From 6951051416ff686612e652f0045e5966516f388a Mon Sep 17 00:00:00 2001
From: aniketfuryrocks <contact@aniketprajapati.me>
Date: Tue, 21 Mar 2023 15:53:59 +0530
Subject: [PATCH] bather

---
 src/batcher.rs | 100 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs     |   1 +
 2 files changed, 101 insertions(+)
 create mode 100644 src/batcher.rs

diff --git a/src/batcher.rs b/src/batcher.rs
new file mode 100644
index 00000000..047a3858
--- /dev/null
+++ b/src/batcher.rs
@@ -0,0 +1,100 @@
+/// Maintain a virtual len, returning slices according to batch_size
+/// Removes batched elements on drop
+///
+/// Prevents re-sizing of vector after every batch
+pub struct Batcher<'a, T> {
+    batch_from: &'a mut Vec<T>,
+    batch_size: usize,
+    pointer: usize,
+    strategy: BatcherStrategy
+}
+
+pub enum BatcherStrategy {
+    Start, 
+    End 
+}
+
+
+impl<'a, T> Batcher<'a, T> {
+    pub fn new(batch_from: &'a mut Vec<T>, batch_size: usize, strategy: BatcherStrategy) -> Self {
+        Self {
+            pointer: match strategy {
+                BatcherStrategy::Start => 0,
+                BatcherStrategy::End => batch_from.len()
+            },
+            batch_from,
+            batch_size,
+            strategy
+        }
+    }
+
+    pub fn next_batch(&mut self) -> Option<&[T]> {
+        let range = match self.strategy {
+            BatcherStrategy::Start => {
+                let new_start = self.pointer + self.batch_size;
+                
+                if new_start >= self.batch_from.len() {
+                    return None;
+                }
+
+                let range = self.pointer .. new_start;
+                self.pointer = new_start;
+                range
+            },
+            BatcherStrategy::End => {
+                let Some(new_len) = self.pointer.checked_sub(self.batch_size) else {
+                    return None;
+                };
+        
+                let range = new_len.. self.pointer;
+                self.pointer = new_len;
+                range
+
+            },
+        };
+
+        Some(&self.batch_from[range])
+    }
+}
+
+
+impl<'a, T> Drop for Batcher<'a, T> {
+    fn drop(&mut self) {
+        let range = match self.strategy {
+            BatcherStrategy::Start => 0..self.pointer,
+            BatcherStrategy::End => self.pointer..self.batch_from.len(),
+        };
+
+        self.batch_from.drain(range);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{BatcherStrategy, Batcher};
+
+    #[test]
+    fn start() {
+        let mut elements = vec![1, 2, 3, 4, 5, 6, 7];
+        let mut batcher = Batcher::new(&mut elements, 2, BatcherStrategy::Start);
+        assert_eq!(Some(&[1, 2][..]), batcher.next_batch());
+        assert_eq!(Some(&[3, 4][..]), batcher.next_batch());
+        assert_eq!(Some(&[5, 6][..]), batcher.next_batch());
+        assert_eq!(None, batcher.next_batch());
+        drop(batcher);
+        assert_eq!(&[7][..], &elements);
+    }
+
+    #[test]
+    fn end() {
+        let mut elements = vec![1, 2, 3, 4, 5, 6, 7];
+        let mut batcher = Batcher::new(&mut elements, 2, BatcherStrategy::End);
+        assert_eq!(Some(&[6, 7][..]), batcher.next_batch());
+        assert_eq!(Some(&[4, 5][..]), batcher.next_batch());
+        assert_eq!(Some(&[2, 3][..]), batcher.next_batch());
+        assert_eq!(None, batcher.next_batch());
+        drop(batcher);
+        assert_eq!(&[1][..], &elements);
+    }
+
+}
diff --git a/src/lib.rs b/src/lib.rs
index 5e0b4c6c..25a3ae04 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -10,6 +10,7 @@ pub mod errors;
 pub mod rpc;
 pub mod tpu_manager;
 pub mod workers;
+pub mod batcher;
 
 #[from_env]
 pub const DEFAULT_RPC_ADDR: &str = "http://0.0.0.0:8899";