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344 lines
8.1 KiB
C++
344 lines
8.1 KiB
C++
//
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// TapeUEF.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 18/01/2016.
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// Copyright 2016 Thomas Harte. All rights reserved.
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//
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#include "TapeUEF.hpp"
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#include <cstring>
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#include <cstdio>
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#include <cstdlib>
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#include <cmath>
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#define LOG_PREFIX "[UEF] "
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#include "../../../Outputs/Log.hpp"
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// MARK: - ZLib extensions
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static float gzgetfloat(gzFile file) {
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uint8_t bytes[4];
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gzread(file, bytes, 4);
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/* assume a four byte array named Float exists, where Float[0]
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was the first byte read from the UEF, Float[1] the second, etc */
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/* decode mantissa */
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int mantissa;
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mantissa = bytes[0] | (bytes[1] << 8) | ((bytes[2]&0x7f)|0x80) << 16;
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float result = float(mantissa);
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result = float(ldexp(result, -23));
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/* decode exponent */
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int exponent;
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exponent = ((bytes[2]&0x80) >> 7) | (bytes[3]&0x7f) << 1;
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exponent -= 127;
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result = float(ldexp(result, exponent));
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/* flip sign if necessary */
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if(bytes[3]&0x80)
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result = -result;
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return result;
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}
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static uint8_t gzget8(gzFile file) {
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// This is a workaround for gzgetc, which seems to be broken in ZLib 1.2.8.
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uint8_t result;
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gzread(file, &result, 1);
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return result;
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}
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static int gzget16(gzFile file) {
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uint8_t bytes[2];
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gzread(file, bytes, 2);
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return bytes[0] | (bytes[1] << 8);
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}
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static int gzget24(gzFile file) {
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uint8_t bytes[3];
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gzread(file, bytes, 3);
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return bytes[0] | (bytes[1] << 8) | (bytes[2] << 16);
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}
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static int gzget32(gzFile file) {
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uint8_t bytes[4];
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gzread(file, bytes, 4);
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return bytes[0] | (bytes[1] << 8) | (bytes[2] << 16) | (bytes[3] << 24);
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}
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using namespace Storage::Tape;
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UEF::UEF(const std::string &file_name) {
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file_ = gzopen(file_name.c_str(), "rb");
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char identifier[10];
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int bytes_read = gzread(file_, identifier, 10);
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if(bytes_read < 10 || std::strcmp(identifier, "UEF File!")) {
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throw ErrorNotUEF;
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}
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uint8_t version[2];
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gzread(file_, version, 2);
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if(version[1] > 0 || version[0] > 10) {
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throw ErrorNotUEF;
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}
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set_platform_type();
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}
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UEF::~UEF() {
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gzclose(file_);
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}
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// MARK: - Public methods
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void UEF::virtual_reset() {
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gzseek(file_, 12, SEEK_SET);
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set_is_at_end(false);
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clear();
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}
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// MARK: - Chunk navigator
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bool UEF::get_next_chunk(UEF::Chunk &result) {
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const uint16_t chunk_id = uint16_t(gzget16(file_));
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const uint32_t chunk_length = uint32_t(gzget32(file_));
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const z_off_t start_of_next_chunk = gztell(file_) + chunk_length;
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if(gzeof(file_)) {
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return false;
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}
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result.id = chunk_id;
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result.length = chunk_length;
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result.start_of_next_chunk = start_of_next_chunk;
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return true;
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}
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void UEF::get_next_pulses() {
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while(empty()) {
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// read chunk details
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Chunk next_chunk;
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if(!get_next_chunk(next_chunk)) {
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set_is_at_end(true);
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return;
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}
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switch(next_chunk.id) {
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case 0x0100: queue_implicit_bit_pattern(next_chunk.length); break;
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case 0x0102: queue_explicit_bit_pattern(next_chunk.length); break;
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case 0x0112: queue_integer_gap(); break;
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case 0x0116: queue_floating_point_gap(); break;
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case 0x0110: queue_carrier_tone(); break;
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case 0x0111: queue_carrier_tone_with_dummy(); break;
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case 0x0114: queue_security_cycles(); break;
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case 0x0104: queue_defined_data(next_chunk.length); break;
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// change of base rate
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case 0x0113: {
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// TODO: something smarter than just converting this to an int
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const float new_time_base = gzgetfloat(file_);
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time_base_ = unsigned(roundf(new_time_base));
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}
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break;
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case 0x0117: {
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const int baud_rate = gzget16(file_);
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is_300_baud_ = (baud_rate == 300);
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}
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break;
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default:
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LOG("Skipping chunk of type " << PADHEX(4) << next_chunk.id);
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break;
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}
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gzseek(file_, next_chunk.start_of_next_chunk, SEEK_SET);
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}
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}
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// MARK: - Chunk parsers
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void UEF::queue_implicit_bit_pattern(uint32_t length) {
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while(length--) {
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queue_implicit_byte(gzget8(file_));
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}
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}
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void UEF::queue_explicit_bit_pattern(uint32_t length) {
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const std::size_t length_in_bits = (length << 3) - size_t(gzget8(file_));
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uint8_t current_byte = 0;
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for(std::size_t bit = 0; bit < length_in_bits; bit++) {
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if(!(bit&7)) current_byte = gzget8(file_);
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queue_bit(current_byte&1);
