bt_obex/header/
obex_string.rs

1// Copyright 2023 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use crate::error::PacketError;
6
7/// Represents the String type that is sent/received in an OBEX packet.
8/// Encoded as null-terminated UTF-16 text.
9/// Defined in OBEX 1.5. Section 2.1.
10#[derive(Clone, Debug, PartialEq)]
11pub struct ObexString(pub String);
12
13impl ObexString {
14    pub fn len(&self) -> usize {
15        self.to_be_bytes().len()
16    }
17
18    pub fn to_be_bytes(&self) -> Vec<u8> {
19        self.0
20            .encode_utf16()
21            .chain([0]) // Add the null terminator
22            .map(|v| v.to_be_bytes())
23            .flatten()
24            .collect()
25    }
26}
27
28impl From<String> for ObexString {
29    fn from(src: String) -> ObexString {
30        ObexString(src)
31    }
32}
33
34impl From<&str> for ObexString {
35    fn from(src: &str) -> ObexString {
36        ObexString(src.to_string())
37    }
38}
39
40impl TryFrom<&[u8]> for ObexString {
41    type Error = PacketError;
42
43    fn try_from(src: &[u8]) -> Result<Self, Self::Error> {
44        if src.len() == 0 {
45            return Ok(Self(String::new()));
46        }
47
48        let unicode_array = src
49            .chunks_exact(2)
50            .into_iter()
51            .map(|a| u16::from_be_bytes([a[0], a[1]]))
52            .collect::<Vec<u16>>();
53        let mut text = String::from_utf16(&unicode_array).map_err(PacketError::external)?;
54        // OBEX Strings are represented as null terminated Unicode text. See OBEX 1.5 Section 2.1.
55        if !text.ends_with('\0') {
56            return Err(PacketError::data("text missing null terminator"));
57        }
58
59        let _ = text.pop();
60        Ok(Self(text))
61    }
62}
63
64impl ToString for ObexString {
65    fn to_string(&self) -> String {
66        self.0.clone()
67    }
68}
69
70#[cfg(test)]
71mod tests {
72    use super::*;
73
74    use assert_matches::assert_matches;
75
76    fn expect_strings_equal(s1: ObexString, s2: String) {
77        assert_eq!(s1.0, s2);
78    }
79
80    #[fuchsia::test]
81    fn obex_string_from_bytes() {
82        // Empty buf
83        let converted = ObexString::try_from(&[][..]).expect("can convert to String");
84        expect_strings_equal(converted, "".to_string());
85
86        // Just a null terminator.
87        let buf = [0x00, 0x00];
88        let converted = ObexString::try_from(&buf[..]).expect("can convert to String");
89        expect_strings_equal(converted, "".to_string());
90
91        // "hello"
92        let buf = [0x00, 0x68, 0x00, 0x65, 0x00, 0x6c, 0x00, 0x6c, 0x00, 0x6f, 0x00, 0x00];
93        let converted = ObexString::try_from(&buf[..]).expect("can convert to String");
94        expect_strings_equal(converted, "hello".to_string());
95
96        // "bob" with two null terminators - only last is removed.
97        let buf = [0x00, 0x62, 0x00, 0x6f, 0x00, 0x62, 0x00, 0x00, 0x00, 0x00];
98        let converted = ObexString::try_from(&buf[..]).expect("can convert to String");
99        expect_strings_equal(converted, "bob\0".to_string());
100    }
101
102    #[fuchsia::test]
103    fn obex_string_missing_terminator_is_error() {
104        // `foo.txt` with no null terminator.
105        let buf =
106            [0x00, 0x66, 0x00, 0x6f, 0x00, 0x6f, 0x00, 0x2e, 0x00, 0x74, 0x00, 0x78, 0x00, 0x74];
107        let converted = ObexString::try_from(&buf[..]);
108        assert_matches!(converted, Err(PacketError::Data(_)));
109    }
110
111    #[fuchsia::test]
112    fn obex_string_invalid_utf16_is_error() {
113        // Invalid utf-16 bytes.
114        let buf =
115            [0xd8, 0x34, 0xdd, 0x1e, 0x00, 0x6d, 0x00, 0x75, 0xd8, 0x00, 0x00, 0x69, 0x00, 0x63];
116        let converted = ObexString::try_from(&buf[..]);
117        assert_matches!(converted, Err(PacketError::Other(_)));
118    }
119}
bt_obex/header/obex_string.rs

bt_obex/header/
obex_string.rs
