Merge to M47: Sanitize CJBig2_SymbolDict's memory usage.

- Use std::vector<JBig2ArithCtx> instead of storing pointers to arrays.
- Make CJBig2_SymbolDict's members private with accessors.
- Use std::vector<JBig2ArithCtx> in related places.
- Steal Chromium's vector_as_array() and use it as an adaptor as needed.

BUG=514891
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1388203003 .

(cherry picked from commit 3acb1ef909a22368507ed13817c4988c818e3aee)

Review URL: https://codereview.chromium.org/1399243003 .

8 files changed, 167 insertions, 128 deletions

diff --git a/core/src/fxcodec/jbig2/JBig2_Context.cpp b/core/src/fxcodec/jbig2/JBig2_Context.cpp
index 4e21a8cca4..d0afbae341 100644
--- a/core/src/fxcodec/jbig2/JBig2_Context.cpp
+++ b/core/src/fxcodec/jbig2/JBig2_Context.cpp
@@ -16,6 +16,18 @@
 #include "JBig2_SddProc.h"
 #include "JBig2_TrdProc.h"
 
+namespace {
+
+size_t GetHuffContextSize(uint8_t val) {
+  return val == 0 ? 65536 : val == 1 ? 8192 : 1024;
+}
+
+size_t GetRefAggContextSize(FX_BOOL val) {
+  return val ? 1024 : 8192;
+}
+
+}  // namespace
+
 // Implement a very small least recently used (LRU) cache. It is very
 // common for a JBIG2 dictionary to span multiple pages in a PDF file,
 // and we do not want to decode the same dictionary over and over
@@ -437,11 +449,7 @@ int32_t CJBig2_Context::parseSymbolDict(CJBig2_Segment* pSegment,
   int32_t i, nIndex, nRet;
   CJBig2_Segment* pSeg = nullptr;
   CJBig2_Segment* pLRSeg = nullptr;
-  FX_BOOL bUsed;
   CJBig2_Image** SDINSYMS = nullptr;
-  JBig2ArithCtx* gbContext = nullptr;
-  JBig2ArithCtx* grContext = nullptr;
-  CJBig2_ArithDecoder* pArithDecoder;
   CJBig2_SDDProc* pSymbolDictDecoder = new CJBig2_SDDProc();
   const uint8_t* key = pSegment->m_pData;
   FX_BOOL cache_hit = false;
@@ -592,90 +600,93 @@ int32_t CJBig2_Context::parseSymbolDict(CJBig2_Segment* pSegment,
       }
     }
   }
-  if ((wFlags & 0x0100) && pLRSeg && pLRSeg->m_Result.sd->m_bContextRetained) {
-    if (pSymbolDictDecoder->SDHUFF == 0) {
-      dwTemp = pSymbolDictDecoder->SDTEMPLATE == 0
-                   ? 65536
-                   : pSymbolDictDecoder->SDTEMPLATE == 1 ? 8192 : 1024;
-      gbContext = FX_Alloc(JBig2ArithCtx, dwTemp);
-      JBIG2_memcpy(gbContext, pLRSeg->m_Result.sd->m_gbContext,
-                   sizeof(JBig2ArithCtx) * dwTemp);
-    }
-    if (pSymbolDictDecoder->SDREFAGG == 1) {
-      dwTemp = pSymbolDictDecoder->SDRTEMPLATE ? 1 << 10 : 1 << 13;
-      grContext = FX_Alloc(JBig2ArithCtx, dwTemp);
-      JBIG2_memcpy(grContext, pLRSeg->m_Result.sd->m_grContext,
-                   sizeof(JBig2ArithCtx) * dwTemp);
-    }
-  } else {
-    if (pSymbolDictDecoder->SDHUFF == 0) {
-      dwTemp = pSymbolDictDecoder->SDTEMPLATE == 0
-                   ? 65536
-                   : pSymbolDictDecoder->SDTEMPLATE == 1 ? 8192 : 1024;
-      gbContext = FX_Alloc(JBig2ArithCtx, dwTemp);
