LLVM  10.0.0svn
MemoryBuffer.h
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1 //===--- MemoryBuffer.h - Memory Buffer Interface ---------------*- 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 // This file defines the MemoryBuffer interface.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_SUPPORT_MEMORYBUFFER_H
14 #define LLVM_SUPPORT_MEMORYBUFFER_H
15 
16 #include "llvm-c/Types.h"
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Twine.h"
21 #include "llvm/Support/ErrorOr.h"
23 #include <cstddef>
24 #include <cstdint>
25 #include <memory>
26 
27 namespace llvm {
28 
29 class MemoryBufferRef;
30 
31 /// This interface provides simple read-only access to a block of memory, and
32 /// provides simple methods for reading files and standard input into a memory
33 /// buffer. In addition to basic access to the characters in the file, this
34 /// interface guarantees you can read one character past the end of the file,
35 /// and that this character will read as '\0'.
36 ///
37 /// The '\0' guarantee is needed to support an optimization -- it's intended to
38 /// be more efficient for clients which are reading all the data to stop
39 /// reading when they encounter a '\0' than to continually check the file
40 /// position to see if it has reached the end of the file.
41 class MemoryBuffer {
42  const char *BufferStart; // Start of the buffer.
43  const char *BufferEnd; // End of the buffer.
44 
45 protected:
46  MemoryBuffer() = default;
47 
48  void init(const char *BufStart, const char *BufEnd,
49  bool RequiresNullTerminator);
50 
53 
54 public:
55  MemoryBuffer(const MemoryBuffer &) = delete;
56  MemoryBuffer &operator=(const MemoryBuffer &) = delete;
57  virtual ~MemoryBuffer();
58 
59  const char *getBufferStart() const { return BufferStart; }
60  const char *getBufferEnd() const { return BufferEnd; }
61  size_t getBufferSize() const { return BufferEnd-BufferStart; }
62 
63  StringRef getBuffer() const {
64  return StringRef(BufferStart, getBufferSize());
65  }
66 
67  /// Return an identifier for this buffer, typically the filename it was read
68  /// from.
69  virtual StringRef getBufferIdentifier() const { return "Unknown buffer"; }
70 
71  /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
72  /// if successful, otherwise returning null. If FileSize is specified, this
73  /// means that the client knows that the file exists and that it has the
74  /// specified size.
75  ///
76  /// \param IsVolatile Set to true to indicate that the contents of the file
77  /// can change outside the user's control, e.g. when libclang tries to parse
78  /// while the user is editing/updating the file or if the file is on an NFS.
80  getFile(const Twine &Filename, int64_t FileSize = -1,
81  bool RequiresNullTerminator = true, bool IsVolatile = false);
82 
83  /// Read all of the specified file into a MemoryBuffer as a stream
84  /// (i.e. until EOF reached). This is useful for special files that
85  /// look like a regular file but have 0 size (e.g. /proc/cpuinfo on Linux).
87  getFileAsStream(const Twine &Filename);
88 
89  /// Given an already-open file descriptor, map some slice of it into a
90  /// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
91  /// Since this is in the middle of a file, the buffer is not null terminated.
93  getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
94  int64_t Offset, bool IsVolatile = false);
95 
96  /// Given an already-open file descriptor, read the file and return a
97  /// MemoryBuffer.
98  ///
99  /// \param IsVolatile Set to true to indicate that the contents of the file
100  /// can change outside the user's control, e.g. when libclang tries to parse
101  /// while the user is editing/updating the file or if the file is on an NFS.
103  getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
104  bool RequiresNullTerminator = true, bool IsVolatile = false);
105 
106  /// Open the specified memory range as a MemoryBuffer. Note that InputData
107  /// must be null terminated if RequiresNullTerminator is true.
108  static std::unique_ptr<MemoryBuffer>
109  getMemBuffer(StringRef InputData, StringRef BufferName = "",
110  bool RequiresNullTerminator = true);
111 
112  static std::unique_ptr<MemoryBuffer>
113  getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
114 
115  /// Open the specified memory range as a MemoryBuffer, copying the contents
116  /// and taking ownership of it. InputData does not have to be null terminated.
117  static std::unique_ptr<MemoryBuffer>
118  getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
119 
120  /// Read all of stdin into a file buffer, and return it.
122 
123  /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
124  /// is "-".
126  getFileOrSTDIN(const Twine &Filename, int64_t FileSize = -1,
127  bool RequiresNullTerminator = true);
128 
129  /// Map a subrange of the specified file as a MemoryBuffer.
131  getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
132  bool IsVolatile = false);
133 
134  //===--------------------------------------------------------------------===//
135  // Provided for performance analysis.
