71 lines
2.6 KiB
Rust
71 lines
2.6 KiB
Rust
use super::*;
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use text_processing::grapheme_clusters::Graphemes;
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pub fn encode_header(value: &str) -> String {
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let mut ret = String::with_capacity(value.len());
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let graphemes = value.graphemes_indices();
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let mut is_current_window_ascii = true;
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let mut current_window_start = 0;
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for (idx, g) in graphemes {
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match (g.is_ascii(), is_current_window_ascii) {
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(true, true) => {
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ret.push_str(g);
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}
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(true, false) => {
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/* If !g.is_whitespace()
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*
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* Whitespaces inside encoded tokens must be greedily taken,
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* instead of splitting each non-ascii word into separate encoded tokens. */
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if !g.split_whitespace().collect::<Vec<&str>>().is_empty() {
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ret.push_str(&format!(
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"=?UTF-8?B?{}?=",
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BASE64_MIME
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.encode(value[current_window_start..idx].as_bytes())
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.trim()
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));
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if idx != value.len() - 1 {
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ret.push(' ');
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}
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is_current_window_ascii = true;
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current_window_start = idx;
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ret.push_str(g);
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}
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}
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(false, true) => {
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current_window_start = idx;
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is_current_window_ascii = false;
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}
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/* RFC2047 recommends:
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* 'While there is no limit to the length of a multiple-line header field, each line of
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* a header field that contains one or more 'encoded-word's is limited to 76
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* characters.'
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* This is a rough compliance.
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*/
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(false, false) if (((4 * (idx - current_window_start) / 3) + 3) & !3) > 33 => {
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ret.push_str(&format!(
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"=?UTF-8?B?{}?=",
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BASE64_MIME
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.encode(value[current_window_start..idx].as_bytes())
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.trim()
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));
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if idx != value.len() - 1 {
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ret.push(' ');
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}
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current_window_start = idx;
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}
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(false, false) => {}
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}
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}
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/* If the last part of the header value is encoded, it won't be pushed inside the previous for
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* block */
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if !is_current_window_ascii {
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ret.push_str(&format!(
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"=?UTF-8?B?{}?=",
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BASE64_MIME
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.encode(value[current_window_start..].as_bytes())
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.trim()
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));
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}
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ret
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}
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