erasure encode janitor duty

pkg/encoding/erasure/ctypes.go

@@ -24,7 +24,7 @@ import (
 )
 
 // Integer to Int conversion
-func int2cInt(src_err_list []int) *C.int32_t {
+func int2CInt(src_err_list []int) *C.int32_t {
 	var sizeErrInt = int(unsafe.Sizeof(src_err_list[0]))
 	switch sizeInt {
 	case sizeErrInt:

pkg/encoding/erasure/erasure_decode.go

@@ -32,47 +32,47 @@ import (
 //
 // Decoded data is exactly similar in length and content as the original data.
 func (e *Encoder) Decode(chunks [][]byte, length int) ([]byte, error) {
-	var decode_matrix *C.uint8_t
-	var decode_tbls *C.uint8_t
-	var decode_index *C.uint32_t
+	var decodeMatrix *C.uint8_t
+	var decodeTbls *C.uint8_t
+	var decodeIndex *C.uint32_t
 	var source, target **C.uint8_t
 
-	k := e.params.K
-	m := e.params.M
+	k := int(e.params.K)
+	m := int(e.params.M)
 	n := k + m
-	if len(chunks) != int(n) {
+	if len(chunks) != n {
 		return nil, errors.New(fmt.Sprintf("chunks length must be %d", n))
 	}
-	chunk_size := GetEncodedChunkLen(length, uint8(k))
+	chunkLen := GetEncodedBlockLen(length, uint8(k))
 
-	error_index := make([]int, n+1)
-	var err_count int = 0
+	errorIndex := make([]int, n+1)
+	var errCount int = 0
 
 	for i := range chunks {
 		// Check of chunks are really null
 		if chunks[i] == nil || len(chunks[i]) == 0 {
-			error_index[err_count] = i
-			err_count++
+			errorIndex[errCount] = i
+			errCount++
 		}
 	}
-	error_index[err_count] = -1
-	err_count++
+	errorIndex[errCount] = -1
+	errCount++
 
 	// Too many missing chunks, cannot be more than parity `m`
-	if err_count-1 > int(n-k) {
+	if errCount-1 > int(n-k) {
 		return nil, errors.New("too many erasures requested, can't decode")
 	}
 
-	error_index_ptr := int2cInt(error_index[:err_count])
+	errorIndex_ptr := int2CInt(errorIndex[:errCount])
 
 	for i := range chunks {
 		if chunks[i] == nil || len(chunks[i]) == 0 {
-			chunks[i] = make([]byte, chunk_size)
+			chunks[i] = make([]byte, chunkLen)
 		}
 	}
 
-	C.minio_init_decoder(error_index_ptr, C.int(k), C.int(n), C.int(err_count-1),
-		e.encode_matrix, &decode_matrix, &decode_tbls, &decode_index)
+	C.minio_init_decoder(errorIndex_ptr, C.int(k), C.int(n), C.int(errCount-1),
+		e.encodeMatrix, &decodeMatrix, &decodeTbls, &decodeIndex)
 
 	pointers := make([]*byte, n)
 	for i := range chunks {
@@ -81,24 +81,24 @@ func (e *Encoder) Decode(chunks [][]byte, length int) ([]byte, error) {
 
 	data := (**C.uint8_t)(unsafe.Pointer(&pointers[0]))
 
-	ret := C.minio_get_source_target(C.int(err_count-1), C.int(k), C.int(m), error_index_ptr,
-		decode_index, data, &source, &target)
+	ret := C.minio_get_source_target(C.int(errCount-1), C.int(k), C.int(m), errorIndex_ptr,
+		decodeIndex, data, &source, &target)
 
 	if int(ret) == -1 {
 		return nil, errors.New("Decoding source target failed")
 	}
 
-	C.ec_encode_data(C.int(chunk_size), C.int(k), C.int(err_count-1), decode_tbls,
+	C.ec_encode_data(C.int(chunkLen), C.int(k), C.int(errCount-1), decodeTbls,
 		source, target)
 
-	recovered_output := make([]byte, 0, chunk_size*int(k))
+	recoveredOutput := make([]byte, 0, chunkLen*int(k))
 	for i := 0; i < int(k); i++ {
-		recovered_output = append(recovered_output, chunks[i]...)
+		recoveredOutput = append(recoveredOutput, chunks[i]...)
 	}
 
