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Add comments clarifying copyWithBuffer implementation

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Signed-off-by: Amr Mahdi <amramahdi@gmail.com>
This commit is contained in:
Amr Mahdi 2020-11-03 04:23:52 +00:00
parent f6834d4c0b
commit b81917ee72
1 changed files with 6 additions and 0 deletions
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6
content/helpers.go
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@ -229,6 +229,10 @@ func seekReader(r io.Reader, offset, size int64) (io.Reader, error) {
return r, nil return r, nil
} }
// copyWithBuffer is very similar to io.CopyBuffer https://golang.org/pkg/io/#CopyBuffer
// but instead of using Read to read from the src, we use ReadAtLeast to make sure we have
// a full buffer before we do a write operation to dst to reduce overheads associated
// with the write operations of small buffers.
func copyWithBuffer(dst io.Writer, src io.Reader) (written int64, err error) { func copyWithBuffer(dst io.Writer, src io.Reader) (written int64, err error) {
// If the reader has a WriteTo method, use it to do the copy. // If the reader has a WriteTo method, use it to do the copy.
// Avoids an allocation and a copy. // Avoids an allocation and a copy.
@ -259,6 +263,8 @@ func copyWithBuffer(dst io.Writer, src io.Reader) (written int64, err error) {
} }
} }
if er != nil { if er != nil {
// If an EOF happens after reading fewer than the requested bytes,
// ReadAtLeast returns ErrUnexpectedEOF.
if er != io.EOF && er != io.ErrUnexpectedEOF { if er != io.EOF && er != io.ErrUnexpectedEOF {
err = er err = er
} }