soong_jar: Parallel compression

This compresses multiple files in parallel, and will split up larger
files (5MB+) into smaller chunks (1MB) to compress in parallel.

There is a small size overhead to recombine the chunks, but it's only a
few bytes per chunk, so for a 1MB chunk, it's minimal.

Rough numbers, with everything in the page cache, this can compress
~4GB (1000 files) down to 1GB in 6.5 seconds, instead of 120 seconds with
the non-parallel soong_jar and 150 seconds with zip.

Go's DEFLATE algorithm is still a bit worse than zip's -- about 3.5%
larger file sizes, but for most of our "dist" targets that is fine.

Change-Id: Ie4886c7d0f954ace46e599156e35fea7e74d6dd7

third_party/zip/android.go

@@ -15,6 +15,7 @@
 package zip
 
 import (
+	"errors"
 	"io"
 )
 
@@ -68,3 +69,108 @@ func (w *Writer) CopyFrom(orig *File, newName string) error {
 	_, err = w.cw.Write(buf)
 	return err
 }
+
+// CreateCompressedHeader adds a file to the zip file using the provied
+// FileHeader for the file metadata.
+// It returns a Writer to which the already compressed file contents
+// should be written.
+//
+// The UncompressedSize64 and CRC32 entries in the FileHeader must be filled
+// out already.
+//
+// The file's contents must be written to the io.Writer before the next
+// call to Create, CreateHeader, CreateCompressedHeader, or Close. The
+// provided FileHeader fh must not be modified after a call to
+// CreateCompressedHeader
+func (w *Writer) CreateCompressedHeader(fh *FileHeader) (io.WriteCloser, error) {
+	if w.last != nil && !w.last.closed {
+		if err := w.last.close(); err != nil {
+			return nil, err
+		}
+	}
+	if len(w.dir) > 0 && w.dir[len(w.dir)-1].FileHeader == fh {
+		// See https://golang.org/issue/11144 confusion.
+		return nil, errors.New("archive/zip: invalid duplicate FileHeader")
+	}
+
+	fh.Flags |= 0x8 // we will write a data descriptor
+
+	fh.CreatorVersion = fh.CreatorVersion&0xff00 | zipVersion20 // preserve compatibility byte
+	fh.ReaderVersion = zipVersion20
+
+	fw := &compressedFileWriter{
+		fileWriter{
+			zipw:      w.cw,
+			compCount: &countWriter{w: w.cw},
+		},
+	}
+
+	h := &header{
+		FileHeader: fh,
+		offset:     uint64(w.cw.count),
+	}
+	w.dir = append(w.dir, h)
+	fw.header = h
+
+	if err := writeHeader(w.cw, fh); err != nil {
+		return nil, err
+	}
+
+	w.last = &fw.fileWriter
+	return fw, nil
+}
+
+type compressedFileWriter struct {
+	fileWriter
+}
+
+func (w *compressedFileWriter) Write(p []byte) (int, error) {
+	if w.closed {
+		return 0, errors.New("zip: write to closed file")
+	}
+	return w.compCount.Write(p)
+}
+
+func (w *compressedFileWriter) Close() error {
+	if w.closed {
+		return errors.New("zip: file closed twice")
+	}
+	w.closed = true
+
+	// update FileHeader
+	fh := w.header.FileHeader
+	fh.CompressedSize64 = uint64(w.compCount.count)
+
+	if fh.isZip64() {
+		fh.CompressedSize = uint32max
+		fh.UncompressedSize = uint32max
+		fh.ReaderVersion = zipVersion45 // requires 4.5 - File uses ZIP64 format extensions
+	} else {
+		fh.CompressedSize = uint32(fh.CompressedSize64)
+		fh.UncompressedSize = uint32(fh.UncompressedSize64)
+	}
+
+	// Write data descriptor. This is more complicated than one would
+	// think, see e.g. comments in zipfile.c:putextended() and
+	// http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7073588.
+	// The approach here is to write 8 byte sizes if needed without
+	// adding a zip64 extra in the local header (too late anyway).
+	var buf []byte
+	if fh.isZip64() {
+		buf = make([]byte, dataDescriptor64Len)
+	} else {
+		buf = make([]byte, dataDescriptorLen)
+	}
+	b := writeBuf(buf)
+	b.uint32(dataDescriptorSignature) // de-facto standard, required by OS X
+	b.uint32(fh.CRC32)
+	if fh.isZip64() {
+		b.uint64(fh.CompressedSize64)
+		b.uint64(fh.UncompressedSize64)
+	} else {
+		b.uint32(fh.CompressedSize)
+		b.uint32(fh.UncompressedSize)
+	}
+	_, err := w.zipw.Write(buf)
+	return err
+}