1 //===-- DataBuffer.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 LLDB_UTILITY_DATABUFFER_H
10 #define LLDB_UTILITY_DATABUFFER_H
11 #if defined(__cplusplus)
12 
13 #include <cstdint>
14 #include <cstring>
15 
16 #include "lldb/lldb-types.h"
17 
18 #include "llvm/ADT/ArrayRef.h"
19 
20 namespace lldb_private {
21 
22 /// \class DataBuffer DataBuffer.h "lldb/Core/DataBuffer.h"
23 /// A pure virtual protocol class for abstracted read only data buffers.
24 ///
25 /// DataBuffer is an abstract class that gets packaged into a shared
26 /// pointer that can use to implement various ways to store data (on the heap,
27 /// memory mapped, cached inferior memory). It gets used by DataExtractor so
28 /// many DataExtractor objects can share the same data and sub-ranges of that
29 /// shared data, and the last object that contains a reference to the shared
30 /// data will free it.
31 ///
32 /// Subclasses can implement as many different constructors or member
33 /// functions that allow data to be stored in the object's buffer prior to
34 /// handing the shared data to clients that use these buffers.
35 ///
36 /// All subclasses must override all of the pure virtual functions as they are
37 /// used by clients to access the data. Having a common interface allows
38 /// different ways of storing data, yet using it in one common way.
39 ///
40 /// This class currently expects all data to be available without any extra
41 /// calls being made, but we can modify it to optionally get data on demand
42 /// with some extra function calls to load the data before it gets accessed.
43 class DataBuffer {
44 public:
45   virtual ~DataBuffer() = default;
46 
47   /// Get the number of bytes in the data buffer.
48   ///
49   /// \return
50   ///     The number of bytes this object currently contains.
51   virtual lldb::offset_t GetByteSize() const = 0;
52 
53   /// Get a const pointer to the data.
54   ///
55   /// \return
56   ///     A const pointer to the bytes owned by this object, or NULL
57   ///     if the object contains no bytes.
58   const uint8_t *GetBytes() const { return GetBytesImpl(); }
59 
60   llvm::ArrayRef<uint8_t> GetData() const {
61     return llvm::ArrayRef<uint8_t>(GetBytes(), GetByteSize());
62   }
63 
64   /// LLVM RTTI support.
65   /// {
66   static char ID;
67   virtual bool isA(const void *ClassID) const { return ClassID == &ID; }
68   static bool classof(const DataBuffer *data_buffer) {
69     return data_buffer->isA(&ID);
70   }
71   /// }
72 
73 protected:
74   /// Get a const pointer to the data.
75   ///
76   /// \return
77   ///     A const pointer to the bytes owned by this object, or NULL
78   ///     if the object contains no bytes.
79   virtual const uint8_t *GetBytesImpl() const = 0;
80 };
81 
82 /// \class DataBuffer DataBuffer.h "lldb/Core/DataBuffer.h"
83 /// A pure virtual protocol class for abstracted writable data buffers.
84 ///
85 /// DataBuffer is an abstract class that gets packaged into a shared pointer
86 /// that can use to implement various ways to store data (on the heap, memory
87 /// mapped, cached inferior memory). It gets used by DataExtractor so many
88 /// DataExtractor objects can share the same data and sub-ranges of that
89 /// shared data, and the last object that contains a reference to the shared
90 /// data will free it.
91 class WritableDataBuffer : public DataBuffer {
92 public:
93   /// Destructor
94   ///
95   /// The destructor is virtual as other classes will inherit from this class
96   /// and be downcast to the DataBuffer pure virtual interface. The virtual
97   /// destructor ensures that destructing the base class will destruct the
98   /// class that inherited from it correctly.
99   ~WritableDataBuffer() override = default;
100 
101   using DataBuffer::GetBytes;
102   using DataBuffer::GetData;
103 
104   /// Get a pointer to the data.
105   ///
106   /// \return
107   ///     A pointer to the bytes owned by this object, or NULL if the
108   ///     object contains no bytes.
109   uint8_t *GetBytes() { return const_cast<uint8_t *>(GetBytesImpl()); }
110 
111   llvm::MutableArrayRef<uint8_t> GetData() {
112     return llvm::MutableArrayRef<uint8_t>(GetBytes(), GetByteSize());
113   }
114 
115   /// LLVM RTTI support.
116   /// {
117   static char ID;
118   bool isA(const void *ClassID) const override {
119     return ClassID == &ID || DataBuffer::isA(ClassID);
120   }
121   static bool classof(const DataBuffer *data_buffer) {
122     return data_buffer->isA(&ID);
123   }
124   /// }
125 };
126 
127 class DataBufferUnowned : public WritableDataBuffer {
128 public:
129   DataBufferUnowned(uint8_t *bytes, lldb::offset_t size)
130       : m_bytes(bytes), m_size(size) {}
131 
132   const uint8_t *GetBytesImpl() const override { return m_bytes; }
133   lldb::offset_t GetByteSize() const override { return m_size; }
134 
135   /// LLVM RTTI support.
136   /// {
137   static char ID;
138   bool isA(const void *ClassID) const override {
139     return ClassID == &ID || WritableDataBuffer::isA(ClassID);
140   }
141   static bool classof(const DataBuffer *data_buffer) {
142     return data_buffer->isA(&ID);
143   }
144   /// }
145 private:
146   uint8_t *m_bytes;
147   lldb::offset_t m_size;
148 };
149 
150 } // namespace lldb_private
151 
152 #endif /// #if defined(__cplusplus)
153 #endif // LLDB_UTILITY_DATABUFFER_H
154