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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"
20 : #include "llvm/Support/Alignment.h"
21 : #include "llvm/Support/CBindingWrapping.h"
22 : #include "llvm/Support/ErrorOr.h"
23 : #include "llvm/Support/MemoryBufferRef.h"
24 : #include <cstddef>
25 : #include <cstdint>
26 : #include <memory>
27 :
28 : namespace llvm {
29 : namespace sys {
30 : namespace fs {
31 : // Duplicated from FileSystem.h to avoid a dependency.
32 : #if defined(_WIN32)
33 : // A Win32 HANDLE is a typedef of void*
34 : using file_t = void *;
35 : #else
36 : using file_t = int;
37 : #endif
38 : } // namespace fs
39 : } // namespace sys
40 :
41 : /// This interface provides simple read-only access to a block of memory, and
42 : /// provides simple methods for reading files and standard input into a memory
43 : /// buffer. In addition to basic access to the characters in the file, this
44 : /// interface guarantees you can read one character past the end of the file,
45 : /// and that this character will read as '\0'.
46 : ///
47 : /// The '\0' guarantee is needed to support an optimization -- it's intended to
48 : /// be more efficient for clients which are reading all the data to stop
49 : /// reading when they encounter a '\0' than to continually check the file
50 : /// position to see if it has reached the end of the file.
51 : class MemoryBuffer {
52 : const char *BufferStart; // Start of the buffer.
53 : const char *BufferEnd; // End of the buffer.
54 :
55 : protected:
56 : MemoryBuffer() = default;
57 :
58 : void init(const char *BufStart, const char *BufEnd,
59 : bool RequiresNullTerminator);
60 :
61 : public:
62 : MemoryBuffer(const MemoryBuffer &) = delete;
63 : MemoryBuffer &operator=(const MemoryBuffer &) = delete;
64 : virtual ~MemoryBuffer();
65 :
66 : const char *getBufferStart() const { return BufferStart; }
67 : const char *getBufferEnd() const { return BufferEnd; }
68 : size_t getBufferSize() const { return BufferEnd-BufferStart; }
69 :
70 : StringRef getBuffer() const {
71 : return StringRef(BufferStart, getBufferSize());
72 : }
73 :
74 : /// Return an identifier for this buffer, typically the filename it was read
75 : /// from.
76 : virtual StringRef getBufferIdentifier() const { return "Unknown buffer"; }
77 :
78 : /// For read-only MemoryBuffer_MMap, mark the buffer as unused in the near
79 : /// future and the kernel can free resources associated with it. Further
80 : /// access is supported but may be expensive. This calls
81 : /// madvise(MADV_DONTNEED) on read-only file mappings on *NIX systems. This
82 : /// function should not be called on a writable buffer.
83 : virtual void dontNeedIfMmap() {}
84 :
85 : /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
86 : /// if successful, otherwise returning null.
87 : ///
88 : /// \param IsText Set to true to indicate that the file should be read in
89 : /// text mode.
90 : ///
91 : /// \param IsVolatile Set to true to indicate that the contents of the file
92 : /// can change outside the user's control, e.g. when libclang tries to parse
93 : /// while the user is editing/updating the file or if the file is on an NFS.
94 : ///
95 : /// \param Alignment Set to indicate that the buffer should be aligned to at
96 : /// least the specified alignment.
97 : static ErrorOr<std::unique_ptr<MemoryBuffer>>
98 : getFile(const Twine &Filename, bool IsText = false,
99 : bool RequiresNullTerminator = true, bool IsVolatile = false,
100 45 : std::optional<Align> Alignment = std::nullopt);
101 :
102 : /// Read all of the specified file into a MemoryBuffer as a stream
103 : /// (i.e. until EOF reached). This is useful for special files that
104 : /// look like a regular file but have 0 size (e.g. /proc/cpuinfo on Linux).
