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Made an attempt to implement seek_to on PCMSegmentEventSource, taking account of off-by-half counting.

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This commit is contained in:
Thomas Harte 2016-12-17 22:44:33 -05:00
parent 3116a2cf4c
commit 3297f6d545
3 changed files with 84 additions and 10 deletions
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37
Storage/Disk/PCMSegment.cpp
View File

@ -47,3 +47,40 @@ Storage::Disk::Track::Event PCMSegmentEventSource::get_next_event()
next_event_.type = Track::Event::IndexHole;
return next_event_;
}
Storage::Time PCMSegmentEventSource::get_length()
{
return segment_.length_of_a_bit * segment_.number_of_bits;
}
Storage::Time PCMSegmentEventSource::seek_to(const Time &time_from_start)
{
// test for requested time being beyond the end
Time length = get_length();
if(time_from_start >= length)
{
next_event_.type = Track::Event::IndexHole;
bit_pointer_ = segment_.number_of_bits;
return length;
}
// if not beyond the end then make an initial assumption that the next thing encountered will be a flux transition
next_event_.type = Track::Event::FluxTransition;
// test for requested time being before the first bit
Time half_bit_length = segment_.length_of_a_bit;
half_bit_length.length >>= 1;
if(time_from_start < half_bit_length)
{
bit_pointer_ = 0;
Storage::Time zero;
return zero;
}
// adjust for time to get to bit zero and determine number of bits in
Time relative_time = time_from_start - half_bit_length;
bit_pointer_ = (relative_time / segment_.length_of_a_bit).get_unsigned_int();
// map up to the correct amount of time
return half_bit_length + segment_.length_of_a_bit * (unsigned int)bit_pointer_;
}

3
Storage/Disk/PCMSegment.hpp
View File

@ -36,6 +36,9 @@ class PCMSegmentEventSource {
Track::Event get_next_event();
void reset();
Time seek_to(const Time &time_from_start);
Time get_length();
private:
PCMSegment segment_;
size_t bit_pointer_;

54
Storage/Storage.hpp
View File

@ -36,17 +36,37 @@ struct Time {
/*!
@returns the floating point conversion of this @c Time. This will often be less precise.
*/
inline float get_float()
inline float get_float() const
{
return (float)length / (float)clock_rate;
}
inline bool operator < (Time other)
inline unsigned int get_unsigned_int() const
{
return length / clock_rate;
}
inline bool operator < (const Time &other) const
{
return other.clock_rate * length < clock_rate * other.length;
}
inline Time operator + (Time other)
inline bool operator <= (const Time &other) const
{
return other.clock_rate * length <= clock_rate * other.length;
}
inline bool operator > (const Time &other) const
{
return other.clock_rate * length > clock_rate * other.length;
}
inline bool operator >= (const Time &other) const
{
return other.clock_rate * length >= clock_rate * other.length;
}
inline Time operator + (const Time &other) const
{
Time result;
result.clock_rate = NumberTheory::least_common_multiple(clock_rate, other.clock_rate);
@ -54,7 +74,7 @@ struct Time {
return result;
}
inline Time &operator += (Time other)
inline Time &operator += (const Time &other)
{
unsigned int combined_clock_rate = NumberTheory::least_common_multiple(clock_rate, other.clock_rate);
length = length * (combined_clock_rate / clock_rate) + other.length * (combined_clock_rate / other.clock_rate);
@ -62,7 +82,7 @@ struct Time {
return *this;
}
inline Time operator - (Time other)
inline Time operator - (const Time &other) const
{
Time result;
result.clock_rate = NumberTheory::least_common_multiple(clock_rate, other.clock_rate);
@ -70,7 +90,7 @@ struct Time {
return result;
}
inline Time operator -= (Time other)
inline Time operator -= (const Time &other)
{
unsigned int combined_clock_rate = NumberTheory::least_common_multiple(clock_rate, other.clock_rate);
length = length * (combined_clock_rate / clock_rate) - other.length * (combined_clock_rate / other.clock_rate);
@ -78,7 +98,7 @@ struct Time {
return *this;
}
inline Time operator * (Time other)
inline Time operator * (const Time &other) const
{
Time result;
result.clock_rate = clock_rate * other.clock_rate;
@ -86,14 +106,28 @@ struct Time {
return result;
}
inline Time &operator *= (Time other)
inline Time &operator *= (const Time &other)
{
length *= other.length;
clock_rate *= other.clock_rate;
return *this;
}
inline Time operator / (Time other)
inline Time operator * (unsigned int multiplier) const
{
Time result;
result.clock_rate = clock_rate * multiplier;
result.length = length;
return result;
}
inline Time &operator *= (unsigned int multiplier)
{
length *= multiplier;
return *this;
}
inline Time operator / (const Time &other) const
{
Time result;
result.clock_rate = clock_rate * other.length;
@ -101,7 +135,7 @@ struct Time {
return result;
}
inline Time &operator /= (Time other)
inline Time &operator /= (const Time &other)
{
length *= other.clock_rate;
clock_rate *= other.length;