136  //===--------------------------------------------------------------------===//
137 
138  /// The kind of memory backing used to support the MemoryBuffer.
139  enum BufferKind {
142  };
143 
144  /// Return information on the memory mechanism used to support the
145  /// MemoryBuffer.
146  virtual BufferKind getBufferKind() const = 0;
147 
149 };
150 
151 /// This class is an extension of MemoryBuffer, which allows copy-on-write
152 /// access to the underlying contents. It only supports creation methods that
153 /// are guaranteed to produce a writable buffer. For example, mapping a file
154 /// read-only is not supported.
156 protected:
157  WritableMemoryBuffer() = default;
158 
161 
162 public:
166 
167  // const_cast is well-defined here, because the underlying buffer is
168  // guaranteed to have been initialized with a mutable buffer.
169  char *getBufferStart() {
170  return const_cast<char *>(MemoryBuffer::getBufferStart());
171  }
172  char *getBufferEnd() {
173  return const_cast<char *>(MemoryBuffer::getBufferEnd());
174  }
176  return {getBufferStart(), getBufferEnd()};
177  }
178 
180  getFile(const Twine &Filename, int64_t FileSize = -1,
181  bool IsVolatile = false);
182 
183  /// Map a subrange of the specified file as a WritableMemoryBuffer.
185  getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
186  bool IsVolatile = false);
187 
188  /// Allocate a new MemoryBuffer of the specified size that is not initialized.
189  /// Note that the caller should initialize the memory allocated by this
190  /// method. The memory is owned by the MemoryBuffer object.
191  static std::unique_ptr<WritableMemoryBuffer>
192  getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "");
193 
194  /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
195  /// that the caller need not initialize the memory allocated by this method.
196  /// The memory is owned by the MemoryBuffer object.
197  static std::unique_ptr<WritableMemoryBuffer>
198  getNewMemBuffer(size_t Size, const Twine &BufferName = "");
199 
200 private:
201  // Hide these base class factory function so one can't write
202  // WritableMemoryBuffer::getXXX()
203  // and be surprised that he got a read-only Buffer.
211 };
212 
213 /// This class is an extension of MemoryBuffer, which allows write access to
214 /// the underlying contents and committing those changes to the original source.
215 /// It only supports creation methods that are guaranteed to produce a writable
216 /// buffer. For example, mapping a file read-only is not supported.
218 protected:
219  WriteThroughMemoryBuffer() = default;
220 
223 
224 public:
228 
229  // const_cast is well-defined here, because the underlying buffer is
230  // guaranteed to have been initialized with a mutable buffer.
231  char *getBufferStart() {
232  return const_cast<char *>(MemoryBuffer::getBufferStart());
233  }
234  char *getBufferEnd() {
235  return const_cast<char *>(MemoryBuffer::getBufferEnd());
236  }
238  return {getBufferStart(), getBufferEnd()};
239  }
240 
242  getFile(const Twine &Filename, int64_t FileSize = -1);
243 
244  /// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
246  getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
247 
248 private:
249  // Hide these base class factory function so one can't write
250  // WritableMemoryBuffer::getXXX()
251  // and be surprised that he got a read-only Buffer.
259 };
260 
262  StringRef Buffer;
263  StringRef Identifier;
264 
265 public:
266  MemoryBufferRef() = default;
268  : Buffer(Buffer.getBuffer()), Identifier(Buffer.getBufferIdentifier()) {}
269  MemoryBufferRef(StringRef Buffer, StringRef Identifier)
270  : Buffer(Buffer), Identifier(Identifier) {}
271 
272  StringRef getBuffer() const { return Buffer; }
273 
274  StringRef getBufferIdentifier() const { return Identifier; }
275 
276  const char *getBufferStart() const { return Buffer.begin(); }
277  const char *getBufferEnd() const { return Buffer.end(); }
278  size_t getBufferSize() const { return Buffer.size(); }
279 };
280 
281 // Create wrappers for C Binding types (see CBindingWrapping.h).
283 
284 } // end namespace llvm
285 
286 #endif // LLVM_SUPPORT_MEMORYBUFFER_H
virtual StringRef getBufferIdentifier() const
Return an identifier for this buffer, typically the filename it was read from.
Definition: MemoryBuffer.h:69
void init(const char *BufStart, const char *BufEnd, bool RequiresNullTerminator)
init - Initialize this MemoryBuffer as a reference to externally allocated memory, memory that we know is already null terminated.
Represents either an error or a value T.
Definition: ErrorOr.h:56
StringRef getBuffer() const
Definition: MemoryBuffer.h:63
This class represents lattice values for constants.
