compress/flate: fix a typo, improve compression rate by 3-4%.

R=rsc
CC=golang-dev
https://golang.org/cl/5556077

diff --git a/src/pkg/compress/flate/deflate.go b/src/pkg/compress/flate/deflate.go
index c61087672e2f8463765cd4a53f7d993052e78320..5f5100db830d49f43e22e819c8d7a19db4d9be52 100644 (file)
--- a/src/pkg/compress/flate/deflate.go
+++ b/src/pkg/compress/flate/deflate.go
@@ -112,7 +112,7 @@ func (d *compressor) fillDeflate(b []byte) int {
                        d.hashHead[i] = v
                }
                for i, h := range d.hashPrev {
-                       v := -h - windowSize
+                       v := h - windowSize
                        if v < -1 {
                                v = -1
                        }

diff --git a/src/pkg/compress/flate/deflate_test.go b/src/pkg/compress/flate/deflate_test.go
index 9cf93479a22c9b9b6b85dbce11356320c5d9e99e..24881d31c069ff7e5f9fd72c6ffee29e21f4597f 100644 (file)
--- a/src/pkg/compress/flate/deflate_test.go
+++ b/src/pkg/compress/flate/deflate_test.go
@@ -291,7 +291,7 @@ var deflateInflateStringTests = []deflateInflateStringTest{
        {
                "../testdata/Mark.Twain-Tom.Sawyer.txt",
                "Mark.Twain-Tom.Sawyer",
-               [...]int{416188, 191483, 185232, 179560, 175233, 171263, 169908, 169758, 169712, 169712},
+               [...]int{407330, 187598, 180361, 172974, 169160, 163476, 160936, 160506, 160295, 160295},
        },
 }