From b44d2100db9b169a854af075ffe94bc280b81acc Mon Sep 17 00:00:00 2001
From: "Anand Babu (AB) Periasamy" <ab@unlocksmith.org>
Date: Wed, 25 Mar 2015 19:09:34 -0700
Subject: [PATCH] cache decode matrix tables and matrix

---
 pkg/encoding/erasure/erasure_decode.go | 27 ++++++++++++++------------
 pkg/encoding/erasure/erasure_encode.go | 10 +++++-----
 2 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/pkg/encoding/erasure/erasure_decode.go b/pkg/encoding/erasure/erasure_decode.go
index e3fbba596..158e3f0c8 100644
--- a/pkg/encoding/erasure/erasure_decode.go
+++ b/pkg/encoding/erasure/erasure_decode.go
@@ -37,9 +37,6 @@ import (
 //    blocks.
 // "dataLen" is the length of original source data
 func (e *Encoder) Decode(encodedDataBlocks [][]byte, dataLen int) (decodedData []byte, err error) {
-	var decodeMatrix *C.uint8_t
-	var decodeTbls *C.uint8_t
-	var decodeIndex *C.uint32_t
 	var source, target **C.uint8_t
 
 	k := int(e.params.K)
@@ -82,9 +79,19 @@ func (e *Encoder) Decode(encodedDataBlocks [][]byte, dataLen int) (decodedData [
 		}
 	}
 
-	// Initialzie decoder
-	C.minio_init_decoder(missingEncodedBlocksC, C.int(k), C.int(n), C.int(missingEncodedBlocksCount-1),
-		e.encodeMatrix, &decodeMatrix, &decodeTbls, &decodeIndex)
+	// If not already initialized, recompute and cache
+	if e.decodeMatrix == nil || e.decodeTbls == nil || e.decodeIndex == nil {
+		var decodeMatrix, decodeTbls *C.uint8_t
+		var decodeIndex *C.uint32_t
+
+		C.minio_init_decoder(missingEncodedBlocksC, C.int(k), C.int(n), C.int(missingEncodedBlocksCount-1),
+			e.encodeMatrix, &decodeMatrix, &decodeTbls, &decodeIndex)
+
+		// cache this for future needs
+		e.decodeMatrix = decodeMatrix
+		e.decodeTbls = decodeTbls
+		e.decodeIndex = decodeIndex
+	}
 
 	// Make a slice of pointers to encoded blocks. Necessary to bridge to the C world.
 	pointers := make([]*byte, n)
@@ -94,13 +101,13 @@ func (e *Encoder) Decode(encodedDataBlocks [][]byte, dataLen int) (decodedData [
 
 	// Get pointers to source "data" and target "parity" blocks from the output byte array.
 	ret := C.minio_get_source_target(C.int(missingEncodedBlocksCount-1), C.int(k), C.int(m), missingEncodedBlocksC,
-		decodeIndex, (**C.uint8_t)(unsafe.Pointer(&pointers[0])), &source, &target)
+		e.decodeIndex, (**C.uint8_t)(unsafe.Pointer(&pointers[0])), &source, &target)
 	if int(ret) == -1 {
 		return nil, errors.New("Unable to decode data")
 	}
 
 	// Decode data
-	C.ec_encode_data(C.int(encodedBlockLen), C.int(k), C.int(missingEncodedBlocksCount-1), decodeTbls,
+	C.ec_encode_data(C.int(encodedBlockLen), C.int(k), C.int(missingEncodedBlocksCount-1), e.decodeTbls,
 		source, target)
 
 	// Allocate buffer to output buffer
@@ -109,9 +116,5 @@ func (e *Encoder) Decode(encodedDataBlocks [][]byte, dataLen int) (decodedData [
 		decodedData = append(decodedData, encodedDataBlocks[i]...)
 	}
 
-	// TODO cache this if necessary
-	e.decodeMatrix = decodeMatrix
-	e.decodeTbls = decodeTbls
-
 	return decodedData[:dataLen], nil
 }
diff --git a/pkg/encoding/erasure/erasure_encode.go b/pkg/encoding/erasure/erasure_encode.go
index 98f9b63ac..f6664ce5e 100644
--- a/pkg/encoding/erasure/erasure_encode.go
+++ b/pkg/encoding/erasure/erasure_encode.go
@@ -56,11 +56,10 @@ type EncoderParams struct {
 
 // Encoder is an object used to encode and decode data.
 type Encoder struct {
-	params *EncoderParams
-	encodeMatrix,
-	encodeTbls,
-	decodeMatrix,
-	decodeTbls *C.uint8_t
+	params                   *EncoderParams
+	encodeMatrix, encodeTbls *C.uint8_t
+	decodeMatrix, decodeTbls *C.uint8_t
+	decodeIndex              *C.uint32_t
 }
 
 // ParseEncoderParams creates an EncoderParams object.
@@ -114,6 +113,7 @@ func NewEncoder(ep *EncoderParams) *Encoder {
 		encodeTbls:   encodeTbls,
 		decodeMatrix: nil,
 		decodeTbls:   nil,
+		decodeIndex:  nil,
 	}
 }