-      JBIG2_memset(gbContext, 0, sizeof(JBig2ArithCtx) * dwTemp);
-    }
-    if (pSymbolDictDecoder->SDREFAGG == 1) {
-      dwTemp = pSymbolDictDecoder->SDRTEMPLATE ? 1 << 10 : 1 << 13;
-      grContext = FX_Alloc(JBig2ArithCtx, dwTemp);
-      JBIG2_memset(grContext, 0, sizeof(JBig2ArithCtx) * dwTemp);
-    }
-  }
-  pSegment->m_nResultType = JBIG2_SYMBOL_DICT_POINTER;
-  for (std::list<CJBig2_CachePair>::iterator it = m_pSymbolDictCache->begin();
-       it != m_pSymbolDictCache->end(); ++it) {
-    if (it->first == key) {
-      nonstd::unique_ptr<CJBig2_SymbolDict> copy(it->second->DeepCopy());
-      pSegment->m_Result.sd = copy.release();
-      m_pSymbolDictCache->push_front(*it);
-      m_pSymbolDictCache->erase(it);
-      cache_hit = true;
-      break;
-    }
-  }
-  if (!cache_hit) {
-    if (pSymbolDictDecoder->SDHUFF == 0) {
-      pArithDecoder = new CJBig2_ArithDecoder(m_pStream.get());
-      pSegment->m_Result.sd =
-          pSymbolDictDecoder->decode_Arith(pArithDecoder, gbContext, grContext);
-      delete pArithDecoder;
-      if (pSegment->m_Result.sd == NULL) {
-        nRet = JBIG2_ERROR_FATAL;
-        goto failed;
+
+  // The code below is in its own block to avoid issues with gotos jumping over
+  // variable declarations. The master branch does not have this issue since the
+  // gotos have been removed.
+  {
+    const bool bUseGbContext = (pSymbolDictDecoder->SDHUFF == 0);
+    const bool bUseGrContext = (pSymbolDictDecoder->SDREFAGG == 1);
+    const size_t gbContextSize =
+        GetHuffContextSize(pSymbolDictDecoder->SDTEMPLATE);
+    const size_t grContextSize =
+        GetRefAggContextSize(pSymbolDictDecoder->SDRTEMPLATE);
+    std::vector<JBig2ArithCtx> gbContext;
+    std::vector<JBig2ArithCtx> grContext;
+    if ((wFlags & 0x0100) && pLRSeg) {
+      if (bUseGbContext) {
+        gbContext = pLRSeg->m_Result.sd->GbContext();
+        if (gbContext.size() != gbContextSize) {
+          nRet = JBIG2_ERROR_FATAL;
+          goto failed;
+        }
       }
-      m_pStream->alignByte();
-      m_pStream->offset(2);
-    } else {
-      pSegment->m_Result.sd = pSymbolDictDecoder->decode_Huffman(
-          m_pStream.get(), gbContext, grContext, pPause);
-      if (pSegment->m_Result.sd == NULL) {
-        nRet = JBIG2_ERROR_FATAL;
-        goto failed;
+      if (bUseGrContext) {
+        grContext = pLRSeg->m_Result.sd->GrContext();
+        if (grContext.size() != grContextSize) {
+          nRet = JBIG2_ERROR_FATAL;
+          goto failed;
+        }
       }
-      m_pStream->alignByte();
+    } else {
+      if (bUseGbContext)
+        gbContext.resize(gbContextSize);
+      if (bUseGrContext)
+        grContext.resize(grContextSize);
     }
-    nonstd::unique_ptr<CJBig2_SymbolDict> value =
-        pSegment->m_Result.sd->DeepCopy();
-    if (value && kSymbolDictCacheMaxSize > 0) {
-      while (m_pSymbolDictCache->size() >= kSymbolDictCacheMaxSize) {
