dl_api 0.3.0

The easiest, simplest and safest way to load dynamic (shared object) libraries from Rust!
Documentation 
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// dl_api
//
// Copyright (c) 2018 Jeron A. Lau
// Copyright (c) 2017 Szymon Wieloch
// Distributed under the MIT LICENSE (See accompanying file LICENSE.txt)

use libc::{c_int, c_void, dlclose, dlerror, dlopen, dlsym, RTLD_LAZY, RTLD_LOCAL};
use std::ffi::{CStr, OsStr};
use std::io::{Error as IoError, ErrorKind};
use std::os::unix::ffi::OsStrExt;
use std::ptr::null_mut;
use crate::Error;

const DEFAULT_FLAGS: c_int = RTLD_LOCAL | RTLD_LAZY;

use std::sync::Mutex;

// calls to dlerror are not thread unsafe. Therefore we need to guard each call with a mutex

lazy_static! {
    static ref DLERROR_MUTEX: Mutex<()> = Mutex::new(());
}

pub type Handle = *mut c_void;

#[inline]
pub unsafe fn get_sym(handle: Handle, name: &CStr) -> Result<*mut (), Error> {
    let _lock = DLERROR_MUTEX.lock();
    //clear the dlerror in order to be able to distinguish between NULL pointer and error
    let _ = dlerror();
    let symbol = dlsym(handle, name.as_ptr());
    //This can be either error or just the library has a NULl pointer - legal
    if symbol.is_null() {
        let msg = dlerror();
        if !msg.is_null() {
            return Err(Error::SymbolGettingError(IoError::new(
                ErrorKind::Other,
                CStr::from_ptr(msg).to_string_lossy().to_string(),
            )));
        }
    }
    Ok(symbol as *mut ())
}

#[inline]
pub unsafe fn open_lib(name: &OsStr) -> Result<Handle, Error> {
    let mut v: Vec<u8> = Vec::new();
    //as_bytes i a unix-specific extension
    let cstr = if name.len() > 0 && name.as_bytes()[name.len() - 1] == 0 {
        //don't need to convert
        CStr::from_bytes_with_nul_unchecked(name.as_bytes())
    } else {
        //need to convert
        v.extend_from_slice(name.as_bytes());
        v.push(0);
        CStr::from_bytes_with_nul_unchecked(v.as_slice())
    };
    let _lock = DLERROR_MUTEX.lock();
    let handle = dlopen(cstr.as_ptr(), DEFAULT_FLAGS);
    if handle.is_null() {
        Err(Error::OpeningLibraryError(IoError::new(
            ErrorKind::Other,
            CStr::from_ptr(dlerror()).to_string_lossy().to_string(),
        )))
    } else {
        Ok(handle)
    }
}

#[inline]
pub fn close_lib(handle: Handle) -> Handle {
    let result = unsafe { dlclose(handle) };
    if result != 0 {
        panic!("Call to dlclose() failed");
    }
    null_mut()
}