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current_byte >>= 1;
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}
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}
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void UEF::queue_integer_gap() {
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Time duration;
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duration.length = unsigned(gzget16(file_));
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duration.clock_rate = time_base_;
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emplace_back(Pulse::Zero, duration);
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}
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void UEF::queue_floating_point_gap() {
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const float length = gzgetfloat(file_);
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Time duration;
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duration.length = unsigned(length * 4000000);
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duration.clock_rate = 4000000;
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emplace_back(Pulse::Zero, duration);
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}
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void UEF::queue_carrier_tone() {
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unsigned int number_of_cycles = unsigned(gzget16(file_));
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while(number_of_cycles--) queue_bit(1);
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}
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void UEF::queue_carrier_tone_with_dummy() {
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unsigned int pre_cycles = unsigned(gzget16(file_));
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unsigned int post_cycles = unsigned(gzget16(file_));
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while(pre_cycles--) queue_bit(1);
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queue_implicit_byte(0xaa);
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while(post_cycles--) queue_bit(1);
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}
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void UEF::queue_security_cycles() {
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int number_of_cycles = gzget24(file_);
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bool first_is_pulse = gzget8(file_) == 'P';
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bool last_is_pulse = gzget8(file_) == 'P';
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uint8_t current_byte = 0;
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for(int cycle = 0; cycle < number_of_cycles; cycle++) {
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if(!(cycle&7)) current_byte = gzget8(file_);
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int bit = (current_byte >> 7);
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current_byte <<= 1;
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Time duration;
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duration.length = bit ? 1 : 2;
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duration.clock_rate = time_base_ * 4;
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if(!cycle && first_is_pulse) {
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emplace_back(Pulse::High, duration);
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} else if(cycle == number_of_cycles-1 && last_is_pulse) {
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emplace_back(Pulse::Low, duration);
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} else {
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emplace_back(Pulse::Low, duration);
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emplace_back(Pulse::High, duration);
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}
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}
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}
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void UEF::queue_defined_data(uint32_t length) {
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if(length < 3) return;
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const int bits_per_packet = gzget8(file_);
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const char parity_type = char(gzget8(file_));
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int number_of_stop_bits = gzget8(file_);
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const bool has_extra_stop_wave = (number_of_stop_bits < 0);
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number_of_stop_bits = abs(number_of_stop_bits);
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length -= 3;
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while(length--) {
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uint8_t byte = gzget8(file_);
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uint8_t parity_value = byte;
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parity_value ^= (parity_value >> 4);
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parity_value ^= (parity_value >> 2);
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parity_value ^= (parity_value >> 1);
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queue_bit(0);
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int c = bits_per_packet;
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while(c--) {
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queue_bit(byte&1);
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byte >>= 1;
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}
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switch(parity_type) {
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default: break;
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case 'E': queue_bit(parity_value&1); break;
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case 'O': queue_bit((parity_value&1) ^ 1); break;
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}
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int stop_bits = number_of_stop_bits;
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while(stop_bits--) queue_bit(1);
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if(has_extra_stop_wave) {
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Time duration;
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duration.length = 1;
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duration.clock_rate = time_base_ * 4;
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emplace_back(Pulse::Low, duration);
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emplace_back(Pulse::High, duration);
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}
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}
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}
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// MARK: - Queuing helpers
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void UEF::queue_implicit_byte(uint8_t byte) {
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queue_bit(0);
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int c = 8;
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while(c--) {
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queue_bit(byte&1);
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byte >>= 1;
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}
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queue_bit(1);
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}
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void UEF::queue_bit(int bit) {
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int number_of_cycles;
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Time duration;
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duration.clock_rate = time_base_ * 4;
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if(bit) {
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// encode high-frequency waves
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duration.length = 1;
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number_of_cycles = 2;
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} else {
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// encode low-frequency waves
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duration.length = 2;
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number_of_cycles = 1;
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}
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if(is_300_baud_) number_of_cycles *= 4;
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while(number_of_cycles--) {
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emplace_back(Pulse::Low, duration);
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emplace_back(Pulse::High, duration);
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}
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}
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// MARK: - TypeDistinguisher
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TargetPlatform::Type UEF::target_platform_type() {
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return platform_type_;
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}
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void UEF::set_platform_type() {
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// If a chunk of type 0005 exists anywhere in the UEF then the UEF specifies its target machine.
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// So check and, if so, update the list of machines for which this file thinks it is suitable.
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Chunk next_chunk;
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while(get_next_chunk(next_chunk)) {
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if(next_chunk.id == 0x0005) {
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uint8_t target = gzget8(file_);
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switch(target >> 4) {
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case 0: platform_type_ = TargetPlatform::BBCModelA; break;
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case 1: platform_type_ = TargetPlatform::AcornElectron; break;
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case 2: platform_type_ = TargetPlatform::BBCModelB; break;
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case 3: platform_type_ = TargetPlatform::BBCMaster; break;
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case 4: platform_type_ = TargetPlatform::AcornAtom; break;
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default: break;
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}
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}
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gzseek(file_, next_chunk.start_of_next_chunk, SEEK_SET);
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}
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reset();
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}
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