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shrinkable_reader.go
51 lines (43 loc) · 1.14 KB
/
shrinkable_reader.go
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package walparser
import (
"fmt"
"io"
"github.com/pkg/errors"
"github.com/wal-g/tracelog"
)
type NotEnoughDataToShrinkError struct {
error
}
func NewNotEnoughDataToShrinkError(dataRemained int, toShrink int) error {
return NotEnoughDataToShrinkError{
errors.Errorf("not enough data to shrink: dataRemained: %v, toShrink: %v", dataRemained, toShrink)}
}
func (err NotEnoughDataToShrinkError) Error() string {
return fmt.Sprintf(tracelog.GetErrorFormatter(), err.error)
}
type ShrinkableReader struct {
innerReader io.Reader
dataRemained int
}
func (reader *ShrinkableReader) Read(p []byte) (n int, err error) {
if reader.dataRemained == 0 {
return 0, io.EOF
}
if len(p) <= reader.dataRemained {
n, err = reader.innerReader.Read(p)
reader.dataRemained -= n
return n, err
}
remained := make([]byte, reader.dataRemained)
n, err = reader.innerReader.Read(remained)
copy(p, remained)
reader.dataRemained -= n
return n, err
}
func (reader *ShrinkableReader) Shrink(length int) error {
if reader.dataRemained < length {
return NewNotEnoughDataToShrinkError(reader.dataRemained, length)
}
reader.dataRemained -= length
return nil
}