mdcat/resources/
curl.rs

1// This Source Code Form is subject to the terms of the Mozilla Public
2// License, v. 2.0. If a copy of the MPL was not distributed with this
3// file, You can obtain one at http://mozilla.org/MPL/2.0/.
4
5//! Curl-based resource handler for HTTP/FTP URLs.
6
7use std::{cell::RefCell, time::Duration};
8
9use curl::easy::{Easy2, Handler, WriteError};
10use mime::Mime;
11use tracing::{event, instrument, Level};
12use url::Url;
13
14use super::{filter_schemes, MimeData, ResourceUrlHandler};
15
16/// Handle curl data by writing into a buffer.
17#[derive(Debug, Clone, Default)]
18pub struct CollectBuffer {
19    read_limit: u64,
20    buffer: Vec<u8>,
21}
22
23impl Handler for CollectBuffer {
24    fn write(&mut self, data: &[u8]) -> Result<usize, WriteError> {
25        if self.read_limit < (self.buffer.len() + data.len()).try_into().unwrap() {
26            // Do not handle data and tell curl that we didn't handle it;
27            // this will make curl fail with a write error
28            Ok(0)
29        } else {
30            self.buffer.extend_from_slice(data);
31            Ok(data.len())
32        }
33    }
34}
35
36/// A [`curl`]-based resource handler for remote HTTP/FTP URLs.
37pub struct CurlResourceHandler {
38    easy: RefCell<Easy2<CollectBuffer>>,
39}
40
41impl CurlResourceHandler {
42    /// Create a new resource handler.
43    ///
44    /// `read_limit` is the maximum amount of data to be read from a resource.
45    /// `useragent` is the value of the user agent header.
46    pub fn create(read_limit: u64, useragent: &str) -> std::io::Result<Self> {
47        let mut easy = Easy2::new(CollectBuffer {
48            buffer: Vec::new(),
49            read_limit,
50        });
51        // Use somewhat aggressive timeouts to avoid blocking rendering for long; we have graceful
52        // fallbacks since we have to support terminals without image capabilities anyways.
53
54        easy.timeout(Duration::from_secs(1))?;
55        easy.connect_timeout(Duration::from_secs(1))?;
56        easy.follow_location(true)?;
57        easy.fail_on_error(true)?;
58        easy.tcp_nodelay(true)?;
59        easy.useragent(useragent)?;
60        Ok(Self::new(easy))
61    }
62
63    /// Create a new resource handler.
64    pub fn new(easy: Easy2<CollectBuffer>) -> Self {
65        Self {
66            easy: RefCell::new(easy),
67        }
68    }
69}
70
71impl ResourceUrlHandler for CurlResourceHandler {
72    #[instrument(level = "debug", skip(self), fields(url = %url))]
73    fn read_resource(&self, url: &Url) -> std::io::Result<MimeData> {
74        // See https://curl.se/docs/url-syntax.html for all schemas curl supports
75        // We omit the more exotic ones :)
76        filter_schemes(&["http", "https", "ftp", "ftps", "smb"], url).and_then(|url| {
77            let mut easy = self.easy.borrow_mut();
78            easy.url(url.as_str())?;
79            easy.perform()?;
80
81            let mime_type = easy.content_type()?.and_then(|content_type| {
82                event!(
83                    Level::DEBUG,
84                    "Raw Content-Type of remote resource {}: {:?}",
85                    &url,
86                    content_type
87                );
88                content_type.parse::<Mime>().ok()
89            });
90            let data = easy.get_ref().buffer.clone();
91            easy.get_mut().buffer.clear();
92            Ok(MimeData { mime_type, data })
93        })
94    }
95}
mdcat/resources/curl.rs

mdcat/resources/
curl.rs
