Feature Flags

PulseMap uses Cargo feature flags to control optional functionality.

Available Features

Feature Details

std (default)

Enables:

• ConcurrentPulseMap (requires RwLock, Mutex, AtomicU8)
• ShardedPulseMap (16 shards, requires std)
• SlabPool (requires heap allocation)
• Display and Debug formatting

# With std (default)
pulse_map = "0.6"

# Without std (no_std mode)
pulse_map = { version = "0.6", default-features = false }

no_std Mode

When std is disabled, only the core data structures are available:

• MetaWord — 8-byte metadata packing
• Slot — 14-byte inline/slab storage
• Bucket — 64-byte cache line unit
• PulseMapRaw — basic insert/get/remove/TTL

Use case: Embedded systems, OS kernels, WebAssembly.

Works on targets without native 64-bit atomics (WASM32, ARMv7-M, 32-bit) via portable-atomic fallback. For targets without any atomic CAS (Cortex-M0, ESP32-C3), enable the critical-section feature.

See Embedded & no_std for the full target matrix, QEMU testing, and memory footprint on microcontrollers.

critical-section

Required for targets without hardware atomic CAS (Cortex-M0, RISC-V without the A extension). Routes AtomicU64 operations through interrupt masking.

pulse_map = { version = "0.6", default-features = false, features = ["critical-section"] }

The critical-section implementation must come from your HAL (e.g. cortex-m with critical-section-single-core, or esp-hal). See Embedded & no_std for details.

simd

Enables SIMD-accelerated H2 fingerprint matching on x86_64:

pulse_map = { version = "0.6", features = ["simd"] }

Uses SSE2 _mm_cmpeq_epi8 to compare all 4 H2 fingerprints simultaneously:

#![allow(unused)]
fn main() {
// Without SIMD: sequential comparison
fn match_mask_scalar(h2: u8) -> u8 {
    let mut mask = 0;
    for i in 0..4 {
        if self.get_h2(i) == h2 { mask |= 1 << i; }
    }
    mask
}

// With SIMD: single instruction
fn match_mask_simd(h2: u8) -> u8 {
    let needle = _mm_set1_epi8(h2 as i8);
    let result = _mm_cmpeq_epi8(self.as_xmm(), needle);
    _mm_movemask_epi8(result) as u8 & 0x0F
}
}

Performance impact: ~15% faster lookups on x86_64 with high bucket occupancy.

Compile-Time Configuration

# Build with all features
cargo build --all-features

# Build for no_std
cargo build --no-default-features

# Build with SIMD only
cargo build --features simd

# Test specific feature combination
cargo test --no-default-features
cargo test --features simd

# Docs.rs (all features)
cargo doc --all-features --no-deps --open