feat(ffi): Initial C API for hyper

src/ffi/error.rs

@@ -0,0 +1,80 @@
+use libc::size_t;
+
+pub struct hyper_error(crate::Error);
+
+#[repr(C)]
+pub enum hyper_code {
+    /// All is well.
+    HYPERE_OK,
+    /// General error, details in the `hyper_error *`.
+    HYPERE_ERROR,
+    /// A function argument was invalid.
+    HYPERE_INVALID_ARG,
+    /// The IO transport returned an EOF when one wasn't expected.
+    ///
+    /// This typically means an HTTP request or response was expected, but the
+    /// connection closed cleanly without sending (all of) it.
+    HYPERE_UNEXPECTED_EOF,
+    /// Aborted by a user supplied callback.
+    HYPERE_ABORTED_BY_CALLBACK,
+    /// An optional hyper feature was not enabled.
+    #[cfg_attr(feature = "http2", allow(unused))]
+    HYPERE_FEATURE_NOT_ENABLED,
+}
+
+// ===== impl hyper_error =====
+
+impl hyper_error {
+    fn code(&self) -> hyper_code {
+        use crate::error::Kind as ErrorKind;
+        use crate::error::User;
+
+        match self.0.kind() {
+            ErrorKind::IncompleteMessage => hyper_code::HYPERE_UNEXPECTED_EOF,
+            ErrorKind::User(User::AbortedByCallback) => hyper_code::HYPERE_ABORTED_BY_CALLBACK,
+            // TODO: add more variants
+            _ => hyper_code::HYPERE_ERROR
+        }
+    }
+
+    fn print_to(&self, dst: &mut [u8]) -> usize {
+        use std::io::Write;
+
+        let mut dst = std::io::Cursor::new(dst);
+
+        // A write! error doesn't matter. As much as possible will have been
+        // written, and the Cursor position will know how far that is (even
+        // if that is zero).
+        let _ = write!(dst, "{}", &self.0);
+        dst.position() as usize
+    }
+}
+
+ffi_fn! {
+    /// Frees a `hyper_error`.
+    fn hyper_error_free(err: *mut hyper_error) {
+        drop(unsafe { Box::from_raw(err) });
+    }
+}
+
+ffi_fn! {
+    /// Get an equivalent `hyper_code` from this error.
+    fn hyper_error_code(err: *const hyper_error) -> hyper_code {
+        unsafe { &*err }.code()
+    }
+}
+
+ffi_fn! {
+    /// Print the details of this error to a buffer.
+    ///
+    /// The `dst_len` value must be the maximum length that the buffer can
+    /// store.
+    ///
+    /// The return value is number of bytes that were written to `dst`.
+    fn hyper_error_print(err: *const hyper_error, dst: *mut u8, dst_len: size_t) -> size_t {
+        let dst = unsafe {
+            std::slice::from_raw_parts_mut(dst, dst_len)
+        };
+        unsafe { &*err }.print_to(dst)
+    }
+}