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0220cd3 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 | //! # format=flowed support.
//!
//! Format=flowed is defined in
//! [RFC 3676](https://tools.ietf.org/html/rfc3676).
//!
//! Older [RFC 2646](https://tools.ietf.org/html/rfc2646) is used
//! during formatting, i.e., DelSp parameter introduced in RFC 3676
//! is assumed to be set to "no".
//!
//! For received messages, DelSp parameter is honoured.
#![cfg_attr(not(test), forbid(clippy::indexing_slicing))]
#![cfg_attr(not(test), forbid(clippy::string_slice))]
/// Wraps line to 72 characters using format=flowed soft breaks.
///
/// 72 characters is the limit recommended by RFC 3676.
///
/// The function breaks line only after SP and before non-whitespace
/// characters. It also does not insert breaks before ">" to avoid the
/// need to do space stuffing (see RFC 3676) for quotes.
///
/// If there are long words, line may still exceed the limits on line
/// length. However, this should be rare and should not result in
/// immediate mail rejection: SMTP (RFC 2821) limit is 998 characters,
/// and Spam Assassin limit is 78 characters.
fn format_line_flowed(line: &str, prefix: &str) -> String {
let mut result = String::new();
let mut buffer = prefix.to_string();
let mut after_space = prefix.ends_with(' ');
for c in line.chars() {
if c == ' ' {
if buffer.is_empty() {
// Space stuffing, see RFC 3676
buffer.push(' ');
}
buffer.push(c);
after_space = true;
} else if c == '>' {
if buffer.is_empty() {
// Space stuffing, see RFC 3676
buffer.push(' ');
}
buffer.push(c);
after_space = false;
} else {
if after_space && buffer.len() >= 72 && !c.is_whitespace() {
// Flush the buffer and insert soft break (SP CRLF).
result += &buffer;
result += "\r\n";
buffer = prefix.to_string();
}
buffer.push(c);
after_space = false;
}
}
result + &buffer
}
/// Returns text formatted according to RFC 3676 (format=flowed).
///
/// This function accepts text separated by LF, but returns text
/// separated by CRLF.
///
/// RFC 2646 technique is used to insert soft line breaks, so DelSp
/// SHOULD be set to "no" when sending.
pub fn format_flowed(text: &str) -> String {
let mut result = String::new();
for line in text.split('\n') {
if !result.is_empty() {
result += "\r\n";
}
let line = line.trim_end();
let quote_depth = line.chars().take_while(|&c| c == '>').count();
let (prefix, mut line) = line.split_at(quote_depth);
let mut prefix = prefix.to_string();
if quote_depth > 0 {
if let Some(s) = line.strip_prefix(' ') {
line = s;
prefix += " ";
}
}
result += &format_line_flowed(line, &prefix);
}
result
}
/// Same as format_flowed(), but adds "> " prefix to each line.
pub fn format_flowed_quote(text: &str) -> String {
let mut result = String::new();
for line in text.split('\n') {
if !result.is_empty() {
result += "\n";
}
result += "> ";
result += line;
}
format_flowed(&result)
}
/// Joins lines in format=flowed text.
///
/// Lines must be separated by single LF.
///
/// Signature separator line is not processed here, it is assumed to
/// be stripped beforehand.
pub fn unformat_flowed(text: &str, delsp: bool) -> String {
let mut result = String::new();
let mut skip_newline = true;
for line in text.split('\n') {
let line = if !result.is_empty() && skip_newline {
line.trim_start_matches('>')
} else {
line
};
// Revert space-stuffing
let line = line.strip_prefix(' ').unwrap_or(line);
if !skip_newline {
result.push('\n');
}
if let Some(line) = line.strip_suffix(' ') {
// Flowed line
result += line;
if !delsp {
result.push(' ');
}
skip_newline = true;
} else {
// Fixed line
result += line;
skip_newline = false;
}
}
result
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_format_flowed() {
let text = "";
assert_eq!(format_flowed(text), "");
let text = "Foo bar baz";
assert_eq!(format_flowed(text), text);
let text = ">Foo bar";
assert_eq!(format_flowed(text), text);
let text = "> Foo bar";
assert_eq!(format_flowed(text), text);
let text = ">\n\nA";
assert_eq!(format_flowed(text), ">\r\n\r\nA");
let text = "This is the Autocrypt Setup Message used to transfer your key between clients.\n\
\n\
To decrypt and use your key, open the message in an Autocrypt-compliant client and enter the setup code presented on the generating device.";
let expected = "This is the Autocrypt Setup Message used to transfer your key between clients.\r\n\
\r\n\
To decrypt and use your key, open the message in an Autocrypt-compliant \r\n\
client and enter the setup code presented on the generating device.";
assert_eq!(format_flowed(text), expected);
let text = "> A quote";
assert_eq!(format_flowed(text), "> A quote");
let text = "> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > A";
assert_eq!(
format_flowed(text),
"> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > \r\n> A"
);
// Test space stuffing of wrapped lines
let text = "> This is the Autocrypt Setup Message used to transfer your key between clients.\n\
> \n\
> To decrypt and use your key, open the message in an Autocrypt-compliant client and enter the setup code presented on the generating device.";
let expected = "> This is the Autocrypt Setup Message used to transfer your key between \r\n\
> clients.\r\n\
>\r\n\
> To decrypt and use your key, open the message in an Autocrypt-compliant \r\n\
> client and enter the setup code presented on the generating device.";
assert_eq!(format_flowed(text), expected);
let text = ">> This is the Autocrypt Setup Message used to transfer your key between clients.\n\
>> \n\
>> To decrypt and use your key, open the message in an Autocrypt-compliant client and enter the setup code presented on the generating device.";
let expected = ">> This is the Autocrypt Setup Message used to transfer your key between \r\n\
>> clients.\r\n\
>>\r\n\
>> To decrypt and use your key, open the message in an Autocrypt-compliant \r\n\
>> client and enter the setup code presented on the generating device.";
assert_eq!(format_flowed(text), expected);
// Test space stuffing of spaces.
let text = " Foo bar baz";
assert_eq!(format_flowed(text), " Foo bar baz");
let text = " Foo bar baz";
assert_eq!(format_flowed(text), " Foo bar baz");
let text =
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAA";
let expected =
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA \r\nAAAAAA";
assert_eq!(format_flowed(text), expected);
}
#[test]
fn test_unformat_flowed() {
let text = "this is a very long message that should be wrapped using format=flowed and \n\
unwrapped on the receiver";
let expected =
"this is a very long message that should be wrapped using format=flowed and \
unwrapped on the receiver";
assert_eq!(unformat_flowed(text, false), expected);
let text = " Foo bar";
let expected = " Foo bar";
assert_eq!(unformat_flowed(text, false), expected);
let text =
"> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > \n> A";
let expected =
"> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > A";
assert_eq!(unformat_flowed(text, false), expected);
}
#[test]
fn test_format_flowed_quote() {
let quote = "this is a quoted line";
let expected = "> this is a quoted line";
assert_eq!(format_flowed_quote(quote), expected);
let quote = "first quoted line\nsecond quoted line";
let expected = "> first quoted line\r\n> second quoted line";
assert_eq!(format_flowed_quote(quote), expected);
let quote = "> foo bar baz";
let expected = "> > foo bar baz";
assert_eq!(format_flowed_quote(quote), expected);
let quote = "this is a very long quote that should be wrapped using format=flowed and unwrapped on the receiver";
let expected =
"> this is a very long quote that should be wrapped using format=flowed and \r\n\
> unwrapped on the receiver";
assert_eq!(format_flowed_quote(quote), expected);
}
}
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