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car_helpers.go
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/
car_helpers.go
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package client
import (
"fmt"
"io"
"github.com/ipfs/go-cid"
cbor "github.com/ipfs/go-ipld-cbor"
"github.com/ipld/go-car/util"
"github.com/multiformats/go-varint"
)
// —————————————————————————————————————————————————————————
//
// This code is temporary, and should be deleted when
// https://github.com/ipld/go-car/issues/196 is resolved.
//
// —————————————————————————————————————————————————————————
func init() {
cbor.RegisterCborType(CarHeader{})
}
type CarHeader struct {
Roots []cid.Cid
Version uint64
}
func readHeader(r io.Reader) (*CarHeader, error) {
hb, err := ldRead(r, false)
if err != nil {
return nil, err
}
var ch CarHeader
if err := cbor.DecodeInto(hb, &ch); err != nil {
return nil, fmt.Errorf("invalid header: %v", err)
}
return &ch, nil
}
func writeHeader(h *CarHeader, w io.Writer) error {
hb, err := cbor.DumpObject(h)
if err != nil {
return err
}
return util.LdWrite(w, hb)
}
func ldRead(r io.Reader, zeroLenAsEOF bool) ([]byte, error) {
l, err := varint.ReadUvarint(toByteReader(r))
if err != nil {
// If the length of bytes read is non-zero when the error is EOF then signal an unclean EOF.
if l > 0 && err == io.EOF {
return nil, io.ErrUnexpectedEOF
}
return nil, err
} else if l == 0 && zeroLenAsEOF {
return nil, io.EOF
}
buf := make([]byte, l)
if _, err := io.ReadFull(r, buf); err != nil {
return nil, err
}
return buf, nil
}
type readerPlusByte struct {
io.Reader
}
func (rb readerPlusByte) ReadByte() (byte, error) {
return readByte(rb)
}
func readByte(r io.Reader) (byte, error) {
var p [1]byte
_, err := io.ReadFull(r, p[:])
return p[0], err
}
func toByteReader(r io.Reader) io.ByteReader {
if br, ok := r.(io.ByteReader); ok {
return br
}
return &readerPlusByte{r}
}