feat(runtime-c-api) Split the big lib.rs file into modules

lib/runtime-c-api/src/error.rs

@@ -0,0 +1,102 @@
+//! Errors.
+
+use libc::{c_char, c_int};
+use std::cell::RefCell;
+use std::error::Error;
+use std::fmt::{self, Display, Formatter};
+use std::ptr;
+use std::slice;
+
+thread_local! {
+    static LAST_ERROR: RefCell<Option<Box<Error>>> = RefCell::new(None);
+}
+
+pub(crate) fn update_last_error<E: Error + 'static>(err: E) {
+    LAST_ERROR.with(|prev| {
+        *prev.borrow_mut() = Some(Box::new(err));
+    });
+}
+
+/// Retrieve the most recent error, clearing it in the process.
+pub(crate) fn take_last_error() -> Option<Box<Error>> {
+    LAST_ERROR.with(|prev| prev.borrow_mut().take())
+}
+
+/// Gets the length in bytes of the last error.
+/// This can be used to dynamically allocate a buffer with the correct number of
+/// bytes needed to store a message.
+///
+/// # Example
+///
+/// ```c
+/// int error_len = wasmer_last_error_length();
+/// char *error_str = malloc(error_len);
+/// ```
+#[no_mangle]
+pub extern "C" fn wasmer_last_error_length() -> c_int {
+    LAST_ERROR.with(|prev| match *prev.borrow() {
+        Some(ref err) => err.to_string().len() as c_int + 1,
+        None => 0,
+    })
+}
+
+/// Stores the last error message into the provided buffer up to the given `length`.
+/// The `length` parameter must be large enough to store the last error message.
+///
+/// Returns the length of the string in bytes.
+/// Returns `-1` if an error occurs.
+///
+/// # Example
+///
+/// ```c
+/// int error_len = wasmer_last_error_length();
+/// char *error_str = malloc(error_len);
+/// wasmer_last_error_message(error_str, error_len);
+/// printf("Error str: `%s`\n", error_str);
+/// ```
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_last_error_message(buffer: *mut c_char, length: c_int) -> c_int {
+    if buffer.is_null() {
+        // buffer pointer is null
+        return -1;
+    }
+
+    let last_error = match take_last_error() {
+        Some(err) => err,
+        None => return 0,
+    };
+
+    let error_message = last_error.to_string();
+
+    let buffer = slice::from_raw_parts_mut(buffer as *mut u8, length as usize);
+
+    if error_message.len() >= buffer.len() {
+        // buffer to small for err  message
+        return -1;
+    }
+
+    ptr::copy_nonoverlapping(
+        error_message.as_ptr(),
+        buffer.as_mut_ptr(),
+        error_message.len(),
+    );
+
+    // Add a trailing null so people using the string as a `char *` don't
+    // accidentally read into garbage.
+    buffer[error_message.len()] = 0;
+
+    error_message.len() as c_int
+}
+
+#[derive(Debug)]
+pub(crate) struct CApiError {
+    pub(crate) msg: String,
+}
+
+impl Display for CApiError {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{}", &self.msg)
+    }
+}
+
+impl Error for CApiError {}