fix locking logic

Cargo.toml

@@ -0,0 +1,6 @@
+[workspace]
+members = [
+    "patch-db",
+    "patch-db-derive",
+    "patch-db-derive-internals",
+]

patch-db-derive-internals/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "patch-db-derive-internals"
+version = "0.1.0"
+authors = ["Aiden McClelland <me@drbonez.dev>"]
+edition = "2018"
+description = "internals for derive macros for defining typed patch dbs"
+license = "MIT"
+repository = "https://github.com/dr-bonez/patch-db"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+syn = { version = "1.0.5", features = ["full", "extra-traits"] }
+quote = "1.0.1"
+proc-macro2 = "1.0.1"

patch-db-derive-internals/src/lib.rs

@@ -0,0 +1,42 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+
+pub fn build_model(input: &syn::DeriveInput) -> TokenStream {
+    match &input.data {
+        syn::Data::Struct(struct_ast) => build_model_struct(input, struct_ast),
+        syn::Data::Enum(enum_ast) => build_model_enum(enum_ast),
+        syn::Data::Union(_) => panic!("Unions are not supported"),
+    }
+}
+
+fn build_model_struct(input: &syn::DeriveInput, ast: &syn::DataStruct) -> TokenStream {
+    let model_name = syn::Ident::new(
+        &format!("{}Model", input.ident),
+        proc_macro2::Span::call_site(),
+    );
+    let base_name = &input.ident;
+    let model_vis = &input.vis;
+    quote! {
+        #model_vis struct #model_name<Tx: patch_db::Checkpoint> {
+            data: Option<Box<#base_name>>,
+            ptr: json_ptr::JsonPointer,
+            tx: Tx,
+        }
+        impl<Tx: patch_db::Checkpoint> #model_name<Tx> {
+            pub fn get(&mut self, lock: patch_db::LockType) -> Result<&#base_name, patch_db::Error> {
+                if let Some(data) = self.data.as_ref() {
+                    match lock {
+                        patch_db::LockType::None => Ok(data),
+
+                    }
+                } else {
+                    self.tx.get(&self.ptr, lock)
+                }
+            }
+        }
+    }
+}
+
+fn build_model_enum(ast: &syn::DataEnum) -> TokenStream {
+    todo!()
+}

patch-db-derive/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "patch-db-derive"
+version = "0.1.0"
+authors = ["Aiden McClelland <me@drbonez.dev>"]
+edition = "2018"
+description = "derive macros for defining typed patch dbs"
+license = "MIT"
+repository = "https://github.com/dr-bonez/patch-db"
+
+[lib]
+proc-macro = true
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+patch-db-derive-internals = { path = "../patch-db-derive-internals" }
+syn = "1.0.62"

patch-db-derive/src/lib.rs

@@ -0,0 +1,13 @@
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(Model, attributes(serde))]
+pub fn model_derive(input: TokenStream) -> TokenStream {
+    // Construct a representation of Rust code as a syntax tree
+    // that we can manipulate
+    let ast = syn::parse(input).unwrap();
+
+    // Build the trait implementation
+    patch_db_derive_internals::build_model(&ast).into()
+}

patch-db/Cargo.toml

@@ -12,7 +12,7 @@ fd-lock-rs = "0.1.3"
 futures = "0.3.8"
 json-patch = { path = "../../json-patch" }
 json-ptr = { path = "../../json-ptr" }
-nix = "0.19.1"
+nix = "0.20.0"
 qutex-2 = { path = "../../qutex" }
 serde = { version = "1.0.118", features = ["rc"] }
 serde_json = "1.0.61"

patch-db/src/lib.rs

@@ -16,7 +16,7 @@ use tokio::{
     fs::File,
     sync::{
         broadcast::{Receiver, Sender},
-        RwLock,
+        Mutex, RwLock,
     },
 };
 
@@ -228,9 +228,28 @@ pub trait Checkpoint {
         &'a self,
         ptr: &'a JsonPointer<S, V>,
     ) -> BoxFuture<Result<Value, Error>>;
-    fn locks(&self) -> &[(JsonPointer, LockerGuard)];
+    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, LockerGuard)]>);
-    fn locker(&self) -> &Locker;
     fn apply(&mut self, patch: DiffPatch);
+    fn get<
+        'a,
+        T: for<'de> Deserialize<'de> + 'a,
+        S: AsRef<str> + Clone + Send + Sync + 'a,
+        V: SegList + Clone + Send + Sync + 'a,
+    >(
+        &'a mut self,
+        ptr: &'a JsonPointer<S, V>,
+        lock: LockType,
+    ) -> BoxFuture<'a, Result<T, Error>>;
+    fn put<
+        'a,
+        T: Serialize + Send + Sync + 'a,
+        S: AsRef<str> + Send + Sync + 'a,
+        V: SegList + Send + Sync + 'a,
+    >(
+        &'a mut self,
+        ptr: &'a JsonPointer<S, V>,
+        value: &'a T,
+    ) -> BoxFuture<'a, Result<(), Error>>;
 }
 
