compiler-rt/lib/scudo/standalone/vector.h

   1 //===-- vector.h ------------------------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef SCUDO_VECTOR_H_
  10 #define SCUDO_VECTOR_H_
  11
  12 #include "mem_map.h"
  13
  14 #include <string.h>
  15
  16 namespace scudo {
  17
  18 // A low-level vector based on map. It stores the contents inline up to a fixed
  19 // capacity, or in an external memory buffer if it grows bigger than that. May
  20 // incur a significant memory overhead for small vectors. The current
  21 // implementation supports only POD types.
  22 //
  23 // NOTE: This class is not meant to be used directly, use Vector<T> instead.
  24 template <typename T> class VectorNoCtor {
  25 public:
  26   T &operator[](uptr I) {
  27     DCHECK_LT(I, Size);
  28     return Data[I];
  29   }
  30   const T &operator[](uptr I) const {
  31     DCHECK_LT(I, Size);
  32     return Data[I];
  33   }
  34   void push_back(const T &Element) {
  35     DCHECK_LE(Size, capacity());
  36     if (Size == capacity()) {
  37       const uptr NewCapacity = roundUpPowerOfTwo(Size + 1);
  38       reallocate(NewCapacity);
  39     }
  40     memcpy(&Data[Size++], &Element, sizeof(T));
  41   }
  42   T &back() {
  43     DCHECK_GT(Size, 0);
  44     return Data[Size - 1];
  45   }
  46   void pop_back() {
  47     DCHECK_GT(Size, 0);
  48     Size--;
  49   }
  50   uptr size() const { return Size; }
  51   const T *data() const { return Data; }
  52   T *data() { return Data; }
  53   constexpr uptr capacity() const { return CapacityBytes / sizeof(T); }
  54   void reserve(uptr NewSize) {
  55     // Never downsize internal buffer.
  56     if (NewSize > capacity())
  57       reallocate(NewSize);
  58   }
  59   void resize(uptr NewSize) {
  60     if (NewSize > Size) {
  61       reserve(NewSize);
  62       memset(&Data[Size], 0, sizeof(T) * (NewSize - Size));
  63     }
  64     Size = NewSize;
  65   }
  66
  67   void clear() { Size = 0; }
  68   bool empty() const { return size() == 0; }
  69
  70   const T *begin() const { return data(); }
  71   T *begin() { return data(); }
  72   const T *end() const { return data() + size(); }
  73   T *end() { return data() + size(); }
  74
  75 protected:
  76   constexpr void init(uptr InitialCapacity = 0) {
  77     Data = &LocalData[0];
  78     CapacityBytes = sizeof(LocalData);
  79     if (InitialCapacity > capacity())
  80       reserve(InitialCapacity);
  81   }
  82   void destroy() {
  83     if (Data != &LocalData[0])
  84       ExternalBuffer.unmap(ExternalBuffer.getBase(),
  85                            ExternalBuffer.getCapacity());
  86   }
  87
  88 private:
  89   void reallocate(uptr NewCapacity) {
  90     DCHECK_GT(NewCapacity, 0);
  91     DCHECK_LE(Size, NewCapacity);
  92
  93     MemMapT NewExternalBuffer;
  94     NewCapacity = roundUp(NewCapacity * sizeof(T), getPageSizeCached());
  95     NewExternalBuffer.map(/*Addr=*/0U, NewCapacity, "scudo:vector");
  96     T *NewExternalData = reinterpret_cast<T *>(NewExternalBuffer.getBase());
  97
  98     memcpy(NewExternalData, Data, Size * sizeof(T));
  99     destroy();
 100
 101     Data = NewExternalData;
 102     CapacityBytes = NewCapacity;
 103     ExternalBuffer = NewExternalBuffer;
 104   }
 105
 106   T *Data = nullptr;
 107   uptr CapacityBytes = 0;
 108   uptr Size = 0;
 109
 110   T LocalData[256 / sizeof(T)] = {};
 111   MemMapT ExternalBuffer;
 112 };
 113
 114 template <typename T> class Vector : public VectorNoCtor<T> {
 115 public:
 116   constexpr Vector() { VectorNoCtor<T>::init(); }
 117   explicit Vector(uptr Count) {
 118     VectorNoCtor<T>::init(Count);
 119     this->resize(Count);
 120   }
 121   ~Vector() { VectorNoCtor<T>::destroy(); }
 122   // Disallow copies and moves.
 123   Vector(const Vector &) = delete;
 124   Vector &operator=(const Vector &) = delete;
 125   Vector(Vector &&) = delete;
 126   Vector &operator=(Vector &&) = delete;
 127 };
 128
 129 } // namespace scudo
 130
 131 #endif // SCUDO_VECTOR_H_