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//! Implementation for WASI Preview 1
use crate::Error;
use core::mem::MaybeUninit;
pub use crate::util::{inner_u32, inner_u64};
// This linking is vendored from the wasi crate:
#[link(wasm_import_module = "wasi_snapshot_preview1")]
extern "C" {
fn random_get(arg0: i32, arg1: i32) -> i32;
}
/// WASI p1 uses `u16` for error codes in its witx definitions:
const MAX_ERROR_CODE: i32 = u16::MAX as i32;
#[inline]
pub fn fill_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
// Based on the wasi code:
// Note that size of an allocated object can not be bigger than isize::MAX bytes.
// WASI 0.1 supports only 32-bit WASM, so casting length to `i32` is safe.
#[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
let ret = unsafe { random_get(dest.as_mut_ptr() as i32, dest.len() as i32) };
match ret {
0 => Ok(()),
// WASI functions should return positive error codes which are smaller than `MAX_ERROR_CODE`
code if code <= MAX_ERROR_CODE => Err(Error::from_neg_error_code(-code)),
_ => Err(Error::UNEXPECTED),
}
}