1 //===--- MemoryBuffer.h - Memory Buffer Interface ---------------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 // This file defines the MemoryBuffer interface.
11 //===----------------------------------------------------------------------===//
13 #ifndef LLVM_SUPPORT_MEMORYBUFFER_H
14 #define LLVM_SUPPORT_MEMORYBUFFER_H
16 #include "llvm-c/Types.h"
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Twine.h"
20 #include "llvm/Support/CBindingWrapping.h"
21 #include "llvm/Support/ErrorOr.h"
22 #include "llvm/Support/MemoryBufferRef.h"
30 // Duplicated from FileSystem.h to avoid a dependency.
32 // A Win32 HANDLE is a typedef of void*
33 using file_t = void *;
40 /// This interface provides simple read-only access to a block of memory, and
41 /// provides simple methods for reading files and standard input into a memory
42 /// buffer. In addition to basic access to the characters in the file, this
43 /// interface guarantees you can read one character past the end of the file,
44 /// and that this character will read as '\0'.
46 /// The '\0' guarantee is needed to support an optimization -- it's intended to
47 /// be more efficient for clients which are reading all the data to stop
48 /// reading when they encounter a '\0' than to continually check the file
49 /// position to see if it has reached the end of the file.
51 const char *BufferStart; // Start of the buffer.
52 const char *BufferEnd; // End of the buffer.
55 MemoryBuffer() = default;
57 void init(const char *BufStart, const char *BufEnd,
58 bool RequiresNullTerminator);
61 MemoryBuffer(const MemoryBuffer &) = delete;
62 MemoryBuffer &operator=(const MemoryBuffer &) = delete;
63 virtual ~MemoryBuffer();
65 const char *getBufferStart() const { return BufferStart; }
66 const char *getBufferEnd() const { return BufferEnd; }
67 size_t getBufferSize() const { return BufferEnd-BufferStart; }
69 StringRef getBuffer() const {
70 return StringRef(BufferStart, getBufferSize());
73 /// Return an identifier for this buffer, typically the filename it was read
75 virtual StringRef getBufferIdentifier() const { return "Unknown buffer"; }
77 /// For read-only MemoryBuffer_MMap, mark the buffer as unused in the near
78 /// future and the kernel can free resources associated with it. Further
79 /// access is supported but may be expensive. This calls
80 /// madvise(MADV_DONTNEED) on read-only file mappings on *NIX systems. This
81 /// function should not be called on a writable buffer.
82 virtual void dontNeedIfMmap() {}
84 /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
85 /// if successful, otherwise returning null.
87 /// \param IsText Set to true to indicate that the file should be read in
90 /// \param IsVolatile Set to true to indicate that the contents of the file
91 /// can change outside the user's control, e.g. when libclang tries to parse
92 /// while the user is editing/updating the file or if the file is on an NFS.
93 static ErrorOr<std::unique_ptr<MemoryBuffer>>
94 getFile(const Twine &Filename, bool IsText = false,
95 bool RequiresNullTerminator = true, bool IsVolatile = false);
97 /// Read all of the specified file into a MemoryBuffer as a stream
98 /// (i.e. until EOF reached). This is useful for special files that
99 /// look like a regular file but have 0 size (e.g. /proc/cpuinfo on Linux).
100 static ErrorOr<std::unique_ptr<MemoryBuffer>>
101 getFileAsStream(const Twine &Filename);
103 /// Given an already-open file descriptor, map some slice of it into a
104 /// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
105 /// Since this is in the middle of a file, the buffer is not null terminated.
106 static ErrorOr<std::unique_ptr<MemoryBuffer>>
107 getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
108 int64_t Offset, bool IsVolatile = false);
110 /// Given an already-open file descriptor, read the file and return a
113 /// \param IsVolatile Set to true to indicate that the contents of the file
114 /// can change outside the user's control, e.g. when libclang tries to parse
115 /// while the user is editing/updating the file or if the file is on an NFS.
116 static ErrorOr<std::unique_ptr<MemoryBuffer>>
117 getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
118 bool RequiresNullTerminator = true, bool IsVolatile = false);
120 /// Open the specified memory range as a MemoryBuffer. Note that InputData
121 /// must be null terminated if RequiresNullTerminator is true.
122 static std::unique_ptr<MemoryBuffer>
123 getMemBuffer(StringRef InputData, StringRef BufferName = "",
124 bool RequiresNullTerminator = true);
126 static std::unique_ptr<MemoryBuffer>
127 getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
129 /// Open the specified memory range as a MemoryBuffer, copying the contents
130 /// and taking ownership of it. InputData does not have to be null terminated.
131 static std::unique_ptr<MemoryBuffer>
132 getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
134 /// Read all of stdin into a file buffer, and return it.
