remove std dependencies

Cargo.toml

@@ -7,3 +7,6 @@ repository = "https://github.com/mcpherrinm/goertzel.git"
 keywords = ["dsp", "goertzel", "fft", "fourier"]
 license = "MIT"
 description = "An nostd implementation of Goertzel's Algoritm"
+
+[dependencies]
+libm = "0.2.1"

src/lib.rs

 // This (implicitly/naively) uses a rectangular window.  Some way to set up a window function
 // will be needed probably -- if mutating your samples before calling this isn't sufficient.
-use std::f32;
-use std::f32::consts::PI;
+
+// allow std in tests
+#![cfg_attr(not(test), no_std)]
+
+use core::f32::consts::PI;
 
 /// Set up parameters (and some precomputed values for those).
 #[derive(Clone, Copy)]
@@ -25,11 +28,11 @@ impl Parameters {
 	pub fn new(target_freq: f32, sample_rate: u32, window_size: usize) -> Self {
 		let k = target_freq * (window_size as f32) / (sample_rate as f32);
 		let omega = (PI * 2. * k) / (window_size as f32);
-		let cosine = omega.cos();
+		let cosine = libm::cosf(omega);
 		Parameters {
-			window_size: window_size,
-			sine: omega.sin(),
-			cosine: cosine,
+			window_size,
+			sine: libm::sinf(omega),
+			cosine,
 			term_coefficient: 2. * cosine,
 		}
 	}
@@ -44,12 +47,12 @@ impl Parameters {
 	}
 
 	pub fn mag(self, samples: &[i16]) -> f32 {
-		self.start().add(samples).finish_mag()
+		self.start().add_samples(samples).finish_mag()
 	}
 }
 
 impl Partial {
-	pub fn add(mut self, samples: &[i16]) -> Self {
+	pub fn add_samples(mut self, samples: &[i16]) -> Self {
 		for &sample in samples {
 			let this = self.params.term_coefficient * self.prev - self.prevprev + (sample as f32);
 			self.prevprev = self.prev;
@@ -67,15 +70,21 @@ impl Partial {
 
 	pub fn finish_mag(self) -> f32 {
 		let (real, imag) = self.finish();
-		(real * real + imag * imag).sqrt()
+		libm::sqrtf(real * real + imag * imag)
 	}
 }
 
 #[test]
 fn zero_data() {
 	let p = Parameters::new(1800., 8000, 256);
-	assert!(p.start().add(&[0; 256]).finish_mag() == 0.);
-	assert!(p.start().add(&[0; 128]).add(&[0; 128]).finish_mag() == 0.);
+	assert!(p.start().add_samples(&[0; 256]).finish_mag() == 0.);
+	assert!(
+		p.start()
+			.add_samples(&[0; 128])
+			.add_samples(&[0; 128])
+			.finish_mag()
+			== 0.
+	);
 }
 
 #[test]
@@ -84,13 +93,13 @@ fn sine() {
 	for &freq in [697., 1200., 1800., 1633.].iter() {
 		// Generate a 1 second sine wave at freq hz
 		let step = 1. / 8000.;
-		for sample in (0..8000) {
-			let time = sample as f32 * step;
-			buf[sample] = ((time * freq * PI * 2.).sin() * std::i16::MAX as f32) as i16;
+		for (i, v) in buf.iter_mut().enumerate() {
+			let time = i as f32 * step;
+			*v = ((time * freq * PI * 2.).sin() * std::i16::MAX as f32) as i16;
 		}
 
 		let p = Parameters::new(freq, 8000, 8000);
-		let mag = p.start().add(&buf[..]).finish_mag();
+		let mag = p.start().add_samples(&buf[..]).finish_mag();
 		for testfreq in (0..30).map(|x| (x * 100) as f32) {
 			let p = Parameters::new(testfreq, 8000, 8000);
 			let testmag = p.mag(&buf[..]);