introduce iovec

Signed-off-by: qupeng <qupeng@pingcap.com>

Cargo.toml

@@ -16,11 +16,14 @@ fxhash = "0.2"
 nix = "0.18.0"
 crossbeam = "0.7"
 thiserror = "1.0"
+libc = "0.2"
 
 [dev-dependencies]
 raft = { git = "https://github.com/tikv/raft-rs", branch = "master", default-features = false, features = ["protobuf-codec"] }
 tempfile = "3.1"
 toml = "0.5"
+ctor = "0.1"
+env_logger = "0.8"
 
 [patch.crates-io]
-protobuf = { git = "https://github.com/pingcap/rust-protobuf", rev = "ec745253ab847481647887bc4c7cac3949449cfe" }
+protobuf = { git = "https://github.com/pingcap/rust-protobuf", rev = "ac10abf324a6f2b3e19e10f82b568a293ca5bd3d" }

src/compression.rs

@@ -0,0 +1,176 @@
+use std::i32;
+use std::ptr::{copy_nonoverlapping, read_unaligned};
+
+use libc::c_int;
+use lz4_sys::{
+    LZ4StreamEncode, LZ4_compressBound, LZ4_compress_default, LZ4_createStreamDecode,
+    LZ4_decompress_safe, LZ4_decompress_safe_continue, LZ4_freeStreamDecode,
+};
+
+// Layout of single block compression:
+// header + decoded_size + content + cap(tail).
+pub fn encode_block(src: &[u8], head_reserve: usize, tail_alloc: usize) -> Vec<u8> {
+    unsafe {
+        let bound = LZ4_compressBound(src.len() as i32);
+        assert!(bound > 0 && src.len() <= i32::MAX as usize);
+
+        let capacity = head_reserve + 4 + bound as usize + tail_alloc;
+        let mut output: Vec<u8> = Vec::with_capacity(capacity);
+
+        let le_len = src.len().to_le_bytes();
+        copy_nonoverlapping(le_len.as_ptr(), output.as_mut_ptr().add(head_reserve), 4);
+
+        let size = LZ4_compress_default(
+            src.as_ptr() as _,
+            output.as_mut_ptr().add(head_reserve + 4) as _,
+            src.len() as i32,
+            bound,
+        );
+        assert!(size > 0);
+        output.set_len(head_reserve + 4 + size as usize);
+        output
+    }
+}
+
+pub fn decode_block(src: &[u8]) -> Vec<u8> {
+    assert!(src.len() > 4, "data is too short: {} <= 4", src.len());
+    unsafe {
+        let len = u32::from_le(read_unaligned(src.as_ptr() as *const u32));
+        let mut dst = Vec::with_capacity(len as usize);
+        let l = LZ4_decompress_safe(
+            src.as_ptr().add(4) as _,
+            dst.as_mut_ptr() as _,
+            src.len() as i32 - 4,
+            dst.capacity() as i32,
+        );
+        assert_eq!(l, len as i32);
+        dst.set_len(l as usize);
+        dst
+    }
+}
+
+// Layout of multi blocks compression:
+// header + decoded_size + vec[encoded_len_and_content] + cap(tail).
+pub fn encode_blocks<'a, F, I>(inputs: F, head_reserve: usize, tail_alloc: usize) -> Vec<u8>
+where
+    F: Fn() -> I,
+    I: Iterator<Item = &'a [u8]>,
+{
+    let (mut encoded_len, mut decoded_len) = (0, 0u64);
+    for buffer in inputs() {
+        let len = buffer.len();
+        decoded_len += len as u64;
+        let size = unsafe { lz4_sys::LZ4_compressBound(len as i32) };
+        assert!(size > 0);
+        encoded_len += (4 + size) as usize; // Length and content.
+    }
+
+    let capacity = head_reserve + 8 + encoded_len + tail_alloc;
+    let mut output: Vec<u8> = Vec::with_capacity(capacity);
+    unsafe {
+        copy_nonoverlapping(
+            decoded_len.to_le_bytes().as_ptr(),
+            output.as_mut_ptr().add(head_reserve),
+            8,
+        );
+
+        let (stream, mut offset) = (lz4_sys::LZ4_createStream(), head_reserve + 8);
+        for buffer in inputs() {
+            let bytes = LZ4_compress_fast_continue(
+                stream,
+                buffer.as_ptr() as _,
+                output.as_mut_ptr().add(offset + 4),
+                buffer.len() as i32,
+                (capacity - offset) as i32,
+                1, /* acceleration */
+            );
+            assert!(bytes > 0);
+            copy_nonoverlapping(
+                (bytes as u32).to_le_bytes().as_ptr(),
+                output.as_mut_ptr().add(offset),
+                4,
+            );
+            offset += (bytes + 4) as usize;
+        }
+
+        lz4_sys::LZ4_freeStream(stream);
+        output.set_len(offset);
+    }
+    output
+}
+
+pub fn decode_blocks(mut src: &[u8]) -> Vec<u8> {
+    assert!(src.len() > 8, "data is too short: {} <= 8", src.len());
+    unsafe {
+        let decoded_len = u64::from_le(read_unaligned(src.as_ptr() as *const u64));
+        let mut dst: Vec<u8> = Vec::with_capacity(decoded_len as usize);
+        src = &src[8..];
+
+        let (decoder, mut offset) = (LZ4_createStreamDecode(), 0);
+        while !src.is_empty() {
+            let len = u32::from_le(read_unaligned(src.as_ptr() as *const u32));
+            let bytes = LZ4_decompress_safe_continue(
+                decoder,
+                src.as_ptr().add(4) as _,
+                dst.as_mut_ptr().add(offset) as _,
+                len as i32,
+                (dst.capacity() - offset) as i32,
+            );
+            assert!(bytes >= 0);
+            offset += bytes as usize;
+            src = &src[(4 + len as usize)..];
+        }
+        LZ4_freeStreamDecode(decoder);
+        assert_eq!(offset, decoded_len as usize);
+        dst.set_len(offset);
+        dst
+    }
+}
+
+extern "C" {
+    // It's not in lz4_sys.
+    fn LZ4_compress_fast_continue(
+        LZ4_stream: *mut LZ4StreamEncode,
+        source: *const u8,
+        dest: *mut u8,
+        input_size: c_int,
+        dest_capacity: c_int,
+        acceleration: c_int,
+    ) -> c_int;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic() {
+        let data: Vec<&'static [u8]> = vec![b"", b"123", b"12345678910"];
+        for d in data {
+            let compressed = encode_block(d, 0, 0);
+            assert!(compressed.len() > 4);
+            let res = decode_block(&compressed);
+            assert_eq!(res, d);
+        }
+    }
+
+    #[test]
+    fn test_blocks() {
+        let raw_inputs = vec![
+            b"".to_vec(),
+            b"123".to_vec(),
+            b"12345678910".to_vec(),
+            vec![b'x'; 99999],
+            vec![0; 33333],
+        ];
+
+        let mut input = Vec::with_capacity(raw_inputs.iter().map(|x| x.len()).sum());
+        for x in &raw_inputs {
+            input.extend_from_slice(x);
+        }
+
+        let encoded = encode_blocks(|| raw_inputs.iter().map(|x| x.as_slice()), 0, 0);
+        let decoded = decode_blocks(&encoded);
+        assert_eq!(input, decoded);
+    }
+}