 	// TODO cache this if necessary
-	e.decode_matrix = decode_matrix
-	e.decode_tbls = decode_tbls
+	e.decodeMatrix = decodeMatrix
+	e.decodeTbls = decodeTbls
 
-	return recovered_output[:length], nil
+	return recoveredOutput[:length], nil
 }

pkg/encoding/erasure/erasure_encode.go

@@ -26,7 +26,7 @@ import (
 	"unsafe"
 )
 
-type Technique int
+type Technique uint8
 
 const (
 	Vandermonde Technique = iota
@@ -52,10 +52,10 @@ type EncoderParams struct {
 // Encoder is an object used to encode and decode data.
 type Encoder struct {
 	params *EncoderParams
-	encode_matrix,
-	encode_tbls,
-	decode_matrix,
-	decode_tbls *C.uint8_t
+	encodeMatrix,
+	encodeTbls,
+	decodeMatrix,
+	decodeTbls *C.uint8_t
 }
 
 // ParseEncoderParams creates an EncoderParams object.
@@ -94,30 +94,30 @@ func ParseEncoderParams(k, m uint8, technique Technique) (*EncoderParams, error)
 
 // NewEncoder creates an encoder object with a given set of parameters.
 func NewEncoder(ep *EncoderParams) *Encoder {
-	var encode_matrix *C.uint8_t
-	var encode_tbls *C.uint8_t
+	var k = C.int(ep.K)
+	var m = C.int(ep.M)
 
-	k := C.int(ep.K)
-	m := C.int(ep.M)
+	var encodeMatrix *C.uint8_t
+	var encodeTbls *C.uint8_t
 
-	C.minio_init_encoder(C.int(ep.Technique), k, m, &encode_matrix,
-		&encode_tbls)
+	C.minio_init_encoder(C.int(ep.Technique), k, m, &encodeMatrix,
+		&encodeTbls)
 
 	return &Encoder{
-		params:        ep,
-		encode_matrix: encode_matrix,
-		encode_tbls:   encode_tbls,
-		decode_matrix: nil,
-		decode_tbls:   nil,
+		params:       ep,
+		encodeMatrix: encodeMatrix,
+		encodeTbls:   encodeTbls,
+		decodeMatrix: nil,
+		decodeTbls:   nil,
 	}
 }
 
-func GetEncodedLen(inputLen int, k, m uint8) (outputLen int) {
-	outputLen = GetEncodedChunkLen(inputLen, k) * int(k+m)
+func GetEncodedBlocksLen(inputLen int, k, m uint8) (outputLen int) {
+	outputLen = GetEncodedBlockLen(inputLen, k) * int(k+m)
 	return outputLen
 }
 
-func GetEncodedChunkLen(inputLen int, k uint8) (outputChunkLen int) {
+func GetEncodedBlockLen(inputLen int, k uint8) (encodedOutputLen int) {
 	alignment := int(k) * SIMDAlign
 	remainder := inputLen % alignment
 
@@ -125,55 +125,66 @@ func GetEncodedChunkLen(inputLen int, k uint8) (outputChunkLen int) {
 	if remainder != 0 {
 		paddedInputLen = inputLen + (alignment - remainder)
 	}
-	outputChunkLen = paddedInputLen / int(k)
-	return outputChunkLen
+	encodedOutputLen = paddedInputLen / int(k)
+	return encodedOutputLen
 }
 
-// Encode encodes a block of data. The input is the original data. The output
-// is a 2 tuple containing (k + m) chunks of erasure encoded data and the
-// length of the original object.
-func (e *Encoder) Encode(input []byte) ([][]byte, error) {
-	inputLen := len(input)
-	k := C.int(e.params.K)
-	m := C.int(e.params.M)
-	n := k + m
+// Encode erasure codes a block of data in "k" data blocks and "m" parity blocks.
+// Output is [k+m][]blocks of data and parity slices.
+func (e *Encoder) Encode(inputData []byte) (encodedBlocks [][]byte, err error) {
+	k := int(e.params.K) // "k" data blocks
+	m := int(e.params.M) // "m" parity blocks
+	n := k + m           // "n" total encoded blocks
 
