fix wrong git ignore

internal/pdf/core/stream.go

@@ -0,0 +1,129 @@
+package core
+
+import (
+	"fmt"
+
+	"gitea.tecamino.com/paadi/pdfmerge/internal/pdf/common"
+)
+
+// NewEncoderFromStream creates a StreamEncoder based on the stream's dictionary.
+func NewEncoderFromStream(streamObj *PdfObjectStream) (StreamEncoder, error) {
+	filterObj := TraceToDirectObject(streamObj.PdfObjectDictionary.Get("Filter"))
+	if filterObj == nil {
+		// No filter, return raw data back.
+		return NewRawEncoder(), nil
+	}
+
+	if _, isNull := filterObj.(*PdfObjectNull); isNull {
+		// Filter is null -> raw data.
+		return NewRawEncoder(), nil
+	}
+
+	// The filter should be a name or an array with a list of filter names.
+	method, ok := filterObj.(*PdfObjectName)
+	if !ok {
+		array, ok := filterObj.(*PdfObjectArray)
+		if !ok {
+			return nil, fmt.Errorf("filter not a Name or Array object")
+		}
+		if len(*array) == 0 {
+			// Empty array -> indicates raw filter (no filter).
+			return NewRawEncoder(), nil
+		}
+
+		if len(*array) != 1 {
+			menc, err := newMultiEncoderFromStream(streamObj)
+			if err != nil {
+				common.Log.Error("Failed creating multi encoder: %v", err)
+				return nil, err
+			}
+
+			common.Log.Trace("Multi enc: %s\n", menc)
+			return menc, nil
+		}
+
+		// Single element.
+		filterObj = (*array)[0]
+		method, ok = filterObj.(*PdfObjectName)
+		if !ok {
+			return nil, fmt.Errorf("filter array member not a Name object")
+		}
+	}
+
+	switch *method {
+	case StreamEncodingFilterNameFlate:
+		return newFlateEncoderFromStream(streamObj, nil)
+	case StreamEncodingFilterNameLZW:
+		return newLZWEncoderFromStream(streamObj, nil)
+	case StreamEncodingFilterNameDCT:
+		return newDCTEncoderFromStream(streamObj, nil)
+	case StreamEncodingFilterNameRunLength:
+		return newRunLengthEncoderFromStream()
+	case StreamEncodingFilterNameASCIIHex:
+		return NewASCIIHexEncoder(), nil
+	case StreamEncodingFilterNameASCII85, "A85":
+		return NewASCII85Encoder(), nil
+	case StreamEncodingFilterNameCCITTFax:
+		return NewCCITTFaxEncoder(), nil
+	case StreamEncodingFilterNameJBIG2:
+		return NewJBIG2Encoder(), nil
+	case StreamEncodingFilterNameJPX:
+		return NewJPXEncoder(), nil
+	default:
+		common.Log.Debug("error: Unsupported encoding method!")
+		return nil, fmt.Errorf("unsupported encoding method (%s)", *method)
+	}
+}
+
+// DecodeStream decodes the stream data and returns the decoded data.
+// An error is returned upon failure.
+func DecodeStream(streamObj *PdfObjectStream) ([]byte, error) {
+	common.Log.Trace("Decode stream")
+
+	encoder, err := NewEncoderFromStream(streamObj)
+	if err != nil {
+		common.Log.Debug("Stream decoding failed: %v", err)
+		return nil, err
+	}
+	common.Log.Trace("Encoder: %#v\n", encoder)
+
+	decoded, err := encoder.DecodeStream(streamObj)
+	if err != nil {
+		common.Log.Debug("Stream decoding failed: %v", err)
+		return nil, err
+	}
+
+	return decoded, nil
+}
+
+// EncodeStream encodes the stream data using the encoded specified by the stream's dictionary.
+func EncodeStream(streamObj *PdfObjectStream) error {
+	common.Log.Trace("Encode stream")
+
+	encoder, err := NewEncoderFromStream(streamObj)
+	if err != nil {
+		common.Log.Debug("Stream decoding failed: %v", err)
+		return err
+	}
+
+	if lzwenc, is := encoder.(*LZWEncoder); is {
+		// If LZW:
+		// Make sure to use EarlyChange 0.. We do not have write support for 1 yet.
+		lzwenc.EarlyChange = 0
+		streamObj.PdfObjectDictionary.Set("EarlyChange", MakeInteger(0))
+	}
+
+	common.Log.Trace("Encoder: %+v\n", encoder)
+	encoded, err := encoder.EncodeBytes(streamObj.Stream)
+	if err != nil {
+		common.Log.Debug("Stream encoding failed: %v", err)
+		return err
+	}
+
+	streamObj.Stream = encoded
+
+	// Update length
+	streamObj.PdfObjectDictionary.Set("Length", MakeInteger(int64(len(encoded))))
+
+	return nil
+}