LibPDF: Parse nested Page Tree structures

We now follow nested page tree nodes to find all of the actual
page dicts, whereas previously we just assumed the root level
page tree node contained all of the page children directly.

1 files changed, 46 insertions, 2 deletions

diff --git a/Userland/Libraries/LibPDF/Parser.cpp b/Userland/Libraries/LibPDF/Parser.cpp
index eb37bf47d7..2e7d5ab57e 100644
--- a/Userland/Libraries/LibPDF/Parser.cpp
+++ b/Userland/Libraries/LibPDF/Parser.cpp
@@ -363,14 +363,14 @@ Value Parser::parse_number()
         }
     }
 
+    consume_whitespace();
+
     auto string = String(m_reader.bytes().slice(start_offset, m_reader.offset() - start_offset));
     float f = strtof(string.characters(), nullptr);
     if (is_float)
         return Value(f);
 
     VERIFY(floorf(f) == f);
-    consume_whitespace();
-
     return Value(static_cast<int>(f));
 }
 
@@ -567,6 +567,50 @@ NonnullRefPtr<DictObject> Parser::parse_dict()
     return make_object<DictObject>(map);
 }
 
+RefPtr<DictObject> Parser::conditionally_parse_page_tree_node_at_offset(size_t offset)
+{
+    m_reader.move_to(offset);
+    parse_number();
+    parse_number();
+    VERIFY(m_reader.matches("obj"));
+    m_reader.move_by(3);
+    consume_whitespace();
+
+    consume('<');
+    consume('<');
+    consume_whitespace();
+    HashMap<FlyString, Value> map;
+
+    while (true) {
+        if (m_reader.matches(">>"))
+            break;
+        auto name = parse_name();
+        auto name_string = name->name();
+        if (!name_string.is_one_of("Type", "Parent", "Kids", "Count")) {
+            // This is a page, not a page tree node
+            return {};
+        }
+        auto value = parse_value();
+        if (name_string == "Type") {
+            if (!value.is_object())
+                return {};
+            auto type_object = value.as_object();
+            if (!type_object->is_name())
+                return {};
+            auto type_name = object_cast<NameObject>(type_object);
+            if (type_name->name() != "Pages")
+                return {};
+        }
+        map.set(name->name(), value);
+    }
+
+    consume('>');
+    consume('>');
+    consume_whitespace();
+
+    return make_object<DictObject>(map);
+}
+
 NonnullRefPtr<StreamObject> Parser::parse_stream(NonnullRefPtr<DictObject> dict)
 {
     VERIFY(m_reader.matches("stream"));