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package display
import (
"errors"
"io"
)
var ErrClosed = errors.New("RestartReader: closed")
type RestartReader struct {
r io.Reader
buf []byte
// Where in the buffer we are. If it's equal to len(buf) then the reader
// should be used.
i int64
}
func (rr *RestartReader) Read(p []byte) (n int, err error) {
if rr.buf == nil {
return 0, ErrClosed
}
if rr.i >= int64(len(rr.buf)) {
// Read new data
tmp := make([]byte, len(p))
n, err = rr.r.Read(tmp)
if n > 0 {
rr.buf = append(rr.buf, tmp[:n]...)
copy(p, tmp[:n])
}
rr.i = int64(len(rr.buf))
return
}
// Reading from buffer
bufSize := len(rr.buf[rr.i:])
if len(p) > bufSize {
// It wants more data then what's in the buffer
tmp := make([]byte, len(p)-bufSize)
n, err = rr.r.Read(tmp)
if n > 0 {
rr.buf = append(rr.buf, tmp[:n]...)
}
copy(p, rr.buf[rr.i:])
n += bufSize
rr.i = int64(len(rr.buf))
return
}
// All the required data is in the buffer
end := rr.i + int64(len(p))
copy(p, rr.buf[rr.i:end])
rr.i = end
n = len(p)
err = nil
return
}
// Restart causes subsequent Read calls to read from the beginning, instead
// of where they left off.
func (rr *RestartReader) Restart() {
rr.i = 0
}
// Close clears the buffer and closes the underlying io.Reader if possible,
// returning its error.
func (rr *RestartReader) Close() error {
rr.buf = nil
if closer, ok := rr.r.(io.ReadCloser); ok {
return closer.Close()
}
return nil
}
// NewRestartReader creates and initializes a new RestartReader that reads from
// the provided io.Reader.
func NewRestartReader(r io.Reader) *RestartReader {
return &RestartReader{
r: r,
buf: make([]byte, 0),
}
}
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