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221 lines
7.0 KiB
C++
221 lines
7.0 KiB
C++
//
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// Disk.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 18/09/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "Disk.hpp"
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#include "../../Storage/Disk/DiskDrive.hpp"
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#include "../../Storage/Disk/Encodings/MFM.hpp"
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#include "../../NumberTheory/CRC.hpp"
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#include <algorithm>
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using namespace StaticAnalyser::Acorn;
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class FMParser: public Storage::Disk::Drive {
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public:
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FMParser() :
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Storage::Disk::Drive(4000000, 1, 300),
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crc_generator_(0x1021, 0xffff),
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shift_register_(0), track_(0)
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{
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// Make sure this drive really is at track '1'.
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while(!get_is_track_zero()) step(-1);
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Storage::Time bit_length;
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bit_length.length = 1;
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bit_length.clock_rate = 250000; // i.e. 250 kbps (including clocks)
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set_expected_bit_length(bit_length);
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}
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/*!
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Attempts to read the sector located at @c track and @c sector.
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@returns a sector if one was found; @c nullptr otherwise.
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*/
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std::shared_ptr<Storage::Encodings::MFM::Sector> get_sector(uint8_t track, uint8_t sector)
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{
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int difference = (int)track - (int)track_;
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track_ = track;
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if(difference)
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{
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int direction = difference < 0 ? -1 : 1;
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difference *= direction;
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for(int c = 0; c < difference; c++) step(direction);
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}
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return get_sector(sector);
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}
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private:
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unsigned int shift_register_;
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int index_count_;
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uint8_t track_;
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int bit_count_;
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std::shared_ptr<Storage::Encodings::MFM::Sector> sector_cache_[65536];
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NumberTheory::CRC16 crc_generator_;
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void process_input_bit(int value, unsigned int cycles_since_index_hole)
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{
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shift_register_ = ((shift_register_ << 1) | (unsigned int)value) & 0xffff;
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bit_count_++;
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}
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void process_index_hole()
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{
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index_count_++;
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}
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uint8_t get_next_byte()
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{
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bit_count_ = 0;
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while(bit_count_ < 16) run_for_cycles(1);
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uint8_t byte = (uint8_t)(
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((shift_register_&0x0001) >> 0) |
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((shift_register_&0x0004) >> 1) |
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((shift_register_&0x0010) >> 2) |
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((shift_register_&0x0040) >> 3) |
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((shift_register_&0x0100) >> 4) |
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((shift_register_&0x0400) >> 5) |
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((shift_register_&0x1000) >> 6) |
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((shift_register_&0x4000) >> 7));
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crc_generator_.add(byte);
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return byte;
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}
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std::shared_ptr<Storage::Encodings::MFM::Sector> get_next_sector()
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{
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std::shared_ptr<Storage::Encodings::MFM::Sector> sector(new Storage::Encodings::MFM::Sector);
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index_count_ = 0;
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while(index_count_ < 2)
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{
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// look for an ID address mark
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while(1)
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{
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run_for_cycles(1);
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if(shift_register_ == Storage::Encodings::MFM::FMIDAddressMark) break;
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if(index_count_ >= 2) return nullptr;
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}
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crc_generator_.reset();
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sector->track = get_next_byte();
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sector->side = get_next_byte();
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sector->sector = get_next_byte();
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uint8_t size = get_next_byte();
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uint16_t header_crc = crc_generator_.get_value();
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if((header_crc >> 8) != get_next_byte()) continue;
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if((header_crc & 0xff) != get_next_byte()) continue;
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// look for data mark
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while(1)
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{
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run_for_cycles(1);
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if(shift_register_ == Storage::Encodings::MFM::FMDataAddressMark) break;
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if(shift_register_ == Storage::Encodings::MFM::FMIDAddressMark) return nullptr;
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if(index_count_ >= 2) return nullptr;
