Add gzip-wrapping functions to CompressedResource

cmd/rwp/cmd/serve/api.go

@@ -256,11 +256,20 @@ func (s *Server) getAsset(w http.ResponseWriter, r *http.Request) {
 	}
 
 	cres, ok := res.(fetcher.CompressedResource)
-	if ok && cres.CompressedAs(archive.CompressionMethodDeflate) && start == 0 && end == 0 && supportsDeflate(r) {
-		// Stream the asset in compressed format
-		w.Header().Set("content-encoding", "deflate")
-		w.Header().Set("content-length", strconv.FormatInt(cres.CompressedLength(), 10))
-		_, err = cres.StreamCompressed(w)
+	if ok && cres.CompressedAs(archive.CompressionMethodDeflate) && start == 0 && end == 0 {
+		// Stream the asset in compressed format if supported by the user agent
+		if supportsEncoding(r, "deflate") {
+			w.Header().Set("content-encoding", "deflate")
+			w.Header().Set("content-length", strconv.FormatInt(cres.CompressedLength(), 10))
+			_, err = cres.StreamCompressed(w)
+		} else if supportsEncoding(r, "gzip") && l <= archive.GzipMaxLength {
+			w.Header().Set("content-encoding", "gzip")
+			w.Header().Set("content-length", strconv.FormatInt(cres.CompressedLength()+archive.GzipWrapperLength, 10))
+			_, err = cres.StreamCompressedGzip(w)
+		} else {
+			// Fall back to normal streaming
+			_, rerr = res.Stream(w, start, end)
+		}
 	} else {
 		// Stream the asset
 		_, rerr = res.Stream(w, start, end)

cmd/rwp/cmd/serve/helpers.go

@@ -74,15 +74,15 @@ func conformsToAsMimetype(conformsTo manifest.Profiles) string {
 	return mime
 }
 
-func supportsDeflate(r *http.Request) bool {
+func supportsEncoding(r *http.Request, encoding string) bool {
 	vv := r.Header.Values("Accept-Encoding")
 	for _, v := range vv {
 		for _, sv := range strings.Split(v, ",") {
 			coding := parseCoding(sv)
 			if coding == "" {
 				continue
 			}
-			if coding == "deflate" {
+			if coding == encoding {
 				return true
 			}
 		}

pkg/archive/archive.go

@@ -58,8 +58,12 @@ type Entry interface {
 	CompressedAs(compressionMethod CompressionMethod) bool     // Whether the entry is compressed using the given method.
 	Read(start int64, end int64) ([]byte, error)               // Reads the whole content of this entry, or a portion when [start] or [end] are specified.
 	Stream(w io.Writer, start int64, end int64) (int64, error) // Streams the whole content of this entry to a writer, or a portion when [start] or [end] are specified.
-	StreamCompressed(w io.Writer) (int64, error)               // Streams the compressed content of this entry to a writer.
-	ReadCompressed() ([]byte, error)                           // Reads the compressed content of this entry.
+
+	StreamCompressed(w io.Writer) (int64, error)     // Streams the compressed content of this entry to a writer.
+	StreamCompressedGzip(w io.Writer) (int64, error) // Streams the compressed content of this entry to a writer in a GZIP container.
+	ReadCompressed() ([]byte, error)                 // Reads the compressed content of this entry.
+	ReadCompressedGzip() ([]byte, error)             // Reads the compressed content of this entry inside a GZIP container.
+
 }
 
 // Represents an immutable archive.

pkg/archive/archive_exploded.go

@@ -90,10 +90,18 @@ func (e explodedArchiveEntry) StreamCompressed(w io.Writer) (int64, error) {
 	return -1, errors.New("entry is not compressed")
 }
 
+func (e explodedArchiveEntry) StreamCompressedGzip(w io.Writer) (int64, error) {
+	return -1, errors.New("entry is not compressed")
+}
+
 func (e explodedArchiveEntry) ReadCompressed() ([]byte, error) {
 	return nil, errors.New("entry is not compressed")
 }
 
+func (e explodedArchiveEntry) ReadCompressedGzip() ([]byte, error) {
+	return nil, errors.New("entry is not compressed")
+}
+
 // An archive exploded on the file system as a directory.
 type explodedArchive struct {
 	directory string // Directory, already cleaned!

