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fullreader.go
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fullreader.go
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package data
import (
"io"
"github.com/sylabs/squashfs/internal/decompress"
"github.com/sylabs/squashfs/internal/toreader"
)
type FullReader struct {
r io.ReaderAt
d decompress.Decompressor
fragRdr func() (io.Reader, error)
sizes []uint32
blockSize uint32
start uint64
}
func NewFullReader(r io.ReaderAt, start uint64, d decompress.Decompressor, blockSizes []uint32, blockSize uint32) *FullReader {
return &FullReader{
r: r,
start: start,
blockSize: blockSize,
sizes: blockSizes,
d: d,
}
}
func (r *FullReader) AddFragment(rdr func() (io.Reader, error)) {
r.fragRdr = rdr
r.sizes = append(r.sizes, 0)
}
type outDat struct {
err error
data []byte
i int
}
func (r FullReader) process(index int, offset int64, out chan outDat) {
var err error
var dat []byte
var rdr io.ReadCloser
size := realSize(r.sizes[index])
if size == 0 {
out <- outDat{
i: index,
err: nil,
data: make([]byte, r.blockSize),
}
return
}
// rdr := io.LimitReader(toreader.NewReader(r.r, offset), int64(size))
if size == r.sizes[index] {
//Special workaround for zstd for increased performancce.
if zstd, ok := r.d.(*decompress.Zstd); ok {
dat = make([]byte, size)
_, err = r.r.ReadAt(dat, offset)
if err == nil {
dat, err = zstd.Decode(dat)
}
} else {
rdr, err = r.d.Reader(io.LimitReader(toreader.NewReader(r.r, offset), int64(size)))
if err == nil {
dat, err = io.ReadAll(rdr)
}
}
} else {
dat = make([]byte, size)
_, err = r.r.ReadAt(dat, offset)
}
out <- outDat{
i: index,
err: err,
data: dat,
}
if clr, ok := rdr.(io.Closer); ok {
clr.Close()
}
}
func (r FullReader) WriteTo(w io.Writer) (n int64, err error) {
out := make(chan outDat, len(r.sizes))
offset := r.start
num := len(r.sizes)
for i := 0; i < num; i++ {
if i == num-1 && r.fragRdr != nil {
go func() {
rdr, e := r.fragRdr()
if err != nil {
out <- outDat{
i: num - 1,
err: e,
}
return
}
dat, e := io.ReadAll(rdr)
out <- outDat{
i: num - 1,
err: e,
data: dat,
}
if clr, ok := rdr.(io.Closer); ok {
clr.Close()
}
}()
continue
}
go r.process(i, int64(offset), out)
offset += uint64(realSize(r.sizes[i]))
}
cache := make(map[int]outDat)
var tmpN int
for cur := 0; cur < num; {
dat := <-out
if dat.err != nil {
err = dat.err
return
}
if dat.i != cur {
cache[dat.i] = dat
continue
}
tmpN, err = w.Write(dat.data)
n += int64(tmpN)
if err != nil {
return
}
cur++
var ok bool
for {
dat, ok = cache[cur]
if !ok {
break
}
tmpN, err = w.Write(dat.data)
n += int64(tmpN)
if err != nil {
return
}
cur++
}
}
return
}