66 lines
1.9 KiB
Zig
66 lines
1.9 KiB
Zig
const std = @import("std");
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const core = @import("main.zig");
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const Timer = @import("Timer.zig");
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pub const Frequency = @This();
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/// The target frequency (e.g. 60hz) or zero for unlimited
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target: u32 = 0,
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/// The estimated delay that is needed to achieve the target frequency. Updated during tick()
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delay_ns: u64 = 0,
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/// The actual measured frequency. This is updated every second.
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rate: u32 = 0,
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delta_time: ?*f32 = null,
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delta_time_ns: *u64 = undefined,
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/// Internal fields, this must be initialized via a call to start().
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internal: struct {
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// The frame number in this second's cycle. e.g. zero to 59
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count: u32,
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timer: Timer,
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last_time: u64,
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} = undefined,
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/// Starts the timer used for frequency calculation. Must be called once before anything else.
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pub fn start(f: *Frequency) !void {
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f.internal = .{
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.count = 0,
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.timer = try Timer.start(),
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.last_time = 0,
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};
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}
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/// Tick should be called at each occurrence (e.g. frame)
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pub inline fn tick(f: *Frequency) void {
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var current_time = f.internal.timer.readPrecise();
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if (f.delta_time) |delta_time| {
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f.delta_time_ns.* = current_time -| f.internal.last_time;
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delta_time.* = @as(f32, @floatFromInt(f.delta_time_ns.*)) / @as(f32, @floatFromInt(std.time.ns_per_s));
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}
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if (current_time >= std.time.ns_per_s) {
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f.rate = f.internal.count;
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f.internal.count = 0;
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f.internal.timer.reset();
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current_time -= std.time.ns_per_s;
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}
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f.internal.last_time = current_time;
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f.internal.count += 1;
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if (f.target != 0) {
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const limited_count = @min(f.target, f.internal.count);
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const target_time_per_tick: u64 = (std.time.ns_per_s / f.target);
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const target_time = target_time_per_tick * limited_count;
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if (current_time > target_time) {
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f.delay_ns = 0;
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} else {
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f.delay_ns = target_time - current_time;
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}
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} else {
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f.delay_ns = 0;
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}
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}
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