104 lines
1.9 KiB
Go
104 lines
1.9 KiB
Go
package multihash
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import (
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"encoding/binary"
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"errors"
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"io"
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"math"
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)
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// Reader is an io.Reader wrapper that exposes a function
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// to read a whole multihash, parse it, and return it.
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type Reader interface {
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io.Reader
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ReadMultihash() (Multihash, error)
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}
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// Writer is an io.Writer wrapper that exposes a function
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// to write a whole multihash.
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type Writer interface {
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io.Writer
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WriteMultihash(Multihash) error
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}
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// NewReader wraps an io.Reader with a multihash.Reader
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func NewReader(r io.Reader) Reader {
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return &mhReader{r}
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}
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// NewWriter wraps an io.Writer with a multihash.Writer
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func NewWriter(w io.Writer) Writer {
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return &mhWriter{w}
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}
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type mhReader struct {
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r io.Reader
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}
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func (r *mhReader) Read(buf []byte) (n int, err error) {
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return r.r.Read(buf)
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}
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func (r *mhReader) ReadByte() (byte, error) {
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if br, ok := r.r.(io.ByteReader); ok {
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return br.ReadByte()
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}
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var b [1]byte
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n, err := r.r.Read(b[:])
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if n == 1 {
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return b[0], nil
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}
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if err == nil {
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if n != 0 {
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panic("reader returned an invalid length")
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}
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err = io.ErrNoProgress
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}
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return 0, err
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}
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func (r *mhReader) ReadMultihash() (Multihash, error) {
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code, err := binary.ReadUvarint(r)
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if err != nil {
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return nil, err
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}
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length, err := binary.ReadUvarint(r)
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if err != nil {
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return nil, err
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}
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if length > math.MaxInt32 {
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return nil, errors.New("digest too long, supporting only <= 2^31-1")
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}
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pre := make([]byte, 2*binary.MaxVarintLen64)
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spot := pre
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n := binary.PutUvarint(spot, code)
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spot = pre[n:]
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n += binary.PutUvarint(spot, length)
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buf := make([]byte, int(length)+n)
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copy(buf, pre[:n])
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if _, err := io.ReadFull(r.r, buf[n:]); err != nil {
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return nil, err
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}
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return Cast(buf)
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}
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type mhWriter struct {
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w io.Writer
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}
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func (w *mhWriter) Write(buf []byte) (n int, err error) {
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return w.w.Write(buf)
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}
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func (w *mhWriter) WriteMultihash(m Multihash) error {
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_, err := w.w.Write([]byte(m))
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return err
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}
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