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Spotted that pilot and data segments have different encodings — of course! — and attempted to adapt.

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This commit is contained in:
Thomas Harte 2017-07-17 07:34:10 -04:00
parent b63971caf7
commit fa617eac6b
3 changed files with 81 additions and 17 deletions
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43
Storage/FileHolder.hpp
View File

@ -71,6 +71,49 @@ class FileHolder {
*/
void ensure_file_is_at_least_length(long length);
class BitStream {
public:
BitStream(FILE *f, bool lsb_first) :
file_(f),
lsb_first_(lsb_first),
next_value_(0),
bits_remaining_(0) {}
uint8_t get_bits(int q) {
uint8_t result = 0;
while(q--) {
result = (uint8_t)((result << 1) | get_bit());
}
return result;
}
private:
FILE *file_;
bool lsb_first_;
uint8_t next_value_;
int bits_remaining_;
uint8_t get_bit() {
if(!bits_remaining_) {
bits_remaining_ = 8;
next_value_ = (uint8_t)fgetc(file_);
}
uint8_t bit;
if(lsb_first_) {
bit = next_value_ & 1;
next_value_ >>= 1;
} else {
bit = next_value_ >> 7;
next_value_ <<= 1;
}
bits_remaining_--;
return bit;
}
};
FILE *file_;
struct stat file_stats_;
bool is_read_only_;

53
Storage/Tape/Formats/TZX.cpp
View File

@ -77,12 +77,12 @@ void TZX::get_generalised_data_block() {
uint8_t maximum_pulses_per_data_symbol = (uint8_t)fgetc(file_);
uint8_t symbols_in_data_table = (uint8_t)fgetc(file_);
get_generalised_segment(total_pilot_symbols, maximum_pulses_per_pilot_symbol, symbols_in_pilot_table);
get_generalised_segment(total_data_symbols, maximum_pulses_per_data_symbol, symbols_in_data_table);
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));
}
void TZX::get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_per_symbol, uint8_t number_of_symbols) {
void TZX::get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_per_symbol, uint8_t number_of_symbols, bool is_data) {
if(!output_symbols) return;
// Construct the symbol table.
@ -97,27 +97,48 @@ void TZX::get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_pe
for(int ic = 0; ic < max_pulses_per_symbol; ic++) {
symbol.pulse_lengths.push_back(fgetc16le());
}
symbol_table.push_back(symbol);
}
// Hence produce the output.
BitStream stream(file_, false);
int base = 2;
int bits = 1;
while(base < number_of_symbols) {
base <<= 1;
bits++;
}
for(int c = 0; c < output_symbols; c++) {
uint8_t symbol_value = (uint8_t)fgetc(file_);
uint8_t symbol_value;
int count;
if(is_data) {
symbol_value = stream.get_bits(bits);
count = 1;
} else {
symbol_value = (uint8_t)fgetc(file_);
count = fgetc16le();
}
if(symbol_value > number_of_symbols) {
continue;
}
Symbol &symbol = symbol_table[symbol_value];
// Mutate initial output level.
switch(symbol.flags & 3) {
case 0: break;
case 1: is_high_ ^= true; break;
case 2: is_high_ = true; break;
case 3: is_high_ = false; break;
}
while(count--) {
// Mutate initial output level.
switch(symbol.flags & 3) {
case 0: break;
case 1: is_high_ ^= true; break;
case 2: is_high_ = true; break;
case 3: is_high_ = false; break;
}
// Output waves.
for(auto length : symbol.pulse_lengths) {
if(!length) break;
// Output waves.
for(auto length : symbol.pulse_lengths) {
if(!length) break;
is_high_ ^= true;
emplace_back(is_high_ ? Tape::Pulse::High : Tape::Pulse::Low, Storage::Time((unsigned int)length, StandardTZXClock));
is_high_ ^= true;
emplace_back(is_high_ ? Tape::Pulse::High : Tape::Pulse::Low, Storage::Time((unsigned int)length, StandardTZXClock));
}
}
}
}

2
Storage/Tape/Formats/TZX.hpp
View File

@ -38,7 +38,7 @@ class TZX: public PulseQueuedTape, public Storage::FileHolder {
bool is_high_;
void get_generalised_data_block();
void get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_per_symbol, uint8_t number_of_symbols);
void get_generalised_segment(uint32_t output_symbols, uint8_t max_pulses_per_symbol, uint8_t number_of_symbols, bool is_data);
};
}