From c4631925ccd0ba4d471f5beed2d20a1a6de9368e Mon Sep 17 00:00:00 2001 From: Tom Sepez Date: Thu, 30 Apr 2015 15:28:51 -0700 Subject: Take adavange of unused bytes at end of widestring Follow-on to https://codereview.chromium.org/1120703003/ R=thestig@chromium.org Review URL: https://codereview.chromium.org/1112423003 --- core/src/fxcrt/fx_basic_wstring.cpp | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/core/src/fxcrt/fx_basic_wstring.cpp b/core/src/fxcrt/fx_basic_wstring.cpp index 2ea23e4f19..42a7ad72a6 100644 --- a/core/src/fxcrt/fx_basic_wstring.cpp +++ b/core/src/fxcrt/fx_basic_wstring.cpp @@ -9,23 +9,32 @@ static CFX_StringDataW* FX_AllocStringW(int nLen) { + // TODO(palmer): |nLen| should really be declared as |size_t|, or + // at least unsigned. if (nLen == 0 || nLen < 0) { return NULL; } - pdfium::base::CheckedNumeric iSize = static_cast(sizeof(FX_WCHAR)); - iSize *= nLen + 1; - iSize += sizeof(long) * 3; + int overhead = 3 * sizeof(long) + sizeof(FX_WCHAR); // +WCHAR is for NUL. + pdfium::base::CheckedNumeric iSize = nLen; + iSize *= sizeof(FX_WCHAR); + iSize += overhead; + + // Now round to an 8-byte boundary. We'd expect that this is the minimum + // granularity of any of the underlying allocators, so there may be cases + // where we can save a re-alloc when adding a few characters to a string + // by using this otherwise wasted space. + iSize += 7; + int totalSize = iSize.ValueOrDie() & ~7; + int usableLen = (totalSize - overhead) / sizeof(FX_WCHAR); + FXSYS_assert(usableLen >= nLen); + CFX_StringDataW* pData = (CFX_StringDataW*)FX_Alloc(FX_BYTE, iSize.ValueOrDie()); if (!pData) { return NULL; } - // TODO(palmer): |nLen| should really be declared as |size_t|, but for - // now I just want to fix the overflow without changing any interfaces. - // Declaring |nLen| as |size_t| will also simplify the above code - // somewhat. - pData->m_nAllocLength = nLen; + pData->m_nAllocLength = usableLen; pData->m_nDataLength = nLen; pData->m_nRefs = 1; pData->m_String[nLen] = 0; -- cgit v1.2.3