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//! Dynamic library facilities.
//!
//! A simple wrapper over the platform's dynamic library facilities
use std::ffi::CString;
use std::path::Path;
pub struct DynamicLibrary {
handle: *mut u8,
}
impl Drop for DynamicLibrary {
fn drop(&mut self) {
unsafe { dl::close(self.handle) }
}
}
impl DynamicLibrary {
/// Lazily open a dynamic library. When passed None it gives a
/// handle to the calling process
pub fn open(filename: Option<&Path>) -> Result<DynamicLibrary, String> {
let maybe_library = dl::open(filename.map(|path| path.as_os_str()));
// The dynamic library must not be constructed if there is
// an error opening the library so the destructor does not
// run.
match maybe_library {
Err(err) => Err(err),
Ok(handle) => Ok(DynamicLibrary { handle }),
}
}
/// Accesses the value at the symbol of the dynamic library.
pub unsafe fn symbol<T>(&self, symbol: &str) -> Result<*mut T, String> {
// This function should have a lifetime constraint of 'a on
// T but that feature is still unimplemented
let raw_string = CString::new(symbol).unwrap();
let maybe_symbol_value = dl::symbol(self.handle, raw_string.as_ptr());
// The value must not be constructed if there is an error so
// the destructor does not run.
match maybe_symbol_value {
Err(err) => Err(err),
Ok(symbol_value) => Ok(symbol_value as *mut T),
}
}
}
#[cfg(test)]
mod tests;
#[cfg(unix)]
mod dl {
use std::ffi::{CStr, CString, OsStr};
use std::os::unix::prelude::*;
use std::ptr;
use std::str;
pub(super) fn open(filename: Option<&OsStr>) -> Result<*mut u8, String> {
check_for_errors_in(|| unsafe {
match filename {
Some(filename) => open_external(filename),
None => open_internal(),
}
})
}
unsafe fn open_external(filename: &OsStr) -> *mut u8 {
let s = CString::new(filename.as_bytes()).unwrap();
libc::dlopen(s.as_ptr(), libc::RTLD_LAZY) as *mut u8
}
unsafe fn open_internal() -> *mut u8 {
libc::dlopen(ptr::null(), libc::RTLD_LAZY) as *mut u8
}
fn check_for_errors_in<T, F>(f: F) -> Result<T, String>
where
F: FnOnce() -> T,
{
use std::sync::{Mutex, Once};
static INIT: Once = Once::new();
static mut LOCK: *mut Mutex<()> = ptr::null_mut();
unsafe {
INIT.call_once(|| {
LOCK = Box::into_raw(Box::new(Mutex::new(())));
});
// dlerror isn't thread safe, so we need to lock around this entire
// sequence
let _guard = (*LOCK).lock();
let _old_error = libc::dlerror();
let result = f();
let last_error = libc::dlerror() as *const _;
if ptr::null() == last_error {
Ok(result)
} else {
let s = CStr::from_ptr(last_error).to_bytes();
Err(str::from_utf8(s).unwrap().to_owned())
}
}
}
pub(super) unsafe fn symbol(
handle: *mut u8,
symbol: *const libc::c_char,
) -> Result<*mut u8, String> {
check_for_errors_in(|| libc::dlsym(handle as *mut libc::c_void, symbol) as *mut u8)
}
pub(super) unsafe fn close(handle: *mut u8) {
libc::dlclose(handle as *mut libc::c_void);
}
}
#[cfg(windows)]
mod dl {
use std::ffi::OsStr;
use std::io;
use std::os::windows::prelude::*;
use std::ptr;
use winapi::shared::minwindef::HMODULE;
use winapi::um::errhandlingapi::SetThreadErrorMode;
use winapi::um::libloaderapi::{FreeLibrary, GetModuleHandleExW, GetProcAddress, LoadLibraryW};
use winapi::um::winbase::SEM_FAILCRITICALERRORS;
pub(super) fn open(filename: Option<&OsStr>) -> Result<*mut u8, String> {
// disable "dll load failed" error dialog.
let prev_error_mode = unsafe {
let new_error_mode = SEM_FAILCRITICALERRORS;
let mut prev_error_mode = 0;
let result = SetThreadErrorMode(new_error_mode, &mut prev_error_mode);
if result == 0 {
return Err(io::Error::last_os_error().to_string());
}
prev_error_mode
};
let result = match filename {
Some(filename) => {
let filename_str: Vec<_> = filename.encode_wide().chain(Some(0)).collect();
let result = unsafe { LoadLibraryW(filename_str.as_ptr()) } as *mut u8;
ptr_result(result)
}
None => {
let mut handle = ptr::null_mut();
let succeeded = unsafe { GetModuleHandleExW(0, ptr::null(), &mut handle) };
if succeeded == 0 {
Err(io::Error::last_os_error().to_string())
} else {
Ok(handle as *mut u8)
}
}
};
unsafe {
SetThreadErrorMode(prev_error_mode, ptr::null_mut());
}
result
}
pub(super) unsafe fn symbol(
handle: *mut u8,
symbol: *const libc::c_char,
) -> Result<*mut u8, String> {
let ptr = GetProcAddress(handle as HMODULE, symbol) as *mut u8;
ptr_result(ptr)
}
pub(super) unsafe fn close(handle: *mut u8) {
FreeLibrary(handle as HMODULE);
}
fn ptr_result<T>(ptr: *mut T) -> Result<*mut T, String> {
if ptr.is_null() { Err(io::Error::last_os_error().to_string()) } else { Ok(ptr) }
}
}
|
