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-rw-r--r--core/src/fxcrt/fx_basic_bstring.cpp18
-rw-r--r--core/src/fxcrt/fx_basic_wstring.cpp25
2 files changed, 32 insertions, 11 deletions
diff --git a/core/src/fxcrt/fx_basic_bstring.cpp b/core/src/fxcrt/fx_basic_bstring.cpp
index 961aebe69c..2c8f7a766b 100644
--- a/core/src/fxcrt/fx_basic_bstring.cpp
+++ b/core/src/fxcrt/fx_basic_bstring.cpp
@@ -52,13 +52,25 @@ static CFX_StringData* FX_AllocString(int nLen)
if (nLen == 0 || nLen < 0) {
return NULL;
}
+
+ int overhead = sizeof(long) * 3 + 1; // 3 longs in header plus 1 for NUL.
pdfium::base::CheckedNumeric<int> nSize = nLen;
- nSize += sizeof(long) * 3 + 1;
- CFX_StringData* pData = (CFX_StringData*)FX_Alloc(FX_BYTE, nSize.ValueOrDie());
+ nSize += 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.
+ nSize += 7;
+ int totalSize = nSize.ValueOrDie() & ~7;
+ int usableSize = totalSize - overhead;
+ FXSYS_assert(usableSize >= nLen);
+
+ CFX_StringData* pData = (CFX_StringData*)FX_Alloc(FX_BYTE, totalSize);
if (!pData) {
return NULL;
}
- pData->m_nAllocLength = nLen;
+ pData->m_nAllocLength = usableSize;
pData->m_nDataLength = nLen;
pData->m_nRefs = 1;
pData->m_String[nLen] = 0;
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;