autocxx-engine 0.25.0

Safe autogenerated interop between Rust and C++
Documentation 
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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use syn::{Type, TypePtr};

use crate::conversion::{
    analysis::fun::function_wrapper::{CppConversionType, TypeConversionPolicy},
    api::Pointerness,
    ConvertErrorFromCpp,
};

use super::type_to_cpp::{type_to_cpp, CppNameMap};

impl TypeConversionPolicy {
    pub(super) fn unconverted_type(
        &self,
        cpp_name_map: &CppNameMap,
    ) -> Result<String, ConvertErrorFromCpp> {
        match self.cpp_conversion {
            CppConversionType::FromUniquePtrToValue => self.unique_ptr_wrapped_type(cpp_name_map),
            CppConversionType::FromPtrToValue => {
                Ok(format!("{}*", self.unwrapped_type_as_string(cpp_name_map)?))
            }
            _ => self.unwrapped_type_as_string(cpp_name_map),
        }
    }

    pub(super) fn converted_type(
        &self,
        cpp_name_map: &CppNameMap,
    ) -> Result<String, ConvertErrorFromCpp> {
        match self.cpp_conversion {
            CppConversionType::FromValueToUniquePtr => self.unique_ptr_wrapped_type(cpp_name_map),
            CppConversionType::FromReferenceToPointer => {
                let (const_string, ty) = match self.cxxbridge_type() {
                    Type::Ptr(TypePtr {
                        mutability: Some(_),
                        elem,
                        ..
                    }) => ("", elem.as_ref()),
                    Type::Ptr(TypePtr { elem, .. }) => ("const ", elem.as_ref()),
                    _ => panic!("Not a pointer"),
                };
                Ok(format!(
                    "{}{}*",
                    const_string,
                    type_to_cpp(ty, cpp_name_map)?
                ))
            }
            _ => self.unwrapped_type_as_string(cpp_name_map),
        }
    }

    fn unwrapped_type_as_string(
        &self,
        cpp_name_map: &CppNameMap,
    ) -> Result<String, ConvertErrorFromCpp> {
        type_to_cpp(self.cxxbridge_type(), cpp_name_map)
    }

    pub(crate) fn is_a_pointer(&self) -> Pointerness {
        match self.cxxbridge_type() {
            Type::Ptr(TypePtr {
                mutability: Some(_),
                ..
            }) => Pointerness::MutPtr,
            Type::Ptr(_) => Pointerness::ConstPtr,
            _ => Pointerness::Not,
        }
    }

    fn unique_ptr_wrapped_type(
        &self,
        original_name_map: &CppNameMap,
    ) -> Result<String, ConvertErrorFromCpp> {
        Ok(format!(
            "std::unique_ptr<{}>",
            self.unwrapped_type_as_string(original_name_map)?
        ))
    }

    pub(super) fn cpp_conversion(
        &self,
        var_name: &str,
        cpp_name_map: &CppNameMap,
        is_return: bool,
    ) -> Result<Option<String>, ConvertErrorFromCpp> {
        // If is_return we want to avoid unnecessary std::moves because they
        // make RVO less effective
        Ok(match self.cpp_conversion {
            CppConversionType::None | CppConversionType::FromReturnValueToPlacementPtr => {
                Some(var_name.to_string())
            }
            CppConversionType::FromPointerToReference { .. } => Some(format!("(*{var_name})")),
            CppConversionType::Move => Some(format!("std::move({var_name})")),
            CppConversionType::FromUniquePtrToValue | CppConversionType::FromPtrToMove => {
                Some(format!("std::move(*{var_name})"))
            }
            CppConversionType::FromValueToUniquePtr => Some(format!(
                "std::make_unique<{}>({})",
                self.unconverted_type(cpp_name_map)?,
                var_name
            )),
            CppConversionType::FromPtrToValue => {
                let dereference = format!("*{var_name}");
                Some(if is_return {
                    dereference
                } else {
                    format!("std::move({dereference})")
                })
            }
            CppConversionType::IgnoredPlacementPtrParameter => None,
            CppConversionType::FromReferenceToPointer { .. } => Some(format!("&{var_name}")),
        })
    }
}