Merge pull request #1161 from m-holger/writer

Tune QPDFWriter

Merge pull request #1161 from m-holger/writer
Tune QPDFWriter
Jay Berkenbilt · GitHub
2 parents 69b9bc72 aa2e0d23
Showing 12 changed files with 715 additions and 316 deletions
include/qpdf/QPDF.hh
include/qpdf/QPDFWriter.hh
libqpdf/QPDF.cc
libqpdf/QPDFWriter.cc
libqpdf/QPDF_linearization.cc
libqpdf/QPDF_optimization.cc
libqpdf/qpdf/ObjTable.hh
libqpdf/qpdf/QPDFWriter_private.hh
libtests/CMakeLists.txt
libtests/obj_table.cc
libtests/qtest/obj_table.test
libtests/qtest/obj_table/obj_table.out
@@ -41,6 +41,7 @@
 #include <qpdf/QPDFObjectHandle.hh>
 #include <qpdf/QPDFStreamFilter.hh>
 #include <qpdf/QPDFTokenizer.hh>
+#include <qpdf/QPDFWriter.hh>
 #include <qpdf/QPDFXRefEntry.hh>
  
 class QPDF_Stream;
@@ -727,43 +728,62 @@ class QPDF
  
       private:
         static void
+        optimize(
+            QPDF& qpdf,
+            QPDFWriter::ObjTable const& obj,
+            std::function<int(QPDFObjectHandle&)> skip_stream_parameters)
+        {
+            return qpdf.optimize(obj, skip_stream_parameters);
+        }
+
+        static void
         getLinearizedParts(
             QPDF& qpdf,
-            std::map<int, int> const& object_stream_data,
+            QPDFWriter::ObjTable const& obj,
             std::vector<QPDFObjectHandle>& part4,
             std::vector<QPDFObjectHandle>& part6,
             std::vector<QPDFObjectHandle>& part7,
             std::vector<QPDFObjectHandle>& part8,
             std::vector<QPDFObjectHandle>& part9)
         {
-            qpdf.getLinearizedParts(object_stream_data, part4, part6, part7, part8, part9);
+            qpdf.getLinearizedParts(obj, part4, part6, part7, part8, part9);
         }
  
         static void
         generateHintStream(
             QPDF& qpdf,
-            std::map<int, QPDFXRefEntry> const& xref,
-            std::map<int, qpdf_offset_t> const& lengths,
-            std::map<int, int> const& obj_renumber,
+            QPDFWriter::NewObjTable const& new_obj,
+            QPDFWriter::ObjTable const& obj,
             std::shared_ptr<Buffer>& hint_stream,
             int& S,
             int& O,
             bool compressed)
         {
-            return qpdf.generateHintStream(
-                xref, lengths, obj_renumber, hint_stream, S, O, compressed);
+            return qpdf.generateHintStream(new_obj, obj, hint_stream, S, O, compressed);
         }
  
-        static void
-        getObjectStreamData(QPDF& qpdf, std::map<int, int>& omap)
+        static std::vector<QPDFObjGen>
+        getCompressibleObjGens(QPDF& qpdf)
         {
-            qpdf.getObjectStreamData(omap);
+            return qpdf.getCompressibleObjVector();
         }
  
-        static std::vector<QPDFObjGen>
-        getCompressibleObjGens(QPDF& qpdf)
+        static std::vector<bool>
+        getCompressibleObjSet(QPDF& qpdf)
         {
-            return qpdf.getCompressibleObjGens();
+            return qpdf.getCompressibleObjSet();
+        }
+
+        static std::map<QPDFObjGen, QPDFXRefEntry> const&
+        getXRefTable(QPDF& qpdf)
+        {
+            return qpdf.getXRefTableInternal();
+        }
+
+        static size_t
+        tableSize(QPDF& qpdf)
+        {
+            return qpdf.tableSize();
         }
     };
  
@@ -1083,10 +1103,21 @@ class QPDF
  
     // For QPDFWriter:
  
+    std::map<QPDFObjGen, QPDFXRefEntry> const& getXRefTableInternal();
+    template <typename T>
+    void optimize_internal(
+        T const& object_stream_data,
+        bool allow_changes = true,
+        std::function<int(QPDFObjectHandle&)> skip_stream_parameters = nullptr);
+    void optimize(
+        QPDFWriter::ObjTable const& obj,
+        std::function<int(QPDFObjectHandle&)> skip_stream_parameters);
+    size_t tableSize();
+
     // Get lists of all objects in order according to the part of a linearized file that they belong
     // to.
     void getLinearizedParts(
-        std::map<int, int> const& object_stream_data,
+        QPDFWriter::ObjTable const& obj,
         std::vector<QPDFObjectHandle>& part4,
         std::vector<QPDFObjectHandle>& part6,
         std::vector<QPDFObjectHandle>& part7,
@@ -1094,19 +1125,18 @@ class QPDF
         std::vector<QPDFObjectHandle>& part9);
  
     void generateHintStream(
-        std::map<int, QPDFXRefEntry> const& xref,
-        std::map<int, qpdf_offset_t> const& lengths,
-        std::map<int, int> const& obj_renumber,
+        QPDFWriter::NewObjTable const& new_obj,
+        QPDFWriter::ObjTable const& obj,
         std::shared_ptr<Buffer>& hint_stream,
         int& S,
         int& O,
         bool compressed);
  
-    // Map object to object stream that contains it
-    void getObjectStreamData(std::map<int, int>&);
-
     // Get a list of objects that would be permitted in an object stream.
-    std::vector<QPDFObjGen> getCompressibleObjGens();
+    template <typename T>
+    std::vector<T> getCompressibleObjGens();
+    std::vector<QPDFObjGen> getCompressibleObjVector();
+    std::vector<bool> getCompressibleObjSet();
  
     // methods to support page handling
  
@@ -1352,6 +1382,7 @@ class QPDF
     qpdf_offset_t getLinearizationOffset(QPDFObjGen const&);
     QPDFObjectHandle
     getUncompressedObject(QPDFObjectHandle&, std::map<int, int> const& object_stream_data);
+    QPDFObjectHandle getUncompressedObject(QPDFObjectHandle&, QPDFWriter::ObjTable const& obj);
     int lengthNextN(int first_object, int n);
     void
     checkHPageOffset(std::vector<QPDFObjectHandle> const& pages, std::map<int, int>& idx_to_obj);
@@ -1362,28 +1393,23 @@ class QPDF
     void dumpHSharedObject();
     void dumpHGeneric(HGeneric&);
     qpdf_offset_t adjusted_offset(qpdf_offset_t offset);
-    void calculateLinearizationData(std::map<int, int> const& object_stream_data);
+    template <typename T>
+    void calculateLinearizationData(T const& object_stream_data);
+    template <typename T>
     void pushOutlinesToPart(
         std::vector<QPDFObjectHandle>& part,
         std::set<QPDFObjGen>& lc_outlines,
-        std::map<int, int> const& object_stream_data);
+        T const& object_stream_data);
     int outputLengthNextN(
         int in_object,
         int n,
-        std::map<int, qpdf_offset_t> const& lengths,
-        std::map<int, int> const& obj_renumber);
-    void calculateHPageOffset(
-        std::map<int, QPDFXRefEntry> const& xref,
-        std::map<int, qpdf_offset_t> const& lengths,
-        std::map<int, int> const& obj_renumber);
-    void calculateHSharedObject(
-        std::map<int, QPDFXRefEntry> const& xref,
-        std::map<int, qpdf_offset_t> const& lengths,
-        std::map<int, int> const& obj_renumber);
-    void calculateHOutline(
-        std::map<int, QPDFXRefEntry> const& xref,
-        std::map<int, qpdf_offset_t> const& lengths,
-        std::map<int, int> const& obj_renumber);
+        QPDFWriter::NewObjTable const& new_obj,
+        QPDFWriter::ObjTable const& obj);
+    void
+    calculateHPageOffset(QPDFWriter::NewObjTable const& new_obj, QPDFWriter::ObjTable const& obj);
+    void
+    calculateHSharedObject(QPDFWriter::NewObjTable const& new_obj, QPDFWriter::ObjTable const& obj);
+    void calculateHOutline(QPDFWriter::NewObjTable const& new_obj, QPDFWriter::ObjTable const& obj);
     void writeHPageOffset(BitWriter&);
     void writeHSharedObject(BitWriter&);
     void writeHGeneric(BitWriter&, HGeneric&);
@@ -1407,6 +1433,7 @@ class QPDF
         QPDFObjGen::set& visited,
         bool top);
     void filterCompressedObjects(std::map<int, int> const& object_stream_data);
+    void filterCompressedObjects(QPDFWriter::ObjTable const& object_stream_data);
  
