From b4e6b34bbece98dd49b4c12bfe00695fb3221f2a Mon Sep 17 00:00:00 2001
From: Dennis Schwerdel <schwerdel@googlemail.com>
Date: Wed, 2 Aug 2017 23:36:01 +0200
Subject: [PATCH] Configurable cut-point-skipping in fastcdc

---
 chunking/benches/all.rs | 4 ++--
 chunking/src/fastcdc.rs | 6 ++++--
 chunking/tests/all.rs   | 4 ++--
 src/chunker.rs          | 2 +-
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/chunking/benches/all.rs b/chunking/benches/all.rs
index 75cf50f..ebe8ec3 100644
--- a/chunking/benches/all.rs
+++ b/chunking/benches/all.rs
@@ -99,7 +99,7 @@ fn test_rabin_8192(b: &mut Bencher) {
 #[bench]
 fn test_fastcdc_init(b: &mut Bencher) {
     b.iter(|| {
-        FastCdcChunker::new(8*1024, 0);
+        FastCdcChunker::new(8*1024, 0, true);
     })
 }
 
@@ -108,7 +108,7 @@ fn test_fastcdc_8192(b: &mut Bencher) {
     let data = random_data(0, 1024*1024);
     b.bytes = data.len() as u64;
     b.iter(|| {
-        let mut chunker = FastCdcChunker::new(8*1024, 0);
+        let mut chunker = FastCdcChunker::new(8*1024, 0, true);
         let mut cursor = Cursor::new(&data);
         while chunker.chunk(&mut cursor, &mut DevNull).unwrap() == ChunkerStatus::Continue {}
     })
diff --git a/chunking/src/fastcdc.rs b/chunking/src/fastcdc.rs
index 974e8f9..39e430a 100644
--- a/chunking/src/fastcdc.rs
+++ b/chunking/src/fastcdc.rs
@@ -54,10 +54,11 @@ pub struct FastCdcChunker {
     avg_size: usize,
     mask_long: u64,
     mask_short: u64,
+    cut_point_skip: bool,
 }
 
 impl FastCdcChunker {
-    pub fn new(avg_size: usize, seed: u64) -> Self {
+    pub fn new(avg_size: usize, seed: u64, cut_point_skip: bool) -> Self {
         let (mask_short, mask_long) = get_masks(avg_size, 2, seed);
         FastCdcChunker {
             buffer: [0; 4096],
@@ -68,6 +69,7 @@ impl FastCdcChunker {
             avg_size: avg_size,
             mask_long: mask_long,
             mask_short: mask_short,
+            cut_point_skip: cut_point_skip,
         }
     }
 }
@@ -99,7 +101,7 @@ impl Chunker for FastCdcChunker {
             let min_size_p = cmp::min(max, cmp::max(self.min_size as isize - pos as isize, 0) as usize);
             let avg_size_p = cmp::min(max, cmp::max(self.avg_size as isize - pos as isize, 0) as usize);
             let max_size_p = cmp::min(max, cmp::max(self.max_size as isize - pos as isize, 0) as usize);
-            if self.min_size > pos {
+            if !self.cut_point_skip && self.min_size > pos {
                 for i in 0..min_size_p {
                     hash = (hash << 1).wrapping_add(self.gear[self.buffer[i] as usize]);
                 }
diff --git a/chunking/tests/all.rs b/chunking/tests/all.rs
index 80a7fe2..53e5196 100644
--- a/chunking/tests/all.rs
+++ b/chunking/tests/all.rs
@@ -84,12 +84,12 @@ fn test_rabin() {
 fn test_fastcdc() {
     let data = random_data(0, 10*1024*1024);
     for n in &[1usize,2,4,8,16,32,64,128,256,512,1024] {
-        let mut chunker = FastCdcChunker::new(1024*n, 0);
+        let mut chunker = FastCdcChunker::new(1024*n, 0, true);
         let len = test_chunking(&mut chunker, &data, None);
         assert!(len >= data.len()/n/1024/4);
         assert!(len <= data.len()/n/1024*4);
     }
-    test_chunking(&mut FastCdcChunker::new(8192, 0), &random_data(0, 128*1024),
+    test_chunking(&mut FastCdcChunker::new(8192, 0, true), &random_data(0, 128*1024),
         Some(&[8712, 8018, 2847, 9157, 8997, 8581, 8867, 5422, 5412, 9478,
         11553, 9206, 4606, 8529, 3821, 11342, 6524]));
 }
diff --git a/src/chunker.rs b/src/chunker.rs
index 337c311..eebcbaa 100644
--- a/src/chunker.rs
+++ b/src/chunker.rs
@@ -48,7 +48,7 @@ impl ChunkerType {
         match *self {
             ChunkerType::Ae(size) => Box::new(AeChunker::new(size)),
             ChunkerType::Rabin((size, seed)) => Box::new(RabinChunker::new(size, seed)),
-            ChunkerType::FastCdc((size, seed)) => Box::new(FastCdcChunker::new(size, seed)),
+            ChunkerType::FastCdc((size, seed)) => Box::new(FastCdcChunker::new(size, seed, true)),
             ChunkerType::Fixed(size) => Box::new(FixedChunker::new(size)),
         }
     }