zlib, flatex: Remove code related to dicts

Git never uses them

3 files changed, 15 insertions, 106 deletions

diff --git a/internal/zlibx/decompress.go b/internal/zlibx/decompress.go
index 68a92587..df4a34be 100644
--- a/internal/zlibx/decompress.go
+++ b/internal/zlibx/decompress.go
@@ -9,28 +9,11 @@ import (
 	"git.sr.ht/~runxiyu/furgit/internal/flatex"
 )
 
-// Decompress inflates the provided zlib wrapped stream and returns the
-// uncompressed data inside a pooled bufpool.Buffer.
 func Decompress(src []byte) (*bufpool.Buffer, error) {
 	return DecompressSized(src, 0)
 }
 
-// DecompressSized inflates the provided zlib stream, using sizeHint to
-// preallocate the output buffer when known (e.g. packfile entries).
 func DecompressSized(src []byte, sizeHint int) (*bufpool.Buffer, error) {
-	return DecompressDictSized(src, nil, sizeHint)
-}
-
-// DecompressDict is like Decompress but accepts a preset dictionary. The
-// dictionary must match the checksum embedded in the stream if the dictionary
-// flag is present.
-func DecompressDict(src []byte, dict []byte) (*bufpool.Buffer, error) {
-	return DecompressDictSized(src, dict, 0)
-}
-
-// DecompressDictSized is like DecompressDict but allows providing an expected
-// uncompressed size to avoid buffer growth copies.
-func DecompressDictSized(src []byte, dict []byte, sizeHint int) (*bufpool.Buffer, error) {
 	if len(src) < 6 {
 		return nil, io.ErrUnexpectedEOF
 	}
@@ -42,19 +25,8 @@ func DecompressDictSized(src []byte, dict []byte, sizeHint int) (*bufpool.Buffer
 	}
 
 	offset := 2
-	haveDict := flg&0x20 != 0
-	if haveDict {
-		if len(src) < offset+4 {
-			return nil, io.ErrUnexpectedEOF
-		}
-		if dict == nil {
-			return nil, ErrDictionary
-		}
-		checksum := binary.BigEndian.Uint32(src[offset : offset+4])
-		if checksum != adler32.Checksum(dict) {
-			return nil, ErrDictionary
-		}
-		offset += 4
+	if flg&0x20 != 0 {
+		return nil, ErrHeader
 	}
 
 	if len(src[offset:]) < 4 {
@@ -62,7 +34,7 @@ func DecompressDictSized(src []byte, dict []byte, sizeHint int) (*bufpool.Buffer
 	}
 
 	deflateData := src[offset:]
-	out, consumed, err := flatex.DecompressDictSized(deflateData, dict, sizeHint)
+	out, consumed, err := flatex.DecompressSized(deflateData, sizeHint)
 	if err != nil {
 		return nil, err
 	}
diff --git a/internal/zlibx/decompress_test.go b/internal/zlibx/decompress_test.go
index 3dfc07a5..8dcc6c02 100644
--- a/internal/zlibx/decompress_test.go
+++ b/internal/zlibx/decompress_test.go
@@ -6,21 +6,10 @@ import (
 	"testing"
 )
 
-func compressZlib(t *testing.T, payload, dict []byte) []byte {
+func compressZlib(t *testing.T, payload []byte) []byte {
 	t.Helper()
 	var buf bytes.Buffer
-	var (
-		w   *stdzlib.Writer
-		err error
-	)
-	if dict != nil {
-		w, err = stdzlib.NewWriterLevelDict(&buf, stdzlib.DefaultCompression, dict)
-	} else {
-		w = stdzlib.NewWriter(&buf)
-	}
-	if err != nil {
-		t.Fatalf("NewWriter: %v", err)
-	}
+	w := stdzlib.NewWriter(&buf)
 	if _, err := w.Write(payload); err != nil {
 		t.Fatalf("Write: %v", err)
 	}
@@ -32,7 +21,7 @@ func compressZlib(t *testing.T, payload, dict []byte) []byte {
 
 func TestDecompress(t *testing.T) {
 	payload := []byte("hello, zlib world!")
-	compressed := compressZlib(t, payload, nil)
+	compressed := compressZlib(t, payload)
 
 	out, err := Decompress(compressed)
 	if err != nil {
@@ -45,37 +34,9 @@ func TestDecompress(t *testing.T) {
 	}
 }
 
