servo-profile 0.3.0

A component of the servo web-engine.
Documentation 
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/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

//! A module for writing time profiler traces out to a self contained HTML file.

use std::io::{self, Write};
use std::{fs, path};

use profile_traits::time::{ProfilerCategory, TimerMetadata};
use serde::Serialize;
use servo_base::cross_process_instant::CrossProcessInstant;

/// An RAII class for writing the HTML trace dump.
#[derive(Debug)]
pub struct TraceDump {
    file: fs::File,
}

#[derive(Debug, Serialize)]
struct TraceEntry {
    category: ProfilerCategory,
    metadata: Option<TimerMetadata>,

    #[serde(rename = "startTime")]
    start_time: u64,

    #[serde(rename = "endTime")]
    end_time: u64,
}

impl TraceDump {
    /// Create a new TraceDump and write the prologue of the HTML file out to
    /// disk.
    pub fn new<P>(trace_file_path: P) -> io::Result<TraceDump>
    where
        P: AsRef<path::Path>,
    {
        let mut file = fs::File::create(trace_file_path)?;
        write_prologue(&mut file)?;
        Ok(TraceDump { file })
    }

    /// Write one trace to the trace dump file.
    pub fn write_one(
        &mut self,
        category: &(ProfilerCategory, Option<TimerMetadata>),
        start_time: CrossProcessInstant,
        end_time: CrossProcessInstant,
    ) {
        let entry = TraceEntry {
            category: category.0,
            metadata: category.1.clone(),
            start_time: (start_time - CrossProcessInstant::epoch()).whole_nanoseconds() as u64,
            end_time: (end_time - CrossProcessInstant::epoch()).whole_nanoseconds() as u64,
        };
        serde_json::to_writer(&mut self.file, &entry).unwrap();
        writeln!(&mut self.file, ",").unwrap();
    }
}

impl Drop for TraceDump {
    /// Write the epilogue of the trace dump HTML file out to disk on
    /// destruction.
    fn drop(&mut self) {
        write_epilogue(&mut self.file).unwrap();
    }
}

fn write_prologue(file: &mut fs::File) -> io::Result<()> {
    writeln!(file, "{}", include_str!("./trace-dump-prologue-1.html"))?;
    writeln!(file, "{}", include_str!("./trace-dump.css"))?;
    writeln!(file, "{}", include_str!("./trace-dump-prologue-2.html"))
}

fn write_epilogue(file: &mut fs::File) -> io::Result<()> {
    writeln!(file, "{}", include_str!("./trace-dump-epilogue-1.html"))?;
    writeln!(file, "{}", include_str!("./trace-dump.js"))?;
    writeln!(file, "{}", include_str!("./trace-dump-epilogue-2.html"))
}