Implement QPDFObjectHandle::parse

Move object parsing code from QPDF to QPDFObjectHandle and parameterize the parts of it that are specific to a QPDF object. Provide a version that can't handle indirect objects and that can be called on an arbitrary string. A side effect of this change is that the offset used when reporting invalid stream length has changed, but since the new value seems like a better value than the old one, the test suite has been updated rather than making the code backward compatible. This only effects the offset reported for invalid streams that lack /Length or have an invalid /Length key. Updated some test code and exmaples to use QPDFObjectHandle::parse. Supporting changes include adding a BufferInputSource constructor that takes a string.

Implement QPDFObjectHandle::parse
Move object parsing code from QPDF to QPDFObjectHandle and parameterize the parts of it that are specific to a QPDF object. Provide a version that can't handle indirect objects and that can be called on an arbitrary string. A side effect of this change is that the offset used when reporting invalid stream length has changed, but since the new value seems like a better value than the old one, the test suite has been updated rather than making the code backward compatible. This only effects the offset reported for invalid streams that lack /Length or have an invalid /Length key. Updated some test code and exmaples to use QPDFObjectHandle::parse. Supporting changes include adding a BufferInputSource constructor that takes a string.
Jay Berkenbilt
1 parent f3e267fc
Showing 18 changed files with 618 additions and 386 deletions
ChangeLog
TODO
examples/pdf-create.cc
include/qpdf/BufferInputSource.hh
include/qpdf/QPDF.hh
include/qpdf/QPDFObjectHandle.hh
libqpdf/BufferInputSource.cc
libqpdf/QPDF.cc
libqpdf/QPDFObjectHandle.cc
libqpdf/QPDF_Stream.cc
libqpdf/qpdf/QPDF_Stream.hh
qpdf/pdf_from_scratch.cc
qpdf/qpdf.testcov
qpdf/qtest/qpdf.test
qpdf/qtest/qpdf/bad22.out
qpdf/qtest/qpdf/bad23.out
qpdf/qtest/qpdf/parse-object.out
qpdf/test_driver.cc
+2012-07-21  Jay Berkenbilt  <ejb@ql.org>
+
+	* Add new method QPDFObjectHandle::replaceDict to replace a
+	stream's dictionary.  Use with caution; see comments in
+	QPDFObjectHandle.hh.
+
+	* Add new method QPDFObjectHandle::parse for creation of
+	QPDFObjectHandle objects from string representations of the
+	objects.  Thanks to Tobias Hoffmann for the idea.
+
 2012-07-15  Jay Berkenbilt  <ejb@ql.org>
 	* add new QPDF::isEncrypted method that returns some additional
@@ -20,16 +20,14 @@ Next
  * Make sure that the release notes call attention to the one API
    breaking change: removal of length from replaceStreamData.
- * Add a way to create new QPDFObjectHandles with a string
-   representation of them, such as
-   QPDFObjectHandle::parse("<< /a 1 /b 2 >>");
-
  * Document thread safety: One individual QPDF or QPDFWriter object
    can only be used by one thread at a time, but multiple threads can
    simultaneously use separate objects.
  * Write some documentation about the design of copyForeignObject.
+ * Mention QPDFObjectHandle::parse in the documentation.
+
  * copyForeignObject still to do:
     - qpdf command
@@ -81,24 +81,28 @@ static void create_pdf(char const* filename)
     // Add an indirect object to contain a font descriptor for the
     // built-in Helvetica font.
     QPDFObjectHandle font = pdf.makeIndirectObject(
-        QPDFObjectHandle::newDictionary());
-    font.replaceKey("/Type", newName("/Font"));
-    font.replaceKey("/Subtype", newName("/Type1"));
-    font.replaceKey("/Name", newName("/F1"));
-    font.replaceKey("/BaseFont", newName("/Helvetica"));
-    font.replaceKey("/Encoding", newName("/WinAnsiEncoding"));
+        QPDFObjectHandle::parse(
+            "<<"
+            " /Type /Font"
+            " /Subtype /Type1"
+            " /Name /F1"
+            " /BaseFont /Helvetica"
+            " /Encoding /WinAnsiEncoding"
+            ">>"));
     // Create a stream to encode our image.  We don't have to set the
     // length or filters.  QPDFWriter will fill in the length and
     // compress the stream data using FlateDecode by default.
     QPDFObjectHandle image = QPDFObjectHandle::newStream(&pdf);
-    QPDFObjectHandle image_dict = image.getDict();
-    image_dict.replaceKey("/Type", newName("/XObject"));
-    image_dict.replaceKey("/Subtype", newName("/Image"));
-    image_dict.replaceKey("/ColorSpace", newName("/DeviceRGB"));
-    image_dict.replaceKey("/BitsPerComponent", newInteger(8));
-    image_dict.replaceKey("/Width", newInteger(100));
-    image_dict.replaceKey("/Height", newInteger(100));
+    image.replaceDict(QPDFObjectHandle::parse(
+                          "<<"
+                          " /Type /XObject"
+                          " /Subtype /Image"
+                          " /ColorSpace /DeviceRGB"
+                          " /BitsPerComponent 8"
+                          " /Width 100"
+                          " /Height 100"
+                          ">>"));
     // Provide the stream data.
     ImageProvider* p = new ImageProvider(100, 100);
     PointerHolder<QPDFObjectHandle::StreamDataProvider> provider(p);
@@ -107,10 +111,8 @@ static void create_pdf(char const* filename)
                             QPDFObjectHandle::newNull());
     // Create direct objects as needed by the page dictionary.
