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Ensures no overflow, and adds a couple of consts.

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This commit is contained in:
Thomas Harte 2018-11-14 20:09:57 -05:00
parent 6ba02c44d0
commit 3dca836571
1 changed files with 7 additions and 8 deletions
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15
Outputs/CRT/Internals/Flywheel.hpp
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@ -10,6 +10,7 @@
#define Flywheel_hpp
#include <cstdlib>
#include <cstdint>
namespace Outputs {
namespace CRT {
@ -33,10 +34,8 @@ struct Flywheel {
standard_period_(standard_period),
retrace_time_(retrace_time),
sync_error_window_(sync_error_window),
counter_(0),
counter_before_retrace_(standard_period - retrace_time),
expected_next_sync_(standard_period),
number_of_surprises_(0) {}
expected_next_sync_(standard_period) {}
enum SyncEvent {
/// Indicates that no synchronisation events will occur in the queried window.
@ -64,10 +63,10 @@ struct Flywheel {
// do we recognise this hsync, thereby adjusting future time expectations?
if(sync_is_requested) {
if(counter_ < sync_error_window_ || counter_ > expected_next_sync_ - sync_error_window_) {
int time_now = (counter_ < sync_error_window_) ? expected_next_sync_ + counter_ : counter_;
const int time_now = (counter_ < sync_error_window_) ? expected_next_sync_ + counter_ : counter_;
expected_next_sync_ = (3*expected_next_sync_ + time_now) >> 2;
} else {
number_of_surprises_++;
++number_of_surprises_;
if(counter_ < retrace_time_ + (expected_next_sync_ >> 1)) {
expected_next_sync_ = (3*expected_next_sync_ + standard_period_ + sync_error_window_) >> 2;
@ -124,7 +123,7 @@ struct Flywheel {
*/
inline int get_current_output_position() {
if(counter_ < retrace_time_) {
int retrace_distance = (counter_ * standard_period_) / retrace_time_;
const int retrace_distance = int((int64_t(counter_) * int64_t(standard_period_)) / int64_t(retrace_time_));
if(retrace_distance > counter_before_retrace_) return 0;
return counter_before_retrace_ - retrace_distance;
}
@ -182,11 +181,11 @@ struct Flywheel {
const int retrace_time_; // a constant indicating the amount of time it takes to perform a retrace
const int sync_error_window_; // a constant indicating the window either side of the next expected sync in which we'll accept other syncs
int counter_; // time since the _start_ of the last sync
int counter_ = 0; // time since the _start_ of the last sync
int counter_before_retrace_; // the value of _counter immediately before retrace began
int expected_next_sync_; // our current expection of when the next sync will be encountered (which implies velocity)
int number_of_surprises_; // a count of the surprising syncs
int number_of_surprises_ = 0; // a count of the surprising syncs
/*
Implementation notes: