Add trigger_example from issue #135

Author: diwic

examples/trigger_hstamp.rs

@@ -0,0 +1,58 @@
+use alsa::{
+    pcm::{Access, Format, HwParams},
+    Direction, ValueOr, PCM,
+};
+
+use anyhow::Result; // Sorry for the extra dep :D
+
+fn main() -> Result<()> {
+    // Also tried specifying the hw card name, but it doesn't matter
+    let pcm = PCM::new("default", Direction::Capture, false)?;
+
+    {
+        let hwp = HwParams::any(&pcm)?;
+        hwp.set_channels(2)?;
+        hwp.set_rate(16000, ValueOr::Nearest)?;
+        hwp.set_format(Format::s32())?;
+        hwp.set_access(Access::RWInterleaved)?;
+        pcm.hw_params(&hwp)?;
+    }
+
+    {
+        let swp = pcm.sw_params_current()?;
+        swp.set_tstamp_mode(true)?;
+        swp.set_tstamp_type(alsa::pcm::TstampType::Monotonic)?; // Tried with every kind of timestamp type, it doesn't matter
+        pcm.sw_params(&swp)?;
+    }
+
+    let mut buffer = [0i32; 8000];
+
+    pcm.start()?;
+
+    let pcm_io = pcm.io_i32()?;
+
+    loop {
+        // Debug: check if timestamps are enabled (it returns true as expected)
+        let params = pcm.sw_params_current()?;
+        println!("timestamps enabled: {}", params.get_tstamp_mode()?);
+
+        let read_bytes = pcm_io.readi(&mut buffer)?;
+        assert!(read_bytes > 0);
+
+        // I've also tried to construct the status object just once outside the loop but nothing changes
+        let status = pcm.status()?;
+        
+        dbg!(&status);
+
+        // The following "htstamp" functions all wrongly return a timespec struct with 0 seconds and 0 nanoseconds
+        // when using Rust >=1.88 (even tried on Nightly to check if it worked on there)
+        let audio_htstamp = status.get_audio_htstamp();
+        println!("{} {}", audio_htstamp.tv_sec, audio_htstamp.tv_nsec);
+
+        let htstamp = status.get_htstamp();
+        println!("{} {}", htstamp.tv_sec, htstamp.tv_nsec);
+
+        let trigger_htstamp = status.get_trigger_htstamp();
+        println!("{} {}", trigger_htstamp.tv_sec, trigger_htstamp.tv_nsec);
+    }
+}