src/engine.rs

@@ -9,6 +9,7 @@ use protobuf::Message;
 use crate::cache_evict::{
     CacheSubmitor, CacheTask, Runner as CacheEvictRunner, DEFAULT_CACHE_CHUNK_SIZE,
 };
+use crate::compression::{decode_block, decode_blocks};
 use crate::config::{Config, RecoveryMode};
 use crate::log_batch::{
     self, Command, CompressionType, EntryExt, LogBatch, LogItemContent, OpType, CHECKSUM_LEN,
@@ -520,15 +521,19 @@ where
             let offset = base_offset + offset;
             pipe_log.fread(queue, file_num, offset, len)?
         }
-        CompressionType::Lz4 => {
-            let read_len = batch_len + HEADER_LEN as u64;
+        c_type @ CompressionType::Lz4 | c_type @ CompressionType::Lz4Blocks => {
+            let read_len = batch_len + HEADER_LEN as u64 + CHECKSUM_LEN as u64;
             let compressed = pipe_log.fread(queue, file_num, base_offset, read_len)?;
-            let mut reader = compressed.as_ref();
+            log_batch::test_batch_checksum(compressed.as_slice())?;
+
+            let mut reader = compressed.as_slice();
             let header = codec::decode_u64(&mut reader)?;
             assert_eq!(header >> 8, batch_len);
-
-            log_batch::test_batch_checksum(reader)?;
-            let buf = log_batch::decompress(&reader[..batch_len as usize - CHECKSUM_LEN]);
+            let buf = match c_type {
+                CompressionType::Lz4 => decode_block(&reader[..batch_len as usize]),
+                CompressionType::Lz4Blocks => decode_blocks(&reader[..batch_len as usize]),
+                _ => unreachable!(),
+            };
             let start = offset as usize - HEADER_LEN;
             let end = (offset + len) as usize - HEADER_LEN;
             buf[start..end].to_vec()