Replacing CFX_ByteTextBuf with stringstream in cpdf_streamparser.cpp.

Loaded PDF Reference 1-7.pdf 10 times to test performance, no apparent
changes. All measurements between 62s and 65s in all cases.

Bug: pdfium:731
Change-Id: I0a39bae45fc19a6bae0c634c5c8ef1d952ded26a
Reviewed-on: https://pdfium-review.googlesource.com/6390
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>

1 files changed, 29 insertions, 31 deletions

diff --git a/core/fpdfapi/page/cpdf_streamparser.cpp b/core/fpdfapi/page/cpdf_streamparser.cpp
index e8116cf980..c3dc54a734 100644
--- a/core/fpdfapi/page/cpdf_streamparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamparser.cpp
@@ -8,7 +8,9 @@
 
 #include <limits.h>
 
+#include <algorithm>
 #include <memory>
+#include <sstream>
 #include <utility>
 
 #include "core/fpdfapi/cpdf_modulemgr.h"
@@ -220,7 +222,7 @@ std::unique_ptr<CPDF_Stream> CPDF_StreamParser::ReadInlineStream(
     memcpy(pData.get(), m_pBuf + m_Pos, dwStreamSize);
     m_Pos += dwStreamSize;
   }
-  pDict->SetNewFor<CPDF_Number>("Length", (int)dwStreamSize);
+  pDict->SetNewFor<CPDF_Number>("Length", static_cast<int>(dwStreamSize));
   return pdfium::MakeUnique<CPDF_Stream>(std::move(pData), dwStreamSize,
                                          std::move(pDict));
 }
@@ -473,7 +475,7 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
     return CFX_ByteString();
 
   uint8_t ch = m_pBuf[m_Pos++];
-  CFX_ByteTextBuf buf;
+  std::ostringstream buf;
   int parlevel = 0;
   int status = 0;
   int iEscCode = 0;
@@ -482,20 +484,19 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
       case 0:
         if (ch == ')') {
           if (parlevel == 0) {
-            if (buf.GetLength() > kMaxStringLength) {
-              return CFX_ByteString(buf.GetBuffer(), kMaxStringLength);
-            }
-            return buf.MakeString();
+            return CFX_ByteString(
+                buf.str().c_str(),
+                std::min(static_cast<int>(buf.tellp()), kMaxStringLength));
           }
           parlevel--;
-          buf.AppendChar(')');
+          buf << ')';
         } else if (ch == '(') {
           parlevel++;
-          buf.AppendChar('(');
+          buf << '(';
         } else if (ch == '\\') {
           status = 1;
         } else {
-          buf.AppendChar((char)ch);
+          buf << static_cast<char>(ch);
         }
         break;
       case 1:
@@ -505,21 +506,21 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
           break;
         }
         if (ch == 'n') {
-          buf.AppendChar('\n');
+          buf << '\n';
         } else if (ch == 'r') {
-          buf.AppendChar('\r');
+          buf << '\r';
         } else if (ch == 't') {
-          buf.AppendChar('\t');
+          buf << '\t';
         } else if (ch == 'b') {
-          buf.AppendChar('\b');
+          buf << '\b';
         } else if (ch == 'f') {
-          buf.AppendChar('\f');
+          buf << '\f';
         } else if (ch == '\r') {
           status = 4;
           break;
         } else if (ch == '\n') {
         } else {
-          buf.AppendChar(ch);
+          buf << static_cast<char>(ch);
         }
         status = 0;
         break;
@@ -529,7 +530,7 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
               iEscCode * 8 + FXSYS_DecimalCharToInt(static_cast<char>(ch));
           status = 3;
         } else {
-          buf.AppendChar(iEscCode);
+          buf << static_cast<char>(iEscCode);
           status = 0;
           continue;
         }
@@ -538,19 +539,18 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
         if (ch >= '0' && ch <= '7') {
           iEscCode =
               iEscCode * 8 + FXSYS_DecimalCharToInt(static_cast<char>(ch));
-          buf.AppendChar(iEscCode);
+          buf << static_cast<char>(iEscCode);
           status = 0;
         } else {
-          buf.AppendChar(iEscCode);
+          buf << static_cast<char>(iEscCode);
           status = 0;
           continue;
         }
         break;
       case 4:
         status = 0;
-        if (ch != '\n') {
+        if (ch != '\n')
           continue;
-        }
         break;
     }
     if (!PositionIsInBounds())
@@ -561,17 +561,16 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
   if (PositionIsInBounds())
     ++m_Pos;
 
-  if (buf.GetLength() > kMaxStringLength) {
-    return CFX_ByteString(buf.GetBuffer(), kMaxStringLength);
-  }
-  return buf.MakeString();
+  return CFX_ByteString(
+      buf.str().c_str(),
+      std::min(static_cast<int>(buf.tellp()), kMaxStringLength));
 }
 
 CFX_ByteString CPDF_StreamParser::ReadHexString() {
   if (!PositionIsInBounds())
     return CFX_ByteString();
 
-  CFX_ByteTextBuf buf;
+  std::ostringstream buf;
   bool bFirst = true;
   int code = 0;
   while (PositionIsInBounds()) {
@@ -588,17 +587,16 @@ CFX_ByteString CPDF_StreamParser::ReadHexString() {
       code = val * 16;
     } else {
       code += val;
-      buf.AppendByte((uint8_t)code);
+      buf << static_cast<uint8_t>(code);
     }
     bFirst = !bFirst;
   }
   if (!bFirst)
-    buf.AppendChar((char)code);
-
-  if (buf.GetLength() > kMaxStringLength)
-    return CFX_ByteString(buf.GetBuffer(), kMaxStringLength);
+    buf << static_cast<char>(code);
 
-  return buf.MakeString();
+  return CFX_ByteString(
+      buf.str().c_str(),
+      std::min(static_cast<int>(buf.tellp()), kMaxStringLength));
 }
 
 bool CPDF_StreamParser::PositionIsInBounds() const {