From e5f504b6c5dc34337cc0b316b4a7b1fca7e614b1 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Sat, 17 Aug 2019 22:13:37 -0400
Subject: [PATCH] Use SparseOHArray in QPDF_Array

---
 include/qpdf/QPDFObjectHandle.hh |  5 +++-
 libqpdf/QPDF_Array.cc            | 47 +++++++++++++++-----------------
 libqpdf/qpdf/QPDF_Array.hh       |  5 ++--
 3 files changed, 29 insertions(+), 28 deletions(-)

diff --git a/include/qpdf/QPDFObjectHandle.hh b/include/qpdf/QPDFObjectHandle.hh
index ad542c09..4f18cbda 100644
--- a/include/qpdf/QPDFObjectHandle.hh
+++ b/include/qpdf/QPDFObjectHandle.hh
@@ -544,6 +544,10 @@ class QPDFObjectHandle
     int getArrayNItems();
     QPDF_DLL
     QPDFObjectHandle getArrayItem(int n);
+    // Note: QPDF arrays internally optimize memory for arrays
+    // containing lots of nulls. Calling getArrayAsVector may cause a
+    // lot of memory to be allocated for very large arrays with lots
+    // of nulls.
     QPDF_DLL
     std::vector<QPDFObjectHandle> getArrayAsVector();
     QPDF_DLL
@@ -932,7 +936,6 @@ class QPDFObjectHandle
     class ReleaseResolver
     {
 	friend class QPDF_Dictionary;
-	friend class QPDF_Array;
         friend class QPDF_Stream;
         friend class SparseOHArray;
       private:
diff --git a/libqpdf/QPDF_Array.cc b/libqpdf/QPDF_Array.cc
index a912b2bd..45635f8a 100644
--- a/libqpdf/QPDF_Array.cc
+++ b/libqpdf/QPDF_Array.cc
@@ -8,6 +8,11 @@ QPDF_Array::QPDF_Array(std::vector<QPDFObjectHandle> const& v)
     setFromVector(v);
 }
 
+QPDF_Array::QPDF_Array(SparseOHArray const& items) :
+    elements(items)
+{
+}
+
 QPDF_Array::~QPDF_Array()
 {
 }
@@ -15,21 +20,17 @@ QPDF_Array::~QPDF_Array()
 void
 QPDF_Array::releaseResolved()
 {
-    for (std::vector<QPDFObjectHandle>::iterator iter = this->items.begin();
-	 iter != this->items.end(); ++iter)
-    {
-	QPDFObjectHandle::ReleaseResolver::releaseResolved(*iter);
-    }
+    this->elements.releaseResolved();
 }
 
 std::string
 QPDF_Array::unparse()
 {
     std::string result = "[ ";
-    size_t size = this->items.size();
+    size_t size = this->elements.size();
     for (size_t i = 0; i < size; ++i)
     {
-	result += this->items.at(i).unparse();
+	result += this->elements.at(i).unparse();
 	result += " ";
     }
     result += "]";
@@ -40,10 +41,10 @@ JSON
 QPDF_Array::getJSON()
 {
     JSON j = JSON::makeArray();
-    size_t size = this->items.size();
+    size_t size = this->elements.size();
     for (size_t i = 0; i < size; ++i)
     {
-        j.addArrayElement(this->items.at(i).getJSON());
+        j.addArrayElement(this->elements.at(i).getJSON());
     }
     return j;
 }
@@ -71,46 +72,44 @@ QPDF_Array::getNItems() const
 {
     // This should really return a size_t, but changing it would break
     // a lot of code.
-    return QIntC::to_int(this->items.size());
+    return QIntC::to_int(this->elements.size());
 }
 
 QPDFObjectHandle
 QPDF_Array::getItem(int n) const
 {
-    if ((n < 0) || (n >= QIntC::to_int(this->items.size())))
+    if ((n < 0) || (n >= QIntC::to_int(elements.size())))
     {
 	throw std::logic_error(
 	    "INTERNAL ERROR: bounds error accessing QPDF_Array element");
     }
-    return this->items.at(QIntC::to_size(n));
+    return this->elements.at(QIntC::to_size(n));
 }
 
 void
 QPDF_Array::getAsVector(std::vector<QPDFObjectHandle>& v) const
 {
-    size_t size = this->items.size();
+    size_t size = this->elements.size();
     for (size_t i = 0; i < size; ++i)
     {
-        v.push_back(this->items.at(i));
+        v.push_back(this->elements.at(i));
     }
 }
 
 void
 QPDF_Array::setItem(int n, QPDFObjectHandle const& oh)
 {
-    // Call getItem for bounds checking
-    (void) getItem(n);
-    this->items.at(QIntC::to_size(n)) = oh;
+    this->elements.setAt(QIntC::to_size(n), oh);
 }
 
 void
 QPDF_Array::setFromVector(std::vector<QPDFObjectHandle> const& v)
 {
-    this->items.clear();
+    this->elements = SparseOHArray();
     for (std::vector<QPDFObjectHandle>::const_iterator iter = v.begin();
          iter != v.end(); ++iter)
     {
-        this->items.push_back(*iter);
+        this->elements.append(*iter);
     }
 }
 
@@ -118,24 +117,22 @@ void
 QPDF_Array::insertItem(int at, QPDFObjectHandle const& item)
 {
     // As special case, also allow insert beyond the end
-    if ((at < 0) || (at > QIntC::to_int(this->items.size())))
+    if ((at < 0) || (at > QIntC::to_int(this->elements.size())))
     {
 	throw std::logic_error(
 	    "INTERNAL ERROR: bounds error accessing QPDF_Array element");
     }
-    this->items.insert(this->items.begin() + at, item);
+    this->elements.insert(QIntC::to_size(at), item);
 }
 
 void
 QPDF_Array::appendItem(QPDFObjectHandle const& item)
 {
-    this->items.push_back(item);
+    this->elements.append(item);
 }
 
 void
 QPDF_Array::eraseItem(int at)
 {
-    // Call getItem for bounds checking
-    (void) getItem(at);
-    this->items.erase(this->items.begin() + at);
+    this->elements.erase(QIntC::to_size(at));
 }
diff --git a/libqpdf/qpdf/QPDF_Array.hh b/libqpdf/qpdf/QPDF_Array.hh
index 4d2cb005..08a5a608 100644
--- a/libqpdf/qpdf/QPDF_Array.hh
+++ b/libqpdf/qpdf/QPDF_Array.hh
@@ -4,12 +4,13 @@
 #include <qpdf/QPDFObject.hh>
 
 #include <vector>
-#include <qpdf/QPDFObjectHandle.hh>
+#include <qpdf/SparseOHArray.hh>
 
 class QPDF_Array: public QPDFObject
 {
   public:
     QPDF_Array(std::vector<QPDFObjectHandle> const& items);
+    QPDF_Array(SparseOHArray const& items);
     virtual ~QPDF_Array();
     virtual std::string unparse();
     virtual JSON getJSON();
@@ -31,7 +32,7 @@ class QPDF_Array: public QPDFObject
     virtual void releaseResolved();
 
   private:
-    std::vector<QPDFObjectHandle> items;
+    SparseOHArray elements;
 };
 
 #endif // QPDF_ARRAY_HH