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authorTom Sepez <tsepez@chromium.org>2015-04-30 15:28:51 -0700
committerTom Sepez <tsepez@chromium.org>2015-04-30 15:28:51 -0700
commitc4631925ccd0ba4d471f5beed2d20a1a6de9368e (patch)
tree36ba30517b3cf196bb1f6160c0fd3fb37ae1e9da /core/src/fxcrt
parentcd051604b1b5f8555cf692b91d0105d7a7117feb (diff)
downloadpdfium-c4631925ccd0ba4d471f5beed2d20a1a6de9368e.tar.xz
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
Diffstat (limited to 'core/src/fxcrt')
-rw-r--r--core/src/fxcrt/fx_basic_wstring.cpp25
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;