Reland "Introduce FX_Number class as a replacement for FX_atonum()."

This reverts commit 29e180342e18873babf1c74f7c5c056f90a191b0.

Reason for revert: probably harmless

Original change's description:
> Revert "Introduce FX_Number class as a replacement for FX_atonum()."
>
> This reverts commit a5d7ad3aa8feb08a14b5cca173d673054c1ade23.
>
> Reason for revert: Speculative revert to get back before flake.
>
> Original change's description:
> > 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>
>
> TBR=thestig@chromium.org,tsepez@chromium.org
>
> Change-Id: Ia56270c3daa80408fc2b23eb4384a77f03f45b82
> Reviewed-on: https://pdfium-review.googlesource.com/42392
> Reviewed-by: Tom Sepez <tsepez@chromium.org>
> Commit-Queue: Tom Sepez <tsepez@chromium.org>

TBR=thestig@chromium.org,tsepez@chromium.org

Change-Id: I83c37aa3040a8890f2117753f19ab1d452d411e7
Reviewed-on: https://pdfium-review.googlesource.com/42410
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/core/fxcrt/fx_number.h b/core/fxcrt/fx_number.h
new file mode 100644
index 0000000000..4c789b4130
--- /dev/null
+++ b/core/fxcrt/fx_number.h
@@ -0,0 +1,39 @@
+// Copyright 2018 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#ifndef CORE_FXCRT_FX_NUMBER_H_
+#define CORE_FXCRT_FX_NUMBER_H_
+
+#include <stdint.h>
+
+#include "core/fxcrt/bytestring.h"
+
+class FX_Number {
+ public:
+  FX_Number();
+  explicit FX_Number(uint32_t value);
+  explicit FX_Number(int32_t value);
+  explicit FX_Number(float value);
+  explicit FX_Number(const ByteStringView& str);
+
+  bool IsInteger() const { return m_bInteger; }
+  bool IsSigned() const { return m_bSigned; }
+
+  uint32_t GetUnsigned() const;  // Underflow possible.
+  int32_t GetSigned() const;     // Underflow/Overflow possible.
+  float GetFloat() const;
+
+ private:
+  bool m_bInteger;  // One of the two integers vs. float type.
+  bool m_bSigned;   // Only valid if |m_bInteger|.
+  union {
+    uint32_t m_UnsignedValue;
+    int32_t m_SignedValue;
+    float m_FloatValue;
+  };
+};
+
+#endif  // CORE_FXCRT_FX_NUMBER_H_