     // JSON import
     void importJSON(std::shared_ptr<InputSource>, bool must_be_complete);
@@ -437,6 +437,12 @@ class QPDFWriter
     QPDF_DLL
     std::map<QPDFObjGen, QPDFXRefEntry> getWrittenXRefTable();
  
+    // The following structs / classes are not part of the public API.
+    struct Object;
+    struct NewObject;
+    class ObjTable;
+    class NewObjTable;
+
   private:
     // flags used by unparseObject
     static int const f_stream = 1 << 0;
@@ -550,6 +556,7 @@ class QPDFWriter
     void writeLinearized();
     void enqueuePart(std::vector<QPDFObjectHandle>& part);
     void writeEncryptionDictionary();
+    void initializeTables(size_t extra = 0);
     void doWriteSetup();
     void writeHeader();
     void writeHintStream(int hint_id);
@@ -604,98 +611,7 @@ class QPDFWriter
     void pushMD5Pipeline(PipelinePopper&);
     void computeDeterministicIDData();
  
-    void discardGeneration(std::map<QPDFObjGen, int> const& in, std::map<int, int>& out);
-
-    class Members
-    {
-        friend class QPDFWriter;
-
-      public:
-        QPDF_DLL
-        ~Members();
-
-      private:
-        Members(QPDF& pdf);
-        Members(Members const&) = delete;
-
-        QPDF& pdf;
-        QPDFObjGen root_og{-1, 0};
-        char const* filename{"unspecified"};
-        FILE* file{nullptr};
-        bool close_file{false};
-        Pl_Buffer* buffer_pipeline{nullptr};
-        Buffer* output_buffer{nullptr};
-        bool normalize_content_set{false};
-        bool normalize_content{false};
-        bool compress_streams{true};
-        bool compress_streams_set{false};
-        qpdf_stream_decode_level_e stream_decode_level{qpdf_dl_none};
-        bool stream_decode_level_set{false};
-        bool recompress_flate{false};
-        bool qdf_mode{false};
-        bool preserve_unreferenced_objects{false};
-        bool newline_before_endstream{false};
-        bool static_id{false};
-        bool suppress_original_object_ids{false};
-        bool direct_stream_lengths{true};
-        bool encrypted{false};
-        bool preserve_encryption{true};
-        bool linearized{false};
-        bool pclm{false};
-        qpdf_object_stream_e object_stream_mode{qpdf_o_preserve};
-        std::string encryption_key;
-        bool encrypt_metadata{true};
-        bool encrypt_use_aes{false};
-        std::map<std::string, std::string> encryption_dictionary;
-        int encryption_V{0};
-        int encryption_R{0};
-
-        std::string id1; // for /ID key of
-        std::string id2; // trailer dictionary
-        std::string final_pdf_version;
-        int final_extension_level{0};
-        std::string min_pdf_version;
-        int min_extension_level{0};
-        std::string forced_pdf_version;
-        int forced_extension_level{0};
-        std::string extra_header_text;
-        int encryption_dict_objid{0};
-        std::string cur_data_key;
-        std::list<std::shared_ptr<Pipeline>> to_delete;
-        Pl_Count* pipeline{nullptr};
-        std::vector<QPDFObjectHandle> object_queue;
-        size_t object_queue_front{0};
-        std::map<QPDFObjGen, int> obj_renumber;
-        std::map<int, QPDFXRefEntry> xref;
-        std::map<int, qpdf_offset_t> lengths;
-        int next_objid{1};
-        int cur_stream_length_id{0};
-        size_t cur_stream_length{0};
-        bool added_newline{false};
-        int max_ostream_index{0};
-        std::set<QPDFObjGen> normalized_streams;
-        std::map<QPDFObjGen, int> page_object_to_seq;
-        std::map<QPDFObjGen, int> contents_to_page_seq;
-        std::map<QPDFObjGen, int> object_to_object_stream;
-        std::map<int, std::set<QPDFObjGen>> object_stream_to_objects;
-        std::list<Pipeline*> pipeline_stack;
-        unsigned long long next_stack_id{0};
-        bool deterministic_id{false};
-        Pl_MD5* md5_pipeline{nullptr};
-        std::string deterministic_id_data;
-        bool did_write_setup{false};
-
-        // For linearization only
-        std::string lin_pass1_filename;
-        std::map<int, int> obj_renumber_no_gen;
-        std::map<int, int> object_to_object_stream_no_gen;
-
-        // For progress reporting
-        std::shared_ptr<ProgressReporter> progress_reporter;
-        int events_expected{0};
-        int events_seen{0};
-        int next_progress_report{0};
-    };
+    class Members;
  
     // Keep all member variables inside the Members object, which we dynamically allocate. This
     // makes it possible to add new private members without breaking binary compatibility.
@@ -2370,6 +2370,12 @@ QPDF::getRoot()
 std::map<QPDFObjGen, QPDFXRefEntry>
 QPDF::getXRefTable()
 {
+    return getXRefTableInternal();
+}
+
+std::map<QPDFObjGen, QPDFXRefEntry> const&
+QPDF::getXRefTableInternal()
+{
     if (!m->parsed) {
         throw std::logic_error("QPDF::getXRefTable called before parsing.");
     }
@@ -2377,19 +2383,33 @@ QPDF::getXRefTable()
     return m->xref_table;
 }
  
-void
-QPDF::getObjectStreamData(std::map<int, int>& omap)
+size_t
+QPDF::tableSize()
 {
-    for (auto const& iter: m->xref_table) {
-        QPDFObjGen const& og = iter.first;
-        QPDFXRefEntry const& entry = iter.second;
-        if (entry.getType() == 2) {
-            omap[og.getObj()] = entry.getObjStreamNumber();
-        }
+    // If obj_cache is dense, accommodate all object in tables,else accommodate only original
+    // objects.
+    auto max_xref = m->xref_table.size() ? m->xref_table.crbegin()->first.getObj() : 0;
+    auto max_obj = m->obj_cache.size() ? m->obj_cache.crbegin()->first.getObj() : 0;
+    if (max_obj < 1.1 * std::max(toI(m->obj_cache.size()), max_xref)) {
+        return toS(++max_obj);
     }
+    return toS(++max_xref);
 }
  
 std::vector<QPDFObjGen>
+QPDF::getCompressibleObjVector()
+{
+    return getCompressibleObjGens<QPDFObjGen>();
+}
+
+std::vector<bool>
+QPDF::getCompressibleObjSet()
+{
+    return getCompressibleObjGens<bool>();
+}
+
+template <typename T>
+std::vector<T>
 QPDF::getCompressibleObjGens()
 {
     // Return a list of objects that are allowed to be in object streams.  Walk through the objects
@@ -2407,7 +2427,14 @@ QPDF::getCompressibleObjGens()
     std::vector<QPDFObjectHandle> queue;
     queue.reserve(512);
     queue.push_back(m->trailer);
-    std::vector<QPDFObjGen> result;
+    std::vector<T> result;
+    if constexpr (std::is_same_v<T, QPDFObjGen>) {
+        result.reserve(m->obj_cache.size());
+    } else if constexpr (std::is_same_v<T, bool>) {
+        result.resize(max_obj + 1U, false);
+    } else {
+        throw std::logic_error("Unsupported type in QPDF::getCompressibleObjGens");
+    }
     while (!queue.empty()) {
         auto obj = queue.back();
         queue.pop_back();
@@ -2439,7 +2466,11 @@ QPDF::getCompressibleObjGens()
             } else if (!(obj.isStream() ||
                          (obj.isDictionaryOfType("/Sig") && obj.hasKey("/ByteRange") &&
                           obj.hasKey("/Contents")))) {
-                result.push_back(og);
+                if constexpr (std::is_same_v<T, QPDFObjGen>) {
+                    result.push_back(og);
+                } else if constexpr (std::is_same_v<T, bool>) {
+                    result[id + 1U] = true;
+                }
             }
         }
         if (obj.isStream()) {
@@ -2,7 +2,7 @@
  
