Add type cast definitions for CPDF_Stream.

core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp

 // Copyright 2014 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 <vector>
 
 #include "../../../../third_party/base/nonstd_unique_ptr.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
@@ skipping 747 matching lines @@
       }
     }
   }
   m_bpc = 8;
 }
 CPDF_DIBSource* CPDF_DIBSource::LoadMask(FX_DWORD& MatteColor) {
   MatteColor = 0xFFFFFFFF;
   CPDF_Stream* pSoftMask = m_pDict->GetStream(FX_BSTRC("SMask"));
   if (pSoftMask) {
     CPDF_Array* pMatte = pSoftMask->GetDict()->GetArray(FX_BSTRC("Matte"));
-    if (pMatte != NULL && m_pColorSpace &&
+    if (pMatte && m_pColorSpace &&
         (FX_DWORD)m_pColorSpace->CountComponents() <= m_nComponents) {
       FX_FLOAT* pColor = FX_Alloc(FX_FLOAT, m_nComponents);
       for (FX_DWORD i = 0; i < m_nComponents; i++) {
         pColor[i] = pMatte->GetFloat(i);
       }
       FX_FLOAT R, G, B;
       m_pColorSpace->GetRGB(pColor, R, G, B);
       FX_Free(pColor);
       MatteColor = FXARGB_MAKE(0, FXSYS_round(R * 255), FXSYS_round(G * 255),
                                FXSYS_round(B * 255));
     }
     return LoadMaskDIB(pSoftMask);
   }
-  CPDF_Object* pMask = m_pDict->GetElementValue(FX_BSTRC("Mask"));
-  if (pMask == NULL) {
-    return NULL;
-  }
-  if (pMask->GetType() == PDFOBJ_STREAM) {
-    return LoadMaskDIB((CPDF_Stream*)pMask);
-  }
-  return NULL;
+
+  if (CPDF_Stream* pStream =
+          ToStream(m_pDict->GetElementValue(FX_BSTRC("Mask"))))
+    return LoadMaskDIB(pStream);
+
+  return nullptr;
 }
 int CPDF_DIBSource::StratLoadMask() {
   m_MatteColor = 0XFFFFFFFF;
   m_pMaskStream = m_pDict->GetStream(FX_BSTRC("SMask"));
   if (m_pMaskStream) {
     CPDF_Array* pMatte = m_pMaskStream->GetDict()->GetArray(FX_BSTRC("Matte"));
     if (pMatte != NULL && m_pColorSpace &&
         (FX_DWORD)m_pColorSpace->CountComponents() <= m_nComponents) {
       FX_FLOAT R, G, B;
       FX_FLOAT* pColor = FX_Alloc(FX_FLOAT, m_nComponents);
       for (FX_DWORD i = 0; i < m_nComponents; i++) {
         pColor[i] = pMatte->GetFloat(i);
       }
       m_pColorSpace->GetRGB(pColor, R, G, B);
       FX_Free(pColor);
       m_MatteColor = FXARGB_MAKE(0, FXSYS_round(R * 255), FXSYS_round(G * 255),
                                  FXSYS_round(B * 255));
     }
     return StartLoadMaskDIB();
   }
+
   m_pMaskStream = m_pDict->GetElementValue(FX_BSTRC("Mask"));
-  if (m_pMaskStream == NULL) {
+  if (!m_pMaskStream)

[Tom Sepez, 2015/10/22 17:16:45]

nit: maybe 
  return ToStream(m_pMaskStream) ? StartLoadMaskDIB() : 1;

[dsinclair, 2015/10/22 17:42:56]

Done.

     return 1;
-  }
-  if (m_pMaskStream->GetType() == PDFOBJ_STREAM) {
+  if (m_pMaskStream->IsStream())
     return StartLoadMaskDIB();
-  }
   return 1;
 }
 int CPDF_DIBSource::ContinueLoadMaskDIB(IFX_Pause* pPause) {
   if (m_pMask == NULL) {
     return 1;
   }
   int ret = m_pMask->ContinueLoadDIBSource(pPause);
   if (ret == 2) {
     return ret;
   }
@@ skipping 15 matching lines @@
 CPDF_DIBSource* CPDF_DIBSource::LoadMaskDIB(CPDF_Stream* pMask) {
   CPDF_DIBSource* pMaskSource = new CPDF_DIBSource;
   if (!pMaskSource->Load(m_pDocument, pMask, NULL, NULL, NULL, NULL, TRUE)) {
     delete pMaskSource;
     return NULL;
   }
   return pMaskSource;
 }
 int CPDF_DIBSource::StartLoadMaskDIB() {
   m_pMask = new CPDF_DIBSource;
-  int ret = m_pMask->StartLoadDIBSource(
-      m_pDocument, (CPDF_Stream*)m_pMaskStream, FALSE, NULL, NULL, TRUE);
+  int ret = m_pMask->StartLoadDIBSource(m_pDocument, ToStream(m_pMaskStream),

[Tom Sepez, 2015/10/22 17:16:45]

I worry about this.  At line 809, we may have assigned a non-stream to
m_pMaskStream.  Now we will test type and pass NULL for that case.  Later on,
some clever code may check that the pointer is some other type, and sloppily
cast it to the type.  Please confirm.  Can we make the m_MaskStream be a stream,
not an object?  Can we force ToStream() on it at the time of assignment?

[dsinclair, 2015/10/22 17:42:56]

Done. There are 2 assignments and this one usage. The two assignments are 791
and 809 and 791 is GetStream

[Tom Sepez, 2015/10/22 19:11:55]

Ok.  Looks like were type safe.

+                                        FALSE, nullptr, nullptr, TRUE);
   if (ret == 2) {
-    if (m_Status == 0) {
+    if (m_Status == 0)
       m_Status = 2;
-    }
     return 2;
   }
   if (!ret) {
     delete m_pMask;
-    m_pMask = NULL;
+    m_pMask = nullptr;
     return 1;
   }
   return 1;
 }
 void CPDF_DIBSource::LoadPalette() {
   if (m_bpc == 0) {
     return;
   }
   if (m_bpc * m_nComponents > 8) {
     return;
@@ skipping 779 matching lines @@
 }
 FX_BOOL CPDF_ImageLoader::Continue(void* LoadHandle, IFX_Pause* pPause) {
   return ((CPDF_ProgressiveImageLoaderHandle*)LoadHandle)->Continue(pPause);
 }
 CPDF_ImageLoader::~CPDF_ImageLoader() {
   if (!m_bCached) {
     delete m_pBitmap;
     delete m_pMask;
   }
 }