138 lines
3.3 KiB
Rust
138 lines
3.3 KiB
Rust
use anyhow::*;
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use crate::Mime;
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use crate::util::Cowy;
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#[derive(Debug,Clone,PartialEq,Eq,Default)]
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pub struct Meta(String);
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impl Meta {
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pub const MAX_LEN: usize = 1024;
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/// Creates a new "Meta" string.
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/// Fails if `meta` contains `\n`.
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pub fn new(meta: impl Cowy<str>) -> Result<Self> {
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ensure!(!meta.as_ref().contains('\n'), "Meta must not contain newlines");
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ensure!(meta.as_ref().len() <= Self::MAX_LEN, "Meta must not exceed {} bytes", Self::MAX_LEN);
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Ok(Self(meta.into()))
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}
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/// Creates a new "Meta" string.
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/// Truncates `meta` to before:
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/// - the first occurrence of `\n`
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/// - the character that makes `meta` exceed `Meta::MAX_LEN`
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pub fn new_lossy(meta: impl Cowy<str>) -> Self {
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let meta = meta.as_ref();
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let truncate_pos = meta.char_indices().position(|(i, ch)| {
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let is_newline = ch == '\n';
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let exceeds_limit = (i + ch.len_utf8()) > Self::MAX_LEN;
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is_newline || exceeds_limit
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});
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let meta: String = match truncate_pos {
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None => meta.into(),
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Some(truncate_pos) => meta.get(..truncate_pos).unwrap().into(),
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};
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Self(meta)
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}
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pub fn empty() -> Self {
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Self::default()
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}
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pub fn as_str(&self) -> &str {
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&self.0
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}
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pub fn to_mime(&self) -> Result<Mime> {
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let mime = self.as_str().parse::<Mime>()
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.context("Meta is not a valid MIME")?;
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Ok(mime)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use std::iter::repeat;
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#[test]
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fn new_rejects_newlines() {
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let meta = "foo\nbar";
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let meta = Meta::new(meta);
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assert!(meta.is_err());
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}
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#[test]
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fn new_accepts_max_len() {
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let meta: String = repeat('x').take(Meta::MAX_LEN).collect();
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let meta = Meta::new(meta);
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assert!(meta.is_ok());
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}
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#[test]
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fn new_rejects_exceeding_max_len() {
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let meta: String = repeat('x').take(Meta::MAX_LEN + 1).collect();
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let meta = Meta::new(meta);
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assert!(meta.is_err());
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}
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#[test]
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fn new_lossy_truncates() {
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let meta = "foo\r\nbar\nquux";
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let meta = Meta::new_lossy(meta);
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assert_eq!(meta.as_str(), "foo\r");
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}
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#[test]
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fn new_lossy_no_truncate() {
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let meta = "foo bar\r";
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let meta = Meta::new_lossy(meta);
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assert_eq!(meta.as_str(), "foo bar\r");
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}
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#[test]
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fn new_lossy_empty() {
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let meta = "";
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let meta = Meta::new_lossy(meta);
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assert_eq!(meta.as_str(), "");
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}
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#[test]
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fn new_lossy_truncates_to_empty() {
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let meta = "\n\n\n";
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let meta = Meta::new_lossy(meta);
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assert_eq!(meta.as_str(), "");
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}
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#[test]
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fn new_lossy_truncates_to_max_len() {
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let meta: String = repeat('x').take(Meta::MAX_LEN + 1).collect();
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let meta = Meta::new_lossy(meta);
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assert_eq!(meta.as_str().len(), Meta::MAX_LEN);
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}
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#[test]
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fn new_lossy_truncates_multi_byte_sequences() {
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let mut meta: String = repeat('x').take(Meta::MAX_LEN - 1).collect();
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meta.push('🦀');
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assert_eq!(meta.len(), Meta::MAX_LEN + 3);
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let meta = Meta::new_lossy(meta);
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assert_eq!(meta.as_str().len(), Meta::MAX_LEN - 1);
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}
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}
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