text: // Copyright 2017 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 "xfa/fde/css/cfde_csstextbuf.h"
  
  #include "third_party/base/stl_util.h"
  
  CFDE_CSSTextBuf::CFDE_CSSTextBuf()
      : m_bExtBuf(false),
        m_pBuffer(nullptr),
        m_iBufLen(0),
        m_iDatLen(0),
        m_iDatPos(0) {}
  
  CFDE_CSSTextBuf::~CFDE_CSSTextBuf() {
    Reset();
  }
  
  void CFDE_CSSTextBuf::Reset() {
    if (!m_bExtBuf) {
      FX_Free(m_pBuffer);
      m_pBuffer = nullptr;
    }
    m_iDatPos = m_iDatLen = m_iBufLen;
  }
  
  bool CFDE_CSSTextBuf::AttachBuffer(const wchar_t* pBuffer, int32_t iBufLen) {
    Reset();
    m_pBuffer = const_cast<wchar_t*>(pBuffer);
    m_iDatLen = m_iBufLen = iBufLen;
    return m_bExtBuf = true;
  }
  
  bool CFDE_CSSTextBuf::EstimateSize(int32_t iAllocSize) {
    ASSERT(iAllocSize > 0);
    Clear();
    m_bExtBuf = false;
    return ExpandBuf(iAllocSize);
  }
  
  bool CFDE_CSSTextBuf::ExpandBuf(int32_t iDesiredSize) {
    if (m_bExtBuf)
      return false;
    if (!m_pBuffer)
      m_pBuffer = FX_Alloc(wchar_t, iDesiredSize);
    else if (m_iBufLen != iDesiredSize)
      m_pBuffer = FX_Realloc(wchar_t, m_pBuffer, iDesiredSize);
    else
      return true;
  
    if (!m_pBuffer) {
      m_iBufLen = 0;
      return false;
    }
    m_iBufLen = iDesiredSize;
    return true;
  }
  
  void CFDE_CSSTextBuf::Subtract(int32_t iStart, int32_t iLength) {
    ASSERT(iStart >= 0 && iLength >= 0);
  
    iLength = pdfium::clamp(iLength, 0, m_iDatLen - iStart);
    memmove(m_pBuffer, m_pBuffer + iStart, iLength * sizeof(wchar_t));
    m_iDatLen = iLength;
  }
  