1 // Copyright 2016 PDFium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com 6 7 #ifndef CORE_FXCRT_CFX_STRING_DATA_TEMPLATE_H_ 8 #define CORE_FXCRT_CFX_STRING_DATA_TEMPLATE_H_ 9 10 #include "core/fxcrt/fx_memory.h" 11 #include "core/fxcrt/fx_system.h" 12 #include "third_party/base/numerics/safe_math.h" 13 14 template <typename CharType> 15 class CFX_StringDataTemplate { 16 public: Create(FX_STRSIZE nLen)17 static CFX_StringDataTemplate* Create(FX_STRSIZE nLen) { 18 ASSERT(nLen > 0); 19 20 // Calculate space needed for the fixed portion of the struct plus the 21 // NUL char that is not included in |m_nAllocLength|. 22 int overhead = 23 offsetof(CFX_StringDataTemplate, m_String) + sizeof(CharType); 24 pdfium::base::CheckedNumeric<int> nSize = nLen; 25 nSize *= sizeof(CharType); 26 nSize += overhead; 27 28 // Now round to an 8-byte boundary. We'd expect that this is the minimum 29 // granularity of any of the underlying allocators, so there may be cases 30 // where we can save a re-alloc when adding a few characters to a string 31 // by using this otherwise wasted space. 32 nSize += 7; 33 nSize &= ~7; 34 int totalSize = nSize.ValueOrDie(); 35 int usableLen = (totalSize - overhead) / sizeof(CharType); 36 ASSERT(usableLen >= nLen); 37 38 void* pData = FX_Alloc(uint8_t, totalSize); 39 return new (pData) CFX_StringDataTemplate(nLen, usableLen); 40 } 41 Create(const CFX_StringDataTemplate & other)42 static CFX_StringDataTemplate* Create(const CFX_StringDataTemplate& other) { 43 CFX_StringDataTemplate* result = Create(other.m_nDataLength); 44 result->CopyContents(other); 45 return result; 46 } 47 Create(const CharType * pStr,FX_STRSIZE nLen)48 static CFX_StringDataTemplate* Create(const CharType* pStr, FX_STRSIZE nLen) { 49 CFX_StringDataTemplate* result = Create(nLen); 50 result->CopyContents(pStr, nLen); 51 return result; 52 } 53 Retain()54 void Retain() { ++m_nRefs; } Release()55 void Release() { 56 if (--m_nRefs <= 0) 57 FX_Free(this); 58 } 59 CanOperateInPlace(FX_STRSIZE nTotalLen)60 bool CanOperateInPlace(FX_STRSIZE nTotalLen) const { 61 return m_nRefs <= 1 && nTotalLen <= m_nAllocLength; 62 } 63 CopyContents(const CFX_StringDataTemplate & other)64 void CopyContents(const CFX_StringDataTemplate& other) { 65 ASSERT(other.m_nDataLength <= m_nAllocLength); 66 FXSYS_memcpy(m_String, other.m_String, 67 (other.m_nDataLength + 1) * sizeof(CharType)); 68 } 69 CopyContents(const CharType * pStr,FX_STRSIZE nLen)70 void CopyContents(const CharType* pStr, FX_STRSIZE nLen) { 71 ASSERT(nLen >= 0 && nLen <= m_nAllocLength); 72 FXSYS_memcpy(m_String, pStr, nLen * sizeof(CharType)); 73 m_String[nLen] = 0; 74 } 75 CopyContentsAt(FX_STRSIZE offset,const CharType * pStr,FX_STRSIZE nLen)76 void CopyContentsAt(FX_STRSIZE offset, 77 const CharType* pStr, 78 FX_STRSIZE nLen) { 79 ASSERT(offset >= 0 && nLen >= 0 && offset + nLen <= m_nAllocLength); 80 FXSYS_memcpy(m_String + offset, pStr, nLen * sizeof(CharType)); 81 m_String[offset + nLen] = 0; 82 } 83 84 // To ensure ref counts do not overflow, consider the worst possible case: 85 // the entire address space contains nothing but pointers to this object. 86 // Since the count increments with each new pointer, the largest value is 87 // the number of pointers that can fit into the address space. The size of 88 // the address space itself is a good upper bound on it. 89 intptr_t m_nRefs; 90 91 // |FX_STRSIZE| is currently typedef'd as |int|. 92 // TODO(palmer): It should be a |size_t|, or at least unsigned. 93 // These lengths are in terms of number of characters, not bytes, and do not 94 // include the terminating NUL character, but the underlying buffer is sized 95 // to be capable of holding it. 96 FX_STRSIZE m_nDataLength; 97 FX_STRSIZE m_nAllocLength; 98 99 // Not really 1, variable size. 100 CharType m_String[1]; 101 102 private: CFX_StringDataTemplate(FX_STRSIZE dataLen,FX_STRSIZE allocLen)103 CFX_StringDataTemplate(FX_STRSIZE dataLen, FX_STRSIZE allocLen) 104 : m_nRefs(0), m_nDataLength(dataLen), m_nAllocLength(allocLen) { 105 ASSERT(dataLen >= 0); 106 ASSERT(dataLen <= allocLen); 107 m_String[dataLen] = 0; 108 } 109 110 ~CFX_StringDataTemplate() = delete; 111 }; 112 113 extern template class CFX_StringDataTemplate<FX_CHAR>; 114 extern template class CFX_StringDataTemplate<FX_WCHAR>; 115 116 #endif // CORE_FXCRT_CFX_STRING_DATA_TEMPLATE_H_ 117