Byteview

Cargo.toml

@@ -2,7 +2,7 @@
 name = "value-log"
 description = "Value log implementation for key-value separated LSM storage"
 license = "MIT OR Apache-2.0"
-version = "1.4.1"
+version = "1.5.0"
 edition = "2021"
 rust-version = "1.74.0"
 readme = "README.md"
@@ -22,10 +22,11 @@ serde = ["dep:serde"]
 bytes = ["dep:bytes"]
 
 [dependencies]
+bytes = { version = "1", optional = true }
 byteorder = "1.5.0"
-bytes = { version = "1.8.0", optional = true }
+byteview = "0.4.0"
+interval-heap = "0.0.5"
 log = "0.4.22"
-min-max-heap = "1.3.0"
 path-absolutize = "3.1.1"
 quick_cache = { version = "0.6.5", default-features = false }
 rustc-hash = "2.0.0"

src/segment/merge.rs

@@ -3,10 +3,17 @@
 // (found in the LICENSE-* files in the repository)
 
 use crate::{id::SegmentId, value::UserKey, Compressor, SegmentReader, UserValue};
+use interval_heap::IntervalHeap;
 use std::cmp::Reverse;
 
-// TODO: replace with MinHeap...
-use min_max_heap::MinMaxHeap;
+macro_rules! fail_iter {
+    ($e:expr) => {
+        match $e {
+            Ok(v) => v,
+            Err(e) => return Some(Err(e.into())),
+        }
+    };
+}
 
 type IteratorIndex = usize;
 
@@ -42,16 +49,14 @@ impl Ord for IteratorValue {
 #[allow(clippy::module_name_repetitions)]
 pub struct MergeReader<C: Compressor + Clone> {
     readers: Vec<SegmentReader<C>>,
-    heap: MinMaxHeap<IteratorValue>,
+    heap: IntervalHeap<IteratorValue>,
 }
 
 impl<C: Compressor + Clone> MergeReader<C> {
     /// Initializes a new merging reader
     pub fn new(readers: Vec<SegmentReader<C>>) -> Self {
-        Self {
-            readers,
-            heap: MinMaxHeap::new(),
-        }
+        let heap = IntervalHeap::with_capacity(readers.len());
+        Self { readers, heap }
     }
 
     fn advance_reader(&mut self, idx: usize) -> crate::Result<()> {
@@ -87,22 +92,16 @@ impl<C: Compressor + Clone> Iterator for MergeReader<C> {
 
     fn next(&mut self) -> Option<Self::Item> {
         if self.heap.is_empty() {
-            if let Err(e) = self.push_next() {
-                return Some(Err(e));
-            };
+            fail_iter!(self.push_next());
         }
 
         if let Some(head) = self.heap.pop_min() {
-            if let Err(e) = self.advance_reader(head.index) {
-                return Some(Err(e));
-            }
+            fail_iter!(self.advance_reader(head.index));
 
             // Discard old items
             while let Some(next) = self.heap.pop_min() {
                 if next.key == head.key {
-                    if let Err(e) = self.advance_reader(next.index) {
-                        return Some(Err(e));
-                    }
+                    fail_iter!(self.advance_reader(next.index));
                 } else {
                     // Reached next user key now
                     // Push back non-conflicting item and exit

src/segment/reader.rs

@@ -3,14 +3,23 @@
 // (found in the LICENSE-* files in the repository)
 
 use super::{meta::METADATA_HEADER_MAGIC, writer::BLOB_HEADER_MAGIC};
-use crate::{coding::DecodeError, id::SegmentId, value::UserKey, Compressor, UserValue};
+use crate::{coding::DecodeError, id::SegmentId, value::UserKey, Compressor, Slice, UserValue};
 use byteorder::{BigEndian, ReadBytesExt};
 use std::{
     fs::File,
     io::{BufReader, Read, Seek},
     path::Path,
 };
 
+macro_rules! fail_iter {
+    ($e:expr) => {
+        match $e {
+            Ok(v) => v,
+            Err(e) => return Some(Err(e.into())),
+        }
+    };
+}
+
 /// Reads through a segment in order.
 pub struct Reader<C: Compressor + Clone> {
     pub(crate) segment_id: SegmentId,
@@ -62,10 +71,7 @@ impl<C: Compressor + Clone> Iterator for Reader<C> {
 
         {
             let mut buf = [0; BLOB_HEADER_MAGIC.len()];
-
-            if let Err(e) = self.inner.read_exact(&mut buf) {
-                return Some(Err(e.into()));
-            };
+            fail_iter!(self.inner.read_exact(&mut buf));
 
             if buf == METADATA_HEADER_MAGIC {
                 self.is_terminated = true;
@@ -79,54 +85,26 @@ impl<C: Compressor + Clone> Iterator for Reader<C> {
             }
         }
 
