Crate esp_alloc

A no_std heap allocator for RISC-V and Xtensa processors from Espressif. Supports all currently available ESP32 devices.

NOTE: using this as your global allocator requires using Rust 1.68 or greater, or the nightly release channel.

Using this as your Global Allocator

use esp_alloc as _;

fn init_heap() {
    const HEAP_SIZE: usize = 32 * 1024;
    static mut HEAP: MaybeUninit<[u8; HEAP_SIZE]> = MaybeUninit::uninit();

    unsafe {
        esp_alloc::HEAP.add_region(esp_alloc::HeapRegion::new(
            HEAP.as_mut_ptr() as *mut u8,
            HEAP_SIZE,
            esp_alloc::MemoryCapability::Internal.into(),
        ));
    }
}

Using this with the nightly allocator_api-feature

Sometimes you want to have more control over allocations.

For that, it’s convenient to use the nightly allocator_api-feature, which allows you to specify an allocator for single allocations.

NOTE: To use this, you have to enable the crate’s nightly feature flag.

Create and initialize an allocator to use in single allocations:

static PSRAM_ALLOCATOR: esp_alloc::EspHeap = esp_alloc::EspHeap::empty();

fn init_psram_heap() {
    unsafe {
        PSRAM_ALLOCATOR.add_region(esp_alloc::HeapRegion::new(
            psram::psram_vaddr_start() as *mut u8,
            psram::PSRAM_BYTES,
            esp_alloc::MemoryCapability::Internal.into(),
        ));
    }
}

And then use it in an allocation:

let large_buffer: Vec<u8, _> = Vec::with_capacity_in(1048576, &PSRAM_ALLOCATOR);

Macros

• heap_allocator
  Initialize a global heap allocator providing a heap of the given size in bytes
• psram_allocator
  Initialize a global heap allocator backed by PSRAM

Structs

• EspHeap
  A memory allocator
• HeapRegion
  A memory region to be used as heap memory

Enums

• MemoryCapability
  Describes the properties of a memory region

Statics

• HEAP
  The global allocator instance