Refactor Xref_table::Entry

Replace QPDFXRefEntry with a std::variant of structs.

Refactor Xref_table::Entry
Replace QPDFXRefEntry with a std::variant of structs.
m-holger
1 parent 6b9eb14c
Showing 2 changed files with 107 additions and 43 deletions
libqpdf/QPDF.cc
libqpdf/qpdf/QPDF_private.hh
@@ -574,7 +574,7 @@ QPDF::Xref_table::reconstruct(QPDFExc&amp; e)
     // Delete all references to type 1 (uncompressed) objects
     for (auto& iter: table) {
-        if (iter.entry.getType() == 1) {
+        if (iter.type() == 1) {
             iter = {};
         }
     }
@@ -638,12 +638,12 @@ QPDF::Xref_table::reconstruct(QPDFExc&amp; e)
         qpdf_offset_t max_offset{0};
         // If there are any xref streams, take the last one to appear.
         int i = -1;
-        for (auto const& [gen, entry]: table) {
+        for (auto const& item: table) {
             ++i;
-            if (entry.getType() != 1) {
+            if (item.type() != 1) {
                 continue;
             }
-            auto oh = qpdf.getObject(i, gen);
+            auto oh = qpdf.getObject(i, item.gen());
             try {
                 if (!oh.isStreamOfType("/XRef")) {
                     continue;
@@ -651,7 +651,7 @@ QPDF::Xref_table::reconstruct(QPDFExc&amp; e)
             } catch (std::exception&) {
                 continue;
             }
-            auto offset = entry.getOffset();
+            auto offset = item.offset();
             if (offset > max_offset) {
                 max_offset = offset;
                 trailer_ = oh.getDict();
@@ -1334,9 +1334,9 @@ QPDF::Xref_table::insert(int obj, int f0, qpdf_offset_t f1, int f2)
     }
     auto& entry = table[static_cast<size_t>(obj)];
-    auto old_type = entry.entry.getType();
+    auto old_type = entry.type();
-    if (!old_type && entry.gen > 0) {
+    if (!old_type && entry.gen() > 0) {
         // At the moment we are processing the updates last to first and therefore the gen doesn't
         // matter as long as it > 0 to distinguish it from an uninitialized entry. This will need
         // to be revisited when we want to support incremental updates or more comprhensive
@@ -1351,7 +1351,7 @@ QPDF::Xref_table::insert(int obj, int f0, qpdf_offset_t f1, int f2)
         return;
     }
-    if (old_type && entry.gen >= new_gen) {
+    if (old_type && entry.gen() >= new_gen) {
         QTC::TC("qpdf", "QPDF xref reused object");
         return;
     }
@@ -1360,11 +1360,11 @@ QPDF::Xref_table::insert(int obj, int f0, qpdf_offset_t f1, int f2)
     case 1:
         // f2 is generation
         QTC::TC("qpdf", "QPDF xref gen > 0", (f2 > 0) ? 1 : 0);
-        entry = {f2, QPDFXRefEntry(f1)};
+        entry = {f2, Uncompressed(f1)};
         break;
     case 2:
-        entry = {0, QPDFXRefEntry(toI(f1), f2)};
+        entry = {0, Compressed(toI(f1), f2)};
         break;
     default:
@@ -1400,19 +1400,18 @@ QPDF::Xref_table::show()
 {
     auto& cout = *qpdf.m->log->getInfo();
     int i = -1;
-    for (auto const& [gen, entry]: table) {
+    for (auto const& item: table) {
         ++i;
-        auto type = entry.getType();
-        if (type) {
-            cout << std::to_string(i) << "/" << std::to_string(gen) << ": ";
-            switch (type) {
+        if (item.type()) {
+            cout << std::to_string(i) << "/" << std::to_string(item.gen()) << ": ";
+            switch (item.type()) {
             case 1:
-                cout << "uncompressed; offset = " << entry.getOffset() << "\n";
+                cout << "uncompressed; offset = " << item.offset() << "\n";
                 break;
             case 2:
-                cout << "compressed; stream = " << entry.getObjStreamNumber()
-                     << ", index = " << entry.getObjStreamIndex() << "\n";
+                cout << "compressed; stream = " << item.stream_number()
+                     << ", index = " << item.stream_index() << "\n";
                 break;
             default:
@@ -1430,11 +1429,11 @@ QPDF::Xref_table::resolve()
 {
     bool may_change = !reconstructed_;
     int i = -1;
-    for (auto& iter: table) {
+    for (auto& item: table) {
         ++i;
-        if (iter.entry.getType()) {
-            if (qpdf.isUnresolved(QPDFObjGen(i, iter.gen))) {
-                qpdf.resolve(QPDFObjGen(i, iter.gen));
+        if (item.type()) {
+            if (qpdf.isUnresolved(QPDFObjGen(i, item.gen()))) {
+                qpdf.resolve(QPDFObjGen(i, item.gen()));
                 if (may_change && reconstructed_) {
                     return false;
                 }
@@ -3,6 +3,8 @@
 #include <qpdf/QPDF.hh>
+#include <variant>
+
 // Xref_table encapsulates the pdf's xref table and trailer.
 class QPDF::Xref_table
 {
@@ -34,54 +36,55 @@ class QPDF::Xref_table
     }
     // Returns 0 if og is not in table.