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}
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size_t data_size = (size_t)(128 << size);
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sector->data.reserve(data_size);
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crc_generator_.reset();
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for(size_t c = 0; c < data_size; c++)
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{
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sector->data.push_back(get_next_byte());
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}
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uint16_t data_crc = crc_generator_.get_value();
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if((data_crc >> 8) != get_next_byte()) continue;
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if((data_crc & 0xff) != get_next_byte()) continue;
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return sector;
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}
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return nullptr;
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}
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std::shared_ptr<Storage::Encodings::MFM::Sector> get_sector(uint8_t sector)
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{
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// uint16_t sector_address = (uint16_t)((track_ << 8) | sector);
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// if(sector_cache_[sector_address]) return sector_cache_[sector_address];
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std::shared_ptr<Storage::Encodings::MFM::Sector> first_sector = get_next_sector();
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if(!first_sector) return first_sector;
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if(first_sector->sector == sector) return first_sector;
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while(1)
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{
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std::shared_ptr<Storage::Encodings::MFM::Sector> next_sector = get_next_sector();
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if(next_sector->sector == first_sector->sector) return nullptr;
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if(next_sector->sector == sector) return next_sector;
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}
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}
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};
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std::unique_ptr<Catalogue> StaticAnalyser::Acorn::GetDFSCatalogue(const std::shared_ptr<Storage::Disk::Disk> &disk)
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{
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// c.f. http://beebwiki.mdfs.net/Acorn_DFS_disc_format
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std::unique_ptr<Catalogue> catalogue(new Catalogue);
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FMParser parser;
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parser.set_disk(disk);
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std::shared_ptr<Storage::Encodings::MFM::Sector> names = parser.get_sector(0, 0);
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std::shared_ptr<Storage::Encodings::MFM::Sector> details = parser.get_sector(0, 1);
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if(!names || !details) return catalogue;
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if(names->data.size() != 256 || details->data.size() != 256) return nullptr;
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uint8_t final_file_offset = details->data[5];
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if(final_file_offset&7) return nullptr;
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char disk_name[13];
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snprintf(disk_name, 13, "%.8s%.4s", &names->data[0], &details->data[0]);
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catalogue->name = disk_name;
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switch((details->data[6] >> 4)&3)
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{
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case 0: catalogue->bootOption = Catalogue::BootOption::None; break;
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case 1: catalogue->bootOption = Catalogue::BootOption::LoadBOOT; break;
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case 2: catalogue->bootOption = Catalogue::BootOption::RunBOOT; break;
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case 3: catalogue->bootOption = Catalogue::BootOption::ExecBOOT; break;
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}
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// DFS files are stored contiguously, and listed in descending order of distance from track 0.
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// So iterating backwards implies the least amount of seeking.
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for(size_t file_offset = final_file_offset - 8; file_offset > 0; file_offset -= 8)
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{
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File new_file;
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char name[10];
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snprintf(name, 10, "%c.%.7s", names->data[file_offset + 7] & 0x7f, &names->data[file_offset]);
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new_file.name = name;
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new_file.load_address = (uint32_t)(details->data[file_offset] | (details->data[file_offset+1] << 8) | ((details->data[file_offset+6]&0x0c) << 14));
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new_file.execution_address = (uint32_t)(details->data[file_offset+2] | (details->data[file_offset+3] << 8) | ((details->data[file_offset+6]&0xc0) << 10));
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new_file.is_protected = !!(names->data[file_offset + 7] & 0x80);
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long data_length = (long)(details->data[file_offset+4] | (details->data[file_offset+5] << 8) | ((details->data[file_offset+6]&0x30) << 12));
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int start_sector = details->data[file_offset+7] | ((details->data[file_offset+6]&0x03) << 8);
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new_file.data.reserve((size_t)data_length);
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if(start_sector < 2) continue;
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while(data_length > 0)
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{
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uint8_t sector = (uint8_t)(start_sector % 10);
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uint8_t track = (uint8_t)(start_sector / 10);
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start_sector++;
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std::shared_ptr<Storage::Encodings::MFM::Sector> next_sector = parser.get_sector(track, sector);
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if(!next_sector) break;
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long length_from_sector = std::min(data_length, 256l);
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new_file.data.insert(new_file.data.end(), next_sector->data.begin(), next_sector->data.begin() + length_from_sector);
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data_length -= length_from_sector;
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}
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if(!data_length) catalogue->files.push_front(new_file);
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}
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return catalogue;
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}
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