-    QPDFObjectHandle procset = QPDFObjectHandle::newArray();
-    procset.appendItem(newName("/PDF"));
-    procset.appendItem(newName("/Text"));
-    procset.appendItem(newName("/ImageC"));
+    QPDFObjectHandle procset = QPDFObjectHandle::parse(
+        "[/PDF /Text /ImageC]");
     QPDFObjectHandle rfont = QPDFObjectHandle::newDictionary();
     rfont.replaceKey("/F1", font);
@@ -9,6 +9,8 @@ class BufferInputSource: public InputSource
   public:
     BufferInputSource(std::string const& description, Buffer* buf,
                       bool own_memory = false);
+    BufferInputSource(std::string const& description,
+                      std::string const& contents);
     virtual ~BufferInputSource();
     virtual qpdf_offset_t findAndSkipNextEOL();
     virtual std::string const& getName() const;
@@ -531,6 +531,23 @@ class QPDF
         std::map<ObjGen, QPDFObjectHandle> foreign_streams;
     };
+    class StringDecrypter: public QPDFObjectHandle::StringDecrypter
+    {
+        friend class QPDF;
+
+      public:
+        StringDecrypter(QPDF* qpdf, int objid, int gen);
+        virtual ~StringDecrypter()
+        {
+        }
+        virtual void decryptString(std::string& val);
+
+      private:
+        QPDF* qpdf;
+        int objid;
+        int gen;
+    };
+
     void parse(char const* password);
     void warn(QPDFExc const& e);
     void setTrailer(QPDFObjectHandle obj);
@@ -547,10 +564,6 @@ class QPDF
     QPDFObjectHandle readObject(
 	PointerHolder<InputSource>, std::string const& description,
 	int objid, int generation, bool in_object_stream);
-    QPDFObjectHandle readObjectInternal(
-	PointerHolder<InputSource> input, int objid, int generation,
-	bool in_object_stream,
-	bool in_array, bool in_dictionary);
     size_t recoverStreamLength(
 	PointerHolder<InputSource> input, int objid, int generation,
 	qpdf_offset_t stream_offset);
@@ -18,6 +18,7 @@
 #include <qpdf/PointerHolder.hh>
 #include <qpdf/Buffer.hh>
+#include <qpdf/InputSource.hh>
 #include <qpdf/QPDFObject.hh>
@@ -25,6 +26,7 @@ class Pipeline;
 class QPDF;
 class QPDF_Dictionary;
 class QPDF_Array;
+class QPDFTokenizer;
 class QPDFObjectHandle
 {
@@ -57,6 +59,18 @@ class QPDFObjectHandle
 				       Pipeline* pipeline) = 0;
     };
+    // This class is used by parse to decrypt strings when reading an
+    // object that contains encrypted strings.
+    class StringDecrypter
+    {
+      public:
+        QPDF_DLL
+        virtual ~StringDecrypter()
+        {
+        }
+        virtual void decryptString(std::string& val) = 0;
+    };
+
     QPDF_DLL
     QPDFObjectHandle();
     QPDF_DLL
@@ -95,6 +109,30 @@ class QPDFObjectHandle
     // Public factory methods
+    // Construct an object of any type from a string representation of
+    // the object.  Throws QPDFExc with an empty filename and an
+    // offset into the string if there is an error.  Any indirect
+    // object syntax (obj gen R) will cause a logic_error exception to
+    // be thrown.  If object_description is provided, it will appear
+    // in the message of any QPDFExc exception thrown for invalid
+    // syntax.
+    QPDF_DLL
+    static QPDFObjectHandle parse(std::string const& object_str,
+                                  std::string const& object_description = "");
+
+    // Construct an object as above by reading from the given
+    // InputSource at its current position and using the tokenizer you
+    // supply.  Indirect objects and encrypted strings are permitted.
+    // This method is intended to be called by QPDF for parsing
+    // objects that are ready from the object's input stream.
+    QPDF_DLL
+    static QPDFObjectHandle parse(PointerHolder<InputSource> input,
+                                  std::string const& object_description,
+                                  QPDFTokenizer&, bool& empty,
+                                  StringDecrypter* decrypter,
+                                  QPDF* context);
+
+    // Type-specific factories
     QPDF_DLL
     static QPDFObjectHandle newNull();
     QPDF_DLL
@@ -124,7 +162,8 @@ class QPDFObjectHandle
     // object.  A subsequent call must be made to replaceStreamData()
     // to provide data for the stream.  The stream's dictionary may be
     // retrieved by calling getDict(), and the resulting dictionary
-    // may be modified.
+    // may be modified.  Alternatively, you can create a new
+    // dictionary and call replaceDict to install it.
     QPDF_DLL
     static QPDFObjectHandle newStream(QPDF* qpdf);
@@ -303,6 +342,15 @@ class QPDFObjectHandle
     bool pipeStreamData(Pipeline*, bool filter,
 			bool normalize, bool compress);
+    // Replace a stream's dictionary.  The new dictionary must be
+    // consistent with the stream's data.  This is most appropriately
+    // used when creating streams from scratch that will use a stream
+    // data provider and therefore start with an empty dictionary.  It
+    // may be more convenient in this case than calling getDict and
+    // modifying it for each key.  The pdf-create example does this.