pkg/archive/archive_zip.go

@@ -4,11 +4,14 @@ import (
 	"archive/zip"
 	"bytes"
 	"compress/flate"
-	"errors"
+	"encoding/binary"
 	"io"
 	"io/fs"
+	"math"
 	"path"
 	"sync"
+
+	"github.com/pkg/errors"
 )
 
 type gozipArchiveEntry struct {
@@ -164,6 +167,42 @@ func (e gozipArchiveEntry) StreamCompressed(w io.Writer) (int64, error) {
 	return io.Copy(w, f)
 }
 
+func (e gozipArchiveEntry) StreamCompressedGzip(w io.Writer) (int64, error) {
+	if e.file.Method != zip.Deflate {
+		return -1, errors.New("not a compressed resource")
+	}
+	if e.file.UncompressedSize64 > math.MaxUint32 {
+		return -1, errors.New("uncompressed size > 2^32 too large for GZIP")
+	}
+	f, err := e.file.OpenRaw()
+	if err != nil {
+		return -1, err
+	}
+
+	// Header
+	buf := [10]byte{0: gzipID1, 1: gzipID2, 2: gzipDeflate, 9: 255}
+	// No extra, no name, no comment, no mod time, no compress level hint, unknown OS
+
+	n, err := w.Write(buf[:10])
+	if err != nil {
+		return -1, errors.Wrap(err, "failed to write GZIP header")
+	}
+
+	nn, err := io.Copy(w, f)
+	if err != nil {
+		return int64(n), errors.Wrap(err, "failed copying deflated bytes")
+	}
+
+	// Trailer
+	binary.LittleEndian.PutUint32(buf[:4], e.file.CRC32)
+	binary.LittleEndian.PutUint32(buf[4:8], uint32(e.file.UncompressedSize64))
+	nnn, err := w.Write(buf[:8])
+	if err != nil {
+		return int64(n) + nn, errors.Wrap(err, "failed writing GZIP trailer")
+	}
+	return int64(n) + nn + int64(nnn), nil
+}
+
 func (e gozipArchiveEntry) ReadCompressed() ([]byte, error) {
 	if e.file.Method != zip.Deflate {
 		return nil, errors.New("not a compressed resource")
@@ -182,6 +221,40 @@ func (e gozipArchiveEntry) ReadCompressed() ([]byte, error) {
 	return compressedData, nil
 }
 
+func (e gozipArchiveEntry) ReadCompressedGzip() ([]byte, error) {
+	if e.file.Method != zip.Deflate {
+		return nil, errors.New("not a compressed resource")
+	}
+	if e.file.UncompressedSize64 > math.MaxUint32 {
+		return nil, errors.New("uncompressed size > 2^32 too large for GZIP")
+	}
+	f, err := e.file.OpenRaw()
+	if err != nil {
+		return nil, err
+	}
+
+	compressedData := make([]byte, e.file.CompressedSize64+GzipWrapperLength) // Size of file + header + trailer
+
+	// Deflated data
+	_, err = io.ReadAtLeast(f, compressedData[10:], int(e.file.CompressedSize64))
+	if err != nil {
+		return nil, err
+	}
+
+	// Header
+	compressedData[0] = gzipID1
+	compressedData[1] = gzipID2
+	compressedData[2] = gzipDeflate
+	compressedData[9] = 255
+	// No extra, no name, no comment, no mod time, no compress level hint, unknown OS
+
+	// Trailer
+	binary.LittleEndian.PutUint32(compressedData[10+e.file.CompressedSize64:], e.file.CRC32)
+	binary.LittleEndian.PutUint32(compressedData[10+e.file.CompressedSize64+4:], uint32(e.file.UncompressedSize64))
+
+	return compressedData, nil
+}
+
 // An archive from a zip file using go's stdlib
 type gozipArchive struct {
 	zip           *zip.Reader

pkg/archive/gzip.go

@@ -0,0 +1,12 @@
+package archive
+
+import "math"
+
+const (
+	gzipID1     = 0x1f
+	gzipID2     = 0x8b
+	gzipDeflate = 8
+)
+
+const GzipWrapperLength = 18
+const GzipMaxLength = math.MaxUint32

pkg/fetcher/fetcher_archive.go

@@ -171,6 +171,15 @@ func (r *entryResource) StreamCompressed(w io.Writer) (int64, *ResourceError) {
 	return -1, Other(err)
 }
 
+// StreamCompressedGzip implements CompressedResource
+func (r *entryResource) StreamCompressedGzip(w io.Writer) (int64, *ResourceError) {
+	i, err := r.entry.StreamCompressedGzip(w)
+	if err == nil {
+		return i, nil
+	}
+	return -1, Other(err)
+}
+
 // ReadCompressed implements CompressedResource
 func (r *entryResource) ReadCompressed() ([]byte, *ResourceError) {
 	i, err := r.entry.ReadCompressed()
@@ -180,6 +189,15 @@ func (r *entryResource) ReadCompressed() ([]byte, *ResourceError) {
 	return nil, Other(err)
 }
 