-	chunkLen := GetEncodedChunkLen(inputLen, e.params.K)
-	encodedDataLen := chunkLen * int(k)
-	paddedDataLen := int(encodedDataLen) - inputLen
+	// Length of a single encoded chunk.
+	// Total number of encoded chunks = "k" data  + "m" parity blocks
+	encodedBlockLen := GetEncodedBlockLen(len(inputData), uint8(k))
 
-	if paddedDataLen > 0 {
-		s := make([]byte, paddedDataLen)
+	// Length of total number of "k" data chunks
+	encodedDataBlocksLen := encodedBlockLen * k
+
+	// Length of extra padding required for the data blocks.
+	encodedDataBlocksPadLen := encodedDataBlocksLen - len(inputData)
+
+	// Extend inputData buffer to accommodate coded data blocks if necesssary
+	if encodedDataBlocksPadLen > 0 {
+		padding := make([]byte, encodedDataBlocksPadLen)
 		// Expand with new padded blocks to the byte array
-		input = append(input, s...)
+		inputData = append(inputData, padding...)
 	}
 
-	encodedParityLen := chunkLen * int(e.params.M)
-	c := make([]byte, encodedParityLen)
-	input = append(input, c...)
-
-	// encodedOutLen := encodedDataLen + encodedParityLen
-
-	// Allocate chunks
-	chunks := make([][]byte, k+m)
-	pointers := make([]*byte, k+m)
-
-	var i int
-	// Add data blocks to chunks
-	for i = 0; i < int(k); i++ {
-		chunks[i] = input[i*chunkLen : (i+1)*chunkLen]
-		pointers[i] = &chunks[i][0]
+	// Extend inputData buffer to accommodate coded parity blocks
+	if true { // create a temporary scope to trigger garbage collect
+		encodedParityBlocksLen := encodedBlockLen * m
+		parityBlocks := make([]byte, encodedParityBlocksLen)
+		inputData = append(inputData, parityBlocks...)
 	}
 
-	for i = int(k); i < int(n); i++ {
-		chunks[i] = make([]byte, chunkLen)
-		pointers[i] = &chunks[i][0]
+	// Allocate memory to the "encoded blocks" return buffer
+	encodedBlocks = make([][]byte, n) // Return buffer
+
+	// Nessary to bridge Go to the C world. C requires 2D arry of pointers to
+	// byte array. "encodedBlocks" is a 2D slice.
+	pointersToEncodedBlock := make([]*byte, n) // Pointers to encoded blocks.
+
+	// Copy data block slices to encoded block buffer
+	for i := 0; i < k; i++ {
+		encodedBlocks[i] = inputData[i*encodedBlockLen : (i+1)*encodedBlockLen]
+		pointersToEncodedBlock[i] = &encodedBlocks[i][0]
 	}
 
-	data := (**C.uint8_t)(unsafe.Pointer(&pointers[:k][0]))
-	coding := (**C.uint8_t)(unsafe.Pointer(&pointers[k:][0]))
+	// Copy erasure block slices to encoded block buffer
+	for i := k; i < n; i++ {
+		encodedBlocks[i] = make([]byte, encodedBlockLen)
+		pointersToEncodedBlock[i] = &encodedBlocks[i][0]
+	}
 
-	C.ec_encode_data(C.int(chunkLen), k, m, e.encode_tbls, data,
-		coding)
-	return chunks, nil
+	// Erasure code the data into K data blocks and M parity
+	// blocks. Only the parity blocks are filled. Data blocks remain
+	// intact.
+	C.ec_encode_data(C.int(encodedBlockLen), C.int(k), C.int(m), e.encodeTbls,
+		(**C.uint8_t)(unsafe.Pointer(&pointersToEncodedBlock[:k][0])), // Pointers to data blocks
+		(**C.uint8_t)(unsafe.Pointer(&pointersToEncodedBlock[k:][0]))) // Pointers to parity blocks
+
+	return encodedBlocks, nil
 }

pkg/storage/donut/erasure.go

@@ -75,7 +75,9 @@ func erasureReader(readers []io.ReadCloser, donutMetadata map[string]string, wri
 		if blockSize < totalLeft {
 			curBlockSize = blockSize
 		}
-		curChunkSize := erasure.GetEncodedChunkLen(curBlockSize, uint8(k))
+
+		curChunkSize := erasure.GetEncodedBlockLen(curBlockSize, uint8(k))
+
 		encodedBytes := make([][]byte, 16)
 		for i, reader := range readers {
 			var bytesBuffer bytes.Buffer