-        let checksum = match self.inner.read_u64::<BigEndian>() {
-            Ok(v) => v,
-            Err(e) => {
-                if e.kind() == std::io::ErrorKind::UnexpectedEof {
-                    return None;
-                }
-                return Some(Err(e.into()));
-            }
-        };
+        let checksum = fail_iter!(self.inner.read_u64::<BigEndian>());
 
-        let key_len = match self.inner.read_u16::<BigEndian>() {
-            Ok(v) => v,
-            Err(e) => {
-                if e.kind() == std::io::ErrorKind::UnexpectedEof {
-                    return None;
-                }
-                return Some(Err(e.into()));
-            }
-        };
-
-        let mut key = vec![0; key_len.into()];
-        if let Err(e) = self.inner.read_exact(&mut key) {
-            return Some(Err(e.into()));
-        };
-
-        let val_len = match self.inner.read_u32::<BigEndian>() {
-            Ok(v) => v,
-            Err(e) => {
-                if e.kind() == std::io::ErrorKind::UnexpectedEof {
-                    return None;
-                }
-                return Some(Err(e.into()));
-            }
-        };
-
-        let mut val = vec![0; val_len as usize];
-        if let Err(e) = self.inner.read_exact(&mut val) {
-            return Some(Err(e.into()));
-        };
+        let key_len = fail_iter!(self.inner.read_u16::<BigEndian>());
+        let key = fail_iter!(Slice::from_reader(&mut self.inner, key_len as usize));
 
+        let val_len = fail_iter!(self.inner.read_u32::<BigEndian>());
         let val = match &self.compression {
-            Some(compressor) => match compressor.decompress(&val) {
-                Ok(val) => val,
-                Err(e) => return Some(Err(e)),
-            },
-            None => val,
+            Some(compressor) => {
+                // TODO: https://github.com/PSeitz/lz4_flex/issues/166
+                let mut val = vec![0; val_len as usize];
+                fail_iter!(self.inner.read_exact(&mut val));
+                Slice::from(fail_iter!(compressor.decompress(&val)))
+            }
+            None => {
+                // NOTE: When not using compression, we can skip
+                // the intermediary heap allocation and read directly into a Slice
+                fail_iter!(Slice::from_reader(&mut self.inner, val_len as usize))
+            }
         };
 
-        Some(Ok((key.into(), val.into(), checksum)))
+        Some(Ok((key, val, checksum)))
     }
 }

src/slice.rs

@@ -3,7 +3,7 @@
 // (found in the LICENSE-* files in the repository)
 
 #[cfg(not(feature = "bytes"))]
-mod slice_arc;
+mod slice_default;
 
 #[cfg(feature = "bytes")]
 mod slice_bytes;
@@ -13,10 +13,10 @@ use std::{
     sync::Arc,
 };
 
-#[cfg(not(feature = "bytes"))]
-pub use slice_arc::Slice;
 #[cfg(feature = "bytes")]
 pub use slice_bytes::Slice;
+#[cfg(not(feature = "bytes"))]
+pub use slice_default::Slice;
 
 impl AsRef<[u8]> for Slice {
     fn as_ref(&self) -> &[u8] {
@@ -26,7 +26,21 @@ impl AsRef<[u8]> for Slice {
 
 impl From<&[u8]> for Slice {
     fn from(value: &[u8]) -> Self {
-        Self::new(value)
+        #[cfg(not(feature = "bytes"))]
+        {
+            Self(byteview::ByteView::new(value))
+        }
+
+        #[cfg(feature = "bytes")]
+        {
+            Self(bytes::Bytes::from(value.to_vec()))
+        }
+    }
+}
+
+impl From<Arc<[u8]>> for Slice {
+    fn from(value: Arc<[u8]>) -> Self {
+        Self::from(&*value)
     }
 }
 
@@ -180,6 +194,7 @@ mod serde {
 mod tests {
     use super::Slice;
     use std::{fmt::Debug, sync::Arc};
+    use test_log::test;
 
     fn assert_slice_handles<T>(v: T)
     where
@@ -192,6 +207,17 @@ mod tests {
         assert!(slice >= v, "slice_arc: {slice:?}, v: {v:?}");
     }
 
+    #[test]
+    fn slice_empty() {
+        assert_eq!(Slice::empty(), []);
+    }
+
+    #[test]
+    fn slice_with_size() {
+        assert_eq!(Slice::with_size(5), [0, 0, 0, 0, 0]);
+        assert_eq!(Slice::with_size(50), [0; 50]);
+    }
+
     /// This test verifies that we can create a `Slice` from various types and compare a `Slice` with them.
     #[test]
     fn test_slice_instantiation() {

src/slice/slice_bytes.rs

@@ -2,11 +2,11 @@
 // This source code is licensed under both the Apache 2.0 and MIT License
 // (found in the LICENSE-* files in the repository)
 
