der/asn1/
bmp_string.rs

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1//! ASN.1 `BMPString` support.
2
3use crate::{
4    BytesOwned, DecodeValue, EncodeValue, Error, FixedTag, Header, Length, Reader, Result, Tag,
5    Writer,
6};
7use alloc::{boxed::Box, vec::Vec};
8use core::{fmt, str::FromStr};
9
10/// ASN.1 `BMPString` type.
11///
12/// Encodes Basic Multilingual Plane (BMP) subset of Unicode (ISO 10646),
13/// a.k.a. UCS-2.
14#[derive(Clone, Eq, PartialEq, PartialOrd, Ord)]
15pub struct BmpString {
16    bytes: BytesOwned,
17}
18
19impl BmpString {
20    /// Create a new [`BmpString`] from its UCS-2 encoding.
21    pub fn from_ucs2(bytes: impl Into<Box<[u8]>>) -> Result<Self> {
22        let bytes = bytes.into();
23
24        if bytes.len() % 2 != 0 {
25            return Err(Tag::BmpString.length_error());
26        }
27
28        let ret = Self {
29            bytes: bytes.try_into()?,
30        };
31
32        for maybe_char in char::decode_utf16(ret.codepoints()) {
33            match maybe_char {
34                // All surrogates paired and character is in the Basic Multilingual Plane
35                Ok(c) if (c as u64) < u64::from(u16::MAX) => (),
36                // Unpaired surrogates or characters outside Basic Multilingual Plane
37                _ => return Err(Tag::BmpString.value_error()),
38            }
39        }
40
41        Ok(ret)
42    }
43
44    /// Create a new [`BmpString`] from a UTF-8 string.
45    pub fn from_utf8(utf8: &str) -> Result<Self> {
46        let capacity = utf8
47            .len()
48            .checked_mul(2)
49            .ok_or_else(|| Tag::BmpString.length_error())?;
50
51        let mut bytes = Vec::with_capacity(capacity);
52
53        for code_point in utf8.encode_utf16() {
54            bytes.extend(code_point.to_be_bytes());
55        }
56
57        Self::from_ucs2(bytes)
58    }
59
60    /// Borrow the encoded UCS-2 as bytes.
61    pub fn as_bytes(&self) -> &[u8] {
62        self.bytes.as_ref()
63    }
64
65    /// Obtain the inner bytes.
66    #[inline]
67    pub fn into_bytes(self) -> Box<[u8]> {
68        self.bytes.into()
69    }
70
71    /// Get an iterator over characters in the string.
72    pub fn chars(&self) -> impl Iterator<Item = char> + '_ {
73        char::decode_utf16(self.codepoints())
74            .map(|maybe_char| maybe_char.expect("unpaired surrogates checked in constructor"))
75    }
76
77    /// Get an iterator over the `u16` codepoints.
78    pub fn codepoints(&self) -> impl Iterator<Item = u16> + '_ {
79        // TODO(tarcieri): use `array_chunks`
80        self.as_bytes()
81            .chunks_exact(2)
82            .map(|chunk| u16::from_be_bytes([chunk[0], chunk[1]]))
83    }
84}
85
86impl AsRef<[u8]> for BmpString {
87    fn as_ref(&self) -> &[u8] {
88        self.as_bytes()
89    }
90}
91
92impl<'a> DecodeValue<'a> for BmpString {
93    fn decode_value<R: Reader<'a>>(reader: &mut R, header: Header) -> Result<Self> {
94        Self::from_ucs2(reader.read_vec(header.length)?)
95    }
96}
97
98impl EncodeValue for BmpString {
99    fn value_len(&self) -> Result<Length> {
100        Ok(self.bytes.len())
101    }
102
103    fn encode_value(&self, writer: &mut impl Writer) -> Result<()> {
104        writer.write(self.as_bytes())
105    }
106}
107
108impl FixedTag for BmpString {
109    const TAG: Tag = Tag::BmpString;
110}
111
112impl FromStr for BmpString {
113    type Err = Error;
114
115    fn from_str(s: &str) -> Result<Self> {
116        Self::from_utf8(s)
117    }
118}
119
120impl fmt::Debug for BmpString {
121    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
122        write!(f, "BmpString(\"{}\")", self)
123    }
124}
125
126impl fmt::Display for BmpString {
127    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
128        for c in self.chars() {
129            write!(f, "{}", c)?;
130        }
131        Ok(())
132    }
133}
134
135#[cfg(test)]
136mod tests {
137    use super::BmpString;
138    use crate::{Decode, Encode};
139    use alloc::string::ToString;
140    use hex_literal::hex;
141
142    const EXAMPLE_BYTES: &[u8] = &hex!(
143        "1e 26 00 43 00 65 00 72 00 74"
144        "      00 69 00 66 00 69 00 63"
145        "      00 61 00 74 00 65 00 54"
146        "      00 65 00 6d 00 70 00 6c"
147        "      00 61 00 74 00 65"
148    );
149
150    const EXAMPLE_UTF8: &str = "CertificateTemplate";
151
152    #[test]
153    fn decode() {
154        let bmp_string = BmpString::from_der(EXAMPLE_BYTES).unwrap();
155        assert_eq!(bmp_string.to_string(), EXAMPLE_UTF8);
156    }
157
158    #[test]
159    fn encode() {
160        let bmp_string = BmpString::from_utf8(EXAMPLE_UTF8).unwrap();
161        let encoded = bmp_string.to_der().unwrap();
162        assert_eq!(encoded, EXAMPLE_BYTES);
163    }
164}
der/asn1/bmp_string.rs

der/asn1/
bmp_string.rs
