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package rifs
import (
"fmt"
"io"
)
const (
defaultCopyBufferSize = 1024 * 1024
)
// GracefulCopy willcopy while enduring lesser normal issues.
//
// - We'll ignore EOF if the read byte-count is more than zero. Only an EOF when
// zero bytes were read will terminate the loop.
//
// - Ignore short-writes. If less bytes were written than the bytes that were
// given, we'll keep trying until done.
func GracefulCopy(w io.Writer, r io.Reader, buffer []byte) (copyCount int, err error) {
if buffer == nil {
buffer = make([]byte, defaultCopyBufferSize)
}
for {
readCount, err := r.Read(buffer)
if err != nil {
if err != io.EOF {
err = fmt.Errorf("read error: %s", err.Error())
return 0, err
}
// Only break on EOF if no bytes were actually read.
if readCount == 0 {
break
}
}
writeBuffer := buffer[:readCount]
for len(writeBuffer) > 0 {
writtenCount, err := w.Write(writeBuffer)
if err != nil {
err = fmt.Errorf("write error: %s", err.Error())
return 0, err
}
writeBuffer = writeBuffer[writtenCount:]
}
copyCount += readCount
}
return copyCount, nil
}
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