rust_web_server/compression/
mod.rs

1#[cfg(test)]
2mod tests;
3
4use flate2::Compression;
5use flate2::write::GzEncoder;
6use std::io::Write;
7use crate::header::Header;
8use crate::request::Request;
9use crate::response::Response;
10
11/// MIME types whose responses are worth compressing.
12const COMPRESSIBLE: &[&str] = &[
13    "text/html",
14    "text/css",
15    "text/javascript",
16    "text/plain",
17    "text/xml",
18    "application/json",
19    "application/javascript",
20    "application/xml",
21    "application/xhtml+xml",
22    "image/svg+xml",
23];
24
25/// Bodies smaller than this are sent uncompressed: gzip's framing overhead
26/// and the CPU time outweigh what it saves (Caddy's `encode` uses the same
27/// minimum).
28pub const MIN_COMPRESS_SIZE: usize = 512;
29
30/// If the client accepts gzip and the response body is compressible text of
31/// at least [`MIN_COMPRESS_SIZE`] bytes, compress every content range
32/// in-place and add `Content-Encoding: gzip`; also appends `Accept-Encoding`
33/// to the `Vary` header. A body that gzip doesn't make smaller (already
34/// compressed or random data) is left as it was, and so is a response that
35/// already has a `Content-Encoding` (e.g. a backend that compressed it).
36pub fn apply_gzip(request: &Request, response: &mut Response) {
37    if response.content_range_list.is_empty() {
38        return;
39    }
40    // A partial body (206, one range or several) is a slice of the
41    // representation: gzipping the slice and rewriting Content-Range to the
42    // compressed size describes bytes that don't exist (#52, RFC 9110 §14.4).
43    if response.status_code == 206 || response.content_range_list.len() > 1 {
44        return;
45    }
46    if response.headers.iter().any(|h| h.name.eq_ignore_ascii_case(Header::_CONTENT_ENCODING)) {
47        return;
48    }
49    let original_size: usize = response.content_range_list.iter().map(|cr| cr.body.len()).sum();
50    if original_size < MIN_COMPRESS_SIZE {
51        return;
52    }
53
54    let accepts_gzip = request
55        .get_header(Header::_ACCEPT_ENCODING.to_string())
56        .map(|h| h.value.to_lowercase().contains("gzip"))
57        .unwrap_or(false);
58
59    if !accepts_gzip {
60        return;
61    }
62
63    let content_type = response
64        .content_range_list
65        .first()
66        .map(|cr| cr.content_type.to_lowercase())
67        .unwrap_or_default();
68
69    let is_compressible = COMPRESSIBLE.iter().any(|mime| content_type.starts_with(mime));
70    if !is_compressible {
71        return;
72    }
73
74    let mut compressed_bodies = Vec::with_capacity(response.content_range_list.len());
75    for cr in &response.content_range_list {
76        let mut encoder = GzEncoder::new(Vec::new(), Compression::default());
77        if encoder.write_all(&cr.body).is_err() {
78            return;
79        }
80        match encoder.finish() {
81            Ok(compressed) => compressed_bodies.push(compressed),
82            Err(_) => return,
83        }
84    }
85    let compressed_size: usize = compressed_bodies.iter().map(Vec::len).sum();
86    if compressed_size >= original_size {
87        return;
88    }
89    for (cr, compressed) in response.content_range_list.iter_mut().zip(compressed_bodies) {
90        let new_len = compressed.len() as u64;
91        cr.body = compressed;
92        cr.range.end = new_len;
93        cr.size = new_len.to_string();
94    }
95
96    response.headers.push(Header {
97        name: Header::_CONTENT_ENCODING.to_string(),
98        value: "gzip".to_string(),
99    });
100
101    // append Accept-Encoding to Vary, or add it
102    let vary_pos = response.headers.iter().position(|h| h.name == Header::_VARY);
103    if let Some(i) = vary_pos {
104        let current = response.headers[i].value.clone();
105        if !current.to_lowercase().contains("accept-encoding") {
106            response.headers[i].value = format!("{}, Accept-Encoding", current);
107        }
108    } else {
109        response.headers.push(Header {
110            name: Header::_VARY.to_string(),
111            value: "Accept-Encoding".to_string(),
112        });
113    }
114}
rust_web_server/compression/mod.rs

rust_web_server/compression/
mod.rs