-        delete m_pSymbolDictCache->back().second;
-        m_pSymbolDictCache->pop_back();
+
+    pSegment->m_nResultType = JBIG2_SYMBOL_DICT_POINTER;
+    for (std::list<CJBig2_CachePair>::iterator it = m_pSymbolDictCache->begin();
+         it != m_pSymbolDictCache->end(); ++it) {
+      if (it->first == key) {
+        nonstd::unique_ptr<CJBig2_SymbolDict> copy(it->second->DeepCopy());
+        pSegment->m_Result.sd = copy.release();
+        m_pSymbolDictCache->push_front(*it);
+        m_pSymbolDictCache->erase(it);
+        cache_hit = true;
+        break;
       }
-      m_pSymbolDictCache->push_front(CJBig2_CachePair(key, value.release()));
     }
-  }
-  if (wFlags & 0x0200) {
-    pSegment->m_Result.sd->m_bContextRetained = TRUE;
-    if (pSymbolDictDecoder->SDHUFF == 0) {
-      pSegment->m_Result.sd->m_gbContext = gbContext;
+    if (!cache_hit) {
+      if (bUseGbContext) {
+        nonstd::unique_ptr<CJBig2_ArithDecoder> pArithDecoder(
+            new CJBig2_ArithDecoder(m_pStream.get()));
+        pSegment->m_Result.sd = pSymbolDictDecoder->decode_Arith(
+            pArithDecoder.get(), &gbContext, &grContext);
+        if (!pSegment->m_Result.sd) {
+          nRet = JBIG2_ERROR_FATAL;
+          goto failed;
+        }
+
+        m_pStream->alignByte();
+        m_pStream->offset(2);
+      } else {
+        pSegment->m_Result.sd = pSymbolDictDecoder->decode_Huffman(
+            m_pStream.get(), &gbContext, &grContext, pPause);
+        if (!pSegment->m_Result.sd) {
+          nRet = JBIG2_ERROR_FATAL;
+          goto failed;
+        }
+        m_pStream->alignByte();
+      }
+      nonstd::unique_ptr<CJBig2_SymbolDict> value =
+          pSegment->m_Result.sd->DeepCopy();
+      if (value && kSymbolDictCacheMaxSize > 0) {
+        while (m_pSymbolDictCache->size() >= kSymbolDictCacheMaxSize) {
+          delete m_pSymbolDictCache->back().second;
+          m_pSymbolDictCache->pop_back();
+        }
+        m_pSymbolDictCache->push_front(CJBig2_CachePair(key, value.release()));
+      }
     }
-    if (pSymbolDictDecoder->SDREFAGG == 1) {
-      pSegment->m_Result.sd->m_grContext = grContext;
+    if (wFlags & 0x0200) {
+      if (bUseGbContext)
+        pSegment->m_Result.sd->SetGbContext(gbContext);
+      if (bUseGrContext)
+        pSegment->m_Result.sd->SetGrContext(grContext);
     }
-    bUsed = TRUE;
-  } else {
-    bUsed = FALSE;
   }
+
   delete pSymbolDictDecoder;
   FX_Free(SDINSYMS);
   delete Table_B1;
@@ -683,10 +694,6 @@ int32_t CJBig2_Context::parseSymbolDict(CJBig2_Segment* pSegment,
   delete Table_B3;
   delete Table_B4;
   delete Table_B5;
-  if (bUsed == FALSE) {
-    FX_Free(gbContext);
-    FX_Free(grContext);
-  }
   return JBIG2_SUCCESS;
 failed:
   delete pSymbolDictDecoder;
@@ -696,8 +703,6 @@ failed:
   delete Table_B3;
   delete Table_B4;
   delete Table_B5;
-  FX_Free(gbContext);
-  FX_Free(grContext);
   return nRet;
 }
 
