memapi2

A small, no_std/no_alloc-friendly allocation interface for raw buffers, with explicit layouts, split allocator traits, and structured errors.

MSRV: 1.46.0 (some features require newer compilers or nightly; see Feature flags)

Highlights

• Split allocator traits: Alloc, Dealloc, Grow, Shrink, Realloc, plus BasicAlloc and FullAlloc aliases
• Custom Layout type with conversion to/from alloc::alloc::Layout (unless no_alloc is on)
• Generic Error types for allocation traits
• Structured error reporting via Error and Cause, with optional OS error capture
• Optional allocator implementations: DefaultAlloc, std::alloc::System, c_alloc::CAlloc, stack_alloc::StackAlloc (experimental)
• Data utilities for size/alignment/metadata via data::type_props and data::marker
• no_std by default; alloc is used unless no_alloc is enabled

Installation

[dependencies]
memapi2 = "0.8.1"

If you want common optional features:

[dependencies]
memapi2 = { version = "0.8.1", features = ["os_err_reporting", "c_alloc"] }

Example

use memapi2::{DefaultAlloc, Layout, traits::*};

fn main() -> Result<(), memapi2::error::Error> {
    let alloc = DefaultAlloc;
    let layout = Layout::from_size_align(64, 8)?;

    let ptr = alloc.alloc(layout)?;
    unsafe {
        core::ptr::write_bytes(ptr.as_ptr(), 0xCD, layout.size());
        alloc.try_dealloc(ptr, layout)?;
    }

    Ok(())
}

Feature flags

• std: enable std integration (including std::alloc::System)
• os_err_reporting: best-effort OS error reporting via errno (requires std)
• alloc_mut_traits: mutable allocator trait variants (AllocMut, DeallocMut, ...)
• alloc_temp_trait: scoped/temporary allocation trait (AllocTemp)
• c_alloc: C aligned_alloc-style allocator (c_alloc::CAlloc)
• stack_alloc: alloca-based allocator (stack_alloc::StackAlloc, experimental, requires a C toolchain)
• c_str: enable CStr-specific data traits in no_std (MSRV: 1.64)
• metadata: nightly core::ptr::Pointee metadata support
• sized_hierarchy: nightly core::marker::MetaSized support
• no_alloc: disable the alloc crate (removes DefaultAlloc, StdLayout, and implementations for the System allocator)
• no_nightly: disable automatic nightly detection in build.rs
• full_msrv: convenience bundle (os_err_reporting, c_alloc, stack_alloc, alloc_mut_traits)
• full: full_msrv + c_str
• all_nightly: metadata + sized_hierarchy
• full_nightly: full + all_nightly

Notes

• DefaultAlloc delegates to the global allocator. Do not set it as the global allocator itself, or you will cause infinite recursion.
• This crate is low-level and uses raw pointers. Read the safety contracts on trait methods and layout constructors carefully.

Documentation

• API reference: https://docs.rs/memapi2

License

Licensed under GPL-3.0 OR MIT. See LICENSE-GPL and LICENSE-MIT.