75 lines
1.4 KiB
Go
75 lines
1.4 KiB
Go
package clock
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import (
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"math"
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"time"
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)
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const (
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DefaultFixedDelta = 1.0 / 60
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DefaultMaxFrameDelta = 0.1
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DefaultMaxSteps = 4
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stepEpsilon = 1e-9
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)
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type Clock struct {
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start time.Time
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}
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func New() *Clock {
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return &Clock{start: time.Now()}
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}
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func (c *Clock) Now() float64 {
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return time.Since(c.start).Seconds()
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}
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type FixedStepper struct {
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FixedDelta float64
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MaxFrameDelta float64
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MaxSteps int
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accumulator float64
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}
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func (s *FixedStepper) Advance(frameDelta float64) (steps int, alpha float64) {
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s.applyDefaults()
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if frameDelta < 0 || math.IsNaN(frameDelta) {
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frameDelta = 0
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}
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if frameDelta > s.MaxFrameDelta {
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frameDelta = s.MaxFrameDelta
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}
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s.accumulator += frameDelta
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for s.accumulator+stepEpsilon >= s.FixedDelta && steps < s.MaxSteps {
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s.accumulator -= s.FixedDelta
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steps++
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}
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if s.accumulator < 0 {
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s.accumulator = 0
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}
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if s.accumulator >= s.FixedDelta {
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s.accumulator = math.Mod(s.accumulator, s.FixedDelta)
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}
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return steps, s.accumulator / s.FixedDelta
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}
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func (s *FixedStepper) Reset() {
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s.accumulator = 0
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}
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func (s *FixedStepper) Accumulator() float64 {
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return s.accumulator
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}
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func (s *FixedStepper) applyDefaults() {
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if s.FixedDelta <= 0 {
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s.FixedDelta = DefaultFixedDelta
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}
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if s.MaxFrameDelta <= 0 {
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s.MaxFrameDelta = DefaultMaxFrameDelta
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}
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if s.MaxSteps <= 0 {
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s.MaxSteps = DefaultMaxSteps
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}
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}
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