ntfy/util/peak.go

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2022-01-02 23:56:12 +01:00
package util
import (
"bytes"
"io"
"strings"
)
// PeakedReadCloser is a ReadCloser that allows peaking into a stream and buffering it in memory.
// It can be instantiated using the Peak function. After a stream has been peaked, it can still be fully
// read by reading the PeakedReadCloser. It first drained from the memory buffer, and then from the remaining
// underlying reader.
type PeakedReadCloser struct {
PeakedBytes []byte
LimitReached bool
peaked io.Reader
underlying io.ReadCloser
closed bool
}
// Peak reads the underlying ReadCloser into memory up until the limit and returns a PeakedReadCloser
func Peak(underlying io.ReadCloser, limit int) (*PeakedReadCloser, error) {
if underlying == nil {
underlying = io.NopCloser(strings.NewReader(""))
}
peaked := make([]byte, limit)
read, err := io.ReadFull(underlying, peaked)
if err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
return nil, err
}
return &PeakedReadCloser{
PeakedBytes: peaked[:read],
LimitReached: read == limit,
underlying: underlying,
peaked: bytes.NewReader(peaked[:read]),
closed: false,
}, nil
}
// Read reads from the peaked bytes and then from the underlying stream
func (r *PeakedReadCloser) Read(p []byte) (n int, err error) {
if r.closed {
return 0, io.EOF
}
n, err = r.peaked.Read(p)
if err == io.EOF {
return r.underlying.Read(p)
} else if err != nil {
return 0, err
}
return
}
// Close closes the underlying stream
func (r *PeakedReadCloser) Close() error {
if r.closed {
return io.EOF
}
r.closed = true
return r.underlying.Close()
}