157 lines
3.7 KiB
Go
157 lines
3.7 KiB
Go
/*
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* Mini 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-code.h"
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// #include "ec-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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type Technique int
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const (
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Vandermonde Technique = iota
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Cauchy
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)
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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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// EncoderParams is a configuration set for building an encoder. It is created using ValidateParams.
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type EncoderParams 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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// Encoder is an object used to encode and decode data.
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type Encoder struct {
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p *EncoderParams
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k,
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m C.int
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encode_matrix,
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encode_tbls,
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decode_matrix,
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decode_tbls *C.uint8_t
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}
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// ParseEncoderParams creates an EncoderParams 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 ParseEncoderParams(k, m uint8, technique Technique) (*EncoderParams, 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 &EncoderParams{
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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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// NewEncoder creates an encoder object with a given set of parameters.
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func NewEncoder(ep *EncoderParams) *Encoder {
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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 encode_matrix *C.uint8_t
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var encode_tbls *C.uint8_t
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C.minio_init_encoder(C.int(ep.Technique), k, m, &encode_matrix,
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&encode_tbls)
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return &Encoder{
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p: ep,
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k: k,
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m: m,
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encode_matrix: encode_matrix,
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encode_tbls: encode_tbls,
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decode_matrix: nil,
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decode_tbls: nil,
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}
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}
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// Encode encodes a block of data. The input is the original data. The output
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// is a 2 tuple containing (k + m) chunks of erasure encoded data and the
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// length of the original object.
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func (e *Encoder) Encode(block []byte) ([][]byte, int) {
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var block_len = len(block)
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chunk_size := int(C.minio_calc_chunk_size(e.k, C.uint32_t(block_len)))
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chunk_len := chunk_size * int(e.p.K)
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pad_len := chunk_len - block_len
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if pad_len > 0 {
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s := make([]byte, pad_len)
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// Expand with new padded blocks to the byte array
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block = append(block, s...)
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}
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coded_len := chunk_size * int(e.p.M)
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c := make([]byte, coded_len)
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block = append(block, c...)
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// Allocate chunks
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chunks := make([][]byte, e.p.K+e.p.M)
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pointers := make([]*byte, e.p.K+e.p.M)
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var i int
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// Add data blocks to chunks
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for i = 0; i < int(e.p.K); i++ {
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chunks[i] = block[i*chunk_size : (i+1)*chunk_size]
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pointers[i] = &chunks[i][0]
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}
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for i = int(e.p.K); i < int(e.p.K+e.p.M); i++ {
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chunks[i] = make([]byte, chunk_size)
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pointers[i] = &chunks[i][0]
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}
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data := (**C.uint8_t)(unsafe.Pointer(&pointers[:e.p.K][0]))
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coding := (**C.uint8_t)(unsafe.Pointer(&pointers[e.p.K:][0]))
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C.ec_encode_data(C.int(chunk_size), e.k, e.m, e.encode_tbls, data,
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coding)
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return chunks, block_len
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}
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