From 4fc7bc5f09cc5ee538d088aa64a8231c2098630b Mon Sep 17 00:00:00 2001
From: Paul Masurel <paul.masurel@gmail.com>
Date: Fri, 31 Mar 2017 18:54:23 +0900
Subject: [PATCH] Added helper to create Vec with a given sizewq

---
 src/indexer/delete_queue2.rs | 206 +++++++++++++++++++++++++++++++++++
 1 file changed, 206 insertions(+)
 create mode 100644 src/indexer/delete_queue2.rs

diff --git a/src/indexer/delete_queue2.rs b/src/indexer/delete_queue2.rs
new file mode 100644
index 000000000..e2b8230d1
--- /dev/null
+++ b/src/indexer/delete_queue2.rs
@@ -0,0 +1,206 @@
+use super::operation::DeleteOperation;
+use std::sync::{Arc, RwLock};
+use std::mem;
+use std::ops::DerefMut;
+
+
+#[derive(Clone, Default)]
+struct DeleteQueue {
+    writer: Arc<RwLock<Vec<DeleteOperation>>>,
+    next_block: Option<NextBlock>,
+}
+
+impl DeleteQueue {
+
+    pub fn new() -> Arc<DeleteQueue> {
+        let mut delete_queue = Arc::new(DeleteQueue::default());
+        delete_queue.next_block = Some(
+            NextBlock::from(delete_queue)
+        );
+        delete_queue
+    }
+
+    pub fn cursor(&self) -> Cursor {
+        
+        Cursor {
+            current_block: Arc<Block>,
+            pos: 0,
+        }
+    }
+
+    pub fn push(&self, delete_operation: DeleteOperation) {
+        let mut write_lock = self.writer
+            .write()
+            .expect("Failed to acquire write lock on delete queue writer")
+            .push(delete_operation);
+    }
+
+    fn flush(&self) -> Option<Vec<DeleteOperation>> {
+        let mut write_lock = self
+            .writer
+            .write()
+            .expect("Failed to acquire write lock on delete queue writer");
+        if write_lock.is_empty() {
+            return None;
+        }
+        Some(mem::replace(write_lock.deref_mut(), vec!()))
+    }
+}
+
+enum InnerNextBlock {
+    Writer(Arc<DeleteQueue>),
+    Closed(Arc<Block>),
+    Terminated,
+}
+
+struct NextBlock(RwLock<InnerNextBlock>);
+
+impl From<Arc<DeleteQueue>> for NextBlock {
+    fn from(writer_arc: Arc<DeleteQueue>) -> NextBlock {
+        NextBlock(RwLock::new(InnerNextBlock::Writer(writer_arc)))
+    }
+}
+
+impl NextBlock {   
+    pub fn next_block(&self) -> Option<Arc<Block>> {
+        {
+            let next_read_lock = self.0
+                .read()
+                .expect("Failed to acquire write lock in delete queue");
+            match *next_read_lock {
+                InnerNextBlock::Terminated => {
+                    return None;
+                }
+                InnerNextBlock::Closed(ref block) => {
+                    return Some(block.clone());
+                }
+                _ => {}
+            }
+        }
+        let delete_operations;
+        let writer_arc;
+        {
+            let mut next_write_lock = self.0
+                .write()
+                .expect("Failed to acquire write lock in delete queue");
+            match *next_write_lock {
+                InnerNextBlock::Terminated => {
+                    return None;
+                }
+                InnerNextBlock::Closed(ref block) => {
+                    return Some(block.clone());
+                }
+                InnerNextBlock::Writer(ref writer) => {
+                    match writer.flush() {
+                        Some(flushed_delete_operations) => {
+                            delete_operations = flushed_delete_operations;
+                        }
+                        None => {
+                            return None;
+                        }
+                    }
+                    writer_arc = writer.clone();
+                }
+            }
+            let next_block = Arc::new(Block {
+                operations: Arc::new(delete_operations),
+                next: NextBlock::from(writer_arc),
+            });
+            *next_write_lock.deref_mut() = InnerNextBlock::Closed(next_block.clone()); // TODO fix
+            return Some(next_block)
+        }
+    }
+}
+
+struct Block {
+    operations: Arc<Vec<DeleteOperation>>,
+    next: NextBlock,
+}
+
+
+#[derive(Clone)]
+struct Cursor {
+    current_block: Arc<Block>,
+    pos: usize,
+}
+
+impl Cursor {   
+    fn next<'a>(&'a mut self) -> Option<&'a DeleteOperation> {
+        if self.pos >= self.current_block.operations.len() {
+            // we have consumed our operations entirely.
+            // let's ask our writer if he has more for us.
+            // self.go_next_block();
+            match self.current_block.next.next_block() {
+                Some(block) => {
+                    self.current_block = block;
+                    self.pos = 0;
+                }
+                None => {
+                    return None;
+                }
+            }
+        }
+        let operation = &self.current_block.operations[self.pos];
+        self.pos += 1;
+        return Some(operation);
+    }
+}
+
+
+
+
+
+
+#[cfg(test)]
+mod tests {
+
+    use super::{DeleteQueue, DeleteOperation};
+    use schema::{Term, Field};
+
+    #[test]
+    fn test_deletequeue() {
+        let delete_queue = DeleteQueue::new();
+        
+        let make_op = |i: usize| {
+            let field = Field(1u8);
+            DeleteOperation {
+                opstamp: i as u64,
+                term: Term::from_field_u32(field, i as u32)
+            }
+        };
+
+        delete_queue.push(make_op(1));
+        delete_queue.push(make_op(2));
+
+        let snapshot = delete_queue.cursor();
+        {
+            let mut operations_it = snapshot.clone();
+            assert_eq!(operations_it.next().unwrap().opstamp, 1);
+            assert_eq!(operations_it.next().unwrap().opstamp, 2);
+            assert!(operations_it.next().is_none());
+        }
+        {   
+            let mut operations_it = snapshot.clone();
+            assert_eq!(operations_it.next().unwrap().opstamp, 1);
+            assert_eq!(operations_it.next().unwrap().opstamp, 2);
+            assert!(operations_it.next().is_none());
+        }
+        
+        // // operations does not own a lock on the queue.
+        // delete_queue.push(make_op(3));
+        // let snapshot2 = delete_queue.snapshot();
+        // {
+        //     // operations is not affected by
+        //     // the push that occurs after.
+        //     let mut operations_it = snapshot.iter();
+        //     let mut operations2_it = snapshot2.iter();
+        //     assert_eq!(operations_it.next().unwrap().opstamp, 1);
+        //     assert_eq!(operations2_it.next().unwrap().opstamp, 1);
+        //     assert_eq!(operations_it.next().unwrap().opstamp, 2);
+        //     assert_eq!(operations2_it.next().unwrap().opstamp, 2);
+        //     assert!(operations_it.next().is_none());
+        //     assert_eq!(operations2_it.next().unwrap().opstamp, 3);
+        //     assert!(operations2_it.next().is_none());
+        // }
+    }
+}
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