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357 lines
9.9 KiB
C++
357 lines
9.9 KiB
C++
//
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// TZX.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 16/07/2017.
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// Copyright © 2017 Thomas Harte. All rights reserved.
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//
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#include "TZX.hpp"
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using namespace Storage::Tape;
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namespace {
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const unsigned int StandardTZXClock = 3500000;
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const unsigned int TZXClockMSMultiplier = 3500;
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}
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TZX::TZX(const char *file_name) :
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Storage::FileHolder(file_name),
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current_level_(false) {
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// Check for signature followed by a 0x1a
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char identifier[7];
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char signature[] = "ZXTape!";
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fread(identifier, 1, strlen(signature), file_);
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if(memcmp(identifier, signature, strlen(signature))) throw ErrorNotTZX;
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if(fgetc(file_) != 0x1a) throw ErrorNotTZX;
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// Get version number
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uint8_t major_version = (uint8_t)fgetc(file_);
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uint8_t minor_version = (uint8_t)fgetc(file_);
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// Reject if an incompatible version
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if(major_version != 1 || minor_version > 20) throw ErrorNotTZX;
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virtual_reset();
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}
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void TZX::virtual_reset() {
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clear();
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set_is_at_end(false);
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fseek(file_, 0x0a, SEEK_SET);
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// This is a workaround for arguably dodgy ZX80/ZX81 TZXs; they launch straight
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// into data but both machines require a gap before data begins. So impose
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// an initial gap, in the form of a very long wave.
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current_level_ = false;
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post_gap(500);
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}
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void TZX::get_next_pulses() {
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while(empty()) {
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uint8_t chunk_id = (uint8_t)fgetc(file_);
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if(feof(file_)) {
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set_is_at_end(true);
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return;
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}
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// printf("TZX %ld\n", ftell(file_));
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switch(chunk_id) {
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case 0x10: get_standard_speed_data_block(); break;
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case 0x11: get_turbo_speed_data_block(); break;
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case 0x12: get_pure_tone_data_block(); break;
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case 0x13: get_pulse_sequence(); break;
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case 0x14: get_pure_data_block(); break;
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case 0x19: get_generalised_data_block(); break;
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case 0x20: get_pause(); break;
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case 0x21: ignore_group_start(); break;
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case 0x22: ignore_group_end(); break;
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case 0x23: ignore_jump_to_block(); break;
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case 0x24: ignore_loop_start(); break;
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case 0x25: ignore_loop_end(); break;
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case 0x26: ignore_call_sequence(); break;
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case 0x27: ignore_return_from_sequence(); break;
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case 0x28: ignore_select_block(); break;
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case 0x30: ignore_text_description(); break;
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case 0x31: ignore_message_block(); break;
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case 0x33: get_hardware_type(); break;
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default:
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// In TZX each chunk has a different way of stating or implying its length,
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// so there is no route past an unimplemented chunk.
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printf("!!Unknown %02x!!", chunk_id);
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set_is_at_end(true);
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return;
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}
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}
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}
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void TZX::get_generalised_data_block() {
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uint32_t block_length = fgetc32le();
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long endpoint = ftell(file_) + (long)block_length;
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uint16_t pause_after_block = fgetc16le();
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uint32_t total_pilot_symbols = fgetc32le();
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uint8_t maximum_pulses_per_pilot_symbol = (uint8_t)fgetc(file_);
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uint8_t symbols_in_pilot_table = (uint8_t)fgetc(file_);
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uint32_t total_data_symbols = fgetc32le();
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uint8_t maximum_pulses_per_data_symbol = (uint8_t)fgetc(file_);
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uint8_t symbols_in_data_table = (uint8_t)fgetc(file_);
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get_generalised_segment(total_pilot_symbols, maximum_pulses_per_pilot_symbol, symbols_in_pilot_table, false);
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get_generalised_segment(total_data_symbols, maximum_pulses_per_data_symbol, symbols_in_data_table, true);
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post_gap(pause_after_block);
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// This should be unnecessary, but intends to preserve sanity.
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fseek(file_, endpoint, SEEK_SET);
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}
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void TZX::get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_per_symbol, uint8_t number_of_symbols, bool is_data) {
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if(!output_symbols) return;
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// Construct the symbol table.