 #include <qpdf/qpdf-config.h> // include early for large file support
  
-#include <qpdf/QPDFWriter.hh>
+#include <qpdf/QPDFWriter_private.hh>
  
 #include <qpdf/MD5.hh>
 #include <qpdf/Pl_AES_PDF.hh>
@@ -1038,7 +1038,7 @@ QPDFWriter::openObject(int objid)
     if (objid == 0) {
         objid = m->next_objid++;
     }
-    m->xref[objid] = QPDFXRefEntry(m->pipeline->getCount());
+    m->new_obj[objid].xref = QPDFXRefEntry(m->pipeline->getCount());
     writeString(std::to_string(objid));
     writeString(" 0 obj\n");
     return objid;
@@ -1050,7 +1050,8 @@ QPDFWriter::closeObject(int objid)
     // Write a newline before endobj as it makes the file easier to repair.
     writeString("\nendobj\n");
     writeStringQDF("\n");
-    m->lengths[objid] = m->pipeline->getCount() - m->xref[objid].getOffset();
+    auto& new_obj = m->new_obj[objid];
+    new_obj.length = m->pipeline->getCount() - new_obj.xref.getOffset();
 }
  
 void
@@ -1064,7 +1065,7 @@ QPDFWriter::assignCompressedObjectNumbers(QPDFObjGen const&amp; og)
  
     // Reserve numbers for the objects that belong to this object stream.
     for (auto const& iter: m->object_stream_to_objects[objid]) {
-        m->obj_renumber[iter] = m->next_objid++;
+        m->obj[iter].renumber = m->next_objid++;
     }
 }
  
@@ -1093,18 +1094,18 @@ QPDFWriter::enqueueObject(QPDFObjectHandle object)
         }
  
         QPDFObjGen og = object.getObjGen();
+        auto& obj = m->obj[og];
  
-        if (m->obj_renumber.count(og) == 0) {
-            if (m->object_to_object_stream.count(og)) {
+        if (obj.renumber == 0) {
+            if (obj.object_stream > 0) {
                 // This is in an object stream.  Don't process it here.  Instead, enqueue the object
                 // stream.  Object streams always have generation 0.
-                int stream_id = m->object_to_object_stream[og];
-                // Detect loops by storing invalid object ID 0, which will get overwritten later.
-                m->obj_renumber[og] = 0;
-                enqueueObject(m->pdf.getObjectByID(stream_id, 0));
+                // Detect loops by storing invalid object ID -1, which will get overwritten later.
+                obj.renumber = -1;
+                enqueueObject(m->pdf.getObject(obj.object_stream, 0));
             } else {
                 m->object_queue.push_back(object);
-                m->obj_renumber[og] = m->next_objid++;
+                obj.renumber = m->next_objid++;
  
                 if ((og.getGen() == 0) && m->object_stream_to_objects.count(og.getObj())) {
                     // For linearized files, uncompressed objects go at end, and we take care of
@@ -1117,7 +1118,7 @@ QPDFWriter::enqueueObject(QPDFObjectHandle object)
                     ++m->next_objid;
                 }
             }
-        } else if (m->obj_renumber[og] == 0) {
+        } else if (obj.renumber == -1) {
             // This can happen if a specially constructed file indicates that an object stream is
             // inside itself.
             QTC::TC("qpdf", "QPDFWriter ignore self-referential object stream");
@@ -1147,9 +1148,7 @@ QPDFWriter::unparseChild(QPDFObjectHandle child, int level, int flags)
         enqueueObject(child);
     }
     if (child.isIndirect()) {
-        QPDFObjGen old_og = child.getObjGen();
-        int new_id = m->obj_renumber[old_og];
-        writeString(std::to_string(new_id));
+        writeString(std::to_string(m->obj[child].renumber));
         writeString(" 0 R");
     } else {
         unparseObject(child, level, flags);
@@ -1527,9 +1526,8 @@ QPDFWriter::unparseObject(
         writeString(">>");
     } else if (tc == ::ot_stream) {
         // Write stream data to a buffer.
-        int new_id = m->obj_renumber[old_og];
         if (!m->direct_stream_lengths) {
-            m->cur_stream_length_id = new_id + 1;
+            m->cur_stream_length_id = m->obj[old_og].renumber + 1;
         }
  
         flags |= f_stream;
@@ -1626,7 +1624,7 @@ QPDFWriter::writeObjectStream(QPDFObjectHandle object)
     QPDFObjGen old_og = object.getObjGen();
     qpdf_assert_debug(old_og.getGen() == 0);
     int old_id = old_og.getObj();
-    int new_id = m->obj_renumber[old_og];
+    int new_stream_id = m->obj[old_og].renumber;
  
     std::vector<qpdf_offset_t> offsets;
     qpdf_offset_t first = 0;
@@ -1670,7 +1668,7 @@ QPDFWriter::writeObjectStream(QPDFObjectHandle object)
         int count = -1;
         for (auto const& obj: m->object_stream_to_objects[old_id]) {
             ++count;
-            int new_obj = m->obj_renumber[obj];
+            int new_obj = m->obj[obj].renumber;
             if (first_obj == -1) {
                 first_obj = new_obj;
             }
@@ -1706,13 +1704,13 @@ QPDFWriter::writeObjectStream(QPDFObjectHandle object)
             }
             writeObject(obj_to_write, count);
  
-            m->xref[new_obj] = QPDFXRefEntry(new_id, count);
+            m->new_obj[new_obj].xref = QPDFXRefEntry(new_stream_id, count);
         }
     }
  
     // Write the object
-    openObject(new_id);
-    setDataKey(new_id);
+    openObject(new_stream_id);
+    setDataKey(new_stream_id);
     writeString("<<");
     writeStringQDF("\n ");
     writeString(" /Type /ObjStm");
@@ -1754,7 +1752,7 @@ QPDFWriter::writeObjectStream(QPDFObjectHandle object)
     }
     writeString("endstream");
     m->cur_data_key.clear();
-    closeObject(new_id);
+    closeObject(new_stream_id);
 }
  
 void
@@ -1769,7 +1767,7 @@ QPDFWriter::writeObject(QPDFObjectHandle object, int object_stream_index)
     }
  
     indicateProgress(false, false);
-    int new_id = m->obj_renumber[old_og];
+    auto new_id = m->obj[old_og].renumber;
     if (m->qdf_mode) {
         if (m->page_object_to_seq.count(old_og)) {
             writeString("%% Page ");
@@ -1938,11 +1936,7 @@ QPDFWriter::initializeSpecialStreams()
 void
 QPDFWriter::preserveObjectStreams()
 {
-    std::map<int, int> omap;
-    QPDF::Writer::getObjectStreamData(m->pdf, omap);
-    if (omap.empty()) {
-        return;
-    }
+    auto const& xref = QPDF::Writer::getXRefTable(m->pdf);
     // Our object_to_object_stream map has to map ObjGen -> ObjGen since we may be generating object
     // streams out of old objects that have generation numbers greater than zero. However in an
     // existing PDF, all object stream objects and all objects in them must have generation 0
@@ -1950,20 +1944,43 @@ QPDFWriter::preserveObjectStreams()
     // that are not allowed to be in object streams. In addition to removing objects that were
     // erroneously included in object streams in the source PDF, it also prevents unreferenced
     // objects from being included.
-    std::set<QPDFObjGen> eligible;
-    if (!m->preserve_unreferenced_objects) {
-        std::vector<QPDFObjGen> eligible_v = QPDF::Writer::getCompressibleObjGens(m->pdf);
-        eligible = std::set<QPDFObjGen>(eligible_v.begin(), eligible_v.end());
-    }
-    QTC::TC("qpdf", "QPDFWriter preserve object streams", m->preserve_unreferenced_objects ? 0 : 1);
-    for (auto iter: omap) {
-        QPDFObjGen og(iter.first, 0);
-        if (eligible.count(og) || m->preserve_unreferenced_objects) {
-            m->object_to_object_stream[og] = iter.second;
-        } else {
-            QTC::TC("qpdf", "QPDFWriter exclude from object stream");
+    auto iter = xref.cbegin();
+    auto end = xref.cend();
+
+    // Start by scanning for first compressed object in case we don't have any object streams to
+    // process.
+    for (; iter != end; ++iter) {
+        if (iter->second.getType() == 2) {
+            // Pdf contains object streams.
+            QTC::TC(
+                "qpdf",
+                "QPDFWriter preserve object streams",
+                m->preserve_unreferenced_objects ? 0 : 1);
+
+            if (m->preserve_unreferenced_objects) {
+                for (; iter != end; ++iter) {
+                    if (iter->second.getType() == 2) {
+                        m->obj[iter->first].object_stream = iter->second.getObjStreamNumber();
+                    }
+                }
+            } else {
+                auto eligible = QPDF::Writer::getCompressibleObjSet(m->pdf);
+                for (; iter != end; ++iter) {
+                    if (iter->second.getType() == 2) {
+                        auto id = static_cast<size_t>(iter->first.getObj());
+                        if (id < eligible.size() && eligible[id]) {
+                            m->obj[iter->first].object_stream = iter->second.getObjStreamNumber();
+                        } else {
+                            QTC::TC("qpdf", "QPDFWriter exclude from object stream");
+                        }
+                    }
+                }
+            }
+            return;
         }
     }
+    // No compressed objects found.
+    m->obj.streams_empty = true;
 }
  
