Introduce FX_Number class as a replacement for FX_atonum().

The issue with FX_atonum() is that it doesn't return any information
about whether it range-checked its integer values as a signed or
unsigned type, even though it knows this as part of its processing.

Rather than adding another out parameter to that function, create
a class to hold all this information together.

This is the first place things went astray while diagnosing
bug 882959, in that a large positive value was cast to float as a
negative value. Unfortunately, this doesn't affect the related bug,
but is a step in the right direction.

Change-Id: I0977ec8fccf85e2632a962507bdd30a1cbe6d33c
Reviewed-on: https://pdfium-review.googlesource.com/42353
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

2 files changed, 16 insertions, 19 deletions

diff --git a/core/fpdfapi/parser/cpdf_number.cpp b/core/fpdfapi/parser/cpdf_number.cpp
index b75ce0766a..23c2609e25 100644
--- a/core/fpdfapi/parser/cpdf_number.cpp
+++ b/core/fpdfapi/parser/cpdf_number.cpp
@@ -8,14 +8,13 @@
 #include "core/fxcrt/fx_stream.h"
 #include "third_party/base/ptr_util.h"
 
-CPDF_Number::CPDF_Number() : m_bInteger(true), m_Integer(0) {}
+CPDF_Number::CPDF_Number() {}
 
-CPDF_Number::CPDF_Number(int value) : m_bInteger(true), m_Integer(value) {}
+CPDF_Number::CPDF_Number(int value) : m_Number(value) {}
 
-CPDF_Number::CPDF_Number(float value) : m_bInteger(false), m_Float(value) {}
+CPDF_Number::CPDF_Number(float value) : m_Number(value) {}
 
-CPDF_Number::CPDF_Number(const ByteStringView& str)
-    : m_bInteger(FX_atonum(str, &m_Integer)) {}
+CPDF_Number::CPDF_Number(const ByteStringView& str) : m_Number(str) {}
 
 CPDF_Number::~CPDF_Number() {}
 
@@ -24,16 +23,17 @@ CPDF_Object::Type CPDF_Number::GetType() const {
 }
 
 std::unique_ptr<CPDF_Object> CPDF_Number::Clone() const {
-  return m_bInteger ? pdfium::MakeUnique<CPDF_Number>(m_Integer)
-                    : pdfium::MakeUnique<CPDF_Number>(m_Float);
+  return m_Number.IsInteger()
+             ? pdfium::MakeUnique<CPDF_Number>(m_Number.GetSigned())
+             : pdfium::MakeUnique<CPDF_Number>(m_Number.GetFloat());
 }
 
 float CPDF_Number::GetNumber() const {
-  return m_bInteger ? static_cast<float>(m_Integer) : m_Float;
+  return m_Number.GetFloat();
 }
 
 int CPDF_Number::GetInteger() const {
-  return m_bInteger ? m_Integer : static_cast<int>(m_Float);
+  return m_Number.GetSigned();
 }
 
 bool CPDF_Number::IsNumber() const {
@@ -49,12 +49,12 @@ const CPDF_Number* CPDF_Number::AsNumber() const {
 }
 
 void CPDF_Number::SetString(const ByteString& str) {
-  m_bInteger = FX_atonum(str.AsStringView(), &m_Integer);
+  m_Number = FX_Number(str.AsStringView());
 }
 
 ByteString CPDF_Number::GetString() const {
-  return m_bInteger ? ByteString::FormatInteger(m_Integer)
-                    : ByteString::FormatFloat(m_Float);
+  return m_Number.IsInteger() ? ByteString::FormatInteger(m_Number.GetSigned())
+                              : ByteString::FormatFloat(m_Number.GetFloat());
 }
 
 bool CPDF_Number::WriteTo(IFX_ArchiveStream* archive,
diff --git a/core/fpdfapi/parser/cpdf_number.h b/core/fpdfapi/parser/cpdf_number.h
index b5faf82bb2..724ae9f1f1 100644
--- a/core/fpdfapi/parser/cpdf_number.h
+++ b/core/fpdfapi/parser/cpdf_number.h
@@ -10,6 +10,7 @@
 #include <memory>
 
 #include "core/fpdfapi/parser/cpdf_object.h"
+#include "core/fxcrt/fx_number.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
 
@@ -34,14 +35,10 @@ class CPDF_Number final : public CPDF_Object {
   bool WriteTo(IFX_ArchiveStream* archive,
                const CPDF_Encryptor* encryptor) const override;
 
-  bool IsInteger() const { return m_bInteger; }
+  bool IsInteger() const { return m_Number.IsInteger(); }
 
- protected:
-  bool m_bInteger;
-  union {
-    int m_Integer;
-    float m_Float;
-  };
+ private:
+  FX_Number m_Number;
 };
 
 inline CPDF_Number* ToNumber(CPDF_Object* obj) {