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struct Symbol {
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uint8_t flags;
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std::vector<uint16_t> pulse_lengths;
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};
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std::vector<Symbol> symbol_table;
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for(int c = 0; c < number_of_symbols; c++) {
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Symbol symbol;
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symbol.flags = (uint8_t)fgetc(file_);
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for(int ic = 0; ic < max_pulses_per_symbol; ic++) {
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symbol.pulse_lengths.push_back(fgetc16le());
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}
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symbol_table.push_back(symbol);
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}
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// Hence produce the output.
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BitStream stream(file_, false);
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int base = 2;
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int bits = 1;
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while(base < number_of_symbols) {
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base <<= 1;
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bits++;
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}
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for(size_t c = 0; c < output_symbols; c++) {
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uint8_t symbol_value;
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int count;
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if(is_data) {
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symbol_value = stream.get_bits(bits);
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count = 1;
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} else {
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symbol_value = (uint8_t)fgetc(file_);
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count = fgetc16le();
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}
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if(symbol_value > number_of_symbols) {
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continue;
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}
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Symbol &symbol = symbol_table[symbol_value];
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while(count--) {
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// Mutate initial output level.
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switch(symbol.flags & 3) {
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case 0: break;
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case 1: current_level_ ^= true; break;
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case 2: current_level_ = true; break;
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case 3: current_level_ = false; break;
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}
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// Output waves.
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for(auto length : symbol.pulse_lengths) {
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if(!length) break;
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post_pulse(length);
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}
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}
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}
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}
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void TZX::get_standard_speed_data_block() {
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DataBlock data_block;
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data_block.length_of_pilot_pulse = 2168;
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data_block.length_of_sync_first_pulse = 667;
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data_block.length_of_sync_second_pulse = 735;
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data_block.data.length_of_zero_bit_pulse = 855;
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data_block.data.length_of_one_bit_pulse = 1710;
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data_block.data.number_of_bits_in_final_byte = 8;
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data_block.data.pause_after_block = fgetc16le();
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data_block.data.data_length = fgetc16le();
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if(!data_block.data.data_length) return;
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uint8_t first_byte = (uint8_t)fgetc(file_);
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data_block.length_of_pilot_tone = (first_byte < 128) ? 8063 : 3223;
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ungetc(first_byte, file_);
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get_data_block(data_block);
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}
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void TZX::get_turbo_speed_data_block() {
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DataBlock data_block;
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data_block.length_of_pilot_pulse = fgetc16le();
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data_block.length_of_sync_first_pulse = fgetc16le();
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data_block.length_of_sync_second_pulse = fgetc16le();
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data_block.data.length_of_zero_bit_pulse = fgetc16le();
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data_block.data.length_of_one_bit_pulse = fgetc16le();
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data_block.length_of_pilot_tone = fgetc16le();
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data_block.data.number_of_bits_in_final_byte = (uint8_t)fgetc(file_);
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data_block.data.pause_after_block = fgetc16le();
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data_block.data.data_length = fgetc16le();
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data_block.data.data_length |= (long)(fgetc(file_) << 16);
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get_data_block(data_block);
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}
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void TZX::get_data_block(const DataBlock &data_block) {
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// Output pilot tone.
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for(unsigned int c = 0; c < data_block.length_of_pilot_tone; c++) {
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post_pulse(data_block.length_of_pilot_pulse);
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}
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// Output sync pulses.
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post_pulse(data_block.length_of_sync_first_pulse);
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post_pulse(data_block.length_of_sync_second_pulse);
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get_data(data_block.data);
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}
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void TZX::get_data(const Data &data) {
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// Output data.
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for(unsigned int c = 0; c < data.data_length; c++) {
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uint8_t next_byte = (uint8_t)fgetc(file_);
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unsigned int bits = (c != data.data_length-1) ? 8 : data.number_of_bits_in_final_byte;
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while(bits--) {
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unsigned int pulse_length = (next_byte & 0x80) ? data.length_of_one_bit_pulse : data.length_of_zero_bit_pulse;
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next_byte <<= 1;
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post_pulse(pulse_length);
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post_pulse(pulse_length);
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}
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}
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// Output gap.
