feat: support array of content streams and parse them as a single stream (@romanpickl)

ps.go

@@ -49,77 +49,93 @@ func newDict() Value {
 // in PDF files, such as cmap files that describe the mapping from font code
 // points to Unicode code points.
 //
-// There is no support for executable blocks, among other limitations.
+// A stream can also be represented by an array of streams that has to be handled as a single stream
+// In the case of a simple stream read only once, otherwise get the length of the stream to handle it properly
 //
+// There is no support for executable blocks, among other limitations.
 func Interpret(strm Value, do func(stk *Stack, op string)) {
-	rd := strm.Reader()
-	b := newBuffer(rd, 0)
-	b.allowEOF = true
-	b.allowObjptr = false
-	b.allowStream = false
 	var stk Stack
 	var dicts []dict
-Reading:
-	for {
-		tok := b.readToken()
-		if tok == io.EOF {
-			break
+	s := strm
+	strmlen := 1
+	if strm.Kind() == Array {
+		strmlen = strm.Len()
+	}
+
+	for i := 0; i < strmlen; i++ {
+		if strm.Kind() == Array {
+			s = strm.Index(i)
 		}
-		if kw, ok := tok.(keyword); ok {
-			switch kw {
-			case "null", "[", "]", "<<", ">>":
+
+		rd := s.Reader()
+
+		b := newBuffer(rd, 0)
+		b.allowEOF = true
+		b.allowObjptr = false
+		b.allowStream = false
+
+	Reading:
+		for {
+			tok := b.readToken()
+			if tok == io.EOF {
 				break
-			default:
-				for i := len(dicts) - 1; i >= 0; i-- {
-					if v, ok := dicts[i][name(kw)]; ok {
-						stk.Push(Value{nil, objptr{}, v})
-						continue Reading
+			}
+			if kw, ok := tok.(keyword); ok {
+				switch kw {
+				case "null", "[", "]", "<<", ">>":
+					break
+				default:
+					for i := len(dicts) - 1; i >= 0; i-- {
+						if v, ok := dicts[i][name(kw)]; ok {
+							stk.Push(Value{nil, objptr{}, v})
+							continue Reading
+						}
 					}
+					do(&stk, string(kw))
+					continue
+				case "dict":
+					stk.Pop()
+					stk.Push(Value{nil, objptr{}, make(dict)})
+					continue
+				case "currentdict":
+					if len(dicts) == 0 {
+						panic("no current dictionary")
+					}
+					stk.Push(Value{nil, objptr{}, dicts[len(dicts)-1]})
+					continue
+				case "begin":
+					d := stk.Pop()
+					if d.Kind() != Dict {
+						panic("cannot begin non-dict")
+					}
+					dicts = append(dicts, d.data.(dict))
+					continue
+				case "end":
+					if len(dicts) <= 0 {
+						panic("mismatched begin/end")
+					}
+					dicts = dicts[:len(dicts)-1]
+					continue
+				case "def":
+					if len(dicts) <= 0 {
+						panic("def without open dict")
+					}
+					val := stk.Pop()
+					key, ok := stk.Pop().data.(name)
+					if !ok {
+						panic("def of non-name")
+					}
+					dicts[len(dicts)-1][key] = val.data
+					continue
+				case "pop":
+					stk.Pop()
+					continue
 				}
-				do(&stk, string(kw))
-				continue
-			case "dict":
-				stk.Pop()
-				stk.Push(Value{nil, objptr{}, make(dict)})
-				continue
-			case "currentdict":
-				if len(dicts) == 0 {
-					panic("no current dictionary")
-				}
-				stk.Push(Value{nil, objptr{}, dicts[len(dicts)-1]})
-				continue
-			case "begin":
-				d := stk.Pop()
-				if d.Kind() != Dict {
-					panic("cannot begin non-dict")
-				}
-				dicts = append(dicts, d.data.(dict))
-				continue
-			case "end":
-				if len(dicts) <= 0 {
-					panic("mismatched begin/end")
-				}
-				dicts = dicts[:len(dicts)-1]
-				continue
-			case "def":
-				if len(dicts) <= 0 {
-					panic("def without open dict")
-				}
-				val := stk.Pop()
-				key, ok := stk.Pop().data.(name)
-				if !ok {
-					panic("def of non-name")
-				}
-				dicts[len(dicts)-1][key] = val.data
-				continue
-			case "pop":
-				stk.Pop()
-				continue
 			}
+			b.unreadToken(tok)
+			obj := b.readObject()
+			stk.Push(Value{nil, objptr{}, obj})
 		}
-		b.unreadToken(tok)
-		obj := b.readObject()
-		stk.Push(Value{nil, objptr{}, obj})
 	}
 }