@@ -985,7 +990,7 @@ int32_t CJBig2_Context::parseTextRegion(CJBig2_Segment* pSegment) {
     }
   }
   if (pTRD->SBREFINE == 1) {
-    dwTemp = pTRD->SBRTEMPLATE ? 1 << 10 : 1 << 13;
+    dwTemp = GetRefAggContextSize(pTRD->SBRTEMPLATE);
     grContext = FX_Alloc(JBig2ArithCtx, dwTemp);
     JBIG2_memset(grContext, 0, sizeof(JBig2ArithCtx) * dwTemp);
   }
@@ -1080,8 +1085,7 @@ int32_t CJBig2_Context::parsePatternDict(CJBig2_Segment* pSegment,
   pPDD->HDTEMPLATE = (cFlags >> 1) & 0x03;
   pSegment->m_nResultType = JBIG2_PATTERN_DICT_POINTER;
   if (pPDD->HDMMR == 0) {
-    dwTemp =
-        pPDD->HDTEMPLATE == 0 ? 65536 : pPDD->HDTEMPLATE == 1 ? 8192 : 1024;
+    dwTemp = GetHuffContextSize(pPDD->HDTEMPLATE);
     gbContext = FX_Alloc(JBig2ArithCtx, dwTemp);
     JBIG2_memset(gbContext, 0, sizeof(JBig2ArithCtx) * dwTemp);
     pArithDecoder = new CJBig2_ArithDecoder(m_pStream.get());
@@ -1164,7 +1168,7 @@ int32_t CJBig2_Context::parseHalftoneRegion(CJBig2_Segment* pSegment,
   pHRD->HPH = pPatternDict->HDPATS[0]->m_nHeight;
   pSegment->m_nResultType = JBIG2_IMAGE_POINTER;
   if (pHRD->HMMR == 0) {
-    dwTemp = pHRD->HTEMPLATE == 0 ? 65536 : pHRD->HTEMPLATE == 1 ? 8192 : 1024;
+    dwTemp = GetHuffContextSize(pHRD->HTEMPLATE);
     gbContext = FX_Alloc(JBig2ArithCtx, dwTemp);
     JBIG2_memset(gbContext, 0, sizeof(JBig2ArithCtx) * dwTemp);
     pArithDecoder = new CJBig2_ArithDecoder(m_pStream.get());
@@ -1249,8 +1253,7 @@ int32_t CJBig2_Context::parseGenericRegion(CJBig2_Segment* pSegment,
   }
   pSegment->m_nResultType = JBIG2_IMAGE_POINTER;
   if (m_pGRD->MMR == 0) {
-    dwTemp =
-        m_pGRD->GBTEMPLATE == 0 ? 65536 : m_pGRD->GBTEMPLATE == 1 ? 8192 : 1024;
+    dwTemp = GetHuffContextSize(m_pGRD->GBTEMPLATE);
     if (m_gbContext == NULL) {
       m_gbContext = FX_Alloc(JBig2ArithCtx, dwTemp);
       JBIG2_memset(m_gbContext, 0, sizeof(JBig2ArithCtx) * dwTemp);
@@ -1377,7 +1380,7 @@ int32_t CJBig2_Context::parseGenericRefinementRegion(CJBig2_Segment* pSegment) {
   }
   pGRRD->GRREFERENCEDX = 0;
   pGRRD->GRREFERENCEDY = 0;
-  dwTemp = pGRRD->GRTEMPLATE ? 1 << 10 : 1 << 13;
+  dwTemp = GetRefAggContextSize(pGRRD->GRTEMPLATE);
   grContext = FX_Alloc(JBig2ArithCtx, dwTemp);
   JBIG2_memset(grContext, 0, sizeof(JBig2ArithCtx) * dwTemp);
   pArithDecoder = new CJBig2_ArithDecoder(m_pStream.get());
diff --git a/core/src/fxcodec/jbig2/JBig2_SddProc.cpp b/core/src/fxcodec/jbig2/JBig2_SddProc.cpp
index 1d0393a7e3..ab3b34f583 100644
--- a/core/src/fxcodec/jbig2/JBig2_SddProc.cpp
+++ b/core/src/fxcodec/jbig2/JBig2_SddProc.cpp
@@ -7,6 +7,7 @@
 #include "JBig2_SddProc.h"
 