-use std::sync::Arc;
-
 use bytes::{Bytes, BytesMut};
 
 /// An immutable byte slice that can be cloned without additional heap allocation
+///
+/// There is no guarantee of any sort of alignment for zero-copy (de)serialization.
 #[derive(Debug, Clone, Eq, Hash, Ord)]
 pub struct Slice(pub(super) Bytes);
 
@@ -17,6 +17,26 @@ impl Slice {
         Self(Bytes::copy_from_slice(bytes))
     }
 
+    #[doc(hidden)]
+    #[must_use]
+    pub fn empty() -> Self {
+        Self(Bytes::from_static(&[]))
+    }
+
+    #[doc(hidden)]
+    #[must_use]
+    pub fn slice(&self, range: impl std::ops::RangeBounds<usize>) -> Self {
+        Self(self.0.slice(range))
+    }
+
+    #[must_use]
+    #[doc(hidden)]
+    pub fn with_size(len: usize) -> Self {
+        let bytes = vec![0; len];
+        Self(Bytes::from(bytes))
+    }
+
+    /// Constructs a [`Slice`] from an I/O reader by pulling in `len` bytes.
     #[doc(hidden)]
     pub fn from_reader<R: std::io::Read>(reader: &mut R, len: usize) -> std::io::Result<Self> {
         let mut builder = BytesMut::zeroed(len);
@@ -50,10 +70,3 @@ impl From<String> for Slice {
         Self(Bytes::from(value))
     }
 }
-
-// Needed because slice_arc specializes this impl
-impl From<Arc<[u8]>> for Slice {
-    fn from(value: Arc<[u8]>) -> Self {
-        Self::new(value.as_ref())
-    }
-}

src/slice/slice_arc.rs → src/slice/slice_default.rs

@@ -2,11 +2,13 @@
 // This source code is licensed under both the Apache 2.0 and MIT License
 // (found in the LICENSE-* files in the repository)
 
-use std::sync::Arc;
+use byteview::ByteView;
 
 /// An immutable byte slice that can be cloned without additional heap allocation
+///
+/// There is no guarantee of any sort of alignment for zero-copy (de)serialization.
 #[derive(Debug, Clone, Eq, Hash, Ord)]
-pub struct Slice(pub(super) Arc<[u8]>);
+pub struct Slice(pub(super) ByteView);
 
 impl Slice {
     /// Construct a [`Slice`] from a byte slice.
@@ -15,40 +17,42 @@ impl Slice {
         Self(bytes.into())
     }
 
+    #[doc(hidden)]
+    #[must_use]
+    pub fn empty() -> Self {
+        Self(ByteView::new(&[]))
+    }
+
+    #[doc(hidden)]
+    #[must_use]
+    pub fn slice(&self, range: impl std::ops::RangeBounds<usize>) -> Self {
+        Self(self.0.slice(range))
+    }
+
     #[must_use]
     #[doc(hidden)]
     pub fn with_size(len: usize) -> Self {
-        // TODO: optimize this with byteview to remove the reallocation
-        let v = vec![0; len];
-        Self(v.into())
+        Self(ByteView::with_size(len))
     }
 
+    /// Constructs a [`Slice`] from an I/O reader by pulling in `len` bytes.
     #[doc(hidden)]
     pub fn from_reader<R: std::io::Read>(reader: &mut R, len: usize) -> std::io::Result<Self> {
-        let mut view = Self::with_size(len);
-        let builder = Arc::get_mut(&mut view.0).expect("we are the owner");
-        reader.read_exact(builder)?;
-        Ok(view)
+        let view = ByteView::from_reader(reader, len)?;
+        Ok(Self(view))
     }
 }
 
-// Arc::from<Vec<T>> is specialized
+// Arc::from<Vec<u8>> is specialized
 impl From<Vec<u8>> for Slice {
     fn from(value: Vec<u8>) -> Self {
-        Self(Arc::from(value))
+        Self(ByteView::from(value))
     }
 }
 
-// Arc::from<Vec<T>> is specialized
+// Arc::from<Vec<String>> is specialized
 impl From<String> for Slice {
     fn from(value: String) -> Self {
-        Self(Arc::from(value.into_bytes()))
-    }
-}
-
-// direct conversion
-impl From<Arc<[u8]>> for Slice {
-    fn from(value: Arc<[u8]>) -> Self {
-        Self(value)
+        Self(ByteView::from(value.into_bytes()))
     }
 }