internal/pkg: stream decompress artifact

The tarArtifact predates FileArtifact pipelining. This migrates decompression and buffering into a standalone artifact implementation.

Signed-off-by: Ophestra <cat@gensokyo.uk>

5 files changed, 229 insertions, 4 deletions

diff --git a/internal/pkg/compress.go b/internal/pkg/compress.go
new file mode 100644
index 00000000..310fe065
--- /dev/null
+++ b/internal/pkg/compress.go
@@ -0,0 +1,119 @@
+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
+	}
+}
diff --git a/internal/pkg/compress_test.go b/internal/pkg/compress_test.go
new file mode 100644
index 00000000..5b542dce
--- /dev/null
+++ b/internal/pkg/compress_test.go
@@ -0,0 +1,70 @@
+package pkg_test
+
+import (
+	"bytes"
+	"compress/gzip"
+	"crypto/sha512"
+	"io/fs"
+	"net/http"
+	"testing"
+	"testing/fstest"
+
+	"hakurei.app/check"
+	"hakurei.app/internal/pkg"
+)
+
+func TestDecompress(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+	gw := gzip.NewWriter(&buf)
+	if _, err := gw.Write([]byte{0}); err != nil {
+		t.Fatal(err)
+	} else if err = gw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	testdata := buf.String()
+
+	var transport http.Transport
+	client := http.Client{Transport: &transport}
+	transport.RegisterProtocol("file", http.NewFileTransportFS(fstest.MapFS{
+		"testdata": {Data: []byte(testdata), Mode: 0400},
+	}))
+	testdataChecksum := func() pkg.Checksum {
+		h := sha512.New384()
+		h.Write([]byte(testdata))
+		return (pkg.Checksum)(h.Sum(nil))
+	}()
+
+	checkWithCache(t, []cacheTestCase{
+		{"decompress", 0, nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
+			cureMany(t, c, []cureStep{
+				{"close", pkg.NewDecompress(pkg.NewHTTPGet(
+					&client,
+					"file:///testdata",
+					pkg.Checksum{0xfd},
+				), pkg.Gzip), nil, nil, &pkg.ChecksumMismatchError{
+					Got:  testdataChecksum,
+					Want: pkg.Checksum{0xfd},
+				}},
+
+				{"gzip", pkg.NewDecompress(pkg.NewHTTPGet(
+					&client,
+					"file:///testdata",
+					testdataChecksum,
+				), pkg.Gzip), ignorePathname, expectsChecksum(sha512.Sum384([]byte{0})), nil},
+			})
+		}, expectsFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/" + pkg.Encode(sha512.Sum384([]byte{0})): {Mode: 0400, Data: []byte{0}},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/QpjkahDrz7pz-tv0eAGNXR6x9NAtTjWCK5Hr7G1cIZj9rT7bLYJWUQeLD4wamAlF": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX")},
+
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"work":       {Mode: fs.ModeDir | 0700},
+		}},
+	})
+}
diff --git a/internal/pkg/ir_test.go b/internal/pkg/ir_test.go
index 9a465e55..d49d2c56 100644
--- a/internal/pkg/ir_test.go
+++ b/internal/pkg/ir_test.go
@@ -104,6 +104,8 @@ func TestIRRoundtrip(t *testing.T) {
 
 		{"file anonymous", pkg.NewFile("", []byte{0})},
 		{"file", pkg.NewFile("stub", []byte("stub"))},
+
+		{"decompress", pkg.NewDecompress(pkg.NewFile("", []byte{0}), pkg.Bzip2)},
 	}
 	testCasesCache := make([]cacheTestCase, len(testCases))
 	for i, tc := range testCases {
diff --git a/internal/pkg/pkg.go b/internal/pkg/pkg.go
index 8b022d1f..09d91f73 100644
--- a/internal/pkg/pkg.go
+++ b/internal/pkg/pkg.go
@@ -508,6 +508,8 @@ const (
 	KindExecNet
 	// KindFile is the kind of [Artifact] returned by [NewFile].
 	KindFile
+	// KindDecompress is the kind of [Artifact] returned by [NewDecompress].
+	KindDecompress
 
 	// _kindEnd is the total number of kinds and does not denote a kind.
 	_kindEnd
@@ -795,6 +797,38 @@ func (c *Cache) getReader(r io.Reader) *bufio.Reader {
 // putReader adds br to brPool.
 func (c *Cache) putReader(br *bufio.Reader) { c.brPool.Put(br) }
 
+// bufioReadCloser is the concrete type of value returned by Cache.getReaderRC.
+type bufioReadCloser struct {
+	// Saved close error.
+	closeErr error
+	// Synchronises calls to Close.
+	closeOnce sync.Once
+
+	// For backing freelist.
+	c *Cache
+	// Underlying reader.
+	r io.ReadCloser
+	// Allocated from c.
+	*bufio.Reader
+}
+
+// Close closes the underlying reader, saves its return value, and returns the
+// [bufio.Reader] instance to the backing [Cache].
+func (brc *bufioReadCloser) Close() error {
+	brc.closeOnce.Do(func() {
+		br := brc.Reader
+		brc.Reader = nil
+		brc.c.putReader(br)
+		brc.closeErr = brc.r.Close()
+	})
+	return brc.closeErr
+}
+
+// getReaderRC is like getReader, but returns an [io.ReadCloser].
+func (c *Cache) getReaderRC(r io.ReadCloser) io.ReadCloser {
+	return &bufioReadCloser{c: c, r: r, Reader: c.getReader(r)}
+}
+
 // getWriter is like [bufio.NewWriter] but for bwPool.
 func (c *Cache) getWriter(w io.Writer) *bufio.Writer {
 	bw := c.bwPool.Get().(*bufio.Writer)
diff --git a/internal/pkg/pkg_test.go b/internal/pkg/pkg_test.go
index 25deb95c..ce11fa90 100644
--- a/internal/pkg/pkg_test.go
+++ b/internal/pkg/pkg_test.go
@@ -293,15 +293,15 @@ func TestIdent(t *testing.T) {
 		a    pkg.Artifact
 		want unique.Handle[pkg.ID]
 	}{
-		{"tar", &stubArtifact{
-			pkg.KindTar,
-			[]byte{pkg.TarGzip, 0, 0, 0, 0, 0, 0, 0},
+		{"decompress", &stubArtifact{
+			pkg.KindDecompress,
+			[]byte{pkg.Gzip, 0, 0, 0, 0, 0, 0, 0},
 			[]pkg.Artifact{
 				overrideIdent{pkg.ID{}, new(stubArtifact)},
 			},
 			nil,
 		}, unique.Make[pkg.ID](pkg.MustDecode(
-			"WKErnjTOVbuH2P9a0gM4OcAAO4p-CoX2HQu7CbZrg8ZOzApvWoO3-ISzPw6av_rN",
+			"97Y85QewssfPbNIN9cyNhzD4e6dLHcDTU8rb2c34k-aCrZfBNXFUc0duPiLFFcw_",
 		))},
 	}