+    QPDF_DLL
+    void replaceDict(QPDFObjectHandle);
+
     // Replace this stream's stream data with the given data buffer,
     // and replace the /Filter and /DecodeParms keys in the stream
     // dictionary with the given values.  (If either value is empty,
@@ -489,6 +537,12 @@ class QPDFObjectHandle
     void dereference();
     void makeDirectInternal(std::set<int>& visited);
     void releaseResolved();
+    static QPDFObjectHandle parseInternal(
+        PointerHolder<InputSource> input,
+        std::string const& object_description,
+        QPDFTokenizer& tokenizer, bool& empty,
+        StringDecrypter* decrypter, QPDF* context,
+        bool in_array, bool in_dictionary);
     bool initialized;
@@ -11,6 +11,18 @@ BufferInputSource::BufferInputSource(std::string const&amp; description,
 {
 }
+BufferInputSource::BufferInputSource(std::string const& description,
+                                     std::string const& contents) :
+    own_memory(true),
+    description(description),
+    buf(0),
+    cur_offset(0)
+{
+    this->buf = new Buffer(contents.length());
+    unsigned char* bp = buf->getBuffer();
+    memcpy(bp, (char*)contents.c_str(), contents.length());
+}
+
 BufferInputSource::~BufferInputSource()
 {
     if (own_memory)
@@ -68,6 +68,18 @@ QPDF::CopiedStreamDataProvider::registerForeignStream(
     this->foreign_streams[local_og] = foreign_stream;
 }
+QPDF::StringDecrypter::StringDecrypter(QPDF* qpdf, int objid, int gen) :
+    qpdf(qpdf),
+    objid(objid),
+    gen(gen)
+{
+}
+
+void
+QPDF::StringDecrypter::decryptString(std::string& val)
+{
+    qpdf->decryptString(val, objid, gen);
+}
 std::string const&
 QPDF::QPDFVersion()
@@ -940,358 +952,164 @@ QPDF::readObject(PointerHolder&lt;InputSource&gt; input,
 {
     setLastObjectDescription(description, objid, generation);
     qpdf_offset_t offset = input->tell();
-    QPDFObjectHandle object = readObjectInternal(
-	input, objid, generation, in_object_stream, false, false);
-    // Override last_offset so that it points to the beginning of the
-    // object we just read
-    input->setLastOffset(offset);
-    return object;
-}
-
-QPDFObjectHandle
-QPDF::readObjectInternal(PointerHolder<InputSource> input,
-			 int objid, int generation,
-			 bool in_object_stream,
-			 bool in_array, bool in_dictionary)
-{
-    if (in_dictionary && in_array)
-    {
-	// Although dictionaries and arrays arbitrarily nest, these
-	// variables indicate what is at the top of the stack right
-	// now, so they can, by definition, never both be true.
-	throw std::logic_error(
-	    "INTERNAL ERROR: readObjectInternal: in_dict && in_array");
-    }
-
-    QPDFObjectHandle object;
-    qpdf_offset_t offset = input->tell();
-    std::vector<QPDFObjectHandle> olist;
-    bool done = false;
-    while (! done)
+    bool empty = false;
+    PointerHolder<StringDecrypter> decrypter_ph;
+    StringDecrypter* decrypter = 0;
+    if (this->encrypted && (! in_object_stream))
     {
-	object = QPDFObjectHandle();
-
-	QPDFTokenizer::Token token = readToken(input);
-
-	switch (token.getType())
-	{
-	  case QPDFTokenizer::tt_brace_open:
-	  case QPDFTokenizer::tt_brace_close:
-	    // Don't know what to do with these for now
-	    QTC::TC("qpdf", "QPDF bad brace");
-	    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-			  this->last_object_description,
-			  input->getLastOffset(),
-			  "unexpected brace token");
-	    break;
-
-	  case QPDFTokenizer::tt_array_close:
-	    if (in_array)
-	    {
-		done = true;
-	    }
-	    else
-	    {
-		QTC::TC("qpdf", "QPDF bad array close");
-		throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-			      this->last_object_description,
-			      input->getLastOffset(),
-			      "unexpected array close token");
-	    }
-	    break;
-
-	  case QPDFTokenizer::tt_dict_close:
-	    if (in_dictionary)
-	    {
-		done = true;
-	    }
-	    else
-	    {
-		QTC::TC("qpdf", "QPDF bad dictionary close");
-		throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-			      this->last_object_description,
-			      input->getLastOffset(),
-			      "unexpected dictionary close token");
-	    }
-	    break;
-
-	  case QPDFTokenizer::tt_array_open:
-	    object = readObjectInternal(
-		input, objid, generation, in_object_stream, true, false);
-	    break;
-
-	  case QPDFTokenizer::tt_dict_open:
-	    object = readObjectInternal(
-		input, objid, generation, in_object_stream, false, true);
-	    break;
-
-	  case QPDFTokenizer::tt_bool:
-	    object = QPDFObjectHandle::newBool(
-		(token.getValue() == "true"));
-	    break;
-
-	  case QPDFTokenizer::tt_null:
-	    object = QPDFObjectHandle::newNull();
-	    break;
-
-	  case QPDFTokenizer::tt_integer:
-	    object = QPDFObjectHandle::newInteger(
-		QUtil::string_to_ll(token.getValue().c_str()));
-	    break;
-
-	  case QPDFTokenizer::tt_real:
-	    object = QPDFObjectHandle::newReal(token.getValue());
-	    break;
-
-	  case QPDFTokenizer::tt_name:
-	    object = QPDFObjectHandle::newName(token.getValue());
-	    break;
-
-	  case QPDFTokenizer::tt_word:
-	    {
-		std::string const& value = token.getValue();
-		if ((value == "R") && (in_array || in_dictionary) &&
-		    (olist.size() >= 2) &&
-		    (olist[olist.size() - 1].isInteger()) &&
-		    (olist[olist.size() - 2].isInteger()))
-		{
-		    // Try to resolve indirect objects
-		    object = QPDFObjectHandle::Factory::newIndirect(
-			this,
-			olist[olist.size() - 2].getIntValue(),
-			olist[olist.size() - 1].getIntValue());
-		    olist.pop_back();
-		    olist.pop_back();
-		}
-		else if ((value == "endobj") &&
-			 (! (in_array || in_dictionary)))
-		{
-		    // Nothing in the PDF spec appears to allow empty
-		    // objects, but they have been encountered in
-		    // actual PDF files and Adobe Reader appears to
-		    // ignore them.
