tinywasm_types/
archive.rs

1use core::fmt::{Display, Formatter};
2
3use alloc::vec::Vec;
4
5use crate::Module;
6
7#[rustfmt::skip]
8const TWASM_MAGIC: [u8; 16] = [ TWASM_MAGIC_PREFIX[0], TWASM_MAGIC_PREFIX[1], TWASM_MAGIC_PREFIX[2], TWASM_MAGIC_PREFIX[3], TWASM_VERSION[0], TWASM_VERSION[1], 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
9const TWASM_MAGIC_PREFIX: &[u8; 4] = b"TWAS";
10const TWASM_VERSION: &[u8; 2] = b"03";
11
12fn validate_magic(wasm: &[u8]) -> Result<usize, TwasmError> {
13    if wasm.len() < TWASM_MAGIC.len() || &wasm[..TWASM_MAGIC_PREFIX.len()] != TWASM_MAGIC_PREFIX {
14        return Err(TwasmError::InvalidMagic);
15    }
16    if &wasm[TWASM_MAGIC_PREFIX.len()..TWASM_MAGIC_PREFIX.len() + TWASM_VERSION.len()] != TWASM_VERSION {
17        return Err(TwasmError::InvalidVersion);
18    }
19    if wasm[TWASM_MAGIC_PREFIX.len() + TWASM_VERSION.len()..TWASM_MAGIC.len()] != [0; 10] {
20        return Err(TwasmError::InvalidPadding);
21    }
22
23    Ok(TWASM_MAGIC.len())
24}
25
26#[derive(Debug)]
27pub enum TwasmError {
28    InvalidMagic,
29    InvalidVersion,
30    InvalidPadding,
31    InvalidArchive(postcard::Error),
32}
33
34impl Display for TwasmError {
35    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
36        match self {
37            Self::InvalidMagic => write!(f, "Invalid twasm: invalid magic number"),
38            Self::InvalidVersion => write!(f, "Invalid twasm: invalid version"),
39            Self::InvalidPadding => write!(f, "Invalid twasm: invalid padding"),
40            Self::InvalidArchive(e) => write!(f, "Invalid twasm: {e}"),
41        }
42    }
43}
44
45#[cfg(feature = "std")]
46extern crate std;
47
48impl core::error::Error for TwasmError {}
49
50impl Module {
51    /// Creates a [`Module`] from a slice of bytes.
52    pub fn try_from_twasm(wasm: &[u8]) -> Result<Self, TwasmError> {
53        let len = validate_magic(wasm)?;
54        postcard::from_bytes(&wasm[len..]).map_err(TwasmError::InvalidArchive)
55    }
56
57    /// Serializes the [`Module`] into a vector of bytes.
58    pub fn serialize_twasm(&self) -> Result<Vec<u8>, TwasmError> {
59        let buf = Vec::from(TWASM_MAGIC);
60        postcard::to_extend(self, buf).map_err(TwasmError::InvalidArchive)
61    }
62}
63
64#[cfg(test)]
65mod tests {
66    use super::*;
67
68    #[test]
69    fn test_invalid_magic() {
70        let wasm = Module::default();
71        let mut twasm = wasm.serialize_twasm().expect("should serialize");
72        twasm[0] = 0;
73        assert!(matches!(Module::try_from_twasm(&twasm), Err(TwasmError::InvalidMagic)));
74    }
75
76    #[test]
77    fn test_invalid_version() {
78        let wasm = Module::default();
79        let mut twasm = wasm.serialize_twasm().expect("should serialize");
80        twasm[4] = 0;
81        assert!(matches!(Module::try_from_twasm(&twasm), Err(TwasmError::InvalidVersion)));
82    }
83}
tinywasm_types/archive.rs

tinywasm_types/
archive.rs
