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// Package ioutil implements some I/O utility functions.
package ioutil
import (
"bufio"
"errors"
"io"
)
type readPeeker interface {
io.Reader
Peek(int) ([]byte, error)
}
var (
ErrEmptyReader = errors.New("reader is empty")
)
// NonEmptyReader takes a reader and returns it if it is not empty, or
// `ErrEmptyReader` if it is empty. If there is an error when reading the first
// byte of the given reader, it will be propagated.
func NonEmptyReader(r io.Reader) (io.Reader, error) {
pr, ok := r.(readPeeker)
if !ok {
pr = bufio.NewReader(r)
}
_, err := pr.Peek(1)
if err == io.EOF {
return nil, ErrEmptyReader
}
if err != nil {
return nil, err
}
return pr, nil
}
type readCloser struct {
io.Reader
closer io.Closer
}
func (r *readCloser) Close() error {
return r.closer.Close()
}
// NewReadCloser creates an `io.ReadCloser` with the given `io.Reader` and
// `io.Closer`.
func NewReadCloser(r io.Reader, c io.Closer) io.ReadCloser {
return &readCloser{Reader: r, closer: c}
}
type writeNopCloser struct {
io.Writer
}
func (writeNopCloser) Close() error { return nil }
// WriteNopCloser returns a WriteCloser with a no-op Close method wrapping
// the provided Writer w.
func WriteNopCloser(w io.Writer) io.WriteCloser {
return writeNopCloser{w}
}
// CheckClose is used with defer to close the given io.Closer and check its
// returned error value. If Close returns an error and the given *error
// is not nil, *error is set to the error returned by Close.
//
// CheckClose is typically used with named return values like so:
//
// func do(obj *Object) (err error) {
// w, err := obj.Writer()
// if err != nil {
// return nil
// }
// defer CheckClose(w, &err)
// // work with w
// }
func CheckClose(c io.Closer, err *error) {
if cerr := c.Close(); cerr != nil && *err == nil {
*err = cerr
}
}
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