG::reset()
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{
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_bitPhase = 3;
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fseek(_file, 2, SEEK_SET);
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}
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void TapePRG::get_next_output_token()
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{
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_outputToken = Leader;
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}
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