135 static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
137 /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
139 static ErrorOr<std::unique_ptr<MemoryBuffer>>
140 getFileOrSTDIN(const Twine &Filename, bool IsText = false,
141 bool RequiresNullTerminator = true);
143 /// Map a subrange of the specified file as a MemoryBuffer.
144 static ErrorOr<std::unique_ptr<MemoryBuffer>>
145 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
146 bool IsVolatile = false);
148 //===--------------------------------------------------------------------===//
149 // Provided for performance analysis.
150 //===--------------------------------------------------------------------===//
152 /// The kind of memory backing used to support the MemoryBuffer.
158 /// Return information on the memory mechanism used to support the
160 virtual BufferKind getBufferKind() const = 0;
162 MemoryBufferRef getMemBufferRef() const;
165 /// This class is an extension of MemoryBuffer, which allows copy-on-write
166 /// access to the underlying contents. It only supports creation methods that
167 /// are guaranteed to produce a writable buffer. For example, mapping a file
168 /// read-only is not supported.
169 class WritableMemoryBuffer : public MemoryBuffer {
171 WritableMemoryBuffer() = default;
174 using MemoryBuffer::getBuffer;
175 using MemoryBuffer::getBufferEnd;
176 using MemoryBuffer::getBufferStart;
178 // const_cast is well-defined here, because the underlying buffer is
179 // guaranteed to have been initialized with a mutable buffer.
180 char *getBufferStart() {
181 return const_cast<char *>(MemoryBuffer::getBufferStart());
183 char *getBufferEnd() {
184 return const_cast<char *>(MemoryBuffer::getBufferEnd());
186 MutableArrayRef<char> getBuffer() {
187 return {getBufferStart(), getBufferEnd()};
190 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
191 getFile(const Twine &Filename, bool IsVolatile = false);
193 /// Map a subrange of the specified file as a WritableMemoryBuffer.
194 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
195 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
196 bool IsVolatile = false);
198 /// Allocate a new MemoryBuffer of the specified size that is not initialized.
199 /// Note that the caller should initialize the memory allocated by this
200 /// method. The memory is owned by the MemoryBuffer object.
201 static std::unique_ptr<WritableMemoryBuffer>
202 getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "");
204 /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
205 /// that the caller need not initialize the memory allocated by this method.
206 /// The memory is owned by the MemoryBuffer object.
207 static std::unique_ptr<WritableMemoryBuffer>
208 getNewMemBuffer(size_t Size, const Twine &BufferName = "");
211 // Hide these base class factory function so one can't write
212 // WritableMemoryBuffer::getXXX()
213 // and be surprised that he got a read-only Buffer.
214 using MemoryBuffer::getFileAsStream;
215 using MemoryBuffer::getFileOrSTDIN;
216 using MemoryBuffer::getMemBuffer;
217 using MemoryBuffer::getMemBufferCopy;
218 using MemoryBuffer::getOpenFile;
219 using MemoryBuffer::getOpenFileSlice;
220 using MemoryBuffer::getSTDIN;
223 /// This class is an extension of MemoryBuffer, which allows write access to
224 /// the underlying contents and committing those changes to the original source.
225 /// It only supports creation methods that are guaranteed to produce a writable
226 /// buffer. For example, mapping a file read-only is not supported.
227 class WriteThroughMemoryBuffer : public MemoryBuffer {
229 WriteThroughMemoryBuffer() = default;
232 using MemoryBuffer::getBuffer;
233 using MemoryBuffer::getBufferEnd;
234 using MemoryBuffer::getBufferStart;
236 // const_cast is well-defined here, because the underlying buffer is
237 // guaranteed to have been initialized with a mutable buffer.
238 char *getBufferStart() {
239 return const_cast<char *>(MemoryBuffer::getBufferStart());
241 char *getBufferEnd() {
242 return const_cast<char *>(MemoryBuffer::getBufferEnd());
244 MutableArrayRef<char> getBuffer() {
245 return {getBufferStart(), getBufferEnd()};
248 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
249 getFile(const Twine &Filename, int64_t FileSize = -1);
251 /// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
252 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
253 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
256 // Hide these base class factory function so one can't write
257 // WritableMemoryBuffer::getXXX()
258 // and be surprised that he got a read-only Buffer.
259 using MemoryBuffer::getFileAsStream;
260 using MemoryBuffer::getFileOrSTDIN;
261 using MemoryBuffer::getMemBuffer;
262 using MemoryBuffer::getMemBufferCopy;
263 using MemoryBuffer::getOpenFile;
264 using MemoryBuffer::getOpenFileSlice;
265 using MemoryBuffer::getSTDIN;
268 // Create wrappers for C Binding types (see CBindingWrapping.h).
269 DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
271 } // end namespace llvm
273 #endif // LLVM_SUPPORT_MEMORYBUFFER_H