scuffle-pprof 0.2.0

use std::io::Write;

use flate2::Compression;
use flate2::write::GzEncoder;
use pprof::protos::Message;

use crate::PprofError;

/// A CPU profiler.
///
/// Call [`Cpu::capture`] to capture a pprof profile for the given duration.
pub struct Cpu(pprof::ProfilerGuardBuilder);

impl Cpu {
    /// Create a new CPU profiler.
    ///
    /// - `frequency` is the sampling frequency in Hz.
    /// - `blocklist` is a list of functions to exclude from the profile.
    pub fn new<S: AsRef<str>>(frequency: i32, blocklist: &[S]) -> Self {
        Self(
            pprof::ProfilerGuardBuilder::default()
                .frequency(frequency)
                .blocklist(blocklist),
        )
    }

    /// Capture a pprof profile for the given duration.
    ///
    /// The profile is compressed using gzip.
    /// The profile can be analyzed using the `pprof` tool.
    ///
    /// <div class="warning">
    /// Warning: This method is blocking and may take a long time to complete.
    ///
    /// It is recommended to run it in a separate thread.
    /// </div>
    pub fn capture(&self, duration: std::time::Duration) -> Result<Vec<u8>, PprofError> {
        let profiler = self.0.clone().build()?;

        std::thread::sleep(duration);

        let report = profiler.report().build()?;

        let pprof = report.pprof()?;

        let mut gz = GzEncoder::new(Vec::new(), Compression::default());
        gz.write_all(&pprof.encode_to_vec())?;
        Ok(gz.finish()?)
    }
}