PkmnLib_rs/src/ffi/mod.rs

/// The foreign function interfaces for the dynamic data
mod dynamic_data;
/// The handling of handles for the foreign function interfaces
mod ffi_handle;
/// The foreign function interfaces for that static data
mod static_data;

use ffi_handle::*;

/// Helper type for clearer functions.
#[repr(transparent)]
#[derive(Debug, Copy, Clone)]
struct OwnedPtrString(*mut c_char);

/// Helper type for clearer functions.
type NonOwnedPtrString = *const c_char;

impl Default for OwnedPtrString {
    fn default() -> Self {
        OwnedPtrString(std::ptr::null_mut())
    }
}

/// Generates a basic getter foreign function interface.
macro_rules! ffi_handle_arc_dyn_getter {
    (
        $type:ty, $func:ident, $returns: ty
    ) => {
        paste::paste! {
            #[no_mangle]
            extern "C" fn [< $type:snake _ $func >](ptr: FFIHandle<Arc<dyn $type>>) -> $returns {
                ptr.from_ffi_handle().$func()
            }
        }
    };
}

/// Generates a basic getter foreign function interface where the return type is a [`crate::StringKey`].
macro_rules! ffi_handle_arc_stringkey_getter {
    (
        $type:ty, $func:ident
    ) => {
        paste::paste! {
            #[no_mangle]
            extern "C" fn [< $type:lower _ $func >](ptr: FFIHandle<Arc<dyn $type>>) -> NonOwnedPtrString {
                std::ffi::CString::new(ptr.from_ffi_handle().$func().str()).unwrap().into_raw()
            }
        }
    };
}

/// Generates a foreign function interface for a vec. This generates a length function, and a getter.
macro_rules! ffi_handle_vec_value_getters {
    (
        $name:ident, $type:ty, $func:ident, $returns: ty
    ) => {
        paste::paste! {
            #[no_mangle]
            extern "C" fn [< $name:lower _ $func _length>](ptr: FFIHandle<Arc<$type>>) -> usize {
                ptr.from_ffi_handle().$func().len()
            }
            #[no_mangle]
            extern "C" fn [< $name:lower _ $func _get>](ptr: FFIHandle<Arc<$type>>, index: usize) -> $returns {
                *ptr.from_ffi_handle().$func().get(index).unwrap()
            }
        }
    };
}

/// Generates a foreign function interface for a vec of [`crate::StringKey`]. This generates a
/// length function, and a getter.
macro_rules! ffi_handle_vec_stringkey_getters {
    (
        $type:ty, $func:ident
    ) => {
        paste::paste! {
            #[no_mangle]
            extern "C" fn [< $type:lower _ $func _length>](ptr: FFIHandle<Arc<dyn $type>>) -> usize {
                ptr.from_ffi_handle().$func().len()
            }
            #[no_mangle]
            extern "C" fn [< $type:lower _ $func _get>](ptr: FFIHandle<Arc<dyn $type>>, index: usize) -> OwnedPtrString {
                OwnedPtrString(CString::new(ptr.from_ffi_handle().$func().get(index).unwrap().str()).unwrap().into_raw())
            }
        }
    };
}

use ffi_handle_arc_dyn_getter;
use ffi_handle_arc_stringkey_getter;
use ffi_handle_vec_stringkey_getters;
use ffi_handle_vec_value_getters;
use std::ffi::{c_char, CString};

/// Helper utility class to wrap a pointer for extern functions.
#[repr(C)]
struct ExternPointer<T: ?Sized> {
    /// The wrapped pointer.
    ptr: *mut T,
}

impl<T: ?Sized> ExternPointer<T> {
    /// Get the internal pointer as reference.
    #[allow(clippy::panic)] // We currently allow this as these should never be null, but we might want to change this in the future.
    pub(self) fn as_ref(&self) -> &T {
        unsafe {
            self.ptr
                .as_ref()
                .unwrap_or_else(|| panic!("Given pointer of type '{}' was null", std::any::type_name::<T>()))
        }
    }
}

/// The result of a FFI call that can either be an error or a value.
#[repr(C)]
#[repr(packed)]
pub struct FFIResult<T: Copy + Default> {
    /// If the result is ok, this is null, otherwise this is a pointer to the error string.
    err: NonOwnedPtrString,
    /// The value or error.
    value: T,
}

impl<T: Copy + Default> FFIResult<T> {
    /// Creates a new NativeResult with the given value.
    pub fn ok(value: T) -> Self {
        Self {
            err: std::ptr::null(),
            value,
        }
    }
    /// Creates a new NativeResult with the given error.
    #[allow(clippy::unwrap_used)] // We know for certain this is not empty.
    pub fn err(err: anyhow_ext::Error) -> Self {
        Self {
            err: CString::new(err.to_string()).unwrap().into_raw(),
            value: Default::default(),
        }
    }

    /// Creates a new NativeResult with the given error string.
    #[allow(clippy::unwrap_used)] // We know for certain this is not empty.
    pub fn err_from_str(err: &str) -> Self {
        Self {
            err: CString::new(err).unwrap().into_raw(),
            value: Default::default(),
        }
    }
}

impl<T: Copy + Default> From<anyhow::Result<T>> for FFIResult<T> {
    fn from(value: anyhow::Result<T>) -> Self {
        match value {
            Ok(v) => Self::ok(v),
            Err(e) => Self::err(e),
        }
    }
}

impl<T: Copy + Default> From<T> for FFIResult<T> {
    fn from(value: T) -> Self {
        Self::ok(value)
    }
}