gzip: Add to_deflate/from_deflate functions

Author: wader

format/gzip/gzip.go

@@ -5,12 +5,14 @@ package gz
 // TODO: verify isize?
 
 import (
+	"bytes"
 	"compress/flate"
 	"hash/crc32"
 	"io"
 	"time"
 
 	"github.com/wader/fq/format"
+	"github.com/wader/fq/pkg/bitio"
 	"github.com/wader/fq/pkg/decode"
 	"github.com/wader/fq/pkg/interp"
 	"github.com/wader/fq/pkg/scalar"
@@ -29,6 +31,8 @@ func init() {
 				{Groups: []*decode.Group{format.Probe}, Out: &probeGroup},
 			},
 		})
+	interp.RegisterFunc0("from_deflate", fromDeflate)
+	interp.RegisterFunc0("to_deflate", toDeflate)
 }
 
 const deflateMethod = 8
@@ -126,3 +130,47 @@ func gzDecode(d *decode.D) any {
 
 	return nil
 }
+
+func fromDeflate(_ *interp.Interp, c any) any {
+	inBR, err := interp.ToBitReader(c)
+	if err != nil {
+		return err
+	}
+
+	fr := flate.NewReader(bitio.NewIOReader(inBR))
+	b := &bytes.Buffer{}
+	//nolint:gosec
+	if _, err := io.Copy(b, fr); err != nil {
+		return err
+	}
+	fr.Close()
+
+	bb, err := interp.NewBinaryFromBitReader(bitio.NewBitReader(b.Bytes(), -1), 8, 0)
+	if err != nil {
+		return err
+	}
+	return bb
+}
+
+func toDeflate(_ *interp.Interp, c any) any {
+	inBR, err := interp.ToBitReader(c)
+	if err != nil {
+		return err
+	}
+
+	bb := &bytes.Buffer{}
+	fw, err := flate.NewWriter(bb, 9) // TODO: level option
+	if err != nil {
+		return err
+	}
+	if _, err := io.Copy(fw, bitio.NewIOReader(inBR)); err != nil {
+		return err
+	}
+	fw.Close()
+
+	bib, err := interp.NewBinaryFromBitReader(bitio.NewBitReader(bb.Bytes(), -1), 8, 0)
+	if err != nil {
+		return err
+	}
+	return bib
+}