commit f2c1a74bd9bf15a5ecb7214febac13aa6c50aab5
author Tom Sepez <tsepez@chromium.org> Fri Dec 10 21:55:58 2021 +0000
committer Pdfium LUCI CQ <pdfium-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Dec 10 21:55:58 2021 +0000
tree 74277124a39dbfecce1c239075836343cf9b602a
parent 07dc822fad2b938643ec31ef8ee4aad47af8ceb9

Avoid copy between CFX_WideTextBuf and WideString in CFX_UTF8Decoder.

I suspect CFX_UTF8Decoder initially used WideTextBuf because it
grew exponentially, but widestrings only used to grow at a
constant increment. Buf we changed that a while ago (and strings
now grow at 1.5x vs. WideTextBufs 1.25x).

Change-Id: If56ba6ae1f7eb31d78732282e6ff910d6045fd48
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/87733
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

core/fxcrt/cfx_utf8decoder.cpp

diff --git a/core/fxcrt/cfx_utf8decoder.cpp b/core/fxcrt/cfx_utf8decoder.cpp
index 68ea30a..df29f44 100644
--- a/core/fxcrt/cfx_utf8decoder.cpp
+++ b/core/fxcrt/cfx_utf8decoder.cpp
@@ -6,18 +6,24 @@
 
 #include "core/fxcrt/cfx_utf8decoder.h"
 
+#include <utility>
+
 CFX_UTF8Decoder::CFX_UTF8Decoder() = default;
 
 CFX_UTF8Decoder::~CFX_UTF8Decoder() = default;
 
+WideString CFX_UTF8Decoder::TakeResult() {
+  return std::move(m_Buffer);
+}
+
 void CFX_UTF8Decoder::AppendCodePoint(uint32_t ch) {
-  m_Buffer.AppendChar(static_cast<wchar_t>(ch));
+  m_Buffer += static_cast<wchar_t>(ch);
 }
 
 void CFX_UTF8Decoder::Input(uint8_t byte) {
   if (byte < 0x80) {
     m_PendingBytes = 0;
-    m_Buffer.AppendChar(byte);
+    AppendCodePoint(byte);
   } else if (byte < 0xc0) {
     if (m_PendingBytes == 0) {
       return;

core/fxcrt/cfx_utf8decoder.h

diff --git a/core/fxcrt/cfx_utf8decoder.h b/core/fxcrt/cfx_utf8decoder.h
index af14a04..9e662ea 100644
--- a/core/fxcrt/cfx_utf8decoder.h
+++ b/core/fxcrt/cfx_utf8decoder.h
@@ -7,7 +7,7 @@
 #ifndef CORE_FXCRT_CFX_UTF8DECODER_H_
 #define CORE_FXCRT_CFX_UTF8DECODER_H_
 
-#include "core/fxcrt/cfx_widetextbuf.h"
+#include "core/fxcrt/widestring.h"
 
 class CFX_UTF8Decoder {
  public:
@@ -15,14 +15,14 @@
   ~CFX_UTF8Decoder();
 
   void Input(uint8_t byte);
-  WideStringView GetResult() const { return m_Buffer.AsStringView(); }
+  WideString TakeResult();
 
  private:
   void AppendCodePoint(uint32_t ch);
 
   int m_PendingBytes = 0;
   uint32_t m_PendingChar = 0;
-  CFX_WideTextBuf m_Buffer;
+  WideString m_Buffer;
 };
 
 #endif  // CORE_FXCRT_CFX_UTF8DECODER_H_

core/fxcrt/fx_string.cpp

diff --git a/core/fxcrt/fx_string.cpp b/core/fxcrt/fx_string.cpp
index 46961d4..96675d9 100644
--- a/core/fxcrt/fx_string.cpp
+++ b/core/fxcrt/fx_string.cpp
@@ -28,7 +28,7 @@
   for (size_t i = 0; i < bsStr.GetLength(); i++)
     decoder.Input(bsStr[i]);
 
-  return WideString(decoder.GetResult());
+  return decoder.TakeResult();
 }
 
 namespace {