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post_gap(data.pause_after_block);
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}
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void TZX::get_pure_tone_data_block() {
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uint16_t length_of_pulse = fgetc16le();
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uint16_t nunber_of_pulses = fgetc16le();
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while(nunber_of_pulses--) post_pulse(length_of_pulse);
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}
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void TZX::get_pure_data_block() {
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Data data;
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data.length_of_zero_bit_pulse = fgetc16le();
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data.length_of_one_bit_pulse = fgetc16le();
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data.number_of_bits_in_final_byte = (uint8_t)fgetc(file_);
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data.pause_after_block = fgetc16le();
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data.data_length = fgetc16le();
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data.data_length |= (long)(fgetc(file_) << 16);
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get_data(data);
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}
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void TZX::get_pulse_sequence() {
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uint8_t number_of_pulses = (uint8_t)fgetc(file_);
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while(number_of_pulses--) {
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post_pulse(fgetc16le());
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}
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}
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void TZX::get_pause() {
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uint16_t duration = fgetc16le();
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if(!duration) {
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// TODO (maybe): post a 'pause the tape' suggestion
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} else {
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post_gap(duration);
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}
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}
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#pragma mark - Output
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void TZX::post_pulse(unsigned int length) {
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post_pulse(Storage::Time(length, StandardTZXClock));
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}
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void TZX::post_gap(unsigned int milliseconds) {
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if(!milliseconds) return;
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if(milliseconds > 1 && !current_level_) {
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post_pulse(Storage::Time(TZXClockMSMultiplier, StandardTZXClock));
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post_pulse(Storage::Time((milliseconds - 1u)*TZXClockMSMultiplier, StandardTZXClock));
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} else {
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post_pulse(Storage::Time(milliseconds*TZXClockMSMultiplier, StandardTZXClock));
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}
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}
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void TZX::post_pulse(const Storage::Time &time) {
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emplace_back(current_level_ ? Tape::Pulse::High : Tape::Pulse::Low, time);
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current_level_ ^= true;
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}
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#pragma mark - Flow control; currently ignored
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void TZX::ignore_group_start() {
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printf("Ignoring TZX group\n");
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uint8_t length = (uint8_t)fgetc(file_);
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fseek(file_, length, SEEK_CUR);
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}
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void TZX::ignore_group_end() {
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}
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void TZX::ignore_jump_to_block() {
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__unused uint16_t target = fgetc16le();
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printf("Ignoring TZX jump\n");
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}
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void TZX::ignore_loop_start() {
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__unused uint16_t number_of_repetitions = fgetc16le();
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printf("Ignoring TZX loop\n");
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}
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void TZX::ignore_loop_end() {
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}
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void TZX::ignore_call_sequence() {
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__unused uint16_t number_of_entries = fgetc16le();
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fseek(file_, number_of_entries * sizeof(uint16_t), SEEK_CUR);
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printf("Ignoring TZX call sequence\n");
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}
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void TZX::ignore_return_from_sequence() {
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printf("Ignoring TZX return from sequence\n");
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}
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void TZX::ignore_select_block() {
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__unused uint16_t length_of_block = fgetc16le();
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fseek(file_, length_of_block, SEEK_CUR);
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printf("Ignoring TZX select block\n");
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}
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#pragma mark - Messaging
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void TZX::ignore_text_description() {
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uint8_t length = (uint8_t)fgetc(file_);
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fseek(file_, length, SEEK_CUR);
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printf("Ignoring TZX text description\n");
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}
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void TZX::ignore_message_block() {
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__unused uint8_t time_for_display = (uint8_t)fgetc(file_);
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uint8_t length = (uint8_t)fgetc(file_);
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fseek(file_, length, SEEK_CUR);
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printf("Ignoring TZX message\n");
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}
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void TZX::get_hardware_type() {
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// TODO: pick a way to retain and communicate this.
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uint8_t number_of_machines = (uint8_t)fgetc(file_);
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fseek(file_, number_of_machines * 3, SEEK_CUR);
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printf("Ignoring TZX hardware types (%d)\n", number_of_machines);
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}
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