-		    warn(QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-				 this->last_object_description,
-				 input->getLastOffset(),
-				 "empty object treated as null"));
-		    object = QPDFObjectHandle::newNull();
-		    input->seek(input->getLastOffset(), SEEK_SET);
-		}
-		else
-		{
-		    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-				  this->last_object_description,
-				  input->getLastOffset(),
-				  "unknown token while reading object (" +
-				  value + ")");
-		}
-	    }
-	    break;
-
-	  case QPDFTokenizer::tt_string:
-	    {
-		std::string val = token.getValue();
-		if (this->encrypted && (! in_object_stream))
-		{
-		    decryptString(val, objid, generation);
-		}
-		object = QPDFObjectHandle::newString(val);
-	    }
-	    break;
-
-	  default:
-	    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-			  this->last_object_description,
-			  input->getLastOffset(),
-			  "unknown token type while reading object");
-	    break;
-	}
-
-	if (in_dictionary || in_array)
-	{
-	    if (! done)
-	    {
-		olist.push_back(object);
-	    }
-	}
-	else if (! object.isInitialized())
-	{
-	    throw std::logic_error(
-		"INTERNAL ERROR: uninitialized object (token = " +
-		QUtil::int_to_string(token.getType()) +
-		", " + token.getValue() + ")");
-	}
-	else
-	{
-	    done = true;
-	}
+        decrypter_ph = new StringDecrypter(this, objid, generation);
+        decrypter = decrypter_ph.getPointer();
     }
-
-    if (in_array)
+    QPDFObjectHandle object = QPDFObjectHandle::parse(
+        input, description, this->tokenizer, empty, decrypter, this);
+    if (empty)
     {
-	object = QPDFObjectHandle::newArray(olist);
+        // Nothing in the PDF spec appears to allow empty objects, but
+        // they have been encountered in actual PDF files and Adobe
+        // Reader appears to ignore them.
+        warn(QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+                     this->last_object_description,
+                     input->getLastOffset(),
+                     "empty object treated as null"));
     }
-    else if (in_dictionary)
+    else if (object.isDictionary() && (! in_object_stream))
     {
-	// Convert list to map.  Alternating elements are keys.
-	std::map<std::string, QPDFObjectHandle> dict;
-	if (olist.size() % 2)
-	{
-	    QTC::TC("qpdf", "QPDF dictionary odd number of elements");
-	    throw QPDFExc(
-		qpdf_e_damaged_pdf, input->getName(),
-		this->last_object_description, input->getLastOffset(),
-		"dictionary ending here has an odd number of elements");
-	}
-	for (unsigned int i = 0; i < olist.size(); i += 2)
-	{
-	    QPDFObjectHandle key_obj = olist[i];
-	    QPDFObjectHandle val = olist[i + 1];
-	    if (! key_obj.isName())
-	    {
-		throw QPDFExc(
-		    qpdf_e_damaged_pdf,
-		    input->getName(), this->last_object_description, offset,
-		    std::string("dictionary key not name (") +
-		    key_obj.unparse() + ")");
-	    }
-	    dict[key_obj.getName()] = val;
-	}
-	object = QPDFObjectHandle::newDictionary(dict);
+        // check for stream
+        qpdf_offset_t cur_offset = input->tell();
+        if (readToken(input) ==
+            QPDFTokenizer::Token(QPDFTokenizer::tt_word, "stream"))
+        {
+            // The PDF specification states that the word "stream"
+            // should be followed by either a carriage return and
+            // a newline or by a newline alone.  It specifically
+            // disallowed following it by a carriage return alone
+            // since, in that case, there would be no way to tell
+            // whether the NL in a CR NL sequence was part of the
+            // stream data.  However, some readers, including
+            // Adobe reader, accept a carriage return by itself
+            // when followed by a non-newline character, so that's
+            // what we do here.
+            {
+                char ch;
+                if (input->read(&ch, 1) == 0)
+                {
+                    // A premature EOF here will result in some
+                    // other problem that will get reported at
+                    // another time.
+                }
+                else if (ch == '\n')
+                {
+                    // ready to read stream data
+                    QTC::TC("qpdf", "QPDF stream with NL only");
+                }
+                else if (ch == '\r')
+                {
+                    // Read another character
+                    if (input->read(&ch, 1) != 0)
+                    {
+                        if (ch == '\n')
+                        {
+                            // Ready to read stream data
+                            QTC::TC("qpdf", "QPDF stream with CRNL");
+                        }
+                        else
+                        {
+                            // Treat the \r by itself as the
+                            // whitespace after endstream and
+                            // start reading stream data in spite
+                            // of not having seen a newline.
