elf/
string_table.rs

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1//! Interpreting string table sections: `.strtab`, [SHT_STRTAB][crate::abi::SHT_STRTAB]
2use crate::parse::ParseError;
3use core::str::from_utf8;
4
5#[derive(Debug, Default, Clone, Copy)]
6pub struct StringTable<'data> {
7    data: &'data [u8],
8}
9
10impl<'data> StringTable<'data> {
11    pub fn new(data: &'data [u8]) -> Self {
12        StringTable { data }
13    }
14
15    pub fn get_raw(&self, offset: usize) -> Result<&'data [u8], ParseError> {
16        if self.data.is_empty() {
17            return Err(ParseError::BadOffset(offset as u64));
18        };
19
20        let start = self
21            .data
22            .get(offset..)
23            .ok_or(ParseError::BadOffset(offset as u64))?;
24        let end = start
25            .iter()
26            .position(|&b| b == 0u8)
27            .ok_or(ParseError::StringTableMissingNul(offset as u64))?;
28
29        Ok(start.split_at(end).0)
30    }
31
32    pub fn get(&self, offset: usize) -> Result<&'data str, ParseError> {
33        let raw_data = self.get_raw(offset)?;
34        Ok(from_utf8(raw_data)?)
35    }
36}
37
38#[cfg(test)]
39mod tests {
40    use super::*;
41
42    #[test]
43    fn test_empty_table_errors() {
44        let st = StringTable::default();
45        assert!(matches!(st.get(0), Err(ParseError::BadOffset(0))));
46        assert!(matches!(st.get(1), Err(ParseError::BadOffset(1))));
47    }
48
49    /// Note: ELF string tables are defined to always start with a NUL and use
50    /// index 0 to give an empty string, so getting a string starting at a NUL
51    /// should properly give an empty string.
52    #[test]
53    fn test_get_index_0_gives_empty_string() {
54        let data = [0u8, 42u8, 0u8];
55        let st = StringTable::new(&data);
56        assert_eq!(st.get(0).unwrap(), "");
57    }
58
59    #[test]
60    fn test_get_raw_works() {
61        let data = [0u8, 0x45, 0x4C, 0x46, 0u8];
62        let st = StringTable::new(&data);
63        assert_eq!(st.get_raw(1).unwrap(), [0x45, 0x4c, 0x46]);
64    }
65
66    #[test]
67    fn test_get_string_works() {
68        let data = [0u8, 0x45, 0x4C, 0x46, 0u8];
69        let st = StringTable::new(&data);
70        assert_eq!(st.get(1).unwrap(), "ELF");
71    }
72
73    #[test]
74    fn test_get_raw_index_out_of_bounds_errors() {
75        let data = [0u8, 0x45, 0x4C, 0x46, 0u8];
76        let st = StringTable::new(&data);
77        let result = st.get_raw(7);
78        assert!(
79            matches!(result, Err(ParseError::BadOffset(7))),
80            "Unexpected Error type found: {result:?}"
81        );
82    }
83
84    #[test]
85    fn test_get_index_out_of_bounds_errors() {
86        let data = [0u8, 0x45, 0x4C, 0x46, 0u8];
87        let st = StringTable::new(&data);
88        let result = st.get(7);
89        assert!(
90            matches!(result, Err(ParseError::BadOffset(7))),
91            "Unexpected Error type found: {result:?}"
92        );
93    }
94
95    #[test]
96    fn test_get_raw_with_malformed_table_no_trailing_nul() {
97        let data = [0u8, 0x45, 0x4C, 0x46];
98        let st = StringTable::new(&data);
99        let result = st.get_raw(1);
100        assert!(
101            matches!(result, Err(ParseError::StringTableMissingNul(1))),
102            "Unexpected Error type found: {result:?}"
103        );
104    }
105
106    #[test]
107    fn test_get_with_malformed_table_no_trailing_nul() {
108        let data = [0u8, 0x45, 0x4C, 0x46];
109        let st = StringTable::new(&data);
110        let result = st.get(1);
111        assert!(
112            matches!(result, Err(ParseError::StringTableMissingNul(1))),
113            "Unexpected Error type found: {result:?}"
114        );
115    }
116}
elf/string_table.rs

elf/
string_table.rs
