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// Copyright 2016 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
#ifndef CORE_FXCRT_STRING_DATA_TEMPLATE_H_
#define CORE_FXCRT_STRING_DATA_TEMPLATE_H_
#include "core/fxcrt/fx_memory.h"
#include "core/fxcrt/fx_system.h"
#include "third_party/base/numerics/safe_math.h"
namespace fxcrt {
template <typename CharType>
class StringDataTemplate {
public:
static StringDataTemplate* Create(size_t nLen) {
ASSERT(nLen > 0);
// Calculate space needed for the fixed portion of the struct plus the
// NUL char that is not included in |m_nAllocLength|.
int overhead = offsetof(StringDataTemplate, m_String) + sizeof(CharType);
pdfium::base::CheckedNumeric<size_t> nSize = nLen;
nSize *= sizeof(CharType);
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;
nSize &= ~7;
size_t totalSize = nSize.ValueOrDie();
size_t usableLen = (totalSize - overhead) / sizeof(CharType);
ASSERT(usableLen >= nLen);
void* pData = GetStringPartitionAllocator().root()->Alloc(
totalSize, "StringDataTemplate");
return new (pData) StringDataTemplate(nLen, usableLen);
}
static StringDataTemplate* Create(const CharType* pStr, size_t nLen) {
StringDataTemplate* result = Create(nLen);
result->CopyContents(pStr, nLen);
return result;
}
void Retain() { ++m_nRefs; }
void Release() {
if (--m_nRefs <= 0)
GetStringPartitionAllocator().root()->Free(this);
}
bool CanOperateInPlace(size_t nTotalLen) const {
return m_nRefs <= 1 && nTotalLen <= m_nAllocLength;
}
void CopyContents(const StringDataTemplate& other) {
ASSERT(other.m_nDataLength <= m_nAllocLength);
memcpy(m_String, other.m_String,
(other.m_nDataLength + 1) * sizeof(CharType));
}
void CopyContents(const CharType* pStr, size_t nLen) {
ASSERT(nLen >= 0 && nLen <= m_nAllocLength);
memcpy(m_String, pStr, nLen * sizeof(CharType));
m_String[nLen] = 0;
}
void CopyContentsAt(size_t offset, const CharType* pStr, size_t nLen) {
ASSERT(offset >= 0 && nLen >= 0 && offset + nLen <= m_nAllocLength);
memcpy(m_String + offset, pStr, nLen * sizeof(CharType));
m_String[offset + nLen] = 0;
}
// To ensure ref counts do not overflow, consider the worst possible case:
// the entire address space contains nothing but pointers to this object.
// Since the count increments with each new pointer, the largest value is
// the number of pointers that can fit into the address space. The size of
// the address space itself is a good upper bound on it.
intptr_t m_nRefs;
// These lengths are in terms of number of characters, not bytes, and do not
// include the terminating NUL character, but the underlying buffer is sized
// to be capable of holding it.
size_t m_nDataLength;
size_t m_nAllocLength;
// Not really 1, variable size.
CharType m_String[1];
private:
StringDataTemplate(size_t dataLen, size_t allocLen)
: m_nRefs(0), m_nDataLength(dataLen), m_nAllocLength(allocLen) {
ASSERT(dataLen >= 0);
ASSERT(dataLen <= allocLen);
m_String[dataLen] = 0;
}
~StringDataTemplate() = delete;
};
extern template class StringDataTemplate<char>;
extern template class StringDataTemplate<wchar_t>;
} // namespace fxcrt
using fxcrt::StringDataTemplate;
#endif // CORE_FXCRT_STRING_DATA_TEMPLATE_H_
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