+                            QTC::TC("qpdf", "QPDF stream with CR only");
+                            input->unreadCh(ch);
+                            warn(QPDFExc(
+                                     qpdf_e_damaged_pdf,
+                                     input->getName(),
+                                     this->last_object_description,
+                                     input->tell(),
+                                     "stream keyword followed"
+                                     " by carriage return only"));
+                        }
+                    }
+                }
+                else
+                {
+                    QTC::TC("qpdf", "QPDF stream without newline");
+                    warn(QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+                                 this->last_object_description,
+                                 input->tell(),
+                                 "stream keyword not followed"
+                                 " by proper line terminator"));
+                }
+            }
-	if (! in_object_stream)
-	{
-	    // check for stream
-	    qpdf_offset_t cur_offset = input->tell();
-	    if (readToken(input) ==
-		QPDFTokenizer::Token(QPDFTokenizer::tt_word, "stream"))
-	    {
-		// The PDF specification states that the word "stream"
-		// should be followed by either a carriage return and
-		// a newline or by a newline alone.  It specifically
-		// disallowed following it by a carriage return alone
-		// since, in that case, there would be no way to tell
-		// whether the NL in a CR NL sequence was part of the
-		// stream data.  However, some readers, including
-		// Adobe reader, accept a carriage return by itself
-		// when followed by a non-newline character, so that's
-		// what we do here.
-		{
-		    char ch;
-		    if (input->read(&ch, 1) == 0)
-		    {
-			// A premature EOF here will result in some
-			// other problem that will get reported at
-			// another time.
-		    }
-		    else if (ch == '\n')
-		    {
-			// ready to read stream data
-			QTC::TC("qpdf", "QPDF stream with NL only");
-		    }
-		    else if (ch == '\r')
-		    {
-			// Read another character
-			if (input->read(&ch, 1) != 0)
-			{
-			    if (ch == '\n')
-			    {
-				// Ready to read stream data
-				QTC::TC("qpdf", "QPDF stream with CRNL");
-			    }
-			    else
-			    {
-				// Treat the \r by itself as the
-				// whitespace after endstream and
-				// start reading stream data in spite
-				// of not having seen a newline.
-				QTC::TC("qpdf", "QPDF stream with CR only");
-				input->unreadCh(ch);
-				warn(QPDFExc(
-					 qpdf_e_damaged_pdf,
-					 input->getName(),
-					 this->last_object_description,
-					 input->tell(),
-					 "stream keyword followed"
-					 " by carriage return only"));
-			    }
-			}
-		    }
-		    else
-		    {
-			QTC::TC("qpdf", "QPDF stream without newline");
-			warn(QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-				     this->last_object_description,
-				     input->tell(),
-				     "stream keyword not followed"
-				     " by proper line terminator"));
-		    }
-		}
+            // Must get offset before accessing any additional
+            // objects since resolving a previously unresolved
+            // indirect object will change file position.
+            qpdf_offset_t stream_offset = input->tell();
+            size_t length = 0;
-		// Must get offset before accessing any additional
-		// objects since resolving a previously unresolved
-		// indirect object will change file position.
-		qpdf_offset_t stream_offset = input->tell();
-		size_t length = 0;
+            try
+            {
+                std::map<std::string, QPDFObjectHandle> dict =
+                    object.getDictAsMap();
-		try
-		{
-		    if (dict.count("/Length") == 0)
-		    {
-			QTC::TC("qpdf", "QPDF stream without length");
-			throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-				      this->last_object_description, offset,
-				      "stream dictionary lacks /Length key");
-		    }
+                if (dict.count("/Length") == 0)
+                {
+                    QTC::TC("qpdf", "QPDF stream without length");
+                    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+                                  this->last_object_description, offset,
+                                  "stream dictionary lacks /Length key");
+                }
-		    QPDFObjectHandle length_obj = dict["/Length"];
-		    if (! length_obj.isInteger())
-		    {
-			QTC::TC("qpdf", "QPDF stream length not integer");
-			throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-				      this->last_object_description, offset,
-				      "/Length key in stream dictionary is not "
-				      "an integer");
-		    }
+                QPDFObjectHandle length_obj = dict["/Length"];
+                if (! length_obj.isInteger())
+                {
+                    QTC::TC("qpdf", "QPDF stream length not integer");
+                    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+                                  this->last_object_description, offset,
+                                  "/Length key in stream dictionary is not "
+                                  "an integer");
+                }
-		    length = length_obj.getIntValue();
-		    input->seek(
-                        stream_offset + (qpdf_offset_t)length, SEEK_SET);
-		    if (! (readToken(input) ==
-			   QPDFTokenizer::Token(
-			       QPDFTokenizer::tt_word, "endstream")))
-		    {
-			QTC::TC("qpdf", "QPDF missing endstream");
-			throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
-				      this->last_object_description,
-				      input->getLastOffset(),
-				      "expected endstream");
-		    }
-		}
-		catch (QPDFExc& e)
-		{
-		    if (this->attempt_recovery)
-		    {
-			// may throw an exception
-			length = recoverStreamLength(
-			    input, objid, generation, stream_offset);
-		    }
-		    else
-		    {
-			throw e;
-		    }
-		}
-		object = QPDFObjectHandle::Factory::newStream(
-		    this, objid, generation, object, stream_offset, length);
-	    }
-	    else
-	    {
-		input->seek(cur_offset, SEEK_SET);
-	    }
-	}
+                length = length_obj.getIntValue();
+                input->seek(
+                    stream_offset + (qpdf_offset_t)length, SEEK_SET);
+                if (! (readToken(input) ==
+                       QPDFTokenizer::Token(
+                           QPDFTokenizer::tt_word, "endstream")))
+                {
+                    QTC::TC("qpdf", "QPDF missing endstream");
+                    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+                                  this->last_object_description,
+                                  input->getLastOffset(),
+                                  "expected endstream");
+                }
+            }
+            catch (QPDFExc& e)
