add private module with struct Html to fix wrong html charset

sftse · sftse · commit f3d147587857 · 2025-05-14T14:05:43.000+02:00
diff --git a/src/core/html.rs b/src/core/html.rs
@@ -0,0 +1,85 @@
+use std::borrow::Cow;
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, PartialEq, Clone)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct Html<'x>(Cow<'x, str>);
+
+impl<'x> Html<'x> {
+    pub fn make_owned(self) -> Html<'static> {
+        Html(self.0.into_owned().into())
+    }
+    pub fn new(html: Cow<'x, str>) -> Html<'x> {
+        Html(html)
+    }
+    /// Access the raw html with a potentially wrong charset.
+    ///
+    /// `mail-parser` only returns utf-8 strings, so the only sensible charset for the html is utf-8. Because html can declare its charset in `<meta>` tags, in the process of transcoding to utf-8 these may be incorrect.
+    /// Call [`Html::strip_charset`] before this method if the html will be given to a standard-conforming browser.
+    pub fn potentially_wrong_charset(&self) -> &Cow<'x, str> {
+        &self.0
+    }
+    /// Strip charset from html, making it utf-8 by default.
+    ///
+    /// Call this method if the result is given to a standard-conforming browser.
+    pub fn strip_charset(&mut self) {
+        let mut off = 0;
+        let mut first = true;
+        let mut found = None;
+        'meta: for part in self.0.split("<meta") {
+            if !first {
+                let Some((between, _)) = part.split_once('>') else {
+                    return;
+                };
+                for w in between.as_bytes().windows(b"charset".len()) {
+                    if w.eq_ignore_ascii_case(b"charset") {
+                        found = Some((off, off + "<meta".len() + between.len() + ">".len()));
+                        break 'meta;
+                    }
+                }
+                off += "<meta".len();
+            }
+            off += part.len();
+            first = false;
+        }
+        if let Some((start, end)) = found {
+            self.0.to_mut().replace_range(start..end, "");
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn strip(html: &str) -> Cow<'_, str> {
+        let mut html = Html(html.into());
+        html.strip_charset();
+        html.potentially_wrong_charset().clone()
+    }
+
+    #[test]
+    fn strip_charset() {
+        assert_eq!(
+            strip("<head><meta cHarSet=Windows-1252></head>"),
+            "<head></head>"
+        );
+
+        let stripped = strip("<head><meta cHarSet=\"Windows-1252\"></head>");
+        assert_eq!(stripped, "<head></head>");
+
+        let stripped = strip("<head><meta http-equiv=\"Content-Type\" content=\"text/html; cHarSet=Windows-1252\"></head>");
+        assert_eq!(stripped, "<head></head>");
+
+        let stripped = strip("<head><meta http-equiv=\"Content-Type\" content=\"text/html; cHarSet = &quot;Windows-1252&quot;></head>");
+        assert_eq!(stripped, "<head></head>");
+
+        let stripped = strip("<head><meta name=\"xxx\"><meta http-equiv=\"Content-Type\" content=\"text/html; cHarSet = &quot;Windows-1252&quot;></head>");
+        assert_eq!(stripped, "<head><meta name=\"xxx\"></head>");
+
+        let stripped = strip("<head><meta http-equiv=\"Content-Type\" content=\"text/html; cHarSet = &quot;Windows-1252&quot;><meta name=\"xxx\"></head>");
+        assert_eq!(stripped, "<head><meta name=\"xxx\"></head>");
+    }
+}
diff --git a/src/core/mod.rs b/src/core/mod.rs
@@ -8,6 +8,9 @@ pub mod address;
 pub mod body;
 pub mod builder;
 pub mod header;
+mod html;
 pub mod message;
 #[cfg(feature = "rkyv")]
 pub mod rkyv;
+
+pub use html::Html;
diff --git a/src/lib.rs b/src/lib.rs
@@ -11,6 +11,8 @@ pub mod decoders;
 pub mod mailbox;
 pub mod parsers;
 
+
+use core::Html;
 use parsers::MessageStream;
 use std::{borrow::Cow, collections::HashMap, hash::Hash, net::IpAddr};
 
