func NewChunkReader(r io.Reader, c btncrypt.Cipher) (*ChunkReader, error) {
cr := &ChunkReader{r: r, c: c}
if err := cr.header.ReadFrom(r, c); err != nil {
return nil, fmt.Errorf("Failed to read header: %v", err)
}
var err error
cr.bdr, err = btncrypt.NewReader(cr.r, cr.c, cr.Length())
if err != nil {
return nil, err
}
return cr, nil
}
func (h *ChunkHeader) ReadFrom(r io.Reader, c btncrypt.Cipher) error {
magic := make([]byte, SignatureLength+1)
if _, err := r.Read(magic); err != nil {
if err == io.EOF {
return err
}
return fmt.Errorf("Failed to read signature magic / format bytes: %v", err)
}
if magic[0] != ChunkSignatureMagic1 ||
magic[1] != ChunkSignatureMagic2 {
return errors.New("signature magic mismatch")
}
if magic[2] != CurrentFormat {
return fmt.Errorf("Expected format version %x but got %x", CurrentFormat, magic[2])
}
framelen := ChunkHeaderLength - c.FrameOverhead() - SignatureLength - 1
bdr, err := btncrypt.NewReader(r, c, framelen)
if err != nil {
return err
}
encoded := make([]byte, framelen)
if _, err := io.ReadFull(bdr, encoded); err != nil {
return fmt.Errorf("Failed to read header frame: %v", err)
}
if !bdr.HasReadAll() {
panic("Incomplete read in prologue frame !?!?")
}
dec := gob.NewDecoder(bytes.NewBuffer(encoded))
if err := dec.Decode(h); err != nil {
return err
}
return nil
}
func (ch *ChunkIO) readContentFrame(i int) (*decryptedContentFrame, error) {
// the frame carries a part of the content at offset
offset := i * ContentFramePayloadLength
// payload length of the encrypted frame
framePayloadLen := ContentFramePayloadLength
isLastFrame := false
distToLast := ch.PayloadLen() - offset
if distToLast <= ContentFramePayloadLength {
framePayloadLen = distToLast
isLastFrame = true
}
// the offset of the start of the frame in blob
blobOffset := ch.encryptedFrameOffset(i)
rd := &blobstore.OffsetReader{ch.bh, int64(blobOffset)}
bdr, err := btncrypt.NewReader(rd, ch.c, framePayloadLen)
if err != nil {
return nil, fmt.Errorf("Failed to create BtnDecryptReader: %v", err)
}
p := make([]byte, framePayloadLen, ContentFramePayloadLength)
if _, err := io.ReadFull(bdr, p); err != nil {
return nil, fmt.Errorf("Failed to decrypt frame idx: %d, err: %v", i, err)
}
if !bdr.HasReadAll() {
panic("Incomplete frame read")
}
log.Printf("ChunkIO: Read content frame idx: %d", i)
return &decryptedContentFrame{
P: p, Offset: offset,
IsLastFrame: isLastFrame,
}, nil
}