105 : static ErrorOr<std::unique_ptr<MemoryBuffer>>
106 : getFileAsStream(const Twine &Filename);
107 :
108 : /// Given an already-open file descriptor, map some slice of it into a
109 : /// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
110 : /// Since this is in the middle of a file, the buffer is not null terminated.
111 : static ErrorOr<std::unique_ptr<MemoryBuffer>>
112 : getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
113 : int64_t Offset, bool IsVolatile = false,
114 : std::optional<Align> Alignment = std::nullopt);
115 :
116 : /// Given an already-open file descriptor, read the file and return a
117 : /// MemoryBuffer.
118 : ///
119 : /// \param IsVolatile Set to true to indicate that the contents of the file
120 : /// can change outside the user's control, e.g. when libclang tries to parse
121 : /// while the user is editing/updating the file or if the file is on an NFS.
122 : ///
123 : /// \param Alignment Set to indicate that the buffer should be aligned to at
124 : /// least the specified alignment.
125 : static ErrorOr<std::unique_ptr<MemoryBuffer>>
126 : getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
127 : bool RequiresNullTerminator = true, bool IsVolatile = false,
128 : std::optional<Align> Alignment = std::nullopt);
129 :
130 : /// Open the specified memory range as a MemoryBuffer. Note that InputData
131 : /// must be null terminated if RequiresNullTerminator is true.
132 : static std::unique_ptr<MemoryBuffer>
133 : getMemBuffer(StringRef InputData, StringRef BufferName = "",
134 : bool RequiresNullTerminator = true);
135 :
136 : static std::unique_ptr<MemoryBuffer>
137 : getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
138 :
139 : /// Open the specified memory range as a MemoryBuffer, copying the contents
140 : /// and taking ownership of it. InputData does not have to be null terminated.
141 : static std::unique_ptr<MemoryBuffer>
142 : getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
143 :
144 : /// Read all of stdin into a file buffer, and return it.
145 : static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
146 :
147 : /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
148 : /// is "-".
149 : static ErrorOr<std::unique_ptr<MemoryBuffer>>
150 : getFileOrSTDIN(const Twine &Filename, bool IsText = false,
151 : bool RequiresNullTerminator = true,
152 : std::optional<Align> Alignment = std::nullopt);
153 :
154 : /// Map a subrange of the specified file as a MemoryBuffer.
155 : static ErrorOr<std::unique_ptr<MemoryBuffer>>
156 : getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
157 : bool IsVolatile = false,
158 : std::optional<Align> Alignment = std::nullopt);
159 :
160 : //===--------------------------------------------------------------------===//
161 : // Provided for performance analysis.
162 : //===--------------------------------------------------------------------===//
163 :
164 : /// The kind of memory backing used to support the MemoryBuffer.
165 : enum BufferKind {
166 : MemoryBuffer_Malloc,
167 : MemoryBuffer_MMap
168 : };
169 :
170 : /// Return information on the memory mechanism used to support the
171 : /// MemoryBuffer.
172 : virtual BufferKind getBufferKind() const = 0;
173 :
174 : MemoryBufferRef getMemBufferRef() const;
175 : };
176 :
177 : /// This class is an extension of MemoryBuffer, which allows copy-on-write
178 : /// access to the underlying contents. It only supports creation methods that
179 : /// are guaranteed to produce a writable buffer. For example, mapping a file
180 : /// read-only is not supported.
181 : class WritableMemoryBuffer : public MemoryBuffer {
182 : protected:
183 : WritableMemoryBuffer() = default;
184 :
185 : public:
186 : using MemoryBuffer::getBuffer;
187 : using MemoryBuffer::getBufferEnd;
188 : using MemoryBuffer::getBufferStart;
189 :
190 : // const_cast is well-defined here, because the underlying buffer is
191 : // guaranteed to have been initialized with a mutable buffer.
