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
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://pdfium-review.googlesource.com/42392
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

10 files changed, 154 insertions, 342 deletions

diff --git a/core/fpdfapi/page/cpdf_streamcontentparser.cpp b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
index 20892cc264..2244232ecb 100644
--- a/core/fpdfapi/page/cpdf_streamcontentparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
@@ -338,7 +338,7 @@ void CPDF_StreamContentParser::AddNameParam(const ByteStringView& bsName) {
 void CPDF_StreamContentParser::AddNumberParam(const ByteStringView& str) {
   ContentParam& param = m_ParamBuf[GetNextParamPos()];
   param.m_Type = ContentParam::NUMBER;
-  param.m_Number = FX_Number(str);
+  param.m_Number.m_bInteger = FX_atonum(str, &param.m_Number.m_Integer);
 }
 
 void CPDF_StreamContentParser::AddObjectParam(
@@ -373,9 +373,9 @@ CPDF_Object* CPDF_StreamContentParser::GetObject(uint32_t index) {
   if (param.m_Type == ContentParam::NUMBER) {
     param.m_Type = ContentParam::OBJECT;
     param.m_pObject =
-        param.m_Number.IsInteger()
-            ? pdfium::MakeUnique<CPDF_Number>(param.m_Number.GetSigned())
-            : pdfium::MakeUnique<CPDF_Number>(param.m_Number.GetFloat());
+        param.m_Number.m_bInteger
+            ? pdfium::MakeUnique<CPDF_Number>(param.m_Number.m_Integer)
+            : pdfium::MakeUnique<CPDF_Number>(param.m_Number.m_Float);
     return param.m_pObject.get();
   }
   if (param.m_Type == ContentParam::NAME) {
@@ -411,20 +411,21 @@ ByteString CPDF_StreamContentParser::GetString(uint32_t index) const {
 }
 
 float CPDF_StreamContentParser::GetNumber(uint32_t index) const {
-  if (index >= m_ParamCount)
+  if (index >= m_ParamCount) {
     return 0;
-
+  }
   int real_index = m_ParamStartPos + m_ParamCount - index - 1;
-  if (real_index >= kParamBufSize)
+  if (real_index >= kParamBufSize) {
     real_index -= kParamBufSize;
-
+  }
   const ContentParam& param = m_ParamBuf[real_index];
-  if (param.m_Type == ContentParam::NUMBER)
-    return param.m_Number.GetFloat();
-
+  if (param.m_Type == ContentParam::NUMBER) {
+    return param.m_Number.m_bInteger
+               ? static_cast<float>(param.m_Number.m_Integer)
+               : param.m_Number.m_Float;
+  }
   if (param.m_Type == 0 && param.m_pObject)
     return param.m_pObject->GetNumber();
-
   return 0;
 }
 
@@ -1631,8 +1632,10 @@ void CPDF_StreamContentParser::ParsePathObject() {
         if (nParams == 6)
           break;
 
-        FX_Number number(m_pSyntax->GetWord());
-        params[nParams++] = number.GetFloat();
+        int value;
+        bool bInteger = FX_atonum(m_pSyntax->GetWord(), &value);
+        params[nParams++] = bInteger ? static_cast<float>(value)
+                                     : *reinterpret_cast<float*>(&value);
         break;
       }
       default:
diff --git a/core/fpdfapi/page/cpdf_streamcontentparser.h b/core/fpdfapi/page/cpdf_streamcontentparser.h
index 6417043305..a129894dba 100644
--- a/core/fpdfapi/page/cpdf_streamcontentparser.h
+++ b/core/fpdfapi/page/cpdf_streamcontentparser.h
@@ -15,7 +15,6 @@
 
 #include "core/fpdfapi/page/cpdf_contentmark.h"
 #include "core/fpdfapi/parser/cpdf_stream.h"
-#include "core/fxcrt/fx_number.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxge/cfx_pathdata.h"
 
