feat: update cdylib cstr ffi module

wfassoc-cdylib/src/cstr_ffi.rs

@@ -9,7 +9,7 @@
 //! The only thing that outer programs should note is that this string is volatile,
 //! once they get it, they must dupliate it immediately before any futher calling to this dynamic library.
 use std::cell::RefCell;
-use std::ffi::{CString, c_char};
+use std::ffi::{CString, CStr, c_char};
 
 struct StringCache {
     msg: CString,
@@ -39,21 +39,28 @@ thread_local! {
     static STRING_CACHE: RefCell<StringCache> = RefCell::new(StringCache::new());
 }
 
-/// Set thread local string cache.
-pub fn set_string_cache(msg: &str) {
+/// Set thread local string exposed for C code.
+pub fn set_ffi_string(msg: &str) {
     STRING_CACHE.with(|e| {
         e.borrow_mut().set_msg(msg);
     });
 }
 
-/// Get const pointer to thread local string cache for outside program visiting.
-pub fn get_string_cache() -> *const c_char {
+/// Get const pointer to thread local string exposed for C code.
+pub fn get_ffi_string() -> *const c_char {
     STRING_CACHE.with(|e| e.borrow().get_msg())
 }
 
-/// Clear thread local string cache.
-pub fn clear_string_cache() {
+/// Clear thread local string exposed for C code.
+/// 
+/// This function usually should be called at the beginning of every exposed C functions.
+pub fn clear_ffi_string() {
     STRING_CACHE.with(|e| {
         e.borrow_mut().clear_msg();
     });
 }
+
+/// Parse string given by C code into Rust string.
+pub fn parse_ffi_string<'a>(ptr: *const c_char) -> &'a CStr {
+    unsafe { CStr::from_ptr(ptr) }
+}

wfassoc-cdylib/src/lib.rs

@@ -1,10 +1,10 @@
-use std::cell::RefCell;
+
 use std::ffi::{CString, c_char};
 use thiserror::Error as TeError;
 
 mod object_pool;
 mod last_error;
-mod string_cache;
+mod cstr_ffi;
 mod wrapper;
 
 // region: Error