 pub struct Transaction {
@@ -276,8 +295,18 @@ impl Transaction {
     ) {
         match lock {
             LockType::None => (),
-            LockType::Read => self.db.locker.add_read_lock(ptr, &mut self.locks).await,
+            LockType::Read => {
-            LockType::Write => self.db.locker.add_write_lock(ptr, &mut self.locks).await,
+                self.db
+                    .locker
+                    .add_read_lock(ptr, &mut self.locks, &mut [])
+                    .await
+            }
+            LockType::Write => {
+                self.db
+                    .locker
+                    .add_write_lock(ptr, &mut self.locks, &mut [])
+                    .await
+            }
         }
     }
     pub async fn get<T: for<'de> Deserialize<'de>, S: AsRef<str> + Clone, V: SegList + Clone>(
@@ -292,7 +321,7 @@ impl Transaction {
     }
     pub async fn put<T: Serialize, S: AsRef<str>, V: SegList>(
         &mut self,
-        ptr: &JsonPointer<S>,
+        ptr: &JsonPointer<S, V>,
         value: &T,
     ) -> Result<(), Error> {
         let old = Transaction::get_value(self, ptr).await?;
@@ -314,15 +343,36 @@ impl<'a> Checkpoint for &'a mut Transaction {
     ) -> BoxFuture<'b, Result<Value, Error>> {
         Transaction::get_value(self, ptr).boxed()
     }
-    fn locks(&self) -> &[(JsonPointer, LockerGuard)] {
+    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, LockerGuard)]>) {
-        &self.locks
+        (&self.db.locker, vec![&mut self.locks])
-    }
-    fn locker(&self) -> &Locker {
-        &self.db.locker
     }
     fn apply(&mut self, patch: DiffPatch) {
         (self.updates.0).0.extend((patch.0).0)
     }
+    fn get<
+        'b,
+        T: for<'de> Deserialize<'de> + 'b,
+        S: AsRef<str> + Clone + Send + Sync + 'b,
+        V: SegList + Clone + Send + Sync + 'b,
+    >(
+        &'b mut self,
+        ptr: &'b JsonPointer<S, V>,
+        lock: LockType,
+    ) -> BoxFuture<'b, Result<T, Error>> {
+        Transaction::get(self, ptr, lock).boxed()
+    }
+    fn put<
+        'b,
+        T: Serialize + Send + Sync + 'b,
+        S: AsRef<str> + Send + Sync + 'b,
+        V: SegList + Send + Sync + 'b,
+    >(
+        &'b mut self,
+        ptr: &'b JsonPointer<S, V>,
+        value: &'b T,
+    ) -> BoxFuture<'b, Result<(), Error>> {
+        Transaction::put(self, ptr, value).boxed()
+    }
 }
 