@@ -72,7 +71,13 @@ class CPDF_StreamContentParser {
 
     Type m_Type;
     std::unique_ptr<CPDF_Object> m_pObject;
-    FX_Number m_Number;
+    struct {
+      bool m_bInteger;
+      union {
+        int m_Integer;
+        float m_Float;
+      };
+    } m_Number;
     struct {
       int m_Len;
       char m_Buffer[32];
diff --git a/core/fpdfapi/parser/cpdf_number.cpp b/core/fpdfapi/parser/cpdf_number.cpp
index 23c2609e25..b75ce0766a 100644
--- a/core/fpdfapi/parser/cpdf_number.cpp
+++ b/core/fpdfapi/parser/cpdf_number.cpp
@@ -8,13 +8,14 @@
 #include "core/fxcrt/fx_stream.h"
 #include "third_party/base/ptr_util.h"
 
-CPDF_Number::CPDF_Number() {}
+CPDF_Number::CPDF_Number() : m_bInteger(true), m_Integer(0) {}
 
-CPDF_Number::CPDF_Number(int value) : m_Number(value) {}
+CPDF_Number::CPDF_Number(int value) : m_bInteger(true), m_Integer(value) {}
 
-CPDF_Number::CPDF_Number(float value) : m_Number(value) {}
+CPDF_Number::CPDF_Number(float value) : m_bInteger(false), m_Float(value) {}
 
-CPDF_Number::CPDF_Number(const ByteStringView& str) : m_Number(str) {}
+CPDF_Number::CPDF_Number(const ByteStringView& str)
+    : m_bInteger(FX_atonum(str, &m_Integer)) {}
 
 CPDF_Number::~CPDF_Number() {}
 
@@ -23,17 +24,16 @@ CPDF_Object::Type CPDF_Number::GetType() const {
 }
 
 std::unique_ptr<CPDF_Object> CPDF_Number::Clone() const {
-  return m_Number.IsInteger()
-             ? pdfium::MakeUnique<CPDF_Number>(m_Number.GetSigned())
-             : pdfium::MakeUnique<CPDF_Number>(m_Number.GetFloat());
+  return m_bInteger ? pdfium::MakeUnique<CPDF_Number>(m_Integer)
+                    : pdfium::MakeUnique<CPDF_Number>(m_Float);
 }
 
 float CPDF_Number::GetNumber() const {
-  return m_Number.GetFloat();
+  return m_bInteger ? static_cast<float>(m_Integer) : m_Float;
 }
 
 int CPDF_Number::GetInteger() const {
-  return m_Number.GetSigned();
+  return m_bInteger ? m_Integer : static_cast<int>(m_Float);
 }
 
 bool CPDF_Number::IsNumber() const {
@@ -49,12 +49,12 @@ const CPDF_Number* CPDF_Number::AsNumber() const {
 }
 
 void CPDF_Number::SetString(const ByteString& str) {
-  m_Number = FX_Number(str.AsStringView());
+  m_bInteger = FX_atonum(str.AsStringView(), &m_Integer);
 }
 
 ByteString CPDF_Number::GetString() const {
-  return m_Number.IsInteger() ? ByteString::FormatInteger(m_Number.GetSigned())
-                              : ByteString::FormatFloat(m_Number.GetFloat());
+  return m_bInteger ? ByteString::FormatInteger(m_Integer)
+                    : ByteString::FormatFloat(m_Float);
 }
 
 bool CPDF_Number::WriteTo(IFX_ArchiveStream* archive,
diff --git a/core/fpdfapi/parser/cpdf_number.h b/core/fpdfapi/parser/cpdf_number.h
index 724ae9f1f1..b5faf82bb2 100644
--- a/core/fpdfapi/parser/cpdf_number.h
+++ b/core/fpdfapi/parser/cpdf_number.h
@@ -10,7 +10,6 @@
 #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"
 
@@ -35,10 +34,14 @@ class CPDF_Number final : public CPDF_Object {
   bool WriteTo(IFX_ArchiveStream* archive,
                const CPDF_Encryptor* encryptor) const override;
 
-  bool IsInteger() const { return m_Number.IsInteger(); }
+  bool IsInteger() const { return m_bInteger; }
 
