velesdb-core 1.9.3

//! Vector to bytes conversion utilities for storage.
//!
//! Provides safe conversion between `&[f32]` vectors and `&[u8]` byte slices
//! for persistence in memory-mapped storage.
//!
//! # Safety (EPIC-032/US-001)
//!
//! - `vector_to_bytes`: Safe because f32 has no invalid bit patterns
//! - `bytes_to_vector`: Safe because it copies bytes into a new aligned `Vec<f32>`
//!   using `ptr::copy_nonoverlapping`, which doesn't require source alignment

/// Converts a vector slice to a byte slice.
///
/// # Safety
///
/// This is safe because:
/// - f32 has no invalid bit patterns
/// - The slice layout is well-defined
/// - The lifetime of the returned slice is tied to the input
#[inline]
pub(super) fn vector_to_bytes(vector: &[f32]) -> &[u8] {
    // SAFETY: `from_raw_parts` requires a valid pointer and byte length.
    // - Condition 1: `vector.as_ptr()` is valid for `size_of_val(vector)` bytes.
    // - Condition 2: Lifetime of returned bytes is tied to `vector`.
    // Reason: Zero-copy view avoids allocating during persistence writes.
    unsafe {
        std::slice::from_raw_parts(vector.as_ptr().cast::<u8>(), std::mem::size_of_val(vector))
    }
}

/// Converts bytes back to a vector.
///
/// # Arguments
///
/// * `bytes` - Raw bytes to convert (must be at least `dimension * 4` bytes)
/// * `dimension` - Expected vector dimension
///
/// # Returns
///
/// A new `Vec<f32>` containing the converted data.
///
/// # Panics
///
/// Panics if `bytes.len() < dimension * size_of::<f32>()`.
#[inline]
pub(super) fn bytes_to_vector(bytes: &[u8], dimension: usize) -> Vec<f32> {
    let vector_size = dimension * std::mem::size_of::<f32>();
    assert!(
        bytes.len() >= vector_size,
        "bytes_to_vector: buffer too small ({} < {})",
        bytes.len(),
        vector_size
    );

    let mut vector = vec![0.0f32; dimension];
    // SAFETY: `copy_nonoverlapping` requires valid, non-overlapping ranges.
    // - Condition 1: Source has at least `vector_size` bytes (assert above).
    // - Condition 2: Destination is freshly allocated `Vec<f32>` storage.
    // Reason: Copying into aligned owned memory avoids alignment UB from direct cast reads.
    unsafe {
        std::ptr::copy_nonoverlapping(
            bytes.as_ptr(),
            vector.as_mut_ptr().cast::<u8>(),
            vector_size,
        );
    }
    vector
}