 #include "../../../../third_party/base/nonstd_unique_ptr.h"
+#include "../../../../third_party/base/stl_util.h"
 #include "../../../include/fxcrt/fx_basic.h"
 #include "JBig2_ArithIntDecoder.h"
 #include "JBig2_GrdProc.h"
@@ -16,10 +17,12 @@
 #include "JBig2_SymbolDict.h"
 #include "JBig2_TrdProc.h"
 
+using pdfium::vector_as_array;
+
 CJBig2_SymbolDict* CJBig2_SDDProc::decode_Arith(
     CJBig2_ArithDecoder* pArithDecoder,
-    JBig2ArithCtx* gbContext,
-    JBig2ArithCtx* grContext) {
+    std::vector<JBig2ArithCtx>* gbContext,
+    std::vector<JBig2ArithCtx>* grContext) {
   CJBig2_Image** SDNEWSYMS;
   FX_DWORD HCHEIGHT, NSYMSDECODED;
   int32_t HCDH;
@@ -104,7 +107,7 @@ CJBig2_SymbolDict* CJBig2_SDDProc::decode_Arith(
         pGRD->GBAT[5] = SDAT[5];
         pGRD->GBAT[6] = SDAT[6];
         pGRD->GBAT[7] = SDAT[7];
-        BS = pGRD->decode_Arith(pArithDecoder, gbContext);
+        BS = pGRD->decode_Arith(pArithDecoder, vector_as_array(gbContext));
         if (!BS) {
           goto failed;
         }
@@ -192,7 +195,8 @@ CJBig2_SymbolDict* CJBig2_SDDProc::decode_Arith(
           ids.IARDX = IARDX.get();
           ids.IARDY = IARDY.get();
           ids.IAID = IAID.get();
-          BS = pDecoder->decode_Arith(pArithDecoder, grContext, &ids);
+          BS = pDecoder->decode_Arith(pArithDecoder, vector_as_array(grContext),
+                                      &ids);
           if (!BS) {
             FX_Free(SBSYMS);
             goto failed;
@@ -227,7 +231,7 @@ CJBig2_SymbolDict* CJBig2_SDDProc::decode_Arith(
           pGRRD->GRAT[1] = SDRAT[1];
           pGRRD->GRAT[2] = SDRAT[2];
           pGRRD->GRAT[3] = SDRAT[3];
-          BS = pGRRD->decode(pArithDecoder, grContext);
+          BS = pGRRD->decode(pArithDecoder, vector_as_array(grContext));
           if (!BS) {
             FX_Free(SBSYMS);
             goto failed;
@@ -285,10 +289,11 @@ failed:
   return nullptr;
 }
 
-CJBig2_SymbolDict* CJBig2_SDDProc::decode_Huffman(CJBig2_BitStream* pStream,
-                                                  JBig2ArithCtx* gbContext,
-                                                  JBig2ArithCtx* grContext,
-                                                  IFX_Pause* pPause) {
+CJBig2_SymbolDict* CJBig2_SDDProc::decode_Huffman(
+    CJBig2_BitStream* pStream,
+    std::vector<JBig2ArithCtx>* gbContext,
+    std::vector<JBig2ArithCtx>* grContext,
+    IFX_Pause* pPause) {
   CJBig2_Image** SDNEWSYMS;
   FX_DWORD* SDNEWSYMWIDTHS;
   FX_DWORD HCHEIGHT, NSYMSDECODED;
@@ -440,7 +445,7 @@ CJBig2_SymbolDict* CJBig2_SDDProc::decode_Huffman(CJBig2_BitStream* pStream,
           pDecoder->SBRAT[1] = SDRAT[1];
           pDecoder->SBRAT[2] = SDRAT[2];
           pDecoder->SBRAT[3] = SDRAT[3];
-          BS = pDecoder->decode_Huffman(pStream, grContext);
+          BS = pDecoder->decode_Huffman(pStream, vector_as_array(grContext));
           if (!BS) {
             FX_Free(SBSYMCODES);
             FX_Free(SBSYMS);
@@ -512,7 +517,7 @@ CJBig2_SymbolDict* CJBig2_SDDProc::decode_Huffman(CJBig2_BitStream* pStream,
           pGRRD->GRAT[3] = SDRAT[3];
           nonstd::unique_ptr<CJBig2_ArithDecoder> pArithDecoder(
               new CJBig2_ArithDecoder(pStream));
-          BS = pGRRD->decode(pArithDecoder.get(), grContext);
+          BS = pGRRD->decode(pArithDecoder.get(), vector_as_array(grContext));
           if (!BS) {
             FX_Free(SBSYMS);
             goto failed;
diff --git a/core/src/fxcodec/jbig2/JBig2_SddProc.h b/core/src/fxcodec/jbig2/JBig2_SddProc.h
index 7bc910fea1..01f8014ccc 100644
--- a/core/src/fxcodec/jbig2/JBig2_SddProc.h
+++ b/core/src/fxcodec/jbig2/JBig2_SddProc.h
@@ -7,25 +7,26 @@
 #ifndef CORE_SRC_FXCODEC_JBIG2_JBIG2_SDDPROC_H_
 #define CORE_SRC_FXCODEC_JBIG2_JBIG2_SDDPROC_H_
 