- private:
-  FX_Number m_Number;
+ protected:
+  bool m_bInteger;
+  union {
+    int m_Integer;
+    float m_Float;
+  };
 };
 
 inline CPDF_Number* ToNumber(CPDF_Object* obj) {
diff --git a/core/fxcrt/fx_number.cpp b/core/fxcrt/fx_number.cpp
deleted file mode 100644
index 68d5bd9b32..0000000000
--- a/core/fxcrt/fx_number.cpp
+++ /dev/null
@@ -1,104 +0,0 @@
-// 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
-
-#include "core/fxcrt/fx_number.h"
-
-#include <limits>
-
-#include "core/fxcrt/fx_extension.h"
-#include "core/fxcrt/fx_string.h"
-
-FX_Number::FX_Number()
-    : m_bInteger(true), m_bSigned(false), m_UnsignedValue(0) {}
-
-FX_Number::FX_Number(uint32_t value)
-    : m_bInteger(true), m_bSigned(false), m_UnsignedValue(value) {}
-
-FX_Number::FX_Number(int32_t value)
-    : m_bInteger(true), m_bSigned(true), m_SignedValue(value) {}
-
-FX_Number::FX_Number(float value)
-    : m_bInteger(false), m_bSigned(true), m_FloatValue(value) {}
-
-FX_Number::FX_Number(const ByteStringView& strc)
-    : m_bInteger(true), m_bSigned(false), m_UnsignedValue(0) {
-  if (strc.IsEmpty())
-    return;
-
-  if (strc.Contains('.')) {
-    m_bInteger = false;
-    m_bSigned = true;
-    m_FloatValue = FX_atof(strc);
-    return;
-  }
-
-  // Note, numbers in PDF are typically of the form 123, -123, etc. But,
-  // for things like the Permissions on the encryption hash the number is
-  // actually an unsigned value. We use a uint32_t so we can deal with the
-  // unsigned and then check for overflow if the user actually signed the value.
-  // The Permissions flag is listed in Table 3.20 PDF 1.7 spec.
-  pdfium::base::CheckedNumeric<uint32_t> unsigned_val = 0;
-  bool bNegative = false;
-  size_t cc = 0;
-  if (strc[0] == '+') {
-    cc++;
-    m_bSigned = true;
-  } else if (strc[0] == '-') {
-    bNegative = true;
-    m_bSigned = true;
-    cc++;
-  }
-
-  while (cc < strc.GetLength() && std::isdigit(strc[cc])) {
-    unsigned_val = unsigned_val * 10 + FXSYS_DecimalCharToInt(strc.CharAt(cc));
-    if (!unsigned_val.IsValid())
-      break;
-    cc++;
-  }
-
-  uint32_t uValue = unsigned_val.ValueOrDefault(0);
-  if (!m_bSigned) {
-    m_UnsignedValue = uValue;
-    return;
-  }
-
-  // We have a sign, so if the value was greater then the signed integer
-  // limits, then we've overflowed and must reset to the default value.
-  constexpr uint32_t uLimit =
-      static_cast<uint32_t>(std::numeric_limits<int>::max());
-
-  if (uValue > (bNegative ? uLimit + 1 : uLimit))
-    uValue = 0;
-
-  // Switch back to the int space so we can flip to a negative if we need.
-  int32_t value = static_cast<int32_t>(uValue);
-  if (bNegative) {
-    // |value| is usually positive, except in the corner case of "-2147483648",
-    // where |uValue| is 2147483648. When it gets casted to an int, |value|
-    // becomes -2147483648. For this case, avoid undefined behavior, because
-    // an int32_t cannot represent 2147483648.
-    static constexpr int kMinInt = std::numeric_limits<int>::min();
-    m_SignedValue = LIKELY(value != kMinInt) ? -value : kMinInt;
-  } else {
-    m_SignedValue = value;
-  }
-}
-
-uint32_t FX_Number::GetUnsigned() const {
-  return m_bInteger ? m_UnsignedValue : static_cast<uint32_t>(m_FloatValue);
-}
-
-int32_t FX_Number::GetSigned() const {
-  return m_bInteger ? m_SignedValue : static_cast<int32_t>(m_FloatValue);
-}
-
-float FX_Number::GetFloat() const {
-  if (!m_bInteger)
-    return m_FloatValue;
-
-  return m_bSigned ? static_cast<float>(m_SignedValue)
-                   : static_cast<float>(m_UnsignedValue);
-}
diff --git a/core/fxcrt/fx_number.h b/core/fxcrt/fx_number.h
deleted file mode 100644
index 4c789b4130..0000000000
--- a/core/fxcrt/fx_number.h
+++ /dev/null
@@ -1,39 +0,0 @@
-// 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_
diff --git a/core/fxcrt/fx_number_unittest.cpp b/core/fxcrt/fx_number_unittest.cpp
deleted file mode 100644
index 83702dadcf..0000000000
--- a/core/fxcrt/fx_number_unittest.cpp
+++ /dev/null
@@ -1,165 +0,0 @@
-// 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.
-
-#include <limits>
-
-#include "core/fxcrt/fx_number.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-TEST(fxnumber, Default) {
-  FX_Number number;
-  EXPECT_TRUE(number.IsInteger());
-  EXPECT_FALSE(number.IsSigned());
-  EXPECT_EQ(0u, number.GetUnsigned());
-  EXPECT_EQ(0, number.GetSigned());
-  EXPECT_FLOAT_EQ(0.0f, number.GetFloat());
-}
-
-TEST(fxnumber, FromUnsigned) {
-  FX_Number number(42u);