 void
@@ -1979,7 +1996,10 @@ QPDFWriter::generateObjectStreams()
  
     std::vector<QPDFObjGen> eligible = QPDF::Writer::getCompressibleObjGens(m->pdf);
     size_t n_object_streams = (eligible.size() + 99U) / 100U;
+
+    initializeTables(2U * n_object_streams);
     if (n_object_streams == 0) {
+        m->obj.streams_empty = true;
         return;
     }
     size_t n_per = eligible.size() / n_object_streams;
@@ -1987,20 +2007,18 @@ QPDFWriter::generateObjectStreams()
         ++n_per;
     }
     unsigned int n = 0;
-    int cur_ostream = 0;
-    for (auto const& iter: eligible) {
-        if ((n % n_per) == 0) {
-            if (n > 0) {
-                QTC::TC("qpdf", "QPDFWriter generate >1 ostream");
-            }
+    int cur_ostream = m->pdf.newIndirectNull().getObjectID();
+    for (auto const& item: eligible) {
+        if (n == n_per) {
+            QTC::TC("qpdf", "QPDFWriter generate >1 ostream");
             n = 0;
-        }
-        if (n == 0) {
             // Construct a new null object as the "original" object stream.  The rest of the code
             // knows that this means we're creating the object stream from scratch.
-            cur_ostream = m->pdf.makeIndirectObject(QPDFObjectHandle::newNull()).getObjectID();
+            cur_ostream = m->pdf.newIndirectNull().getObjectID();
         }
-        m->object_to_object_stream[iter] = cur_ostream;
+        auto& obj = m->obj[item];
+        obj.object_stream = cur_ostream;
+        obj.gen = item.getGen();
         ++n;
     }
 }
@@ -2056,6 +2074,14 @@ QPDFWriter::prepareFileForWrite()
 }
  
 void
+QPDFWriter::initializeTables(size_t extra)
+{
+    auto size = QIntC::to_size(QPDF::Writer::tableSize(m->pdf) + 100) + extra;
+    m->obj.initialize(size);
+    m->new_obj.initialize(size);
+}
+
+void
 QPDFWriter::doWriteSetup()
 {
     if (m->did_write_setup) {
@@ -2124,10 +2150,12 @@ QPDFWriter::doWriteSetup()
  
     switch (m->object_stream_mode) {
     case qpdf_o_disable:
-        // no action required
+        initializeTables();
+        m->obj.streams_empty = true;
         break;
  
     case qpdf_o_preserve:
+        initializeTables();
         preserveObjectStreams();
         break;
  
@@ -2138,39 +2166,45 @@ QPDFWriter::doWriteSetup()
         // no default so gcc will warn for missing case tag
     }
  
-    if (m->linearized) {
-        // Page dictionaries are not allowed to be compressed objects.
-        for (auto& page: m->pdf.getAllPages()) {
-            QPDFObjGen og = page.getObjGen();
-            if (m->object_to_object_stream.count(og)) {
-                QTC::TC("qpdf", "QPDFWriter uncompressing page dictionary");
-                m->object_to_object_stream.erase(og);
+    if (!m->obj.streams_empty) {
+        if (m->linearized) {
+            // Page dictionaries are not allowed to be compressed objects.
+            for (auto& page: m->pdf.getAllPages()) {
+                if (m->obj[page].object_stream > 0) {
+                    QTC::TC("qpdf", "QPDFWriter uncompressing page dictionary");
+                    m->obj[page].object_stream = 0;
+                }
             }
         }
-    }
  
-    if (m->linearized || m->encrypted) {
-        // The document catalog is not allowed to be compressed in linearized files either.  It also
-        // appears that Adobe Reader 8.0.0 has a bug that prevents it from being able to handle
-        // encrypted files with compressed document catalogs, so we disable them in that case as
-        // well.
-        if (m->object_to_object_stream.count(m->root_og)) {
-            QTC::TC("qpdf", "QPDFWriter uncompressing root");
-            m->object_to_object_stream.erase(m->root_og);
+        if (m->linearized || m->encrypted) {
+            // The document catalog is not allowed to be compressed in linearized files either.  It
+            // also appears that Adobe Reader 8.0.0 has a bug that prevents it from being able to
+            // handle encrypted files with compressed document catalogs, so we disable them in that
+            // case as well.
+            if (m->obj[m->root_og].object_stream > 0) {
+                QTC::TC("qpdf", "QPDFWriter uncompressing root");
+                m->obj[m->root_og].object_stream = 0;
+            }
         }
-    }
  
-    // Generate reverse mapping from object stream to objects
-    for (auto const& iter: m->object_to_object_stream) {
-        QPDFObjGen const& obj = iter.first;
-        int stream = iter.second;
-        m->object_stream_to_objects[stream].insert(obj);
-        m->max_ostream_index = std::max(
-            m->max_ostream_index, QIntC::to_int(m->object_stream_to_objects[stream].size()) - 1);
-    }
+        // Generate reverse mapping from object stream to objects
+        m->obj.forEach([this](auto id, auto const& item) -> void {
+            if (item.object_stream > 0) {
+                auto& vec = m->object_stream_to_objects[item.object_stream];
+                vec.emplace_back(id, item.gen);
+                if (m->max_ostream_index < vec.size()) {
+                    ++m->max_ostream_index;
+                }
+            }
+        });
+        --m->max_ostream_index;
  
-    if (!m->object_stream_to_objects.empty()) {
-        setMinimumPDFVersion("1.5");
+        if (m->object_stream_to_objects.empty()) {
+            m->obj.streams_empty = true;
+        } else {
+            setMinimumPDFVersion("1.5");
+        }
     }
  
     setMinimumPDFVersion(m->pdf.getPDFVersion(), m->pdf.getExtensionLevel());
@@ -2215,7 +2249,7 @@ QPDFWriter::write()
 QPDFObjGen
 QPDFWriter::getRenumberedObjGen(QPDFObjGen og)
 {
-    return QPDFObjGen(m->obj_renumber[og], 0);
+    return QPDFObjGen(m->obj[og].renumber, 0);
 }
  
 std::map<QPDFObjGen, QPDFXRefEntry>
@@ -2223,12 +2257,12 @@ QPDFWriter::getWrittenXRefTable()
 {
     std::map<QPDFObjGen, QPDFXRefEntry> result;
  
-    for (auto const& iter: m->xref) {
-        if (iter.first != 0 && iter.second.getType() != 0) {
-            result[QPDFObjGen(iter.first, 0)] = iter.second;
+    auto it = result.begin();
+    m->new_obj.forEach([&it, &result](auto id, auto const& item) -> void {
+        if (item.xref.getType() != 0) {
+            it = result.emplace_hint(it, QPDFObjGen(id, 0), item.xref);
         }
-    }
-
+    });
     return result;
 }
  