-#include "../../../core/include/fxcrt/fx_system.h"
+#include <vector>
+
+#include "../../../include/fxcrt/fx_system.h"
+#include "JBig2_ArithDecoder.h"
 
-class CJBig2_ArithDecoder;
 class CJBig2_BitStream;
 class CJBig2_HuffmanTable;
 class CJBig2_Image;
 class CJBig2_SymbolDict;
 class IFX_Pause;
-struct JBig2ArithCtx;
 
 class CJBig2_SDDProc {
  public:
   CJBig2_SymbolDict* decode_Arith(CJBig2_ArithDecoder* pArithDecoder,
-                                  JBig2ArithCtx* gbContext,
-                                  JBig2ArithCtx* grContext);
+                                  std::vector<JBig2ArithCtx>* gbContext,
+                                  std::vector<JBig2ArithCtx>* grContext);
 
   CJBig2_SymbolDict* decode_Huffman(CJBig2_BitStream* pStream,
-                                    JBig2ArithCtx* gbContext,
-                                    JBig2ArithCtx* grContext,
+                                    std::vector<JBig2ArithCtx>* gbContext,
+                                    std::vector<JBig2ArithCtx>* grContext,
                                     IFX_Pause* pPause);
 
  public:
diff --git a/core/src/fxcodec/jbig2/JBig2_SymbolDict.cpp b/core/src/fxcodec/jbig2/JBig2_SymbolDict.cpp
index a8f8a94529..351a8389c8 100644
--- a/core/src/fxcodec/jbig2/JBig2_SymbolDict.cpp
+++ b/core/src/fxcodec/jbig2/JBig2_SymbolDict.cpp
@@ -10,27 +10,19 @@
 #include "JBig2_Image.h"
 
 CJBig2_SymbolDict::CJBig2_SymbolDict() {
-  m_bContextRetained = FALSE;
-  m_gbContext = m_grContext = NULL;
 }
 
 CJBig2_SymbolDict::~CJBig2_SymbolDict() {
-  if (m_bContextRetained) {
-    FX_Free(m_gbContext);
-    FX_Free(m_grContext);
-  }
 }
 
 nonstd::unique_ptr<CJBig2_SymbolDict> CJBig2_SymbolDict::DeepCopy() const {
-  nonstd::unique_ptr<CJBig2_SymbolDict> dst;
   const CJBig2_SymbolDict* src = this;
-  if (src->m_bContextRetained || src->m_gbContext || src->m_grContext)
-    return dst;
-
-  dst.reset(new CJBig2_SymbolDict);
+  nonstd::unique_ptr<CJBig2_SymbolDict> dst(new CJBig2_SymbolDict);
   for (size_t i = 0; i < src->m_SDEXSYMS.size(); ++i) {
     CJBig2_Image* image = src->m_SDEXSYMS.get(i);
     dst->m_SDEXSYMS.push_back(image ? new CJBig2_Image(*image) : nullptr);
   }
+  dst->m_gbContext = src->m_gbContext;
+  dst->m_grContext = src->m_grContext;
   return dst;
 }
diff --git a/core/src/fxcodec/jbig2/JBig2_SymbolDict.h b/core/src/fxcodec/jbig2/JBig2_SymbolDict.h
index bec19f3eb7..bdca2693fe 100644
--- a/core/src/fxcodec/jbig2/JBig2_SymbolDict.h
+++ b/core/src/fxcodec/jbig2/JBig2_SymbolDict.h
@@ -7,12 +7,14 @@
 #ifndef _JBIG2_SYMBOL_DICT_H_
 #define _JBIG2_SYMBOL_DICT_H_
 
