60 lines
1.9 KiB
Rust
60 lines
1.9 KiB
Rust
//! When calling this dynamic library with outside programs,
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//! outer programs may usually need to fetch string resource produced by Rust code.
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//! However it is impossible pass Rust string directly to outer program.
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//!
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//! This module provide **thread independent** string cache for resolving this issue.
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//! When we need pass string to outer programs, we push that string into this string as C-like format,
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//! then return its pointer to outer program.
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//! So that outside program can utilize it like calling C/C++ library.
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//! The only thing that outer programs should note is that this string is volatile,
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//! once they get it, they must dupliate it immediately before any futher calling to this dynamic library.
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use std::cell::RefCell;
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use std::ffi::{CString, c_char};
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struct StringCache {
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msg: CString,
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}
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impl StringCache {
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fn new() -> Self {
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Self {
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msg: CString::new("").expect("empty string must be valid for CString"),
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}
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}
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pub fn set_msg(&mut self, msg: &str) {
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self.msg = CString::new(msg).expect("unexpected blank in string push into string cache");
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}
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pub fn get_msg(&self) -> *const c_char {
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self.msg.as_ptr()
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}
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pub fn clear_msg(&mut self) {
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self.msg = CString::new("").expect("empty string must be valid for CString");
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}
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}
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thread_local! {
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static STRING_CACHE: RefCell<StringCache> = RefCell::new(StringCache::new());
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}
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/// Set thread local string cache.
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pub fn set_string_cache(msg: &str) {
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STRING_CACHE.with(|e| {
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e.borrow_mut().set_msg(msg);
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});
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}
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/// Get const pointer to thread local string cache for outside program visiting.
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pub fn get_string_cache() -> *const c_char {
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STRING_CACHE.with(|e| e.borrow().get_msg())
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}
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/// Clear thread local string cache.
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pub fn clear_string_cache() {
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STRING_CACHE.with(|e| {
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e.borrow_mut().clear_msg();
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});
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}
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