neotron_loader/
traits.rs

1//! Traits to help us load information from different kinds of data source.
2
3// ============================================================================
4// Imports
5// ============================================================================
6
7// ============================================================================
8// Constants
9// ============================================================================
10
11// ============================================================================
12// Static Variables
13// ============================================================================
14
15// ============================================================================
16// Types
17// ============================================================================
18
19/// The error raised if you are reading from a [`Source`] which is a slice of
20/// bytes.
21#[derive(Debug, Clone)]
22pub struct SliceError;
23
24/// Describes something we can read data from
25pub trait Source {
26    type Error: core::fmt::Debug;
27
28    /// Read some bytes from the source.
29    ///
30    /// The bytes are read from the given offset, and there must be enough data
31    /// to fill `buffer` completely, otherwise an error is returned.
32    fn read(&self, offset: u32, buffer: &mut [u8]) -> Result<(), Self::Error>;
33
34    /// Read a 32-bit big-endian value.
35    fn read_u32_be(&self, offset: u32) -> Result<u32, Self::Error> {
36        let mut bytes = [0; 4];
37        self.read(offset, &mut bytes)?;
38        Ok(u32::from_be_bytes(bytes))
39    }
40
41    /// Read a 32-bit little-endian value.
42    fn read_u32_le(&self, offset: u32) -> Result<u32, Self::Error> {
43        let mut bytes = [0; 4];
44        self.read(offset, &mut bytes)?;
45        Ok(u32::from_le_bytes(bytes))
46    }
47
48    /// Read a 16-bit big-endian value.
49    fn read_u16_be(&self, offset: u32) -> Result<u16, Self::Error> {
50        let mut bytes = [0; 2];
51        self.read(offset, &mut bytes)?;
52        Ok(u16::from_be_bytes(bytes))
53    }
54
55    /// Read a 16-bit little-endian value.
56    fn read_u16_le(&self, offset: u32) -> Result<u16, Self::Error> {
57        let mut bytes = [0; 2];
58        self.read(offset, &mut bytes)?;
59        Ok(u16::from_le_bytes(bytes))
60    }
61
62    /// Read an 8-bit value.
63    fn read_u8(&self, offset: u32) -> Result<u8, Self::Error> {
64        let mut bytes = [0; 1];
65        self.read(offset, &mut bytes)?;
66        Ok(bytes[0])
67    }
68}
69
70impl Source for &[u8] {
71    type Error = SliceError;
72
73    fn read(&self, offset: u32, buffer: &mut [u8]) -> Result<(), Self::Error> {
74        let desired_len = buffer.len();
75        assert!(offset < (usize::MAX - desired_len) as u32);
76        let offset = offset as usize;
77        if let Some(sub_slice) = self.get(offset..offset + desired_len) {
78            buffer.copy_from_slice(sub_slice);
79            Ok(())
80        } else {
81            Err(SliceError)
82        }
83    }
84}
85
86// ============================================================================
87// Functions
88// ============================================================================
89
90// ============================================================================
91// Tests
92// ============================================================================
93
94// ============================================================================
95// End of File
96// ============================================================================
neotron_loader/traits.rs

neotron_loader/
traits.rs