-  EXPECT_TRUE(number.IsInteger());
-  EXPECT_FALSE(number.IsSigned());
-  EXPECT_EQ(42u, number.GetUnsigned());
-  EXPECT_EQ(42, number.GetSigned());
-  EXPECT_FLOAT_EQ(42.0f, number.GetFloat());
-
-  // Show that assignment works.
-  FX_Number number2 = number;
-  EXPECT_TRUE(number2.IsInteger());
-  EXPECT_FALSE(number2.IsSigned());
-  EXPECT_EQ(42u, number2.GetUnsigned());
-  EXPECT_EQ(42, number2.GetSigned());
-  EXPECT_FLOAT_EQ(42.0F, number2.GetFloat());
-}
-
-TEST(fxnumber, FromSigned) {
-  FX_Number number(-128);
-  EXPECT_TRUE(number.IsInteger());
-  EXPECT_TRUE(number.IsSigned());
-  EXPECT_EQ(4294967168u, number.GetUnsigned());
-  EXPECT_EQ(-128, number.GetSigned());
-  EXPECT_FLOAT_EQ(-128.0f, number.GetFloat());
-
-  // Show that assignment works.
-  FX_Number number2 = number;
-  EXPECT_TRUE(number2.IsInteger());
-  EXPECT_TRUE(number2.IsSigned());
-  EXPECT_EQ(4294967168u, number2.GetUnsigned());
-  EXPECT_EQ(-128, number2.GetSigned());
-  EXPECT_FLOAT_EQ(-128.0f, number2.GetFloat());
-}
-
-TEST(fxnumber, FromFloat) {
-  FX_Number number(-100.001f);
-  EXPECT_FALSE(number.IsInteger());
-  EXPECT_TRUE(number.IsSigned());
-  EXPECT_EQ(4294967196u, number.GetUnsigned());
-  EXPECT_EQ(-100, number.GetSigned());
-  EXPECT_FLOAT_EQ(-100.001f, number.GetFloat());
-
-  // Show that assignment works.
-  FX_Number number2 = number;
-  EXPECT_FALSE(number2.IsInteger());
-  EXPECT_TRUE(number2.IsSigned());
-  EXPECT_EQ(4294967196u, number2.GetUnsigned());
-  EXPECT_EQ(-100, number2.GetSigned());
-  EXPECT_FLOAT_EQ(-100.001f, number2.GetFloat());
-}
-
-TEST(fxnumber, FromStringUnsigned) {
-  {
-    FX_Number number("");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_FALSE(number.IsSigned());
-    EXPECT_EQ(0u, number.GetUnsigned());
-  }
-  {
-    FX_Number number("0");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_FALSE(number.IsSigned());
-    EXPECT_EQ(0u, number.GetUnsigned());
-  }
-  {
-    FX_Number number("10");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_FALSE(number.IsSigned());
-    EXPECT_EQ(10u, number.GetUnsigned());
-  }
-  {
-    FX_Number number("4294967295");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_FALSE(number.IsSigned());
-    EXPECT_EQ(std::numeric_limits<uint32_t>::max(), number.GetUnsigned());
-  }
-  {
-    // Value overflows.
-    FX_Number number("4223423494965252");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_FALSE(number.IsSigned());
-    EXPECT_EQ(0u, number.GetUnsigned());
-  }
-  {
-    // No explicit sign will allow the number to go negative if we retrieve
-    // it as a signed value. This is needed for things like the encryption
-    // Permissions flag (Table 3.20 PDF 1.7 spec)
-    FX_Number number("4294965252");
-    EXPECT_EQ(-2044, number.GetSigned());
-  }
-}
-
-TEST(fxnumber, FromStringSigned) {
-  {
-    FX_Number number("-0");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_TRUE(number.IsSigned());
-    EXPECT_EQ(0, number.GetSigned());
-  }
-  {
-    FX_Number number("+0");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_TRUE(number.IsSigned());
-    EXPECT_EQ(0, number.GetSigned());
-  }
-  {
-    FX_Number number("-10");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_TRUE(number.IsSigned());
-    EXPECT_EQ(-10, number.GetSigned());
-  }
-  {
-    FX_Number number("+10");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_TRUE(number.IsSigned());
-    EXPECT_EQ(10, number.GetSigned());
-  }
-  {
-    FX_Number number("-2147483648");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_TRUE(number.IsSigned());
-    EXPECT_EQ(std::numeric_limits<int32_t>::min(), number.GetSigned());
-  }
-  {
-    FX_Number number("+2147483647");
-    EXPECT_TRUE(number.IsInteger());
-    EXPECT_TRUE(number.IsSigned());
-    EXPECT_EQ(std::numeric_limits<int32_t>::max(), number.GetSigned());
-  }
-  {
-    // Value underflows.
-    FX_Number number("-2147483649");
-    EXPECT_EQ(0u, number.GetUnsigned());
-    EXPECT_EQ(0, number.GetSigned());
-  }
-  {
-    // Value overflows.
-    FX_Number number("+2147483648");
-    EXPECT_EQ(0u, number.GetUnsigned());
-    EXPECT_EQ(0, number.GetSigned());
-  }
-}
-
-TEST(fxnumber, FromStringFloat) {
-  FX_Number number("3.24");
-  EXPECT_FLOAT_EQ(3.24f, number.GetFloat());
-}
diff --git a/core/fxcrt/fx_string.cpp b/core/fxcrt/fx_string.cpp
index 31eb8e917d..c9993f9ab8 100644
--- a/core/fxcrt/fx_string.cpp
+++ b/core/fxcrt/fx_string.cpp
@@ -47,6 +47,69 @@ float FractionalScale(size_t scale_factor, int value) {
 
