alloc_cat 1.1.1

a simple allocator for small-to-tiny Wasm projects in rust
Documentation 
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use core::arch::wasm32;
use core::fmt;

use super::{Heap, PAGE_SIZE};


unsafe extern "C" {
    /// &__heap_base: the start of the heap
    static __heap_base: u8;
}

#[derive(Debug)]
pub struct WasmHeap {}

impl Heap for WasmHeap {
    fn heap_start(&self) -> usize {
        &raw const __heap_base as usize
    }

    fn heap_end(&self) -> usize {
        wasm32::memory_size(0) * PAGE_SIZE
    }

    fn heap_grow(&self, pages: usize) -> Option<*mut u8> {
        let prev_size = wasm32::memory_grow(0, pages);
        if  prev_size != usize::MAX {
            Some((prev_size * PAGE_SIZE) as *mut u8)
        } else {
            None
        }
    }
}

impl fmt::Display for WasmHeap {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "WASM")
    }
}