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package pack
import (
"compress/zlib"
"io"
)
// ChainBase represents the "base" component of a delta-base chain.
type ChainBase struct {
// offset returns the offset into the given io.ReaderAt where the read
// will begin.
offset int64
// size is the total uncompressed size of the data in the base chain.
size int64
// typ is the type of data that this *ChainBase encodes.
typ PackedObjectType
// r is the io.ReaderAt yielding a stream of zlib-compressed data.
r io.ReaderAt
}
// Unpack inflates and returns the uncompressed data encoded in the base
// element.
//
// If there was any error in reading the compressed data (invalid headers,
// etc.), it will be returned immediately.
func (b *ChainBase) Unpack() ([]byte, error) {
zr, err := zlib.NewReader(&OffsetReaderAt{
r: b.r,
o: b.offset,
})
if err != nil {
return nil, err
}
defer zr.Close()
buf := make([]byte, b.size)
if _, err := io.ReadFull(zr, buf); err != nil {
return nil, err
}
return buf, nil
}
// ChainBase returns the type of the object it encodes.
func (b *ChainBase) Type() PackedObjectType {
return b.typ
}
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