alef 0.23.26

Opinionated polyglot binding generator for Rust libraries
Documentation 
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/// Opaque handle to a {{ service_name }} service instance.
/// Allocated by constructor_{{ service_snake }}(), freed by free_{{ service_snake }}().
/// Thread safety: this handle wraps the Rust owner, which may not be Send/Sync.
/// The JNI binding layer is responsible for thread synchronization via JVM thread attachment.
#[repr(C)]
pub struct {{ opaque_name }} {
    pub inner: {{ owner_path }},
}

/// Allocate a new {{ service_name }} instance.
///
/// Returns the address as a jlong pointer. This pointer must be freed via free_{{ service_snake }}().
/// Never dereference this pointer after freeing it.
#[no_mangle]
pub extern "system" fn {{ ctor_symbol }}() -> jlong {
    let owner = {{ owner_path }}::{{ constructor_name }}();
    let opaque = Box::new({{ opaque_name }} {
        inner: owner,
    });
    Box::into_raw(opaque) as jlong
}

/// Free a {{ service_name }} instance allocated by constructor_{{ service_snake }}().
///
/// # Safety
/// - handle must have been allocated by constructor_{{ service_snake }}().
/// - After this call, handle is invalid and must not be dereferenced.
/// - Calling this twice on the same handle causes undefined behavior.
#[no_mangle]
pub extern "system" fn {{ dtor_symbol }}(_env: EnvUnowned, _class: JClass, handle: jlong) {
    if handle != 0 {
        // SAFETY: handle was allocated by into_raw above; we are the sole owner
        // and this is the final drop.
        unsafe {
            let _ = Box::from_raw(handle as *mut {{ opaque_name }});
        }
    }
}