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package pkg
import (
"compress/bzip2"
"compress/gzip"
"fmt"
"io"
"os"
)
const (
// Gzip denotes a stream compressed via [gzip].
Gzip = iota
// Bzip2 denotes a stream compressed via [bzip2].
Bzip2
)
// A decompressArtifact is a [FileArtifact] decompressing a backing
// [FileArtifact] stream.
type decompressArtifact struct {
// Caller-supplied backing stream.
f Artifact
// Compression on top of the stream.
compress uint32
}
var _ FileArtifact = new(decompressArtifact)
// decompressArtifactNamed embeds decompressArtifact for a [fmt.Stringer] stream.
type decompressArtifactNamed struct {
decompressArtifact
// Copied from decompressArtifact.f.
name string
}
var _ fmt.Stringer = new(decompressArtifactNamed)
// NewDecompress returns a [FileArtifact] decompressing the supplied [Artifact].
func NewDecompress(a Artifact, compress uint32) Artifact {
da := decompressArtifact{a, compress}
if s, ok := a.(fmt.Stringer); ok {
if name := s.String(); name != "" {
return &decompressArtifactNamed{da, name}
}
}
return &da
}
// String returns the name of the underlying [Artifact] suffixed with decompress.
func (a *decompressArtifactNamed) String() string { return a.name + "-decompress" }
// Kind returns the hardcoded [Kind] constant.
func (a *decompressArtifact) Kind() Kind { return KindDecompress }
// Params writes value of compression enum.
func (a *decompressArtifact) Params(ctx *IContext) { ctx.WriteUint32(a.compress) }
func init() {
register(KindDecompress, func(r *IRReader) Artifact {
a := NewDecompress(r.Next(), r.ReadUint32())
if _, ok := r.Finalise(); ok {
panic(ErrUnexpectedChecksum)
}
return a
})
}
// Dependencies returns a slice containing the backing file.
func (a *decompressArtifact) Dependencies() []Artifact {
return []Artifact{a.f}
}
// IsExclusive returns false: decompressor is fully sequential.
func (a *decompressArtifact) IsExclusive() bool { return false }
// compoundCloser is an [io.ReadCloser] with an additional [io.Closer] attached.
type compoundCloser struct {
io.ReadCloser
c io.Closer
}
// Close closes [io.ReadCloser] and the additional [io.Closer]. It returns the
// non-nil error returned by the underlying [io.ReadCloser], otherwise it
// returns the error returned by the additional [io.Closer].
func (c compoundCloser) Close() error {
err := c.ReadCloser.Close()
if _err := c.c.Close(); err == nil {
err = _err
}
return err
}
// Cure returns a decompressor [io.ReadCloser].
func (a *decompressArtifact) Cure(r *RContext) (io.ReadCloser, error) {
sr, err := r.Open(a.f)
if err != nil {
return nil, err
}
br := r.cache.getReaderRC(sr)
var dr io.ReadCloser
switch a.compress {
case Gzip:
if dr, err = gzip.NewReader(br); err != nil {
_ = br.Close()
return nil, err
}
return compoundCloser{dr, br}, nil
case Bzip2:
return struct {
io.Reader
io.Closer
}{bzip2.NewReader(br), br}, nil
default:
return nil, os.ErrInvalid
}
}
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