 }  // namespace
 
+bool FX_atonum(const ByteStringView& strc, void* pData) {
+  if (strc.Contains('.')) {
+    float* pFloat = static_cast<float*>(pData);
+    *pFloat = FX_atof(strc);
+    return false;
+  }
+
+  // Note, numbers in PDF are typically of the form 123, -123, etc. But,
+  // for things like the Permissions on the encryption hash the number is
+  // actually an unsigned value. We use a uint32_t so we can deal with the
+  // unsigned and then check for overflow if the user actually signed the value.
+  // The Permissions flag is listed in Table 3.20 PDF 1.7 spec.
+  pdfium::base::CheckedNumeric<uint32_t> integer = 0;
+  bool bNegative = false;
+  bool bSigned = false;
+  size_t cc = 0;
+  if (strc[0] == '+') {
+    cc++;
+    bSigned = true;
+  } else if (strc[0] == '-') {
+    bNegative = true;
+    bSigned = true;
+    cc++;
+  }
+
+  while (cc < strc.GetLength() && std::isdigit(strc[cc])) {
+    integer = integer * 10 + FXSYS_DecimalCharToInt(strc.CharAt(cc));
+    if (!integer.IsValid())
+      break;
+    cc++;
+  }
+
+  // We have a sign, and the value was greater then a regular integer
+  // we've overflowed, reset to the default value.
+  if (bSigned) {
+    if (bNegative) {
+      if (integer.ValueOrDefault(0) >
+          static_cast<uint32_t>(std::numeric_limits<int>::max()) + 1) {
+        integer = 0;
+      }
+    } else if (integer.ValueOrDefault(0) >
+               static_cast<uint32_t>(std::numeric_limits<int>::max())) {
+      integer = 0;
+    }
+  }
+
+  // Switch back to the int space so we can flip to a negative if we need.
+  uint32_t uValue = integer.ValueOrDefault(0);
+  int32_t value = static_cast<int>(uValue);
+  if (bNegative) {
+    // |value| is usually positive, except in the corner case of "-2147483648",
+    // where |uValue| is 2147483648. When it gets casted to an int, |value|
+    // becomes -2147483648. For this case, avoid undefined behavior, because an
+    // integer cannot represent 2147483648.
+    static constexpr int kMinInt = std::numeric_limits<int>::min();
+    value = LIKELY(value != kMinInt) ? -value : kMinInt;
+  }
+
+  int* pInt = static_cast<int*>(pData);
+  *pInt = value;
+  return true;
+}
+
 float FX_atof(const ByteStringView& strc) {
   if (strc.IsEmpty())
     return 0.0;
diff --git a/core/fxcrt/fx_string.h b/core/fxcrt/fx_string.h
index 670aa4d4b7..2cf823738a 100644
--- a/core/fxcrt/fx_string.h
+++ b/core/fxcrt/fx_string.h
@@ -7,8 +7,6 @@
 #ifndef CORE_FXCRT_FX_STRING_H_
 #define CORE_FXCRT_FX_STRING_H_
 
