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/FileSystem.h"
23#include <cstddef>
24#include <cstdint>
25#include <memory>
26
27namespace llvm {
28
29class 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.
41class MemoryBuffer {
42 const char *BufferStart; // Start of the buffer.
43 const char *BufferEnd; // End of the buffer.
44
45protected:
46 MemoryBuffer() = default;
47
48 void init(const char *BufStart, const char *BufEnd,
49 bool RequiresNullTerminator);
50
51 static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
52 sys::fs::mapped_file_region::readonly;
53
54public:
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.
79 static ErrorOr<std::unique_ptr<MemoryBuffer>>
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).
86 static ErrorOr<std::unique_ptr<MemoryBuffer>>
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.
92 static ErrorOr<std::unique_ptr<MemoryBuffer>>
93 getOpenFileSlice(int 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.
102 static ErrorOr<std::unique_ptr<MemoryBuffer>>
103 getOpenFile(int 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.
121 static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
122
123 /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
124 /// is "-".
125 static ErrorOr<std::unique_ptr<MemoryBuffer>>
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.
130 static ErrorOr<std::unique_ptr<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 {
140 MemoryBuffer_Malloc,
141 MemoryBuffer_MMap
142 };
143
144 /// Return information on the memory mechanism used to support the
145 /// MemoryBuffer.
146 virtual BufferKind getBufferKind() const = 0;
147
148 MemoryBufferRef getMemBufferRef() const;
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.
155class WritableMemoryBuffer : public MemoryBuffer {
156protected:
157 WritableMemoryBuffer() = default;
158
159 static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
160 sys::fs::mapped_file_region::priv;
161
162public:
163 using MemoryBuffer::getBuffer;
164 using MemoryBuffer::getBufferEnd;
165 using MemoryBuffer::getBufferStart;
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 }
175 MutableArrayRef<char> getBuffer() {
176 return {getBufferStart(), getBufferEnd()};
177 }
178
179 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
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.
184 static ErrorOr<std::unique_ptr<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
200private:
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.
204 using MemoryBuffer::getFileAsStream;
205 using MemoryBuffer::getFileOrSTDIN;
206 using MemoryBuffer::getMemBuffer;
207 using MemoryBuffer::getMemBufferCopy;
208 using MemoryBuffer::getOpenFile;
209 using MemoryBuffer::getOpenFileSlice;
210 using MemoryBuffer::getSTDIN;
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.
217class WriteThroughMemoryBuffer : public MemoryBuffer {
218protected:
219 WriteThroughMemoryBuffer() = default;
220
221 static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
222 sys::fs::mapped_file_region::readwrite;
223
224public:
225 using MemoryBuffer::getBuffer;
226 using MemoryBuffer::getBufferEnd;
227 using MemoryBuffer::getBufferStart;
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 }
237 MutableArrayRef<char> getBuffer() {
238 return {getBufferStart(), getBufferEnd()};
239 }
240
241 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
242 getFile(const Twine &Filename, int64_t FileSize = -1);
243
244 /// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
245 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
246 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
247
248private:
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.
252 using MemoryBuffer::getFileAsStream;
253 using MemoryBuffer::getFileOrSTDIN;
254 using MemoryBuffer::getMemBuffer;
255 using MemoryBuffer::getMemBufferCopy;
256 using MemoryBuffer::getOpenFile;
257 using MemoryBuffer::getOpenFileSlice;
258 using MemoryBuffer::getSTDIN;
259};
260
261class MemoryBufferRef {
262 StringRef Buffer;
263 StringRef Identifier;
264
265public:
266 MemoryBufferRef() = default;
267 MemoryBufferRef(MemoryBuffer& Buffer)
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).
282DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
283
284} // end namespace llvm
285
286#endif // LLVM_SUPPORT_MEMORYBUFFER_H
287