Add matching rust implementation for Go HashMessage.

src/bin/mailparse.rs

@@ -1,12 +1,6 @@
-use std::env;
-use std::error::Error;
-use std::fs::File;
-use std::io::prelude::*;
-use std::process::exit;
-use std::slice::Iter;
+use std::{env, error::Error, fs::File, io::prelude::*, process::exit, slice::Iter};
 
-use mailparse::dateparse;
-use mailparse::MailHeaderMap;
+use mailparse::{dateparse, MailHeaderMap};
 
 fn newline(b: &u8) -> bool {
     *b == b'\n'
@@ -57,15 +51,15 @@ fn parse_mbox(mbox_bytes: &Vec<u8>) -> Result<(), Box<dyn Error>> {
         let mail = mailparse::parse_mail(mail_bytes).unwrap();
         println!(
             "{:?} {:?} from {:?}",
-            match mail.headers.get_first_value("Date")? {
+            match mail.headers.get_first_value("Date") {
                 Some(date) => date,
                 None => "NO DATE".to_string(),
             },
-            match mail.headers.get_first_value("Subject")? {
+            match mail.headers.get_first_value("Subject") {
                 Some(subject) => subject,
                 None => "NO SUBJECT".to_string(),
             },
-            match mail.headers.get_first_value("From")? {
+            match mail.headers.get_first_value("From") {
                 Some(from) => from,
                 None => "NO FROM".to_string(),
             },

src/lib.rs

@@ -0,0 +1,53 @@
+use mailparse::{parse_headers, MailHeader, MailHeaderMap};
+use sha1::{Digest, Sha1};
+
+// Keep these sorted to match Go implementation.
+const IMPORTANT_HEADERS: &[&str] = &[
+    "cc",
+    "date",
+    "from",
+    "message-id",
+    "received",
+    "subject",
+    "to",
+];
+
+pub fn hash_headers(hdrs: &[MailHeader]) -> String {
+    // create a Sha1 object
+    let mut hasher = Sha1::new();
+
+    for h in IMPORTANT_HEADERS {
+        if let Some(v) = hdrs.get_first_value(h) {
+            eprintln!("V [{}]", v);
+            hasher.update(v);
+        }
+    }
+    format!("{:x}", hasher.finalize())
+}
+
+#[cfg(test)]
+mod tests {
+    use mailparse::{parse_headers, MailHeader, MailHeaderMap};
+    #[test]
+    fn hash_headers() {
+        let (hdrs, _) = parse_headers(
+            concat!(
+                "Subject: Test\n",
+                "From: me@myself.com\n",
+                "To: you@yourself.com"
+            )
+            .as_bytes(),
+        )
+        .unwrap();
+        assert_eq!(hdrs[1].get_key(), "From");
+        assert_eq!(
+            hdrs.get_first_value("To"),
+            Some("you@yourself.com".to_string())
+        );
+
+        assert_eq!(
+            super::hash_headers(&hdrs),
+            "1b25d59ed0ade6a762145c58643717477b054fd1"
+        );
+    }
+}