You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
104 lines
2.8 KiB
104 lines
2.8 KiB
/*
|
|
* 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-code.h"
|
|
// #include "ec-common.h"
|
|
import "C"
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
"unsafe"
|
|
)
|
|
|
|
// Decode decodes 2 tuple data containing (k + m) chunks back into its original form.
|
|
// Additionally original block length should also be provided as input.
|
|
//
|
|
// 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 source, target **C.uint8_t
|
|
|
|
k := e.params.K
|
|
m := e.params.M
|
|
n := k + m
|
|
if len(chunks) != int(n) {
|
|
return nil, errors.New(fmt.Sprintf("chunks length must be %d", n))
|
|
}
|
|
chunk_size := GetEncodedChunkLen(length, uint8(k))
|
|
|
|
error_index := make([]int, n+1)
|
|
var err_count 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++
|
|
}
|
|
}
|
|
error_index[err_count] = -1
|
|
err_count++
|
|
|
|
// Too many missing chunks, cannot be more than parity `m`
|
|
if err_count-1 > int(n-k) {
|
|
return nil, errors.New("too many erasures requested, can't decode")
|
|
}
|
|
|
|
error_index_ptr := int2cInt(error_index[:err_count])
|
|
|
|
for i := range chunks {
|
|
if chunks[i] == nil || len(chunks[i]) == 0 {
|
|
chunks[i] = make([]byte, chunk_size)
|
|
}
|
|
}
|
|
|
|
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)
|
|
|
|
pointers := make([]*byte, n)
|
|
for i := range chunks {
|
|
pointers[i] = &chunks[i][0]
|
|
}
|
|
|
|
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)
|
|
|
|
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,
|
|
source, target)
|
|
|
|
recovered_output := make([]byte, 0, chunk_size*int(k))
|
|
for i := 0; i < int(k); i++ {
|
|
recovered_output = append(recovered_output, chunks[i]...)
|
|
}
|
|
|
|
// TODO cache this if necessary
|
|
e.decode_matrix = decode_matrix
|
|
e.decode_tbls = decode_tbls
|
|
|
|
return recovered_output[:length], nil
|
|
}
|
|
|