Definition: AllocatorList.h:23
const char * getBufferEnd() const
Definition: MemoryBuffer.h:277
struct LLVMOpaqueMemoryBuffer * LLVMMemoryBufferRef
LLVM uses a polymorphic type hierarchy which C cannot represent, therefore parameters must be passed ...
Definition: Types.h:49
constexpr char IsVolatile[]
Key for Kernel::Arg::Metadata::mIsVolatile.
MemoryBuffer & operator=(const MemoryBuffer &)=delete
static std::unique_ptr< MemoryBuffer > getMemBuffer(StringRef InputData, StringRef BufferName="", bool RequiresNullTerminator=true)
Open the specified memory range as a MemoryBuffer.
size_t getBufferSize() const
Definition: MemoryBuffer.h:61
virtual BufferKind getBufferKind() const =0
Return information on the memory mechanism used to support the MemoryBuffer.
static ErrorOr< std::unique_ptr< MemoryBuffer > > getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize, int64_t Offset, bool IsVolatile=false)
Given an already-open file descriptor, map some slice of it into a MemoryBuffer.
#define DEFINE_SIMPLE_CONVERSION_FUNCTIONS(ty, ref)
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:80
StringRef getBuffer() const
Definition: MemoryBuffer.h:272
static ErrorOr< std::unique_ptr< MemoryBuffer > > getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize, bool RequiresNullTerminator=true, bool IsVolatile=false)
Given an already-open file descriptor, read the file and return a MemoryBuffer.
The access may reference the value stored in memory.
MemoryBufferRef(const MemoryBuffer &Buffer)
Definition: MemoryBuffer.h:267
May access map via data and modify it. Written to path.
Definition: FileSystem.h:1164
May only access map via const_data as read only.
Definition: FileSystem.h:1163
MutableArrayRef< char > getBuffer()
Definition: MemoryBuffer.h:237
LLVM_NODISCARD size_t size() const
size - Get the string size.
Definition: StringRef.h:144
static constexpr sys::fs::mapped_file_region::mapmode Mapmode
Definition: MemoryBuffer.h:51
static ErrorOr< std::unique_ptr< MemoryBuffer > > getSTDIN()
Read all of stdin into a file buffer, and return it.
MutableArrayRef - Represent a mutable reference to an array (0 or more elements consecutively in memo...
Definition: ArrayRef.h:290
size_t getBufferSize() const
Definition: MemoryBuffer.h:278
This class is an extension of MemoryBuffer, which allows write access to the underlying contents and ...
Definition: MemoryBuffer.h:217
MemoryBuffer()=default
MemoryBufferRef getMemBufferRef() const
This interface provides simple read-only access to a block of memory, and provides simple methods for...
Definition: MemoryBuffer.h:41
static std::unique_ptr< MemoryBuffer > getMemBufferCopy(StringRef InputData, const Twine &BufferName="")
Open the specified memory range as a MemoryBuffer, copying the contents and taking ownership of it...
StringRef getBufferIdentifier() const
Definition: MemoryBuffer.h:274
iterator begin() const
Definition: StringRef.h:115
May modify via data, but changes are lost on destruction.
Definition: FileSystem.h:1165
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset, bool IsVolatile=false)
Map a subrange of the specified file as a MemoryBuffer.
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFileOrSTDIN(const Twine &Filename, int64_t FileSize=-1, bool RequiresNullTerminator=true)
Open the specified file as a MemoryBuffer, or open stdin if the Filename is "-".
const char * getBufferEnd() const
Definition: MemoryBuffer.h:60
virtual ~MemoryBuffer()
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFileAsStream(const Twine &Filename)
Read all of the specified file into a MemoryBuffer as a stream (i.e.
This class is an extension of MemoryBuffer, which allows copy-on-write access to the underlying conte...
Definition: MemoryBuffer.h:155
uint32_t Size
Definition: Profile.cpp:46
BufferKind
The kind of memory backing used to support the MemoryBuffer.
Definition: MemoryBuffer.h:139
const char * getBufferStart() const
Definition: MemoryBuffer.h:59
Provides ErrorOr<T> smart pointer.
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFile(const Twine &Filename, int64_t FileSize=-1, bool RequiresNullTerminator=true, bool IsVolatile=false)
Open the specified file as a MemoryBuffer, returning a new MemoryBuffer if successful, otherwise returning null.
const char * getBufferStart() const
Definition: MemoryBuffer.h:276
MemoryBufferRef(StringRef Buffer, StringRef Identifier)
Definition: MemoryBuffer.h:269
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
iterator end() const
Definition: StringRef.h:117
MutableArrayRef< char > getBuffer()
Definition: MemoryBuffer.h:175