+            {
+                if (this->attempt_recovery)
+                {
+                    // may throw an exception
+                    length = recoverStreamLength(
+                        input, objid, generation, stream_offset);
+                }
+                else
+                {
+                    throw e;
+                }
+            }
+            object = QPDFObjectHandle::Factory::newStream(
+                this, objid, generation, object, stream_offset, length);
+        }
+        else
+        {
+            input->seek(cur_offset, SEEK_SET);
+        }
     }
+    // Override last_offset so that it points to the beginning of the
+    // object we just read
+    input->setLastOffset(offset);
     return object;
 }
@@ -11,12 +11,15 @@
 #include <qpdf/QPDF_Dictionary.hh>
 #include <qpdf/QPDF_Stream.hh>
 #include <qpdf/QPDF_Reserved.hh>
+#include <qpdf/BufferInputSource.hh>
+#include <qpdf/QPDFExc.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
 #include <stdexcept>
 #include <stdlib.h>
+#include <ctype.h>
 QPDFObjectHandle::QPDFObjectHandle() :
     initialized(false),
@@ -398,6 +401,13 @@ QPDFObjectHandle::getDict()
     return dynamic_cast<QPDF_Stream*>(obj.getPointer())->getDict();
 }
+void
+QPDFObjectHandle::replaceDict(QPDFObjectHandle new_dict)
+{
+    assertStream();
+    dynamic_cast<QPDF_Stream*>(obj.getPointer())->replaceDict(new_dict);
+}
+
 PointerHolder<Buffer>
 QPDFObjectHandle::getStreamData()
 {
@@ -599,6 +609,265 @@ QPDFObjectHandle::unparseResolved()
 }
 QPDFObjectHandle
+QPDFObjectHandle::parse(std::string const& object_str,
+                        std::string const& object_description)
+{
+    PointerHolder<InputSource> input =
+        new BufferInputSource("parsed object", object_str);
+    QPDFTokenizer tokenizer;
+    bool empty = false;
+    QPDFObjectHandle result =
+        parse(input, object_description, tokenizer, empty, 0, 0);
+    size_t offset = (size_t) input->tell();
+    while (offset < object_str.length())
+    {
+        if (! isspace(object_str[offset]))
+        {
+            QTC::TC("qpdf", "QPDFObjectHandle trailing data in parse");
+            throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+                          object_description,
+                          input->getLastOffset(),
+                          "trailing data found parsing object from string");
+        }
+        ++offset;
+    }
+    return result;
+}
+
+QPDFObjectHandle
+QPDFObjectHandle::parse(PointerHolder<InputSource> input,
+                        std::string const& object_description,
+                        QPDFTokenizer& tokenizer, bool& empty,
+                        StringDecrypter* decrypter, QPDF* context)
+{
+    return parseInternal(input, object_description, tokenizer, empty,
+                         decrypter, context, false, false);
+}
+
+QPDFObjectHandle
+QPDFObjectHandle::parseInternal(PointerHolder<InputSource> input,
+                                std::string const& object_description,
+                                QPDFTokenizer& tokenizer, bool& empty,
+                                StringDecrypter* decrypter, QPDF* context,
+                                bool in_array, bool in_dictionary)
+{
+    empty = false;
+    if (in_dictionary && in_array)
+    {
+	// Although dictionaries and arrays arbitrarily nest, these
+	// variables indicate what is at the top of the stack right
+	// now, so they can, by definition, never both be true.
+	throw std::logic_error(
+	    "INTERNAL ERROR: parseInternal: in_dict && in_array");
+    }
+
+    QPDFObjectHandle object;
+
+    qpdf_offset_t offset = input->tell();
+    std::vector<QPDFObjectHandle> olist;
+    bool done = false;
+    while (! done)
+    {
+	object = QPDFObjectHandle();
+
+	QPDFTokenizer::Token token =
+            tokenizer.readToken(input, object_description);
+
+	switch (token.getType())
+	{
+	  case QPDFTokenizer::tt_brace_open:
+	  case QPDFTokenizer::tt_brace_close:
+	    // Don't know what to do with these for now
+	    QTC::TC("qpdf", "QPDFObjectHandle bad brace");
+	    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+			  object_description,
+			  input->getLastOffset(),
+			  "unexpected brace token");
+	    break;
+
+	  case QPDFTokenizer::tt_array_close:
+	    if (in_array)
+	    {
+		done = true;
+	    }
+	    else
+	    {
+		QTC::TC("qpdf", "QPDFObjectHandle bad array close");
+		throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+			      object_description,
+			      input->getLastOffset(),
+			      "unexpected array close token");
+	    }
+	    break;
+
+	  case QPDFTokenizer::tt_dict_close:
+	    if (in_dictionary)
+	    {
+		done = true;
+	    }
+	    else
+	    {
+		QTC::TC("qpdf", "QPDFObjectHandle bad dictionary close");
+		throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+			      object_description,
+			      input->getLastOffset(),
+			      "unexpected dictionary close token");
+	    }
+	    break;
+
+	  case QPDFTokenizer::tt_array_open:
+	    object = parseInternal(
+		input, object_description, tokenizer, empty,
+                decrypter, context, true, false);
+	    break;
+
+	  case QPDFTokenizer::tt_dict_open:
+	    object = parseInternal(
+		input, object_description, tokenizer, empty,
+                decrypter, context, false, true);
+	    break;
+
+	  case QPDFTokenizer::tt_bool:
+	    object = newBool((token.getValue() == "true"));
+	    break;
+
+	  case QPDFTokenizer::tt_null:
+	    object = newNull();
+	    break;
+
+	  case QPDFTokenizer::tt_integer:
+	    object = newInteger(QUtil::string_to_ll(token.getValue().c_str()));
+	    break;
+
+	  case QPDFTokenizer::tt_real:
+	    object = newReal(token.getValue());
+	    break;
+
+	  case QPDFTokenizer::tt_name:
+	    object = newName(token.getValue());
+	    break;
+
+	  case QPDFTokenizer::tt_word:
+	    {
+		std::string const& value = token.getValue();
+		if ((value == "R") && (in_array || in_dictionary) &&
+		    (olist.size() >= 2) &&
+		    (olist[olist.size() - 1].isInteger()) &&
+		    (olist[olist.size() - 2].isInteger()))
+		{
+                    if (context == 0)
+                    {
+                        QTC::TC("qpdf", "QPDFObjectHandle indirect without context");
+                        throw std::logic_error(
+                            "QPDFObjectHandle::parse called without context"
+                            " on an object with indirect references");
+                    }
+		    // Try to resolve indirect objects
+		    object = newIndirect(
+			context,
+			olist[olist.size() - 2].getIntValue(),
+			olist[olist.size() - 1].getIntValue());
+		    olist.pop_back();
+		    olist.pop_back();
+		}
+		else if ((value == "endobj") &&
+			 (! (in_array || in_dictionary)))
+		{
+		    // We just saw endobj without having read
+		    // anything.  Treat this as a null and do not move
+		    // the input source's offset.
