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Made an attempt to obey the proper TZX rules on gaps, and to hit the common-clock-rate Time optimisation.

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This commit is contained in:
Thomas Harte 2017-07-21 18:21:12 -04:00
parent e152ed2e61
commit d9a2c32aca
2 changed files with 35 additions and 17 deletions
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47
Storage/Tape/Formats/TZX.cpp
View File

@ -12,11 +12,12 @@ using namespace Storage::Tape;
namespace {
const unsigned int StandardTZXClock = 3500000;
const unsigned int TZXClockMSMultiplier = 3500;
}
TZX::TZX(const char *file_name) :
Storage::FileHolder(file_name),
next_is_high_(false) {
current_level_(false) {
// Check for signature followed by a 0x1a
char identifier[7];
@ -37,16 +38,14 @@ TZX::TZX(const char *file_name) :
void TZX::virtual_reset() {
clear();
set_is_at_end(false);
fseek(file_, 0x0a, SEEK_SET);
// This is a workaround for arguably dodgy ZX80/ZX81 TZXs; they launch straight
// into data but both machines require a gap before data begins. So impose
// an initial gap, in the form of a very long wave.
emplace_back(Tape::Pulse::Low, Storage::Time(1, 4));
emplace_back(Tape::Pulse::High, Storage::Time(1, 4));
set_is_at_end(false);
next_is_high_ = false;
fseek(file_, 0x0a, SEEK_SET);
current_level_ = false;
post_gap(500);
}
void TZX::get_next_pulses() {
@ -95,7 +94,7 @@ void TZX::get_generalised_data_block() {
get_generalised_segment(total_pilot_symbols, maximum_pulses_per_pilot_symbol, symbols_in_pilot_table, false);
get_generalised_segment(total_data_symbols, maximum_pulses_per_data_symbol, symbols_in_data_table, true);
emplace_back(Tape::Pulse::Zero, Storage::Time((unsigned int)pause_after_block, 1000u));
post_gap(pause_after_block);
// This should be unnecessary, but intends to preserve sanity.
fseek(file_, endpoint, SEEK_SET);
@ -146,9 +145,9 @@ void TZX::get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_pe
// Mutate initial output level.
switch(symbol.flags & 3) {
case 0: break;
case 1: next_is_high_ ^= true; break;
case 2: next_is_high_ = false; break;
case 3: next_is_high_ = true; break;
case 1: current_level_ ^= true; break;
case 2: current_level_ = true; break;
case 3: current_level_ = false; break;
}
// Output waves.
@ -160,11 +159,6 @@ void TZX::get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_pe
}
}
void TZX::post_pulse(unsigned int length) {
emplace_back(next_is_high_ ? Tape::Pulse::Low : Tape::Pulse::High, Storage::Time(length, StandardTZXClock));
next_is_high_ ^= true;
}
void TZX::get_standard_speed_data_block() {
__unused uint16_t pause_after_block = fgetc16le();
uint16_t data_length = fgetc16le();
@ -208,3 +202,24 @@ void TZX::get_pulse_sequence() {
post_pulse(fgetc16le());
}
}
#pragma mark - Output
void TZX::post_pulse(unsigned int length) {
post_pulse(Storage::Time(length, StandardTZXClock));
}
void TZX::post_gap(unsigned int milliseconds) {
if(!milliseconds) return;
if(milliseconds > 1 && !current_level_) {
post_pulse(Storage::Time(TZXClockMSMultiplier, StandardTZXClock));
post_pulse(Storage::Time((milliseconds - 1u)*TZXClockMSMultiplier, StandardTZXClock));
} else {
post_pulse(Storage::Time(milliseconds*TZXClockMSMultiplier, StandardTZXClock));
}
}
void TZX::post_pulse(const Storage::Time &time) {
emplace_back(current_level_ ? Tape::Pulse::High : Tape::Pulse::Low, time);
current_level_ ^= true;
}

5
Storage/Tape/Formats/TZX.hpp
View File

@ -35,7 +35,7 @@ class TZX: public PulseQueuedTape, public Storage::FileHolder {
void virtual_reset();
void get_next_pulses();
bool next_is_high_;
bool current_level_;
void get_standard_speed_data_block();
void get_turbo_speed_data_block();
@ -46,6 +46,9 @@ class TZX: public PulseQueuedTape, public Storage::FileHolder {
void get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_per_symbol, uint8_t number_of_symbols, bool is_data);
void post_pulse(unsigned int length);
void post_gap(unsigned int milliseconds);
void post_pulse(const Storage::Time &time);
};
}