 pub struct SubTransaction<Tx: Checkpoint> {
@@ -363,23 +413,16 @@ impl<Tx: Checkpoint> SubTransaction<Tx> {
         ptr: &JsonPointer<S, V>,
         lock: LockType,
     ) {
-        for lock in self.locks.iter() {
-            if ptr.starts_with(&lock.0) {
-                return;
-            }
-        }
         match lock {
             LockType::None => (),
             LockType::Read => {
-                self.parent
+                let (locker, mut locks) = self.parent.locker_and_locks();
-                    .locker()
+                locker.add_read_lock(ptr, &mut self.locks, &mut locks).await
-                    .add_read_lock(ptr, &mut self.locks)
-                    .await
             }
             LockType::Write => {
-                self.parent
+                let (locker, mut locks) = self.parent.locker_and_locks();
-                    .locker()
+                locker
-                    .add_write_lock(ptr, &mut self.locks)
+                    .add_write_lock(ptr, &mut self.locks, &mut locks)
                     .await
             }
         }
@@ -400,7 +443,7 @@ impl<Tx: Checkpoint> SubTransaction<Tx> {
     }
     pub async fn put<T: Serialize, S: AsRef<str> + Send + Sync, V: SegList + Send + Sync>(
         &mut self,
-        ptr: &JsonPointer<S>,
+        ptr: &JsonPointer<S, V>,
         value: &T,
     ) -> Result<(), Error> {
         let old = SubTransaction::get_value(self, ptr).await?;
@@ -422,15 +465,38 @@ impl<'a, Tx: Checkpoint + Send + Sync> Checkpoint for &'a mut SubTransaction<Tx>
     ) -> BoxFuture<'b, Result<Value, Error>> {
         SubTransaction::get_value(self, ptr).boxed()
     }
-    fn locks(&self) -> &[(JsonPointer, LockerGuard)] {
+    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, LockerGuard)]>) {
-        &self.locks
+        let (locker, mut locks) = self.parent.locker_and_locks();
-    }
+        locks.push(&mut self.locks);
-    fn locker(&self) -> &Locker {
+        (locker, locks)
-        &self.parent.locker()
     }
     fn apply(&mut self, patch: DiffPatch) {
         (self.updates.0).0.extend((patch.0).0)
     }
+    fn get<
+        'b,
+        T: for<'de> Deserialize<'de> + 'b,
+        S: AsRef<str> + Clone + Send + Sync + 'b,
+        V: SegList + Clone + Send + Sync + 'b,
+    >(
+        &'b mut self,
+        ptr: &'b JsonPointer<S, V>,
+        lock: LockType,
+    ) -> BoxFuture<'b, Result<T, Error>> {
+        SubTransaction::get(self, ptr, lock).boxed()
+    }
+    fn put<
+        'b,
+        T: Serialize + Send + Sync + 'b,
+        S: AsRef<str> + Send + Sync + 'b,
+        V: SegList + Send + Sync + 'b,
+    >(
+        &'b mut self,
+        ptr: &'b JsonPointer<S, V>,
+        value: &'b T,
+    ) -> BoxFuture<'b, Result<(), Error>> {
+        SubTransaction::put(self, ptr, value).boxed()
+    }
 }
 
 #[derive(Debug)]
@@ -442,8 +508,8 @@ pub enum LockType {
 
 pub enum LockerGuard {
     Empty,
-    Read(ReadGuard<HashMap<String, Locker>>),
+    Read(LockerReadGuard),
-    Write(WriteGuard<HashMap<String, Locker>>),
+    Write(LockerWriteGuard),
 }
 impl LockerGuard {
     pub fn take(&mut self) -> Self {
@@ -451,6 +517,44 @@ impl LockerGuard {
     }
 }
 