-func TestDecompressDict(t *testing.T) {
-	dict := []byte("git dictionary for zlib")
-	payload := append([]byte(nil), dict...)
-	payload = append(payload, []byte(" -- extended body -- extended body")...)
-	compressed := compressZlib(t, payload, dict)
-
-	out, err := DecompressDict(compressed, dict)
-	if err != nil {
-		t.Fatalf("DecompressDict: %v", err)
-	}
-	defer out.Release()
-
-	if !bytes.Equal(out.Bytes(), payload) {
-		t.Fatalf("unexpected payload %q", out.Bytes())
-	}
-}
-
-func TestDecompressDictMissing(t *testing.T) {
-	dict := []byte("preset dictionary")
-	payload := append([]byte(nil), dict...)
-	payload = append(payload, []byte(" .. more data ..")...)
-	compressed := compressZlib(t, payload, dict)
-
-	if _, err := Decompress(compressed); err != ErrDictionary {
-		t.Fatalf("expected ErrDictionary, got %v", err)
-	}
-}
-
 func TestDecompressChecksumError(t *testing.T) {
 	payload := []byte("checksum check")
-	compressed := compressZlib(t, payload, nil)
+	compressed := compressZlib(t, payload)
 	compressed[len(compressed)-1] ^= 0xff
 
 	if _, err := Decompress(compressed); err != ErrChecksum {
@@ -85,7 +46,7 @@ func TestDecompressChecksumError(t *testing.T) {
 
 func TestDecompressSizedUsesHint(t *testing.T) {
 	payload := []byte("tiny payload")
-	compressed := compressZlib(t, payload, nil)
+	compressed := compressZlib(t, payload)
 
 	const hint = 1 << 20
 	out, err := DecompressSized(compressed, hint)
diff --git a/internal/zlibx/reader.go b/internal/zlibx/reader.go
index 9a4b4315..6e3a53ea 100644
--- a/internal/zlibx/reader.go
+++ b/internal/zlibx/reader.go
@@ -55,8 +55,6 @@ const (
 var (
 	// ErrChecksum is returned when reading ZLIB data that has an invalid checksum.
 	ErrChecksum = errors.New("zlib: invalid checksum")
-	// ErrDictionary is returned when reading ZLIB data that has an invalid dictionary.
-	ErrDictionary = errors.New("zlib: invalid dictionary")
 	// ErrHeader is returned when reading ZLIB data that has an invalid header.
 	ErrHeader = errors.New("zlib: invalid header")
 )
@@ -82,19 +80,12 @@ type reader struct {
 // data than necessary from r.
 // It is the caller's responsibility to call Close on the ReadCloser when done.
 func NewReader(r io.Reader) (io.ReadCloser, error) {
-	return NewReaderDict(r, nil)
-}
-
-// NewReaderDict is like [NewReader] but uses a preset dictionary.
-// NewReaderDict ignores the dictionary if the compressed data does not refer to it.
-// If the compressed data refers to a different dictionary, NewReaderDict returns [ErrDictionary].
-func NewReaderDict(r io.Reader, dict []byte) (io.ReadCloser, error) {
 	v := pool.Get()
 	z, ok := v.(*reader)
 	if !ok {
 		panic("zlib: pool returned unexpected type")
 	}
-	err := z.Reset(r, dict)
+	err := z.Reset(r)
 	if err != nil {
 		return nil, err
 	}
@@ -147,7 +138,7 @@ func (z *reader) Close() error {
 	return nil
 }
 
-func (z *reader) Reset(r io.Reader, dict []byte) error {
+func (z *reader) Reset(r io.Reader) error {
 	*z = reader{decompressor: z.decompressor}
 	if fr, ok := r.(flatex.Reader); ok {
 		z.r = fr
@@ -168,30 +159,15 @@ func (z *reader) Reset(r io.Reader, dict []byte) error {
 		z.err = ErrHeader
 		return z.err
 	}
-	haveDict := z.scratch[1]&0x20 != 0
-	if haveDict {
-		_, z.err = io.ReadFull(z.r, z.scratch[0:4])
-		if z.err != nil {
-			if z.err == io.EOF {
-				z.err = io.ErrUnexpectedEOF
-			}
-			return z.err
-		}
-		checksum := binary.BigEndian.Uint32(z.scratch[:4])
-		if checksum != adler32.Checksum(dict) {
-			z.err = ErrDictionary
-			return z.err
-		}
+	if z.scratch[1]&0x20 != 0 {
+		z.err = ErrHeader
+		return z.err
 	}
 
 	if z.decompressor == nil {
-		if haveDict {
-			z.decompressor = flatex.NewReaderDict(z.r, dict)
-		} else {
-			z.decompressor = flatex.NewReader(z.r)
-		}
+		z.decompressor = flatex.NewReader(z.r)
 	} else {
-		z.err = z.decompressor.(flatex.Resetter).Reset(z.r, dict)
+		z.err = z.decompressor.(flatex.Resetter).Reset(z.r)
 		if z.err != nil {
 			return z.err
 		}