1 //===--- MemoryBuffer.h - Memory Buffer Interface ---------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //  This file defines the MemoryBuffer interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_SUPPORT_MEMORYBUFFER_H
15 #define LLVM_SUPPORT_MEMORYBUFFER_H
16 
17 #include "llvm-c/Support.h"
18 #include "llvm/ADT/Twine.h"
19 #include "llvm/Support/CBindingWrapping.h"
20 #include "llvm/Support/DataTypes.h"
21 #include "llvm/Support/ErrorOr.h"
22 #include <memory>
23 
24 namespace llvm {
25 class MemoryBufferRef;
26 
27 /// This interface provides simple read-only access to a block of memory, and
28 /// provides simple methods for reading files and standard input into a memory
29 /// buffer.  In addition to basic access to the characters in the file, this
30 /// interface guarantees you can read one character past the end of the file,
31 /// and that this character will read as '\0'.
32 ///
33 /// The '\0' guarantee is needed to support an optimization -- it's intended to
34 /// be more efficient for clients which are reading all the data to stop
35 /// reading when they encounter a '\0' than to continually check the file
36 /// position to see if it has reached the end of the file.
37 class MemoryBuffer {
38   const char *BufferStart; // Start of the buffer.
39   const char *BufferEnd;   // End of the buffer.
40 
41   MemoryBuffer(const MemoryBuffer &) = delete;
42   MemoryBuffer &operator=(const MemoryBuffer &) = delete;
43 protected:
MemoryBuffer()44   MemoryBuffer() {}
45   void init(const char *BufStart, const char *BufEnd,
46             bool RequiresNullTerminator);
47 public:
48   virtual ~MemoryBuffer();
49 
getBufferStart()50   const char *getBufferStart() const { return BufferStart; }
getBufferEnd()51   const char *getBufferEnd() const   { return BufferEnd; }
getBufferSize()52   size_t getBufferSize() const { return BufferEnd-BufferStart; }
53 
getBuffer()54   StringRef getBuffer() const {
55     return StringRef(BufferStart, getBufferSize());
56   }
57 
58   /// Return an identifier for this buffer, typically the filename it was read
59   /// from.
getBufferIdentifier()60   virtual const char *getBufferIdentifier() const {
61     return "Unknown buffer";
62   }
63 
64   /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
65   /// if successful, otherwise returning null. If FileSize is specified, this
66   /// means that the client knows that the file exists and that it has the
67   /// specified size.
68   ///
69   /// \param IsVolatileSize Set to true to indicate that the file size may be
70   /// changing, e.g. when libclang tries to parse while the user is
71   /// editing/updating the file.
72   static ErrorOr<std::unique_ptr<MemoryBuffer>>
73   getFile(const Twine &Filename, int64_t FileSize = -1,
74           bool RequiresNullTerminator = true, bool IsVolatileSize = false);
75 
76   /// Given an already-open file descriptor, map some slice of it into a
77   /// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
78   /// Since this is in the middle of a file, the buffer is not null terminated.
79   static ErrorOr<std::unique_ptr<MemoryBuffer>>
80   getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,
81                    int64_t Offset);
82 
83   /// Given an already-open file descriptor, read the file and return a
84   /// MemoryBuffer.
85   ///
86   /// \param IsVolatileSize Set to true to indicate that the file size may be
87   /// changing, e.g. when libclang tries to parse while the user is
88   /// editing/updating the file.
89   static ErrorOr<std::unique_ptr<MemoryBuffer>>
90   getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,
91               bool RequiresNullTerminator = true, bool IsVolatileSize = false);
92 
93   /// Open the specified memory range as a MemoryBuffer. Note that InputData
94   /// must be null terminated if RequiresNullTerminator is true.
95   static std::unique_ptr<MemoryBuffer>
96   getMemBuffer(StringRef InputData, StringRef BufferName = "",
97                bool RequiresNullTerminator = true);
98 
99   static std::unique_ptr<MemoryBuffer>
100   getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
101 
102   /// Open the specified memory range as a MemoryBuffer, copying the contents
103   /// and taking ownership of it. InputData does not have to be null terminated.
104   static std::unique_ptr<MemoryBuffer>
105   getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
106 
107   /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
108   /// that the caller need not initialize the memory allocated by this method.
109   /// The memory is owned by the MemoryBuffer object.
110   static std::unique_ptr<MemoryBuffer>
111   getNewMemBuffer(size_t Size, StringRef BufferName = "");
112 
113   /// Allocate a new MemoryBuffer of the specified size that is not initialized.
114   /// Note that the caller should initialize the memory allocated by this
115   /// method. The memory is owned by the MemoryBuffer object.
116   static std::unique_ptr<MemoryBuffer>
117   getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "");
118 
119   /// Read all of stdin into a file buffer, and return it.
120   static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
121 
122   /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
123   /// is "-".
124   static ErrorOr<std::unique_ptr<MemoryBuffer>>
125   getFileOrSTDIN(const Twine &Filename, int64_t FileSize = -1);
126 
127   /// Map a subrange of the the specified file as a MemoryBuffer.
128   static ErrorOr<std::unique_ptr<MemoryBuffer>>
129   getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
130 
131   //===--------------------------------------------------------------------===//
132   // Provided for performance analysis.
133   //===--------------------------------------------------------------------===//
134 
135   /// The kind of memory backing used to support the MemoryBuffer.
136   enum BufferKind {
137     MemoryBuffer_Malloc,
138     MemoryBuffer_MMap
139   };
140 
141   /// Return information on the memory mechanism used to support the
142   /// MemoryBuffer.
143   virtual BufferKind getBufferKind() const = 0;
144 
145   MemoryBufferRef getMemBufferRef() const;
146 };
147 
148 class MemoryBufferRef {
149   StringRef Buffer;
150   StringRef Identifier;
151 
152 public:
MemoryBufferRef()153   MemoryBufferRef() {}
MemoryBufferRef(StringRef Buffer,StringRef Identifier)154   MemoryBufferRef(StringRef Buffer, StringRef Identifier)
155       : Buffer(Buffer), Identifier(Identifier) {}
156 
getBuffer()157   StringRef getBuffer() const { return Buffer; }
158 
getBufferIdentifier()159   StringRef getBufferIdentifier() const { return Identifier; }
160 
getBufferStart()161   const char *getBufferStart() const { return Buffer.begin(); }
getBufferEnd()162   const char *getBufferEnd() const { return Buffer.end(); }
getBufferSize()163   size_t getBufferSize() const { return Buffer.size(); }
164 };
165 
166 // Create wrappers for C Binding types (see CBindingWrapping.h).
167 DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
168 
169 } // end namespace llvm
170 
171 #endif
172