twizzler/object/

builder.rs

use std::{marker::PhantomData, mem::MaybeUninit};

use twizzler_abi::{
    object::{ObjID, Protections},
    syscall::{
        BackingType, CreateTieSpec, LifetimeType, ObjectCreate, ObjectCreateFlags, ObjectSource,
    },
};
use twizzler_rt_abi::{bindings::CREATE_KIND_NEW, object::MapFlags};

use super::{Object, TxObject};
use crate::{
    marker::{BaseType, StoreCopy},
    Result,
};

/// An object builder, for constructing objects using a builder API.
#[derive(Clone)]
pub struct ObjectBuilder<Base: BaseType> {
    spec: ObjectCreate,
    src_objs: Vec<ObjectSource>,
    ties: Vec<CreateTieSpec>,
    name: Option<String>,
    _pd: PhantomData<Base>,
}

impl<Base: BaseType> ObjectBuilder<Base> {
    /// Make a new object builder.
    pub fn new(spec: ObjectCreate) -> Self {
        Self {
            spec,
            _pd: PhantomData,
            name: None,
            src_objs: Vec::new(),
            ties: Vec::new(),
        }
    }

    /// Make the object persistent.
    pub fn persist(mut self, persist: bool) -> Self {
        if persist {
            self.spec.lt = LifetimeType::Persistent;
        } else {
            self.spec.lt = LifetimeType::Volatile;
        }
        self
    }
    
    /// Cast the base type.
    pub fn cast<U: BaseType>(self) -> ObjectBuilder<U> {
        ObjectBuilder::<U>::new(self.spec)
    }

    /// Add a Source Object that this new object will copy from.
    pub fn add_src(mut self, obj_src: ObjectSource) -> Self {
        self.src_objs.push(obj_src);
        self
    }

    /// Add a tie specification for this object creation.
    pub fn add_tie(mut self, tie: CreateTieSpec) -> Self {
        self.ties.push(tie);
        self
    }

    pub fn named(mut self, name: impl ToString) -> Self {
        self.name = Some(name.to_string());
        self
    }
}

fn bind_name(id: ObjID, name: &str) -> Result<()> {
    let create = twizzler_rt_abi::bindings::create_options {
        id: id.raw(),
        kind: CREATE_KIND_NEW,
    };
    let fd = twizzler_rt_abi::fd::twz_rt_fd_open(name, create, 0)?;
    twizzler_rt_abi::fd::twz_rt_fd_close(fd);
    Ok(())
}

impl<Base: BaseType + StoreCopy> ObjectBuilder<Base> {
    /// Build an object using the provided base vale.
    /// # Example
    /// ```
    /// # use twizzler::object::ObjectBuilder;
    /// let builder = ObjectBuilder::default();
    /// let obj = builder.build(42u32).unwrap();
    /// ```
    pub fn build(&self, base: Base) -> Result<Object<Base>> {
        self.build_inplace(|tx| tx.write(base))
    }
}

impl<Base: BaseType> ObjectBuilder<Base> {
    /// Build an object using the provided constructor function.
    ///
    /// The constructor should call the .write() method on the TxObject, and
    /// return the result.
    /// # Example
    /// ```
    /// # use twizzler::object::ObjectBuilder;
    /// let builder = ObjectBuilder::default();
    /// let obj = builder.build_inplace(|tx| tx.write(42u32)).unwrap();
    /// ```
    pub fn build_inplace<F>(&self, ctor: F) -> Result<Object<Base>>
    where
        F: FnOnce(TxObject<MaybeUninit<Base>>) -> Result<TxObject<Base>>,
    {
        let id = twizzler_abi::syscall::sys_object_create(
            self.spec,
            self.src_objs.as_slice(),
            self.ties.as_slice(),
        )?;
        let mut flags = MapFlags::READ | MapFlags::WRITE;
        if self.spec.lt == LifetimeType::Persistent {
            flags.insert(MapFlags::PERSIST);
            if let Some(ref name) = self.name {
                bind_name(id, name)?;
            }
        } else {
            if let Some(ref name) = self.name {
                tracing::warn!(
                    "tried to name volatile object at creation time: {} {}",
                    id,
                    name
                );
            }
        }
        let mu_object = unsafe { Object::<MaybeUninit<Base>>::map_unchecked(id, flags) }?;
        let object = ctor(mu_object.into_tx()?)?;
        object.into_object()
    }

    /// Build an object using the provided constructor function.
    ///
    /// The constructor should call the .write() method on the TxObject or
    /// otherwise ensure that it is safe to call .assume_init on the underlying
    /// MaybeUninit.
    ///
    /// # Safety
    /// The caller must ensure that the base is initialized, see MaybeUninit::assume_init.
    ///
    /// # Example
    /// ```
    /// # use twizzler::object::ObjectBuilder;
    /// let builder = ObjectBuilder::default();
    /// let obj = unsafe {
    ///     builder
    ///         .build_ctor(|tx| {
    ///             tx.write(42u32);
    ///         })
    ///         .unwrap()
    /// };
    /// ```
    pub unsafe fn build_ctor<F>(&self, ctor: F) -> Result<Object<Base>>
    where
        F: FnOnce(&mut TxObject<MaybeUninit<Base>>),
    {
        self.build_inplace(|mut tx| {
            ctor(&mut tx);
            Ok(tx.assume_init())
        })
    }
}

impl<Base: BaseType> Default for ObjectBuilder<Base> {
    fn default() -> Self {
        Self::new(ObjectCreate::new(
            BackingType::Normal,
            LifetimeType::Volatile,
            None,
            ObjectCreateFlags::empty(),
            Protections::all(),
        ))
    }
}

#[cfg(test)]
mod tests {
    use super::ObjectBuilder;
    use crate::{marker::BaseType, object::TypedObject, ptr::InvPtr};

    #[test]
    fn builder_simple() {
        let builder = ObjectBuilder::default();
        let obj = builder.build(42u32).unwrap();
        let base = obj.base();
        assert_eq!(*base, 42);
    }

    struct Foo {
        ptr: InvPtr<u32>,
    }
    impl BaseType for Foo {}

    #[test]
    fn builder_complex() {
        let builder = ObjectBuilder::default();
        let obj_1 = builder.build(42u32).unwrap();
        let base = obj_1.base_ref();
        assert_eq!(*base, 42);

        let builder = ObjectBuilder::<Foo>::default();
        let obj = builder
            .build_inplace(|tx| {
                let foo = Foo {
                    ptr: InvPtr::new(&tx, base)?,
                };
                tx.write(foo)
            })
            .unwrap();
        let base_foo = obj.base();
        let r = unsafe { base_foo.ptr.resolve() };
        assert_eq!(*r, 42);
    }
}