+// ReadCompressedGzip implements CompressedResource
+func (r *entryResource) ReadCompressedGzip() ([]byte, *ResourceError) {
+	i, err := r.entry.ReadCompressedGzip()
+	if err == nil {
+		return i, nil
+	}
+	return nil, Other(err)
+}
+
 // Length implements Resource
 func (r *entryResource) Length() (int64, *ResourceError) {
 	return int64(r.entry.Length()), nil

pkg/fetcher/resource.go

@@ -394,6 +394,15 @@ func (r ProxyResource) StreamCompressed(w io.Writer) (int64, *ResourceError) {
 	return cres.StreamCompressed(w)
 }
 
+// StreamCompressedGzip implements CompressedResource
+func (r ProxyResource) StreamCompressedGzip(w io.Writer) (int64, *ResourceError) {
+	cres, ok := r.Res.(CompressedResource)
+	if !ok {
+		return -1, Other(errors.New("resource is not compressed"))
+	}
+	return cres.StreamCompressedGzip(w)
+}
+
 // ReadCompressed implements CompressedResource
 func (r ProxyResource) ReadCompressed() ([]byte, *ResourceError) {
 	cres, ok := r.Res.(CompressedResource)
@@ -403,6 +412,15 @@ func (r ProxyResource) ReadCompressed() ([]byte, *ResourceError) {
 	return cres.ReadCompressed()
 }
 
+// ReadCompressedGzip implements CompressedResource
+func (r ProxyResource) ReadCompressedGzip() ([]byte, *ResourceError) {
+	cres, ok := r.Res.(CompressedResource)
+	if !ok {
+		return nil, Other(errors.New("resource is not compressed"))
+	}
+	return cres.ReadCompressedGzip()
+}
+
 /**
  * Transforms the bytes of [resource] on-the-fly.
  *

pkg/fetcher/traits.go

@@ -10,5 +10,7 @@ type CompressedResource interface {
 	CompressedAs(compressionMethod archive.CompressionMethod) bool
 	CompressedLength() int64
 	StreamCompressed(w io.Writer) (int64, *ResourceError)
+	StreamCompressedGzip(w io.Writer) (int64, *ResourceError)
 	ReadCompressed() ([]byte, *ResourceError)
+	ReadCompressedGzip() ([]byte, *ResourceError)
 }

pkg/parser/epub/deobfuscator.go

@@ -174,8 +174,18 @@ func (d DeobfuscatingResource) StreamCompressed(w io.Writer) (int64, *fetcher.Re
 	return d.ProxyResource.StreamCompressed(w)
 }
 
+// StreamCompressedGzip implements CompressedResource
+func (d DeobfuscatingResource) StreamCompressedGzip(w io.Writer) (int64, *fetcher.ResourceError) {
+	_, v := d.obfuscation()
+	if v > 0 {
+		return 0, fetcher.Other(errors.New("cannot stream compressed resource when obfuscated"))
+	}
+
+	return d.ProxyResource.StreamCompressedGzip(w)
+}
+
 // ReadCompressed implements CompressedResource
-func (d DeobfuscatingResource) ReadCompressed(w io.Writer) ([]byte, *fetcher.ResourceError) {
+func (d DeobfuscatingResource) ReadCompressed() ([]byte, *fetcher.ResourceError) {
 	_, v := d.obfuscation()
 	if v > 0 {
 		return nil, fetcher.Other(errors.New("cannot read compressed resource when obfuscated"))
@@ -184,6 +194,16 @@ func (d DeobfuscatingResource) ReadCompressed(w io.Writer) ([]byte, *fetcher.Res
 	return d.ProxyResource.ReadCompressed()
 }
 
+// ReadCompressedGzip implements CompressedResource
+func (d DeobfuscatingResource) ReadCompressedGzip() ([]byte, *fetcher.ResourceError) {
+	_, v := d.obfuscation()
+	if v > 0 {
+		return nil, fetcher.Other(errors.New("cannot read compressed resource when obfuscated"))
+	}
+
+	return d.ProxyResource.ReadCompressedGzip()
+}
+
 func (d DeobfuscatingResource) getHashKeyAdobe() []byte {
 	hexbytes, _ := hex.DecodeString(
 		strings.Replace(