@@ -2290,8 +2324,7 @@ QPDFWriter::writeHintStream(int hint_id)
     int S = 0;
     int O = 0;
     bool compressed = (m->compress_streams && !m->qdf_mode);
-    QPDF::Writer::generateHintStream(
-        m->pdf, m->xref, m->lengths, m->obj_renumber_no_gen, hint_buffer, S, O, compressed);
+    QPDF::Writer::generateHintStream(m->pdf, m->new_obj, m->obj, hint_buffer, S, O, compressed);
  
     openObject(hint_id);
     setDataKey(hint_id);
@@ -2364,7 +2397,7 @@ QPDFWriter::writeXRefTable(
         } else {
             qpdf_offset_t offset = 0;
             if (!suppress_offsets) {
-                offset = m->xref[i].getOffset();
+                offset = m->new_obj[i].xref.getOffset();
                 if ((hint_id != 0) && (i != hint_id) && (offset >= hint_offset)) {
                     offset += hint_length;
                 }
@@ -2411,13 +2444,13 @@ QPDFWriter::writeXRefStream(
     unsigned int f1_size = std::max(bytesNeeded(max_offset + hint_length), bytesNeeded(max_id));
  
     // field 2 contains object stream indices
-    unsigned int f2_size = bytesNeeded(m->max_ostream_index);
+    unsigned int f2_size = bytesNeeded(QIntC::to_longlong(m->max_ostream_index));
  
     unsigned int esize = 1 + f1_size + f2_size;
  
     // Must store in xref table in advance of writing the actual data rather than waiting for
     // openObject to do it.
-    m->xref[xref_id] = QPDFXRefEntry(m->pipeline->getCount());
+    m->new_obj[xref_id].xref = QPDFXRefEntry(m->pipeline->getCount());
  
     Pipeline* p = pushPipeline(new Pl_Buffer("xref stream"));
     bool compressed = false;
@@ -2435,7 +2468,7 @@ QPDFWriter::writeXRefStream(
         PipelinePopper pp_xref(this, &xref_data);
         activatePipelineStack(pp_xref);
         for (int i = first; i <= last; ++i) {
-            QPDFXRefEntry& e = m->xref[i];
+            QPDFXRefEntry& e = m->new_obj[i].xref;
             switch (e.getType()) {
             case 0:
                 writeBinary(0, 1);
@@ -2507,39 +2540,10 @@ QPDFWriter::calculateXrefStreamPadding(qpdf_offset_t xref_bytes)
 }
  
 void
-QPDFWriter::discardGeneration(std::map<QPDFObjGen, int> const& in, std::map<int, int>& out)
-{
-    // There are deep assumptions in the linearization code in QPDF that there is only one object
-    // with each object number; i.e., you can't have two objects with the same object number and
-    // different generations.  This is a pretty safe assumption because Adobe Reader and Acrobat
-    // can't actually handle this case.  There is not much if any code in QPDF outside linearization
-    // that assumes this, but the linearization code as currently implemented would do weird things
-    // if we found such a case.  In order to avoid breaking ABI changes in QPDF, we will first
-    // assert that this condition holds.  Then we can create new maps for QPDF that throw away
-    // generation numbers.
-
-    out.clear();
-    for (auto const& iter: in) {
-        if (out.count(iter.first.getObj())) {
-            throw std::runtime_error("QPDF cannot currently linearize files that contain"
-                                     " multiple objects with the same object ID and different"
-                                     " generations.  If you see this error message, please file"
-                                     " a bug report and attach the file if possible.  As a"
-                                     " workaround, first convert the file with qpdf without"
-                                     " linearizing, and then linearize the result of that"
-                                     " conversion.");
-        }
-        out[iter.first.getObj()] = iter.second;
-    }
-}
-
-void
 QPDFWriter::writeLinearized()
 {
     // Optimize file and enqueue objects in order
  
-    discardGeneration(m->object_to_object_stream, m->object_to_object_stream_no_gen);
-
     auto skip_stream_parameters = [this](QPDFObjectHandle& stream) {
         bool compress_stream;
         bool is_metadata;
@@ -2550,15 +2554,14 @@ QPDFWriter::writeLinearized()
         }
     };
  
-    m->pdf.optimize(m->object_to_object_stream_no_gen, true, skip_stream_parameters);
+    QPDF::Writer::optimize(m->pdf, m->obj, skip_stream_parameters);
  
     std::vector<QPDFObjectHandle> part4;
     std::vector<QPDFObjectHandle> part6;
     std::vector<QPDFObjectHandle> part7;
     std::vector<QPDFObjectHandle> part8;
     std::vector<QPDFObjectHandle> part9;
-    QPDF::Writer::getLinearizedParts(
-        m->pdf, m->object_to_object_stream_no_gen, part4, part6, part7, part8, part9);
+    QPDF::Writer::getLinearizedParts(m->pdf, m->obj, part4, part6, part7, part8, part9);
  
     // Object number sequence:
     //
@@ -2582,7 +2585,7 @@ QPDFWriter::writeLinearized()
     int after_second_half = 1 + second_half_uncompressed;
     m->next_objid = after_second_half;
     int second_half_xref = 0;
-    bool need_xref_stream = (!m->object_to_object_stream.empty());
+    bool need_xref_stream = !m->obj.streams_empty;
     if (need_xref_stream) {
         second_half_xref = m->next_objid++;
     }
@@ -2690,14 +2693,14 @@ QPDFWriter::writeLinearized()
         writeString("<<");
         if (pass == 2) {
             std::vector<QPDFObjectHandle> const& pages = m->pdf.getAllPages();
-            int first_page_object = m->obj_renumber[pages.at(0).getObjGen()];
+            int first_page_object = m->obj[pages.at(0)].renumber;
             int npages = QIntC::to_int(pages.size());
  
             writeString(" /Linearized 1 /L ");
             writeString(std::to_string(file_size + hint_length));
             // Implementation note 121 states that a space is mandatory after this open bracket.
             writeString(" /H [ ");
-            writeString(std::to_string(m->xref[hint_id].getOffset()));
+            writeString(std::to_string(m->new_obj[hint_id].xref.getOffset()));
             writeString(" ");
             writeString(std::to_string(hint_length));
             writeString(" ] /O ");
@@ -2724,7 +2727,7 @@ QPDFWriter::writeLinearized()
         qpdf_offset_t first_xref_offset = m->pipeline->getCount();
         qpdf_offset_t hint_offset = 0;
         if (pass == 2) {
-            hint_offset = m->xref[hint_id].getOffset();
+            hint_offset = m->new_obj[hint_id].xref.getOffset();
         }
         if (need_xref_stream) {
             // Must pad here too.
@@ -2795,7 +2798,7 @@ QPDFWriter::writeLinearized()
                     writeEncryptionDictionary();
                 }
                 if (pass == 1) {
-                    m->xref[hint_id] = QPDFXRefEntry(m->pipeline->getCount());
+                    m->new_obj[hint_id].xref = QPDFXRefEntry(m->pipeline->getCount());
                 } else {
                     // Part 5: hint stream
                     writeBuffer(hint_buffer);
@@ -2855,8 +2858,6 @@ QPDFWriter::writeLinearized()
         writeString(std::to_string(first_xref_offset));
         writeString("\n%%EOF\n");
  
-        discardGeneration(m->obj_renumber, m->obj_renumber_no_gen);
-
         if (pass == 1) {
             if (m->deterministic_id) {
                 QTC::TC("qpdf", "QPDFWriter linearized deterministic ID", need_xref_stream ? 0 : 1);
@@ -2870,7 +2871,7 @@ QPDFWriter::writeLinearized()
             pp_pass1 = nullptr;
  
             // Save hint offset since it will be set to zero by calling openObject.
-            qpdf_offset_t hint_offset1 = m->xref[hint_id].getOffset();
+            qpdf_offset_t hint_offset1 = m->new_obj[hint_id].xref.getOffset();
  
             // Write hint stream to a buffer
             {
@@ -2882,7 +2883,7 @@ QPDFWriter::writeLinearized()
             hint_length = QIntC::to_offset(hint_buffer->getSize());
  
