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