// Encode takes a data_block as input and produces base + parity chunks from it
// Original data block can then be recovered from any of base chunks
func (e *CauchyEncoder) Encode(data_block []byte) (chunks [][]byte, length int) {
// save original block length
original_length := len(data_block)
// extract required parameters
b := e.p.b
n := e.p.n
word_size := e.p.word_size
packet_size := e.p.packet_size
k := e.k
m := e.m
w := e.w
bitmatrix := e.bitmatrix
// data block length must to be multiple of base, word size, block size
var multiplier int = b * word_size * packet_size
// pad data block if necessary
if r := original_length % multiplier; r != 0 {
// sparse block of length r
// TODO: implement PKCS7 padding
s := make([]byte, multiplier-r)
data_block = append(data_block, s...)
}
// calculate chunk length
chunk_length := len(data_block) / int(b)
// virtually split data_block into k slices
// the last m slices are for coding chunks
chunks = make([][]byte, n)
// aux structure, used to pass chunks into codec
pointers := make([]*byte, n)
var i int
for i = 0; i < b; i++ {
chunks[i] = data_block[i*chunk_length : (i+1)*chunk_length]
pointers[i] = &chunks[i][0]
}
// allocate space for coding blocks
for i = b; i < n; i++ {
chunks[i] = make([]byte, chunk_length)
pointers[i] = &chunks[i][0]
}
// write coding c
data_ptrs := (**C.char)(unsafe.Pointer(&pointers[:b][0]))
coding_ptrs := (**C.char)(unsafe.Pointer(&pointers[b:][0]))
C.jerasure_bitmatrix_encode(k, m, w, bitmatrix, data_ptrs, coding_ptrs, C.int(chunk_length), e.packet_size)
return chunks, original_length
}
// void jerasure_bitmatrix_encode(int k, int m, int w, int *bitmatrix,char **data_ptrs, char **coding_ptrs, int size, int packetsize);
func EncodeBitMatrix(k, m, w int, bitmatrix []int, data, coding [][]byte, stripesize, packetsize int) {
cdata := make([]*C.char, len(data))
for i := range cdata {
cdata[i] = (*C.char)(unsafe.Pointer(&data[i][0]))
}
ccoding := make([]*C.char, len(coding))
for i := range ccoding {
ccoding[i] = (*C.char)(unsafe.Pointer(&coding[i][0]))
}
cints := make([]C.int, len(bitmatrix))
for i := range bitmatrix {
cints[i] = C.int(bitmatrix[i])
}
C.jerasure_bitmatrix_encode(C.int(k), C.int(m), C.int(w), (*C.int)(unsafe.Pointer(&cints[0])),
(**C.char)(unsafe.Pointer(&cdata[0])), (**C.char)(unsafe.Pointer(&ccoding[0])), C.int(stripesize), C.int(packetsize))
}