zstd: Add dictionaries with options (BREAKING)

zstd/README.md

@@ -329,13 +329,13 @@ Data compressed with [dictionaries](https://github.com/facebook/zstd#the-case-fo
 
 Dictionaries are added individually to Decoders.
 Dictionaries are generated by the `zstd --train` command and contains an initial state for the decoder.
-To add a dictionary use the `RegisterDict(data)` with the dictionary data before starting any decompression.
+To add a dictionary use the `WithDecoderDicts(dicts ...[]byte)` option with the dictionary data.
+Several dictionaries can be added at once.
 
 The dictionary will be used automatically for the data that specifies them.
-
 A re-used Decoder will still contain the dictionaries registered.
 
-When registering a dictionary with the same ID it will override the existing.
+When registering multiple dictionaries with the same ID, the last one will be used.
 
 ### Allocation-less operation
 

zstd/decoder.go

@@ -85,6 +85,13 @@ func NewReader(r io.Reader, opts ...DOption) (*Decoder, error) {
 	d.current.output = make(chan decodeOutput, d.o.concurrent)
 	d.current.flushed = true
 
+	// Transfer option dicts.
+	d.dicts = make(map[uint32]dict, len(d.o.dicts))
+	for _, dc := range d.o.dicts {
+		d.dicts[dc.id] = dc
+	}
+	d.o.dicts = nil
+
 	// Create decoders
 	d.decoders = make(chan *blockDec, d.o.concurrent)
 	for i := 0; i < d.o.concurrent; i++ {
@@ -399,19 +406,6 @@ func (d *Decoder) Close() {
 	d.current.err = ErrDecoderClosed
 }
 
-// RegisterDict will load a dictionary
-func (d *Decoder) RegisterDict(b []byte) error {
-	dc, err := loadDict(b)
-	if err != nil {
-		return err
-	}
-	if d.dicts == nil {
-		d.dicts = make(map[uint32]dict, 1)
-	}
-	d.dicts[dc.id] = *dc
-	return nil
-}
-
 // IOReadCloser returns the decoder as an io.ReadCloser for convenience.
 // Any changes to the decoder will be reflected, so the returned ReadCloser
 // can be reused along with the decoder.

zstd/decoder_options.go

@@ -18,6 +18,7 @@ type decoderOptions struct {
 	lowMem         bool
 	concurrent     int
 	maxDecodedSize uint64
+	dicts          []dict
 }
 
 func (o *decoderOptions) setDefault() {
@@ -66,3 +67,18 @@ func WithDecoderMaxMemory(n uint64) DOption {
 		return nil
 	}
 }
+
+// WithDecoderDicts allows to register one or more dictionaries for the decoder.
+// If several dictionaries with the same ID is provided the last one will be used.
+func WithDecoderDicts(dicts ...[]byte) DOption {
+	return func(o *decoderOptions) error {
+		for _, b := range dicts {
+			d, err := loadDict(b)
+			if err != nil {
+				return err
+			}
+			o.dicts = append(o.dicts, *d)
+		}
+		return nil
+	}
+}

zstd/dict_test.go

@@ -20,11 +20,7 @@ func TestDecoder_SmallDict(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	dec, err := NewReader(nil, WithDecoderConcurrency(1))
-	if err != nil {
-		t.Fatal(err)
-		return
-	}
+	var dicts [][]byte
 	for _, tt := range zr.File {
 		if !strings.HasSuffix(tt.Name, ".dict") {
 			continue
@@ -39,12 +35,14 @@ func TestDecoder_SmallDict(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			err = dec.RegisterDict(in)
-			if err != nil {
-				t.Fatal(tt.Name, err)
-			}
+			dicts = append(dicts, in)
 		}()
 	}
+	dec, err := NewReader(nil, WithDecoderConcurrency(1), WithDecoderDicts(dicts...))
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
 	defer dec.Close()
 	for _, tt := range zr.File {
 		if !strings.HasSuffix(tt.Name, ".zst") {
@@ -84,11 +82,8 @@ func TestDecoder_MoreDicts(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	dec, err := NewReader(nil, WithDecoderConcurrency(1))
-	if err != nil {
-		t.Fatal(err)
-		return
-	}
+
+	var dicts [][]byte
 	for _, tt := range zr.File {
 		if !strings.HasSuffix(tt.Name, ".dict") {
 			continue
@@ -103,12 +98,14 @@ func TestDecoder_MoreDicts(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			err = dec.RegisterDict(in)
-			if err != nil {
-				t.Fatal(tt.Name, err)
-			}
+			dicts = append(dicts, in)
 		}()
 	}
+	dec, err := NewReader(nil, WithDecoderConcurrency(1), WithDecoderDicts(dicts...))
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
 	defer dec.Close()
 	for _, tt := range zr.File {
 		if !strings.HasSuffix(tt.Name, ".zst") {