192 : char *getBufferStart() {
193 : return const_cast<char *>(MemoryBuffer::getBufferStart());
194 : }
195 : char *getBufferEnd() {
196 : return const_cast<char *>(MemoryBuffer::getBufferEnd());
197 : }
198 : MutableArrayRef<char> getBuffer() {
199 : return {getBufferStart(), getBufferEnd()};
200 : }
201 :
202 : static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
203 : getFile(const Twine &Filename, bool IsVolatile = false,
204 : std::optional<Align> Alignment = std::nullopt);
205 :
206 : /// Map a subrange of the specified file as a WritableMemoryBuffer.
207 : static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
208 : getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
209 : bool IsVolatile = false,
210 : std::optional<Align> Alignment = std::nullopt);
211 :
212 : /// Allocate a new MemoryBuffer of the specified size that is not initialized.
213 : /// Note that the caller should initialize the memory allocated by this
214 : /// method. The memory is owned by the MemoryBuffer object.
215 : ///
216 : /// \param Alignment Set to indicate that the buffer should be aligned to at
217 : /// least the specified alignment.
218 : static std::unique_ptr<WritableMemoryBuffer>
219 : getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "",
220 : std::optional<Align> Alignment = std::nullopt);
221 :
222 : /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
223 : /// that the caller need not initialize the memory allocated by this method.
224 : /// The memory is owned by the MemoryBuffer object.
225 : static std::unique_ptr<WritableMemoryBuffer>
226 : getNewMemBuffer(size_t Size, const Twine &BufferName = "");
227 :
228 : private:
229 : // Hide these base class factory function so one can't write
230 : // WritableMemoryBuffer::getXXX()
231 : // and be surprised that he got a read-only Buffer.
232 : using MemoryBuffer::getFileAsStream;
233 : using MemoryBuffer::getFileOrSTDIN;
234 : using MemoryBuffer::getMemBuffer;
235 : using MemoryBuffer::getMemBufferCopy;
236 : using MemoryBuffer::getOpenFile;
237 : using MemoryBuffer::getOpenFileSlice;
238 : using MemoryBuffer::getSTDIN;
239 : };
240 :
241 : /// This class is an extension of MemoryBuffer, which allows write access to
242 : /// the underlying contents and committing those changes to the original source.
243 : /// It only supports creation methods that are guaranteed to produce a writable
244 : /// buffer. For example, mapping a file read-only is not supported.
245 : class WriteThroughMemoryBuffer : public MemoryBuffer {
246 : protected:
247 : WriteThroughMemoryBuffer() = default;
248 :
249 : public:
250 : using MemoryBuffer::getBuffer;
251 : using MemoryBuffer::getBufferEnd;
252 : using MemoryBuffer::getBufferStart;
253 :
254 : // const_cast is well-defined here, because the underlying buffer is
255 : // guaranteed to have been initialized with a mutable buffer.
256 : char *getBufferStart() {
257 : return const_cast<char *>(MemoryBuffer::getBufferStart());
258 : }
259 : char *getBufferEnd() {
260 : return const_cast<char *>(MemoryBuffer::getBufferEnd());
261 : }
262 : MutableArrayRef<char> getBuffer() {
263 : return {getBufferStart(), getBufferEnd()};
264 : }
265 :
266 : static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
267 : getFile(const Twine &Filename, int64_t FileSize = -1);
268 :
269 : /// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
270 : static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
271 : getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
272 :
273 : private:
274 : // Hide these base class factory function so one can't write
275 : // WritableMemoryBuffer::getXXX()
276 : // and be surprised that he got a read-only Buffer.
277 : using MemoryBuffer::getFileAsStream;
278 : using MemoryBuffer::getFileOrSTDIN;
279 : using MemoryBuffer::getMemBuffer;
280 : using MemoryBuffer::getMemBufferCopy;
281 : using MemoryBuffer::getOpenFile;
282 : using MemoryBuffer::getOpenFileSlice;
283 : using MemoryBuffer::getSTDIN;
284 : };
285 :
286 : // Create wrappers for C Binding types (see CBindingWrapping.h).
287 : DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
288 :
289 : } // end namespace llvm
290 :
291 : #endif // LLVM_SUPPORT_MEMORYBUFFER_H
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