             // Restore hint offset
-            m->xref[hint_id] = QPDFXRefEntry(hint_offset1);
+            m->new_obj[hint_id].xref = QPDFXRefEntry(hint_offset1);
             if (lin_pass1_file) {
                 // Write some debugging information
                 fprintf(
@@ -9,6 +9,7 @@
 #include <qpdf/Pl_Flate.hh>
 #include <qpdf/QPDFExc.hh>
 #include <qpdf/QPDFLogger.hh>
+#include <qpdf/QPDFWriter_private.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
  
@@ -585,6 +586,17 @@ QPDF::getUncompressedObject(QPDFObjectHandle&amp; obj, std::map&lt;int, int&gt; const&amp; obj
     }
 }
  
+QPDFObjectHandle
+QPDF::getUncompressedObject(QPDFObjectHandle& oh, QPDFWriter::ObjTable const& obj)
+{
+    if (obj.contains(oh)) {
+        if (auto id = obj[oh].object_stream; id > 0) {
+            return oh.isNull() ? oh : getObject(id, 0);
+        }
+    }
+    return oh;
+}
+
 int
 QPDF::lengthNextN(int first_object, int n)
 {
@@ -959,8 +971,9 @@ QPDF::dumpHGeneric(HGeneric&amp; t)
                        << "group_length: " << t.group_length << "\n";
 }
  
+template <typename T>
 void
-QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
+QPDF::calculateLinearizationData(T const& object_stream_data)
 {
     // This function calculates the ordering of objects, divides them into the appropriate parts,
     // and computes some values for the linearization parameter dictionary and hint tables.  The
@@ -1402,11 +1415,12 @@ QPDF::calculateLinearizationData(std::map&lt;int, int&gt; const&amp; object_stream_data)
     }
 }
  
+template <typename T>
 void
 QPDF::pushOutlinesToPart(
     std::vector<QPDFObjectHandle>& part,
     std::set<QPDFObjGen>& lc_outlines,
-    std::map<int, int> const& object_stream_data)
+    T const& object_stream_data)
 {
     QPDFObjectHandle root = getRoot();
     QPDFObjectHandle outlines = root.getKey("/Outlines");
@@ -1433,14 +1447,14 @@ QPDF::pushOutlinesToPart(
  
 void
 QPDF::getLinearizedParts(
-    std::map<int, int> const& object_stream_data,
+    QPDFWriter::ObjTable const& obj,
     std::vector<QPDFObjectHandle>& part4,
     std::vector<QPDFObjectHandle>& part6,
     std::vector<QPDFObjectHandle>& part7,
     std::vector<QPDFObjectHandle>& part8,
     std::vector<QPDFObjectHandle>& part9)
 {
-    calculateLinearizationData(object_stream_data);
+    calculateLinearizationData(obj);
     part4 = m->part4;
     part6 = m->part6;
     part7 = m->part7;
@@ -1456,33 +1470,29 @@ nbits(int val)
  
 int
 QPDF::outputLengthNextN(
-    int in_object,
-    int n,
-    std::map<int, qpdf_offset_t> const& lengths,
-    std::map<int, int> const& obj_renumber)
+    int in_object, int n, QPDFWriter::NewObjTable const& new_obj, QPDFWriter::ObjTable const& obj)
 {
     // Figure out the length of a series of n consecutive objects in the output file starting with
     // whatever object in_object from the input file mapped to.
  
-    if (obj_renumber.count(in_object) == 0) {
+    int first = obj[in_object].renumber;
+    int last = first + n;
+    if (first <= 0) {
         stopOnError("found object that is not renumbered while writing linearization data");
     }
-    int first = (*(obj_renumber.find(in_object))).second;
-    int length = 0;
-    for (int i = 0; i < n; ++i) {
-        if (lengths.count(first + i) == 0) {
+    qpdf_offset_t length = 0;
+    for (int i = first; i < last; ++i) {
+        auto l = new_obj[i].length;
+        if (l == 0) {
             stopOnError("found item with unknown length while writing linearization data");
         }
-        length += toI((*(lengths.find(first + toI(i)))).second);
+        length += l;
     }
-    return length;
+    return toI(length);
 }
  
 void
-QPDF::calculateHPageOffset(
-    std::map<int, QPDFXRefEntry> const& xref,
-    std::map<int, qpdf_offset_t> const& lengths,
-    std::map<int, int> const& obj_renumber)
+QPDF::calculateHPageOffset(QPDFWriter::NewObjTable const& new_obj, QPDFWriter::ObjTable const& obj)
 {
     // Page Offset Hint Table
  
@@ -1497,8 +1507,7 @@ QPDF::calculateHPageOffset(
  
     int min_nobjects = cphe.at(0).nobjects;
     int max_nobjects = min_nobjects;
-    int min_length =
-        outputLengthNextN(pages.at(0).getObjectID(), min_nobjects, lengths, obj_renumber);
+    int min_length = outputLengthNextN(pages.at(0).getObjectID(), min_nobjects, new_obj, obj);
     int max_length = min_length;
     int max_shared = cphe.at(0).nshared_objects;
  
@@ -1515,7 +1524,7 @@ QPDF::calculateHPageOffset(
         // assignments.
  
         int nobjects = cphe.at(i).nobjects;
-        int length = outputLengthNextN(pages.at(i).getObjectID(), nobjects, lengths, obj_renumber);
+        int length = outputLengthNextN(pages.at(i).getObjectID(), nobjects, new_obj, obj);
         int nshared = cphe.at(i).nshared_objects;
  
         min_nobjects = std::min(min_nobjects, nobjects);
@@ -1530,9 +1539,7 @@ QPDF::calculateHPageOffset(
     }
  
     ph.min_nobjects = min_nobjects;
-    int in_page0_id = pages.at(0).getObjectID();
-    int out_page0_id = (*(obj_renumber.find(in_page0_id))).second;
-    ph.first_page_offset = (*(xref.find(out_page0_id))).second.getOffset();
+    ph.first_page_offset = new_obj[obj[pages.at(0)].renumber].xref.getOffset();
     ph.nbits_delta_nobjects = nbits(max_nobjects - min_nobjects);
     ph.min_page_length = min_length;
     ph.nbits_delta_page_length = nbits(max_length - min_length);
@@ -1567,9 +1574,7 @@ QPDF::calculateHPageOffset(
  
 void
 QPDF::calculateHSharedObject(
-    std::map<int, QPDFXRefEntry> const& xref,
-    std::map<int, qpdf_offset_t> const& lengths,
-    std::map<int, int> const& obj_renumber)
+    QPDFWriter::NewObjTable const& new_obj, QPDFWriter::ObjTable const& obj)
 {
     CHSharedObject& cso = m->c_shared_object_data;
     std::vector<CHSharedObjectEntry>& csoe = cso.entries;
@@ -1577,12 +1582,12 @@ QPDF::calculateHSharedObject(
     std::vector<HSharedObjectEntry>& soe = so.entries;
     soe.clear();
  
-    int min_length = outputLengthNextN(csoe.at(0).object, 1, lengths, obj_renumber);
+    int min_length = outputLengthNextN(csoe.at(0).object, 1, new_obj, obj);
     int max_length = min_length;
  
     for (size_t i = 0; i < toS(cso.nshared_total); ++i) {
         // Assign absolute numbers to deltas; adjust later
-        int length = outputLengthNextN(csoe.at(i).object, 1, lengths, obj_renumber);
+        int length = outputLengthNextN(csoe.at(i).object, 1, new_obj, obj);
         min_length = std::min(min_length, length);
         max_length = std::max(max_length, length);
         soe.emplace_back();
@@ -1595,8 +1600,9 @@ QPDF::calculateHSharedObject(
     so.nshared_total = cso.nshared_total;
     so.nshared_first_page = cso.nshared_first_page;
     if (so.nshared_total > so.nshared_first_page) {
-        so.first_shared_obj = (*(obj_renumber.find(cso.first_shared_obj))).second;
-        so.first_shared_offset = (*(xref.find(so.first_shared_obj))).second.getOffset();
+        so.first_shared_obj = obj[cso.first_shared_obj].renumber;
+        so.min_group_length = min_length;
+        so.first_shared_offset = new_obj[so.first_shared_obj].xref.getOffset();
     }
     so.min_group_length = min_length;
     so.nbits_delta_group_length = nbits(max_length - min_length);
@@ -1611,10 +1617,7 @@ QPDF::calculateHSharedObject(
 }
  
 void
-QPDF::calculateHOutline(
-    std::map<int, QPDFXRefEntry> const& xref,
-    std::map<int, qpdf_offset_t> const& lengths,
-    std::map<int, int> const& obj_renumber)
+QPDF::calculateHOutline(QPDFWriter::NewObjTable const& new_obj, QPDFWriter::ObjTable const& obj)
 {
     HGeneric& cho = m->c_outline_data;
  