+#[derive(Debug, Clone)]
+pub struct LockerReadGuard(Arc<Mutex<Option<ReadGuard<HashMap<String, Locker>>>>>);
+impl LockerReadGuard {
+    async fn upgrade(&self) -> Option<LockerWriteGuard> {
+        let guard = self.0.try_lock().unwrap().take();
+        if let Some(g) = guard {
+            Some(LockerWriteGuard(
+                Some(ReadGuard::upgrade(g).await.unwrap()),
+                Some(self.clone()),
+            ))
+        } else {
+            None
+        }
+    }
+}
+impl From<ReadGuard<HashMap<String, Locker>>> for LockerReadGuard {
+    fn from(guard: ReadGuard<HashMap<String, Locker>>) -> Self {
+        LockerReadGuard(Arc::new(Mutex::new(Some(guard))))
+    }
+}
+
+pub struct LockerWriteGuard(
+    Option<WriteGuard<HashMap<String, Locker>>>,
+    Option<LockerReadGuard>,
+);
+impl From<WriteGuard<HashMap<String, Locker>>> for LockerWriteGuard {
+    fn from(guard: WriteGuard<HashMap<String, Locker>>) -> Self {
+        LockerWriteGuard(Some(guard), None)
+    }
+}
+impl Drop for LockerWriteGuard {
+    fn drop(&mut self) {
+        if let (Some(write), Some(read)) = (self.0.take(), self.1.take()) {
+            *read.0.try_lock().unwrap() = Some(WriteGuard::downgrade(write));
+        }
+    }
+}
+
 #[derive(Clone, Debug)]
 pub struct Locker(QrwLock<HashMap<String, Locker>>);
 impl Locker {
@@ -475,24 +579,29 @@ impl Locker {
         }
         lock.unwrap()
     }
-    pub async fn add_read_lock<S: AsRef<str> + Clone, V: SegList + Clone>(
+    async fn add_read_lock<S: AsRef<str> + Clone, V: SegList + Clone>(
         &self,
         ptr: &JsonPointer<S, V>,
         locks: &mut Vec<(JsonPointer, LockerGuard)>,
+        extra_locks: &mut [&mut [(JsonPointer, LockerGuard)]],
     ) {
-        for lock in locks.iter() {
+        for lock in extra_locks
+            .iter()
+            .flat_map(|a| a.iter())
+            .chain(locks.iter())
+        {
             if ptr.starts_with(&lock.0) {
                 return;
             }
         }
         locks.push((
             JsonPointer::to_owned(ptr.clone()),
-            LockerGuard::Read(self.lock_read(ptr).await),
+            LockerGuard::Read(self.lock_read(ptr).await.into()),
         ));
     }
     pub async fn lock_write<S: AsRef<str>, V: SegList>(
         &self,
-        ptr: &JsonPointer<S>,
+        ptr: &JsonPointer<S, V>,
     ) -> WriteGuard<HashMap<String, Locker>> {
         let mut lock = self.0.clone().write().await.unwrap();
         for seg in ptr.iter() {
@@ -506,26 +615,86 @@ impl Locker {
         }
         lock
     }
-    pub async fn add_write_lock<S: AsRef<str> + Clone, V: SegList + Clone>(
+    async fn add_write_lock<S: AsRef<str> + Clone, V: SegList + Clone>(
         &self,
         ptr: &JsonPointer<S, V>,
         locks: &mut Vec<(JsonPointer, LockerGuard)>,
+        extra_locks: &mut [&mut [(JsonPointer, LockerGuard)]],
     ) {
-        for lock in locks.iter_mut() {
+        let mut final_lock = None;
-            if ptr.starts_with(&lock.0) {
+        for lock in extra_locks
+            .iter_mut()
+            .flat_map(|a| a.iter_mut())
+            .chain(locks.iter_mut())
+        {
+            enum Choice {
+                Return,
+                Continue,
+                Break,
+            }
+            let choice: Choice;
+            if let Some(remainder) = ptr.strip_prefix(&lock.0) {
                 let guard = lock.1.take();
                 lock.1 = match guard {
-                    LockerGuard::Read(l) => {
+                    LockerGuard::Read(LockerReadGuard(guard)) if !remainder.is_empty() => {
-                        LockerGuard::Write(ReadGuard::upgrade(l).await.unwrap())
+                        // read guard already exists at higher level
+                        let mut lock = guard.lock().await;
+                        if let Some(l) = lock.take() {
+                            let mut orig_lock = None;
+                            let mut lock = ReadGuard::upgrade(l).await.unwrap();
+                            for seg in remainder.iter() {
+                                let new_lock = if let Some(locker) = lock.get(seg) {
+                                    locker.0.clone().write().await.unwrap()
+                                } else {
+                                    lock.insert(seg.to_owned(), Locker::new());
+                                    lock.get(seg).unwrap().0.clone().write().await.unwrap()
+                                };
+                                if orig_lock.is_none() {
+                                    orig_lock = Some(lock);
+                                }
+                                lock = new_lock;
+                            }
+                            final_lock = Some(LockerGuard::Write(lock.into()));
+                            choice = Choice::Break;
+                            LockerGuard::Read(WriteGuard::downgrade(orig_lock.unwrap()).into())
+                        } else {
+                            drop(lock);
+                            choice = Choice::Return;
+                            LockerGuard::Read(LockerReadGuard(guard))
+                        }
+                    }
+                    LockerGuard::Read(l) => {
+                        // read exists, convert to write
+                        if let Some(upgraded) = l.upgrade().await {
+                            final_lock = Some(LockerGuard::Write(upgraded));
+                            choice = Choice::Break;
+                        } else {
+                            choice = Choice::Continue;
+                        }
+                        LockerGuard::Read(l)
+                    }
+                    LockerGuard::Write(l) => {
+                        choice = Choice::Return;
+                        LockerGuard::Write(l)
+                    } // leave it alone, already sufficiently locked
+                    LockerGuard::Empty => {
+                        unreachable!("LockerGuard found empty");
                     }
-                    a => a,
                 };
-                return;
+                match choice {
+                    Choice::Return => return,
+                    Choice::Break => break,
+                    Choice::Continue => continue,
+                }
             }
         }
         locks.push((
             JsonPointer::to_owned(ptr.clone()),
-            LockerGuard::Read(self.lock_read(ptr).await),
+            if let Some(lock) = final_lock {
+                lock
+            } else {
+                LockerGuard::Write(self.lock_write(ptr).await.into())
+            },
         ));
     }
 }