49 lines
1.3 KiB
Go
49 lines
1.3 KiB
Go
package azure
|
|
|
|
import (
|
|
"bytes"
|
|
"io"
|
|
)
|
|
|
|
type blockBlobWriter interface {
|
|
GetSize(container, blob string) (int64, error)
|
|
WriteBlobAt(container, blob string, offset int64, chunk io.Reader) (int64, error)
|
|
}
|
|
|
|
// zeroFillWriter enables writing to an offset outside a block blob's size
|
|
// by offering the chunk to the underlying writer as a contiguous data with
|
|
// the gap in between filled with NUL (zero) bytes.
|
|
type zeroFillWriter struct {
|
|
blockBlobWriter
|
|
}
|
|
|
|
func newZeroFillWriter(b blockBlobWriter) zeroFillWriter {
|
|
w := zeroFillWriter{}
|
|
w.blockBlobWriter = b
|
|
return w
|
|
}
|
|
|
|
// Write writes the given chunk to the specified existing blob even though
|
|
// offset is out of blob's size. The gaps are filled with zeros. Returned
|
|
// written number count does not include zeros written.
|
|
func (z *zeroFillWriter) Write(container, blob string, offset int64, chunk io.Reader) (int64, error) {
|
|
size, err := z.blockBlobWriter.GetSize(container, blob)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
|
|
var reader io.Reader
|
|
var zeroPadding int64
|
|
if offset <= size {
|
|
reader = chunk
|
|
} else {
|
|
zeroPadding = offset - size
|
|
offset = size // adjust offset to be the append index
|
|
zeros := bytes.NewReader(make([]byte, zeroPadding))
|
|
reader = io.MultiReader(zeros, chunk)
|
|
}
|
|
|
|
nn, err := z.blockBlobWriter.WriteBlobAt(container, blob, offset, reader)
|
|
nn -= zeroPadding
|
|
return nn, err
|
|
}
|