@@ -1624,10 +1627,10 @@ QPDF::calculateHOutline(
  
     HGeneric& ho = m->outline_hints;
  
-    ho.first_object = (*(obj_renumber.find(cho.first_object))).second;
-    ho.first_object_offset = (*(xref.find(ho.first_object))).second.getOffset();
+    ho.first_object = obj[cho.first_object].renumber;
+    ho.first_object_offset = new_obj[ho.first_object].xref.getOffset();
     ho.nobjects = cho.nobjects;
-    ho.group_length = outputLengthNextN(cho.first_object, ho.nobjects, lengths, obj_renumber);
+    ho.group_length = outputLengthNextN(cho.first_object, ho.nobjects, new_obj, obj);
 }
  
 template <class T, class int_type>
@@ -1756,18 +1759,17 @@ QPDF::writeHGeneric(BitWriter&amp; w, HGeneric&amp; t)
  
 void
 QPDF::generateHintStream(
-    std::map<int, QPDFXRefEntry> const& xref,
-    std::map<int, qpdf_offset_t> const& lengths,
-    std::map<int, int> const& obj_renumber,
+    QPDFWriter::NewObjTable const& new_obj,
+    QPDFWriter::ObjTable const& obj,
     std::shared_ptr<Buffer>& hint_buffer,
     int& S,
     int& O,
     bool compressed)
 {
     // Populate actual hint table values
-    calculateHPageOffset(xref, lengths, obj_renumber);
-    calculateHSharedObject(xref, lengths, obj_renumber);
-    calculateHOutline(xref, lengths, obj_renumber);
+    calculateHPageOffset(new_obj, obj);
+    calculateHSharedObject(new_obj, obj);
+    calculateHOutline(new_obj, obj);
  
     // Write the hint stream itself into a compressed memory buffer. Write through a counter so we
     // can get offsets.
@@ -5,6 +5,7 @@
 #include <qpdf/QPDF.hh>
  
