picoalloc 5.2.0

Simple, small and fast memory allocator
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35

use crate::env::System;
use crate::{Env, Size};

#[polkavm_derive::polkavm_import]
extern "C" {
    #[polkavm_import(symbol = "corevm_alloc_ext")]
    pub fn alloc(size: u64) -> u64;
    #[polkavm_import(symbol = "corevm_free_ext")]
    pub fn free(address: u64, size: u64);
}

impl<const SIZE: usize> Env for System<SIZE> {
    #[inline]
    fn total_space(&self) -> Size {
        const { Size::from_bytes_usize(SIZE).unwrap() }
    }

    #[inline]
    unsafe fn allocate_address_space(&mut self) -> *mut u8 {
        // SAFETY: `alloc` always returns a valid pointer or zero on error.
        let address = unsafe { alloc(u64::from(self.total_space().bytes())) };
        core::ptr::with_exposed_provenance_mut(address as usize)
    }

    #[inline]
    unsafe fn expand_memory_until(&mut self, _base: *mut u8, _size: Size) -> bool {
        true
    }

    #[inline]
    unsafe fn free_address_space(&mut self, base: *mut u8) {
        // SAFETY: `free` always succeeds.
        unsafe { free(base.expose_provenance() as u64, u64::from(self.total_space().bytes())) }
    }
}