+		    object = newNull();
+		    input->seek(input->getLastOffset(), SEEK_SET);
+                    empty = true;
+		}
+		else
+		{
+		    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+				  object_description,
+				  input->getLastOffset(),
+				  "unknown token while reading object (" +
+				  value + ")");
+		}
+	    }
+	    break;
+
+	  case QPDFTokenizer::tt_string:
+	    {
+		std::string val = token.getValue();
+                if (decrypter)
+                {
+                    decrypter->decryptString(val);
+                }
+		object = QPDFObjectHandle::newString(val);
+	    }
+
+	    break;
+
+	  default:
+	    throw QPDFExc(qpdf_e_damaged_pdf, input->getName(),
+			  object_description,
+			  input->getLastOffset(),
+			  "unknown token type while reading object");
+	    break;
+	}
+
+	if (in_dictionary || in_array)
+	{
+	    if (! done)
+	    {
+		olist.push_back(object);
+	    }
+	}
+	else if (! object.isInitialized())
+	{
+	    throw std::logic_error(
+		"INTERNAL ERROR: uninitialized object (token = " +
+		QUtil::int_to_string(token.getType()) +
+		", " + token.getValue() + ")");
+	}
+	else
+	{
+	    done = true;
+	}
+    }
+
+    if (in_array)
+    {
+	object = newArray(olist);
+    }
+    else if (in_dictionary)
+    {
+	// Convert list to map.  Alternating elements are keys.
+	std::map<std::string, QPDFObjectHandle> dict;
+	if (olist.size() % 2)
+	{
+	    QTC::TC("qpdf", "QPDFObjectHandle dictionary odd number of elements");
+	    throw QPDFExc(
+		qpdf_e_damaged_pdf, input->getName(),
+		object_description, input->getLastOffset(),
+		"dictionary ending here has an odd number of elements");
+	}
+	for (unsigned int i = 0; i < olist.size(); i += 2)
+	{
+	    QPDFObjectHandle key_obj = olist[i];
+	    QPDFObjectHandle val = olist[i + 1];
+	    if (! key_obj.isName())
+	    {
+		throw QPDFExc(
+		    qpdf_e_damaged_pdf,
+		    input->getName(), object_description, offset,
+		    std::string("dictionary key not name (") +
+		    key_obj.unparse() + ")");
+	    }
+	    dict[key_obj.getName()] = val;
+	}
+	object = newDictionary(dict);
+    }
+
+    return object;
+}
+
+QPDFObjectHandle
 QPDFObjectHandle::newIndirect(QPDF* qpdf, int objid, int generation)
 {
     return QPDFObjectHandle(qpdf, objid, generation);
@@ -464,3 +464,18 @@ QPDF_Stream::replaceFilterData(QPDFObjectHandle const&amp; filter,
             "/Length", QPDFObjectHandle::newInteger((int)length));
     }
 }
+
+void
+QPDF_Stream::replaceDict(QPDFObjectHandle new_dict)
+{
+    this->stream_dict = new_dict;
+    QPDFObjectHandle length_obj = new_dict.getKey("/Length");
+    if (length_obj.isInteger())
+    {
+        this->length = length_obj.getIntValue();
+    }
+    else
+    {
+        this->length = 0;
+    }
+}
@@ -32,6 +32,8 @@ class QPDF_Stream: public QPDFObject
 	QPDFObjectHandle const& filter,
 	QPDFObjectHandle const& decode_parms);
+    void replaceDict(QPDFObjectHandle new_dict);
+
     // Replace object ID and generation.  This may only be called if
     // object ID and generation are 0.  It is used by QPDFObjectHandle
     // when adding streams to files.
@@ -38,25 +38,20 @@ void runtest(int n)
         // Create a minimal PDF from scratch.