-    int
+    size_t
     type(QPDFObjGen og) const
     {
-        if (og.getObj() >= toI(table.size())) {
+        int id = og.getObj();
+        if (id < 1 || static_cast<size_t>(id) >= table.size()) {
             return 0;
         }
-        auto& e = table.at(toS(og.getObj()));
-        return e.gen == og.getGen() ? e.entry.getType() : 0;
+        auto& e = table[static_cast<size_t>(id)];
+        return e.gen() == og.getGen() ? e.type() : 0;
     }
     // Returns 0 if og is not in table.
-    int
-    type(size_t id) const
+    size_t
+    type(size_t id) const noexcept
     {
         if (id >= table.size()) {
             return 0;
         }
-        return table[id].entry.getType();
+        return table[id].type();
     }
     // Returns 0 if og is not in table.
     qpdf_offset_t
-    offset(QPDFObjGen og) const
+    offset(QPDFObjGen og) const noexcept
     {
-        if (og.getObj() >= toI(table.size())) {
+        int id = og.getObj();
+        if (id < 1 || static_cast<size_t>(id) >= table.size()) {
             return 0;
         }
-        auto& e = table.at(toS(og.getObj()));
-        return e.gen == og.getGen() ? e.entry.getOffset() : 0;
+        return table[static_cast<size_t>(id)].offset();
     }
-    // Returns 0 if og is not in table.
+    // Returns 0 if id is not in table.
     int
-    stream_number(int id) const
+    stream_number(int id) const noexcept
     {
         if (id < 1 || static_cast<size_t>(id) >= table.size()) {
             return 0;
         }
-        return table[static_cast<size_t>(id)].entry.getObjStreamNumber();
+        return table[static_cast<size_t>(id)].stream_number();
     }
     int
-    stream_index(int id) const
+    stream_index(int id) const noexcept
     {
         if (id < 1 || static_cast<size_t>(id) >= table.size()) {
             return 0;
         }
-        return table[static_cast<size_t>(id)].entry.getObjStreamIndex();
+        return table[static_cast<size_t>(id)].stream_index();
     }
     // Temporary access to underlying map
@@ -90,9 +93,19 @@ class QPDF::Xref_table
     {
         std::map<QPDFObjGen, QPDFXRefEntry> result;
         int i{0};
-        for (auto const& [gen, entry]: table) {
-            if (entry.getType()) {
-                result.emplace(QPDFObjGen(i, gen), entry);
+        for (auto const& item: table) {
+            switch (item.type()) {
+            case 0:
+                break;
+            case 1:
+                result.emplace(QPDFObjGen(i, item.gen()), item.offset());
+                break;
+            case 2:
+                result.emplace(
+                    QPDFObjGen(i, 0), QPDFXRefEntry(item.stream_number(), item.stream_index()));
+                break;
+            default:
+                throw std::logic_error("Xref_table: invalid entry type");
             }
             ++i;
         }
@@ -149,10 +162,62 @@ class QPDF::Xref_table
     // Object, count, offset of first entry
     typedef std::tuple<int, int, qpdf_offset_t> Subsection;
+    struct Uncompressed
+    {
+        Uncompressed(qpdf_offset_t offset) :
+            offset(offset)
+        {
+        }
+        qpdf_offset_t offset;
+    };
+
+    struct Compressed
+    {
+        Compressed(int stream_number, int stream_index) :
+            stream_number(stream_number),
+            stream_index(stream_index)
+        {
+        }
+        int stream_number{0};
+        int stream_index{0};
+    };
+
+    typedef std::variant<std::monostate, Uncompressed, Compressed> Xref;
+
     struct Entry
     {
-        int gen{0};
-        QPDFXRefEntry entry;
+        int
+        gen() const noexcept
+        {
+            return gen_;
+        }
+
+        size_t
+        type() const noexcept
+        {
+            return entry.index();
+        }
+
+        qpdf_offset_t
+        offset() const noexcept
+        {
+            return type() == 1 ? std::get<1>(entry).offset : 0;
+        }
+
+        int
+        stream_number() const noexcept
+        {
+            return type() == 2 ? std::get<2>(entry).stream_number : 0;
+        }
+
+        int
+        stream_index() const noexcept
+        {
+            return type() == 2 ? std::get<2>(entry).stream_index : 0;
+        }
+
+        int gen_{0};
+        Xref entry;
     };
     void read(qpdf_offset_t offset);