-#include <stdint.h>
-
 #include "core/fxcrt/bytestring.h"
 #include "core/fxcrt/widestring.h"
 
@@ -21,6 +19,7 @@ WideString FX_UTF8Decode(const ByteStringView& bsStr);
 
 float FX_atof(const ByteStringView& str);
 float FX_atof(const WideStringView& wsStr);
+bool FX_atonum(const ByteStringView& str, void* pData);
 size_t FX_ftoa(float f, char* buf);
 
 #endif  // CORE_FXCRT_FX_STRING_H_
diff --git a/core/fxcrt/fx_string_unittest.cpp b/core/fxcrt/fx_string_unittest.cpp
index 3059de3e5c..60e7f07523 100644
--- a/core/fxcrt/fx_string_unittest.cpp
+++ b/core/fxcrt/fx_string_unittest.cpp
@@ -2,9 +2,56 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <limits>
+
 #include "core/fxcrt/fx_string.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+TEST(fxstring, FX_atonum) {
+  int i;
+  EXPECT_TRUE(FX_atonum("10", &i));
+  EXPECT_EQ(10, i);
+
+  EXPECT_TRUE(FX_atonum("-10", &i));
+  EXPECT_EQ(-10, i);
+
+  EXPECT_TRUE(FX_atonum("+10", &i));
+  EXPECT_EQ(10, i);
+
+  EXPECT_TRUE(FX_atonum("-2147483648", &i));
+  EXPECT_EQ(std::numeric_limits<int>::min(), i);
+
+  EXPECT_TRUE(FX_atonum("2147483647", &i));
+  EXPECT_EQ(2147483647, i);
+
+  // Value overflows.
+  EXPECT_TRUE(FX_atonum("-2147483649", &i));
+  EXPECT_EQ(0, i);
+
+  // Value overflows.
+  EXPECT_TRUE(FX_atonum("+2147483648", &i));
+  EXPECT_EQ(0, i);
+
+  // Value overflows.
+  EXPECT_TRUE(FX_atonum("4223423494965252", &i));
+  EXPECT_EQ(0, i);
+
+  // No explicit sign will allow the number to go negative. This is for things
+  // like the encryption Permissions flag (Table 3.20 PDF 1.7 spec)
+  EXPECT_TRUE(FX_atonum("4294965252", &i));
+  EXPECT_EQ(-2044, i);
+
+  EXPECT_TRUE(FX_atonum("-4294965252", &i));
+  EXPECT_EQ(0, i);
+
+  EXPECT_TRUE(FX_atonum("+4294965252", &i));
+  EXPECT_EQ(0, i);
+
+  float f;
+  EXPECT_FALSE(FX_atonum("3.24", &f));
+  EXPECT_FLOAT_EQ(3.24f, f);
+}
+
 TEST(fxstring, FX_UTF8Encode) {
   EXPECT_EQ("", FX_UTF8Encode(WideStringView()));
   EXPECT_EQ(