         QPDFObjectHandle font = pdf.makeIndirectObject(
-            QPDFObjectHandle::newDictionary());
-        font.replaceKey("/Type", newName("/Font"));
-        font.replaceKey("/Subtype", newName("/Type1"));
-        font.replaceKey("/Name", newName("/F1"));
-        font.replaceKey("/BaseFont", newName("/Helvetica"));
-        font.replaceKey("/Encoding", newName("/WinAnsiEncoding"));
+            QPDFObjectHandle::parse("<<"
+                                    " /Type /Font"
+                                    " /Subtype /Type1"
+                                    " /Name /F1"
+                                    " /BaseFont /Helvetica"
+                                    " /Encoding /WinAnsiEncoding"
+                                    ">>"));
         QPDFObjectHandle procset = pdf.makeIndirectObject(
-            QPDFObjectHandle::newArray());
-        procset.appendItem(newName("/PDF"));
-        procset.appendItem(newName("/Text"));
+            QPDFObjectHandle::parse("[/PDF /Text]"));
         QPDFObjectHandle contents = createPageContents(pdf, "First Page");
-        QPDFObjectHandle mediabox = QPDFObjectHandle::newArray();
-        mediabox.appendItem(QPDFObjectHandle::newInteger(0));
-        mediabox.appendItem(QPDFObjectHandle::newInteger(0));
-        mediabox.appendItem(QPDFObjectHandle::newInteger(612));
-        mediabox.appendItem(QPDFObjectHandle::newInteger(792));
+        QPDFObjectHandle mediabox = QPDFObjectHandle::parse("[0 0 612 792]");
         QPDFObjectHandle rfont = QPDFObjectHandle::newDictionary();
         rfont.replaceKey("/F1", font);
@@ -60,13 +60,13 @@ QPDF missing trailer 0
 QPDF trailer lacks size 0
 QPDF trailer size not integer 0
 QPDF trailer prev not integer 0
-QPDF bad brace 0
-QPDF bad array close 0
-QPDF dictionary odd number of elements 0
+QPDFObjectHandle bad brace 0
+QPDFObjectHandle bad array close 0
+QPDFObjectHandle dictionary odd number of elements 0
 QPDF stream without length 0
 QPDF stream length not integer 0
 QPDF missing endstream 0
-QPDF bad dictionary close 0
+QPDFObjectHandle bad dictionary close 0
 QPDF can't find xref 0
 QPDF_Tokenizer bad ) 0
 QPDF_Tokenizer bad > 0
@@ -235,3 +235,5 @@ QPDF not copying pages object 0
 QPDF insert foreign page 0
 QPDFWriter foreign object 0
 QPDFWriter copy use_aes 1
+QPDFObjectHandle indirect without context 0
+QPDFObjectHandle trailing data in parse 0
@@ -149,7 +149,7 @@ $td-&gt;runtest(&quot;remove page we don&#39;t have&quot;,
 	     $td->NORMALIZE_NEWLINES);
 # ----------
 $td->notify("--- Miscellaneous Tests ---");
-$n_tests += 44;
+$n_tests += 45;
 $td->runtest("qpdf version",
 	     {$td->COMMAND => "qpdf --version"},
@@ -370,6 +370,10 @@ $td-&gt;runtest(&quot;detect foreign object in write&quot;,
                   " copy-foreign-objects-in.pdf minimal.pdf"},
              {$td->FILE => "foreign-in-write.out", $td->EXIT_STATUS => 0},
              $td->NORMALIZE_NEWLINES);
+$td->runtest("parse objects from string",
+             {$td->COMMAND => "test_driver 31 minimal.pdf"}, # file not used
+             {$td->FILE => "parse-object.out", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
 show_ntests();
 # ----------
-bad22.pdf (object 4 0, file position 317): stream dictionary lacks /Length key
+bad22.pdf (object 4 0, file position 314): stream dictionary lacks /Length key
-bad23.pdf (object 4 0, file position 317): /Length key in stream dictionary is not an integer
+bad23.pdf (object 4 0, file position 314): /Length key in stream dictionary is not an integer
+[ /name 16059 3.14159 false << /key true /other [ (string1) (string2) ] >> null ]
+logic error parsing indirect: QPDFObjectHandle::parse called without context on an object with indirect references
+trailing data: parsed object (trailing test): trailing data found parsing object from string
+test 31 done
@@ -1054,6 +1054,38 @@ void runtest(int n, char const* filename1, char const* filename2)
                       << std::endl;
         }
     }
+    else if (n == 31)
+    {
+        // Test object parsing from a string.  The input file is not used.
+
+        QPDFObjectHandle o1 =
+            QPDFObjectHandle::parse(
+                "[/name 16059 3.14159 false\n"
+                " << /key true /other [ (string1) (string2) ] >> null]");
+        std::cout << o1.unparse() << std::endl;
+        QPDFObjectHandle o2 = QPDFObjectHandle::parse("   12345 \f  ");
+        assert(o2.isInteger() && (o2.getIntValue() == 12345));
+        try
+        {
+            QPDFObjectHandle::parse("[1 0 R]", "indirect test");
+            std::cout << "oops -- didn't throw" << std::endl;
+        }
+        catch (std::logic_error e)
+        {
+            std::cout << "logic error parsing indirect: " << e.what()
+                      << std::endl;
+        }
+        try
+        {
+            QPDFObjectHandle::parse("0 trailing", "trailing test");
+            std::cout << "oops -- didn't throw" << std::endl;
+        }
+        catch (std::runtime_error e)
+        {
+            std::cout << "trailing data: " << e.what()
+                      << std::endl;
+        }
+    }
     else
     {
 	throw std::runtime_error(std::string("invalid test ") +