minio/pkg/erasure/erasure_encode.go

198 lines
5.6 KiB
Go

/*
* Minimalist Object Storage, (C) 2014 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package erasure
// #cgo CFLAGS: -O0
// #include <stdlib.h>
// #include "ec_isal-l.h"
// #include "ec_minio_common.h"
import "C"
import (
"errors"
"unsafe"
)
// Technique - type of matrix type used in encoding
type Technique uint8
// Different types of supported matrix types
const (
Vandermonde Technique = iota
Cauchy
None
)
// Default Data and Parity blocks
const (
K = 10
M = 3
)
// Block alignment
const (
SIMDAlign = 32
)
// ErasureParams is a configuration set for building an encoder. It is created using ValidateParams().
type ErasureParams struct {
K uint8
M uint8
Technique Technique // cauchy or vandermonde matrix (RS)
}
// Erasure is an object used to encode and decode data.
type Erasure struct {
params *ErasureParams
encodeMatrix, encodeTbls *C.uchar
decodeMatrix, decodeTbls *C.uchar
decodeIndex *C.uint32_t
}
// ValidateParams creates an ErasureParams object.
//
// k and m represent the matrix size, which corresponds to the protection level
// technique is the matrix type. Valid inputs are Cauchy (recommended) or Vandermonde.
//
func ValidateParams(k, m uint8, technique Technique) (*ErasureParams, error) {
if k < 1 {
return nil, errors.New("k cannot be zero")
}
if m < 1 {
return nil, errors.New("m cannot be zero")
}
if k+m > 255 {
return nil, errors.New("(k + m) cannot be bigger than Galois field GF(2^8) - 1")
}
switch technique {
case Vandermonde:
break
case Cauchy:
break
default:
return nil, errors.New("Technique can be either vandermonde or cauchy")
}
return &ErasureParams{
K: k,
M: m,
Technique: technique,
}, nil
}
// NewErasure creates an encoder object with a given set of parameters.
func NewErasure(ep *ErasureParams) *Erasure {
var k = C.int(ep.K)
var m = C.int(ep.M)
var encodeMatrix *C.uchar
var encodeTbls *C.uchar
C.minio_init_encoder(C.int(ep.Technique), k, m, &encodeMatrix,
&encodeTbls)
return &Erasure{
params: ep,
encodeMatrix: encodeMatrix,
encodeTbls: encodeTbls,
decodeMatrix: nil,
decodeTbls: nil,
decodeIndex: nil,
}
}
// GetEncodedBlocksLen - total length of all encoded blocks
func GetEncodedBlocksLen(inputLen int, k, m uint8) (outputLen int) {
outputLen = GetEncodedBlockLen(inputLen, k) * int(k+m)
return outputLen
}
// GetEncodedBlockLen - length per block of encoded blocks
func GetEncodedBlockLen(inputLen int, k uint8) (encodedOutputLen int) {
alignment := int(k) * SIMDAlign
remainder := inputLen % alignment
paddedInputLen := inputLen
if remainder != 0 {
paddedInputLen = inputLen + (alignment - remainder)
}
encodedOutputLen = paddedInputLen / int(k)
return encodedOutputLen
}
// 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 *Erasure) 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
// Length of a single encoded chunk.
// Total number of encoded chunks = "k" data + "m" parity blocks
encodedBlockLen := GetEncodedBlockLen(len(inputData), uint8(k))
// 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
inputData = append(inputData, padding...)
}
// Extend inputData buffer to accommodate coded parity blocks
{ // Local Scope
encodedParityBlocksLen := encodedBlockLen * m
parityBlocks := make([]byte, encodedParityBlocksLen)
inputData = append(inputData, parityBlocks...)
}
// 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]
}
// Copy erasure block slices to encoded block buffer
for i := k; i < n; i++ {
encodedBlocks[i] = make([]byte, encodedBlockLen)
pointersToEncodedBlock[i] = &encodedBlocks[i][0]
}
// 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.uchar)(unsafe.Pointer(&pointersToEncodedBlock[:k][0])), // Pointers to data blocks
(**C.uchar)(unsafe.Pointer(&pointersToEncodedBlock[k:][0]))) // Pointers to parity blocks
return encodedBlocks, nil
}