 #include <qpdf/QPDFExc.hh>
+#include <qpdf/QPDFWriter_private.hh>
 #include <qpdf/QPDF_Array.hh>
 #include <qpdf/QPDF_Dictionary.hh>
 #include <qpdf/QTC.hh>
@@ -59,6 +60,23 @@ QPDF::optimize(
     bool allow_changes,
     std::function<int(QPDFObjectHandle&)> skip_stream_parameters)
 {
+    optimize_internal(object_stream_data, allow_changes, skip_stream_parameters);
+}
+
+void
+QPDF::optimize(
+    QPDFWriter::ObjTable const& obj, std::function<int(QPDFObjectHandle&)> skip_stream_parameters)
+{
+    optimize_internal(obj, true, skip_stream_parameters);
+}
+
+template <typename T>
+void
+QPDF::optimize_internal(
+    T const& object_stream_data,
+    bool allow_changes,
+    std::function<int(QPDFObjectHandle&)> skip_stream_parameters)
+{
     if (!m->obj_user_to_objects.empty()) {
         // already optimized
         return;
@@ -379,3 +397,45 @@ QPDF::filterCompressedObjects(std::map&lt;int, int&gt; const&amp; object_stream_data)
     m->obj_user_to_objects = t_obj_user_to_objects;
     m->object_to_obj_users = t_object_to_obj_users;
 }
+
+void
+QPDF::filterCompressedObjects(QPDFWriter::ObjTable const& obj)
+{
+    if (obj.getStreamsEmpty()) {
+        return;
+    }
+
+    // Transform object_to_obj_users and obj_user_to_objects so that they refer only to uncompressed
+    // objects.  If something is a user of a compressed object, then it is really a user of the
+    // object stream that contains it.
+
+    std::map<ObjUser, std::set<QPDFObjGen>> t_obj_user_to_objects;
+    std::map<QPDFObjGen, std::set<ObjUser>> t_object_to_obj_users;
+
+    for (auto const& i1: m->obj_user_to_objects) {
+        ObjUser const& ou = i1.first;
+        // Loop over objects.
+        for (auto const& og: i1.second) {
+            if (auto const& i2 = obj[og].object_stream; i2 <= 0) {
+                t_obj_user_to_objects[ou].insert(og);
+            } else {
+                t_obj_user_to_objects[ou].insert(QPDFObjGen(i2, 0));
+            }
+        }
+    }
+
+    for (auto const& i1: m->object_to_obj_users) {
+        QPDFObjGen const& og = i1.first;
+        // Loop over obj_users.
+        for (auto const& ou: i1.second) {
+            if (auto i2 = obj[og].object_stream; i2 <= 0) {
+                t_object_to_obj_users[og].insert(ou);
+            } else {
+                t_object_to_obj_users[QPDFObjGen(i2, 0)].insert(ou);
+            }
+        }
+    }
+
+    m->obj_user_to_objects = t_obj_user_to_objects;
+    m->object_to_obj_users = t_object_to_obj_users;
+}
+#ifndef OBJTABLE_HH
+#define OBJTABLE_HH
+
+#include <qpdf/QPDFObjGen.hh>
+#include <qpdf/QPDFObjectHandle.hh>
+
+#include "qpdf/QIntC.hh"
+#include <limits>
+
+// A table of objects indexed by object id. This is intended as a more efficient replacement for
+// std::map<QPDFObjGen, T> containers.
+//
+// The table is implemented as a std::vector, with the object id implicitly represented by the index
+// of the object. This has a number of implications, including:
+// - operations that change the index of existing elements such as insertion and deletions are not
+//   permitted.
+// - operations that extend the table may invalidate iterators and references to objects.
+//
+// The provided overloads of the access operator[] are safe. For out of bounds access they will
+// either extend the table or throw a runtime error.
+//
+// ObjTable has a map 'sparse_elements' to deal with very sparse / extremely large object tables
+// (usually as the result of invalid dangling references). This map may contain objects not found in
+// the xref table of the original pdf if there are dangling references with an id significantly
+// larger than the largest valid object id found in original pdf.
+
+template <class T>
+class ObjTable: public std::vector<T>
+{
+  public:
+    ObjTable() = default;
+    ObjTable(const ObjTable&) = delete;
+    ObjTable(ObjTable&&) = delete;
+    ObjTable& operator[](const ObjTable&) = delete;
+    ObjTable& operator[](ObjTable&&) = delete;
+
+    // Remove unchecked access.
+    T& operator[](unsigned long idx) = delete;
+    T const& operator[](unsigned long idx) const = delete;
+
+    inline T const&
+    operator[](int idx) const
+    {
+        return element(static_cast<size_t>(idx));
+    }
+
+    inline T const&
+    operator[](QPDFObjGen og) const
+    {
+        return element(static_cast<size_t>(og.getObj()));
+    }
+
+    inline T const&
+    operator[](QPDFObjectHandle oh) const
+    {
+        return element(static_cast<size_t>(oh.getObjectID()));
+    }
+
+    inline bool
+    contains(size_t idx) const
+    {
+        return idx < std::vector<T>::size() || sparse_elements.count(idx);
+    }
+
+    inline bool
+    contains(QPDFObjectHandle oh) const
+    {
+        return contains(static_cast<size_t>(oh.getObjectID()));
+    }
+
+  protected:
+    inline T&
+    operator[](int id)
+    {
+        return element(static_cast<size_t>(id));
+    }
+
+    inline T&
+    operator[](QPDFObjGen og)
+    {
+        return element(static_cast<size_t>(og.getObj()));
+    }
+
+    inline T&
+    operator[](QPDFObjectHandle oh)
+    {
+        return element(static_cast<size_t>(oh.getObjectID()));
+    }
+
+    inline T&
+    operator[](unsigned int id)
+    {
+        return element(id);
+    }
+
+    void
+    initialize(size_t idx)
+    {
+        if (std::vector<T>::size() > 0 || sparse_elements.size() > 0) {
+            throw ::std::logic_error("ObjTable accessed before initialization");
+        } else if (
+            idx >= static_cast<size_t>(std::numeric_limits<int>::max()) ||
+            idx >= std::vector<T>::max_size()) {
+            throw std::runtime_error("Invalid maximum object id initializing ObjTable.");
+        } else {
+            std::vector<T>::resize(++idx);
+        }
+    }
+
+    inline void
+    forEach(std::function<void(int, const T&)> fn)
+    {
+        int i = 0;
+        for (auto const& item: *this) {
+            fn(i++, item);
+        }
+        for (auto const& [id, item]: sparse_elements) {
+            fn(QIntC::to_int(id), item);
+        }
+    }
+
+  private:
+    std::map<size_t, T> sparse_elements;
+
+    inline T&
+    element(size_t idx)
+    {
+        if (idx < std::vector<T>::size()) {
+            return std::vector<T>::operator[](idx);
+        } else if (idx < static_cast<size_t>(std::numeric_limits<int>::max())) {
+            return sparse_elements[idx];
+        }
+        throw std::runtime_error("Invalid object id accessing ObjTable.");
+        return element(0); // doesn't return
+    }
+
+    inline T const&
+    element(size_t idx) const
+    {
+        if (idx < std::vector<T>::size()) {
+            return std::vector<T>::operator[](idx);
+        } else if (idx < static_cast<size_t>(std::numeric_limits<int>::max())) {
+            return sparse_elements.at(idx);
+        }
+        throw std::runtime_error("Invalid object id accessing ObjTable.");
+        return element(0); // doesn't return
+    }
+};
+
+#endif // OBJTABLE_HH
+#ifndef QPDFWRITER_PRIVATE_HH
+#define QPDFWRITER_PRIVATE_HH
+
+#include <qpdf/QPDFWriter.hh>
+
+#include <qpdf/ObjTable.hh>
+
+// This file is intended for inclusion by QPDFWriter, QPDF, QPDF_optimization and QPDF_linearization
+// only.
+
+struct QPDFWriter::Object
+{
+    int renumber{0};
+    int gen{0};
+    int object_stream{0};
+};
+
+struct QPDFWriter::NewObject
+{
+    QPDFXRefEntry xref;
+    qpdf_offset_t length{0};
+};
+
+class QPDFWriter::ObjTable: public ::ObjTable<QPDFWriter::Object>
+{
+    friend class QPDFWriter;
+
+  public:
+    bool
+    getStreamsEmpty() const noexcept
+    {
+        return streams_empty;
+    }
+
+  private:
+    // For performance, set by QPDFWriter rather than tracked by ObjTable.
+    bool streams_empty{false};
+};
+
+class QPDFWriter::NewObjTable: public ::ObjTable<QPDFWriter::NewObject>
+{
+    friend class QPDFWriter;
+};
+
+class QPDFWriter::Members
+{
+    friend class QPDFWriter;
+
+  public:
+    QPDF_DLL
+    ~Members();
+
+  private:
+    Members(QPDF& pdf);
+    Members(Members const&) = delete;
+
+    QPDF& pdf;
+    QPDFObjGen root_og{-1, 0};
+    char const* filename{"unspecified"};
+    FILE* file{nullptr};
+    bool close_file{false};
+    Pl_Buffer* buffer_pipeline{nullptr};
+    Buffer* output_buffer{nullptr};
+    bool normalize_content_set{false};
+    bool normalize_content{false};
+    bool compress_streams{true};
+    bool compress_streams_set{false};
+    qpdf_stream_decode_level_e stream_decode_level{qpdf_dl_none};
+    bool stream_decode_level_set{false};
+    bool recompress_flate{false};
+    bool qdf_mode{false};
+    bool preserve_unreferenced_objects{false};
+    bool newline_before_endstream{false};
+    bool static_id{false};
+    bool suppress_original_object_ids{false};
+    bool direct_stream_lengths{true};
+    bool encrypted{false};
+    bool preserve_encryption{true};
+    bool linearized{false};
+    bool pclm{false};
+    qpdf_object_stream_e object_stream_mode{qpdf_o_preserve};
+    std::string encryption_key;
+    bool encrypt_metadata{true};
+    bool encrypt_use_aes{false};
+    std::map<std::string, std::string> encryption_dictionary;
+    int encryption_V{0};
+    int encryption_R{0};
+
+    std::string id1; // for /ID key of
+    std::string id2; // trailer dictionary
+    std::string final_pdf_version;
+    int final_extension_level{0};
+    std::string min_pdf_version;
+    int min_extension_level{0};
+    std::string forced_pdf_version;
+    int forced_extension_level{0};
+    std::string extra_header_text;
+    int encryption_dict_objid{0};
+    std::string cur_data_key;
+    std::list<std::shared_ptr<Pipeline>> to_delete;
+    Pl_Count* pipeline{nullptr};
+    std::vector<QPDFObjectHandle> object_queue;
+    size_t object_queue_front{0};
+    QPDFWriter::ObjTable obj;
+    QPDFWriter::NewObjTable new_obj;
+    int next_objid{1};
+    int cur_stream_length_id{0};
+    size_t cur_stream_length{0};
+    bool added_newline{false};
+    size_t max_ostream_index{0};
+    std::set<QPDFObjGen> normalized_streams;
+    std::map<QPDFObjGen, int> page_object_to_seq;
+    std::map<QPDFObjGen, int> contents_to_page_seq;
+    std::map<int, std::vector<QPDFObjGen>> object_stream_to_objects;
+    std::list<Pipeline*> pipeline_stack;
+    unsigned long long next_stack_id{0};
+    bool deterministic_id{false};
+    Pl_MD5* md5_pipeline{nullptr};
+    std::string deterministic_id_data;
+    bool did_write_setup{false};
+
+    // For linearization only
+    std::string lin_pass1_filename;
+
+    // For progress reporting
+    std::shared_ptr<QPDFWriter::ProgressReporter> progress_reporter;
+    int events_expected{0};
+    int events_seen{0};
+    int next_progress_report{0};
+};
+
+#endif // QPDFWRITER_PRIVATE_HH
@@ -23,6 +23,7 @@ set(TEST_PROGRAMS
   md5
   nntree
   numrange
+  obj_table
   pdf_version
   pl_function
   pointer_holder
+#include <qpdf/ObjTable.hh>
+
+struct Test
+{
+    int value{0};
+};
+
+class Table: public ObjTable<Test>
+{
+  public:
+    Table()
+    {
+        initialize(5);
+    }
+
+    void
+    test()
+    {
+        for (int i = 0; i < 10; ++i) {
+            (*this)[i].value = 2 * i;
+            (*this)[1000 + i].value = 2 * (1000 + i);
+        }
+
+        forEach([](auto i, auto const& item) -> void {
+            std::cout << std::to_string(i) << " : " << std::to_string(item.value) << "\n";
+        });
+
+        std::cout << "2000 : " << std::to_string((*this)[2000].value) << "\n";
+    }
+};
+
+int
+main()
+{
+    Table().test();
+
+    std::cout << "object table tests done\n";
+    return 0;
+}
+#!/usr/bin/env perl
+require 5.008;
+use warnings;
+use strict;
+
+chdir("obj_table") or die "chdir testdir failed: $!\n";
+
+require TestDriver;
+
+my $td = new TestDriver('object table');
+
+$td->runtest("obj_table",
+             {$td->COMMAND => "obj_table"},
+             {$td->FILE => "obj_table.out",
+                  $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
+
+$td->report(1);
+0 : 0
+1 : 2
+2 : 4
+3 : 6
+4 : 8
+5 : 10
+6 : 12
+7 : 14
+8 : 16
+9 : 18
+1000 : 2000
+1001 : 2002
+1002 : 2004
+1003 : 2006
+1004 : 2008
+1005 : 2010
+1006 : 2012
+1007 : 2014
+1008 : 2016
+1009 : 2018
+2000 : 0
+object table tests done