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/CBindingWrapping.h"
21#include "llvm/Support/ErrorOr.h"
22#include "llvm/Support/MemoryBufferRef.h"
23#include <cstddef>
24#include <cstdint>
25#include <memory>
26
27namespace llvm {
28namespace sys {
29namespace fs {
30// Duplicated from FileSystem.h to avoid a dependency.
31#if defined(_WIN32)
32// A Win32 HANDLE is a typedef of void*
33using file_t = void *;
34#else
35using file_t = int;
36#endif
37} // namespace fs
38} // namespace sys
39
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'.
45///
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.
50class MemoryBuffer {
51 const char *BufferStart; // Start of the buffer.
52 const char *BufferEnd; // End of the buffer.
53
54protected:
55 MemoryBuffer() = default;
56
57 void init(const char *BufStart, const char *BufEnd,
58 bool RequiresNullTerminator);
59
60public:
61 MemoryBuffer(const MemoryBuffer &) = delete;
62 MemoryBuffer &operator=(const MemoryBuffer &) = delete;
63 virtual ~MemoryBuffer();
64
65 const char *getBufferStart() const { return BufferStart; }
66 const char *getBufferEnd() const { return BufferEnd; }
67 size_t getBufferSize() const { return BufferEnd-BufferStart; }
68
69 StringRef getBuffer() const {
70 return StringRef(BufferStart, getBufferSize());
71 }
72
73 /// Return an identifier for this buffer, typically the filename it was read
74 /// from.
75 virtual StringRef getBufferIdentifier() const { return "Unknown buffer"; }
76
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() {}
83
84 /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
85 /// if successful, otherwise returning null.
86 ///
87 /// \param IsText Set to true to indicate that the file should be read in
88 /// text mode.
89 ///
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);
96
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);
102
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);
109
110 /// Given an already-open file descriptor, read the file and return a
111 /// MemoryBuffer.
112 ///
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);
119
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);
125
126 static std::unique_ptr<MemoryBuffer>
127 getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
128
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 = "");
133
134 /// Read all of stdin into a file buffer, and return it.
135 static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
136
137 /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
138 /// is "-".
139 static ErrorOr<std::unique_ptr<MemoryBuffer>>
140 getFileOrSTDIN(const Twine &Filename, bool IsText = false,
141 bool RequiresNullTerminator = true);
142
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);
147
148 //===--------------------------------------------------------------------===//
149 // Provided for performance analysis.
150 //===--------------------------------------------------------------------===//
151
152 /// The kind of memory backing used to support the MemoryBuffer.
153 enum BufferKind {
154 MemoryBuffer_Malloc,
155 MemoryBuffer_MMap
156 };
157
158 /// Return information on the memory mechanism used to support the
159 /// MemoryBuffer.
160 virtual BufferKind getBufferKind() const = 0;
161
162 MemoryBufferRef getMemBufferRef() const;
163};
164
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.
169class WritableMemoryBuffer : public MemoryBuffer {
170protected:
171 WritableMemoryBuffer() = default;
172
173public:
174 using MemoryBuffer::getBuffer;
175 using MemoryBuffer::getBufferEnd;
176 using MemoryBuffer::getBufferStart;
177
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());
182 }
183 char *getBufferEnd() {
184 return const_cast<char *>(MemoryBuffer::getBufferEnd());
185 }
186 MutableArrayRef<char> getBuffer() {
187 return {getBufferStart(), getBufferEnd()};
188 }
189
190 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
191 getFile(const Twine &Filename, bool IsVolatile = false);
192
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);
197
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 = "");
203
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 = "");
209
210private:
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;
221};
222
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.
227class WriteThroughMemoryBuffer : public MemoryBuffer {
228protected:
229 WriteThroughMemoryBuffer() = default;
230
231public:
232 using MemoryBuffer::getBuffer;
233 using MemoryBuffer::getBufferEnd;
234 using MemoryBuffer::getBufferStart;
235
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());
240 }
241 char *getBufferEnd() {
242 return const_cast<char *>(MemoryBuffer::getBufferEnd());
243 }
244 MutableArrayRef<char> getBuffer() {
245 return {getBufferStart(), getBufferEnd()};
246 }
247
248 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
249 getFile(const Twine &Filename, int64_t FileSize = -1);
250
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);
254
255private:
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;
266};
267
268// Create wrappers for C Binding types (see CBindingWrapping.h).
269DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
270
271} // end namespace llvm
272
273#endif // LLVM_SUPPORT_MEMORYBUFFER_H
274