diff options
| -rw-r--r-- | core/src/fxcrt/fx_basic_wstring.cpp | 25 |
1 files 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<int> iSize = static_cast<int>(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<int> 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; |