From a6aba2c92a97defa8b6aa6914c52d79df2748361 Mon Sep 17 00:00:00 2001
From: Peter Taoussanis <ptaoussanis@gmail.com>
Date: Sat, 5 Apr 2014 14:20:38 +0700
Subject: [PATCH] Add experimental LZ4 compressors

---
 project.clj                        |  3 +-
 src/taoensso/nippy/compression.clj | 68 ++++++++++++++++++++++++++++--
 2 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/project.clj b/project.clj
index 03daf3e..fb20648 100644
--- a/project.clj
+++ b/project.clj
@@ -14,7 +14,8 @@
    [org.clojure/tools.reader "0.8.4"]
    [com.taoensso/encore      "1.3.1"]
    [org.iq80.snappy/snappy   "0.3"]
-   [org.tukaani/xz           "1.5"]]
+   [org.tukaani/xz           "1.5"]
+   [net.jpountz.lz4/lz4      "1.2.0"]]
 
   :test-paths ["test" "src"]
   :profiles
diff --git a/src/taoensso/nippy/compression.clj b/src/taoensso/nippy/compression.clj
index 3cc5f87..41e49b4 100644
--- a/src/taoensso/nippy/compression.clj
+++ b/src/taoensso/nippy/compression.clj
@@ -1,6 +1,6 @@
-(ns taoensso.nippy.compression
-  "Alpha - subject to change."
+(ns taoensso.nippy.compression "Alpha - subject to change."
   {:author "Peter Taoussanis"}
+  (:require [taoensso.encore :as encore])
   (:import  [java.io ByteArrayInputStream ByteArrayOutputStream DataInputStream
              DataOutputStream]))
 
@@ -23,7 +23,7 @@
   Write speed: very high.
    Read speed: very high.
 
-  A good general-purpose compressor for Redis."
+  A good general-purpose compressor."
   (->SnappyCompressor))
 
 (deftype LZMA2Compressor [compression-level]
@@ -57,5 +57,65 @@
   Write speed: _very_ slow (also currently single-threaded).
    Read speed: slow.
 
-  A specialized compressor for large, low-write data."
+  A specialized compressor for large, low-write data in space-sensitive
+  environments."
   (->LZMA2Compressor 0))
+
+(deftype LZ4Compressor [^net.jpountz.lz4.LZ4Compressor       compressor
+                        ^net.jpountz.lz4.LZ4SafeDecompressor decompressor]
+  ICompressor
+  (compress [_ ba]
+    (let [in-len      (alength ^bytes ba)
+          max-out-len (.maxCompressedLength compressor in-len)
+          ba-out*     (byte-array max-out-len)
+          out-len     (.compress compressor ba 0 in-len ba-out* 0 max-out-len)
+          ba-out      (java.util.Arrays/copyOf ba-out* out-len)]
+      ba-out))
+
+  (decompress [_ ba]
+    (let [in-len      (alength ^bytes ba)
+          max-out-len in-len
+          ba-out*     (byte-array (* max-out-len 3.0)) ; Nb over-sized!
+          out-len     (.decompress decompressor ba 0 in-len ba-out* 0)
+          ba-out      (java.util.Arrays/copyOf ba-out* out-len)]
+      ba-out)))
+
+(def ^:private ^net.jpountz.lz4.LZ4Factory lz4-factory
+  (net.jpountz.lz4.LZ4Factory/fastestInstance))
+
+(def lz4-compressor
+  "Default net.jpountz.lz4 compressor:
+        Ratio: low.
+  Write speed: very high.
+   Read speed: very high.
+
+  A good general-purpose compressor, competitive with Snappy."
+  (->LZ4Compressor (.fastCompressor   lz4-factory)
+                   (.safeDecompressor lz4-factory)))
+
+(def lz4hc-compressor "Like `lz4-compressor` but trades some speed for ratio."
+  (->LZ4Compressor (.highCompressor   lz4-factory)
+                   (.safeDecompressor lz4-factory)))
+
+(comment
+  (def  ba-bench (.getBytes (apply str (repeatedly 1000 rand)) "UTF-8"))
+  (defn bench1 [compressor]
+    {:time  (encore/bench 10000 {:nlaps-warmup 10000}
+              (->> ba-bench (compress compressor) (decompress compressor)))
+     :ratio (encore/round2 (/ (count (compress compressor ba-bench))
+                              (count ba-bench)))})
+
+  (println
+   {:snappy  (bench1 snappy-compressor)
+    ;; :lzma (bench1 lzma2-compressor) ; Slow!
+    :lz4     (bench1 lz4-compressor)
+    :lz4hc   (bench1 lz4hc-compressor)})
+
+  ;;; 2014 April 5, initial benchmarks
+  {:snappy   {:time 2214  :ratio 0.848}
+   :lzma     {:time 46684 :ratio 0.494}
+   :lz4      {:time 1327  :ratio 0.819} ; w/o uncompressed size prefix
+   :lz4hc    {:time 5762  :ratio 0.763} ; ''
+   ;; :lz4   {:time 1404  :ratio 0.819} ; with uncompressed size prefix
+   ;; :lz4hc {:time 6028  :ratio 0.763} ; ''
+   })