Module cvec 

Utilities for transferring heap-allocated Rust Vec<T> values across an FFI boundary.

The primary abstraction offered by this module is CVec, a C-compatible struct that stores a raw pointer (ptr) together with the vector’s logical len and cap. By moving the allocation metadata into a plain repr(C) type we allow the memory created by Rust to be owned, inspected, and ultimately freed by foreign code (or vice-versa) without introducing undefined behaviour.

Only a very small API surface is exposed to C:

• cvec_new – create an empty CVec sentinel that can be returned to foreign code.

De-allocation is intentionally not provided via a generic helper. Instead each FFI module must expose its own type-specific vec_*_drop function which reconstructs the original Vec<T> with Vec::from_raw_parts and allows it to drop. This avoids the size-mismatch risk that a one-size-fits-all cvec_drop had in the past.

All other manipulation happens on the Rust side before relinquishing ownership. This keeps the rules for memory safety straightforward: foreign callers must treat the memory region pointed to by ptr as opaque and interact with it solely through the functions provided here.

Structs

CVec

CVec is a C compatible struct that stores an opaque pointer to a block of memory, it’s length and the capacity of the vector it was allocated from.

Functions

cvec_new

Construct a new empty CVec value for use as initialiser/sentinel in foreign code.