+#include <vector>
+
 #include "../../../../third_party/base/nonstd_unique_ptr.h"
 #include "../../../include/fxcrt/fx_basic.h"
+#include "JBig2_ArithDecoder.h"
 #include "JBig2_List.h"
 
 class CJBig2_Image;
-struct JBig2ArithCtx;
 
 class CJBig2_SymbolDict {
  public:
@@ -27,12 +29,19 @@ class CJBig2_SymbolDict {
   size_t NumImages() const { return m_SDEXSYMS.size(); }
   CJBig2_Image* GetImage(size_t index) const { return m_SDEXSYMS.get(index); }
 
- public:
-  FX_BOOL m_bContextRetained;
-  JBig2ArithCtx* m_gbContext;
-  JBig2ArithCtx* m_grContext;
+  const std::vector<JBig2ArithCtx>& GbContext() const { return m_gbContext; }
+  const std::vector<JBig2ArithCtx>& GrContext() const { return m_grContext; }
+
+  void SetGbContext(const std::vector<JBig2ArithCtx>& gbContext) {
+    m_gbContext = gbContext;
+  }
+  void SetGrContext(const std::vector<JBig2ArithCtx>& grContext) {
+    m_grContext = grContext;
+  }
 
  private:
+  std::vector<JBig2ArithCtx> m_gbContext;
+  std::vector<JBig2ArithCtx> m_grContext;
   CJBig2_List<CJBig2_Image> m_SDEXSYMS;
 };
 
diff --git a/third_party/BUILD.gn b/third_party/BUILD.gn
index 21d3d5db32..f6358147be 100644
--- a/third_party/BUILD.gn
+++ b/third_party/BUILD.gn
@@ -300,6 +300,7 @@ source_set("pdfium_base") {
     "base/numerics/safe_conversions_impl.h",
     "base/numerics/safe_math.h",
     "base/numerics/safe_math_impl.h",
+    "base/stl_util.h",
     "base/template_util.h",
   ]
 }
diff --git a/third_party/base/stl_util.h b/third_party/base/stl_util.h
new file mode 100644
index 0000000000..fcbe5882a2
--- /dev/null
+++ b/third_party/base/stl_util.h
@@ -0,0 +1,27 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_
+#define PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_
+
+#include <vector>
+
+namespace pdfium {
+
+// To treat a possibly-empty vector as an array, use these functions.
+// If you know the array will never be empty, you can use &*v.begin()
+// directly, but that is undefined behaviour if |v| is empty.
+template <typename T>
+inline T* vector_as_array(std::vector<T>* v) {
+  return v->empty() ? nullptr : &*v->begin();
+}
+
+template <typename T>
+inline const T* vector_as_array(const std::vector<T>* v) {
+  return v->empty() ? nullptr : &*v->begin();
+}
+
+}  // namespace pdfium
+
+#endif  // PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_
diff --git a/third_party/third_party.gyp b/third_party/third_party.gyp
index 6ad8beb48c..1ec0509eb2 100644
--- a/third_party/third_party.gyp
+++ b/third_party/third_party.gyp
@@ -281,11 +281,12 @@
         'base/logging.h',
         'base/macros.h',
         'base/nonstd_unique_ptr.h',
-        'base/template_util.h',
         'base/numerics/safe_conversions.h',
         'base/numerics/safe_conversions_impl.h',
         'base/numerics/safe_math.h',
         'base/numerics/safe_math_impl.h',
+        'base/stl_util.h',
+        'base/template_util.h',
       ],
     },
   ],