2019-03-29 13:41:39 +00:00
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//! Errors.
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use libc::{c_char, c_int};
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use std::cell::RefCell;
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use std::error::Error;
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use std::fmt::{self, Display, Formatter};
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use std::ptr;
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use std::slice;
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thread_local! {
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static LAST_ERROR: RefCell<Option<Box<Error>>> = RefCell::new(None);
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}
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pub(crate) fn update_last_error<E: Error + 'static>(err: E) {
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LAST_ERROR.with(|prev| {
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*prev.borrow_mut() = Some(Box::new(err));
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});
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}
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/// Retrieve the most recent error, clearing it in the process.
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pub(crate) fn take_last_error() -> Option<Box<Error>> {
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LAST_ERROR.with(|prev| prev.borrow_mut().take())
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}
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/// Gets the length in bytes of the last error.
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/// This can be used to dynamically allocate a buffer with the correct number of
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/// bytes needed to store a message.
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///
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/// # Example
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///
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/// ```c
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/// int error_len = wasmer_last_error_length();
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/// char *error_str = malloc(error_len);
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/// ```
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#[no_mangle]
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pub extern "C" fn wasmer_last_error_length() -> c_int {
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LAST_ERROR.with(|prev| match *prev.borrow() {
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Some(ref err) => err.to_string().len() as c_int + 1,
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None => 0,
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})
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}
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/// Stores the last error message into the provided buffer up to the given `length`.
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/// The `length` parameter must be large enough to store the last error message.
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///
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/// Returns the length of the string in bytes.
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/// Returns `-1` if an error occurs.
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///
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/// # Example
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///
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/// ```c
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/// int error_len = wasmer_last_error_length();
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/// char *error_str = malloc(error_len);
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/// wasmer_last_error_message(error_str, error_len);
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/// printf("Error str: `%s`\n", error_str);
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/// ```
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#[no_mangle]
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pub unsafe extern "C" fn wasmer_last_error_message(buffer: *mut c_char, length: c_int) -> c_int {
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if buffer.is_null() {
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// buffer pointer is null
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return -1;
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}
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2019-05-10 13:55:02 +00:00
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let error_message = match take_last_error() {
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Some(err) => err.to_string(),
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2019-03-29 13:41:39 +00:00
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None => return 0,
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};
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2019-05-10 13:55:02 +00:00
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let length = length as usize;
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2019-03-29 13:41:39 +00:00
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2019-05-10 13:55:02 +00:00
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if error_message.len() >= length {
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// buffer to small to hold the error message
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2019-03-29 13:41:39 +00:00
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return -1;
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}
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2019-05-10 13:55:02 +00:00
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let buffer = slice::from_raw_parts_mut(buffer as *mut u8, length);
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2019-03-29 13:41:39 +00:00
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ptr::copy_nonoverlapping(
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error_message.as_ptr(),
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buffer.as_mut_ptr(),
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error_message.len(),
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);
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// Add a trailing null so people using the string as a `char *` don't
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// accidentally read into garbage.
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buffer[error_message.len()] = 0;
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2019-05-10 14:00:13 +00:00
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error_message.len() as c_int + 1
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2019-03-29 13:41:39 +00:00
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}
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#[derive(Debug)]
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pub(crate) struct CApiError {
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pub(crate) msg: String,
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}
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impl Display for CApiError {
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fn fmt(&self, f: &mut Formatter) -> fmt::Result {
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write!(f, "{}", &self.msg)
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}
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}
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impl Error for CApiError {}
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