1//===--- MemoryBuffer.h - Memory Buffer Interface ---------------*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines the MemoryBuffer interface.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_SUPPORT_MEMORYBUFFER_H
15#define LLVM_SUPPORT_MEMORYBUFFER_H
16
17#include "llvm-c/Types.h"
18#include "llvm/ADT/ArrayRef.h"
19#include "llvm/ADT/StringRef.h"
20#include "llvm/ADT/Twine.h"
21#include "llvm/Support/CBindingWrapping.h"
22#include "llvm/Support/ErrorOr.h"
23#include "llvm/Support/FileSystem.h"
24#include <cstddef>
25#include <cstdint>
26#include <memory>
27
28namespace llvm {
29
30class MemoryBufferRef;
31
32/// This interface provides simple read-only access to a block of memory, and
33/// provides simple methods for reading files and standard input into a memory
34/// buffer. In addition to basic access to the characters in the file, this
35/// interface guarantees you can read one character past the end of the file,
36/// and that this character will read as '\0'.
37///
38/// The '\0' guarantee is needed to support an optimization -- it's intended to
39/// be more efficient for clients which are reading all the data to stop
40/// reading when they encounter a '\0' than to continually check the file
41/// position to see if it has reached the end of the file.
42class MemoryBuffer {
43 const char *BufferStart; // Start of the buffer.
44 const char *BufferEnd; // End of the buffer.
45
46protected:
47 MemoryBuffer() = default;
48
49 void init(const char *BufStart, const char *BufEnd,
50 bool RequiresNullTerminator);
51
52 static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
53 sys::fs::mapped_file_region::readonly;
54
55public:
56 MemoryBuffer(const MemoryBuffer &) = delete;
57 MemoryBuffer &operator=(const MemoryBuffer &) = delete;
58 virtual ~MemoryBuffer();
59
60 const char *getBufferStart() const { return BufferStart; }
61 const char *getBufferEnd() const { return BufferEnd; }
62 size_t getBufferSize() const { return BufferEnd-BufferStart; }
63
64 StringRef getBuffer() const {
65 return StringRef(BufferStart, getBufferSize());
66 }
67
68 /// Return an identifier for this buffer, typically the filename it was read
69 /// from.
70 virtual StringRef getBufferIdentifier() const { return "Unknown buffer"; }
71
72 /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
73 /// if successful, otherwise returning null. If FileSize is specified, this
74 /// means that the client knows that the file exists and that it has the
75 /// specified size.
76 ///
77 /// \param IsVolatile Set to true to indicate that the contents of the file
78 /// can change outside the user's control, e.g. when libclang tries to parse
79 /// while the user is editing/updating the file or if the file is on an NFS.
80 static ErrorOr<std::unique_ptr<MemoryBuffer>>
81 getFile(const Twine &Filename, int64_t FileSize = -1,
82 bool RequiresNullTerminator = true, bool IsVolatile = false);
83
84 /// Read all of the specified file into a MemoryBuffer as a stream
85 /// (i.e. until EOF reached). This is useful for special files that
86 /// look like a regular file but have 0 size (e.g. /proc/cpuinfo on Linux).
87 static ErrorOr<std::unique_ptr<MemoryBuffer>>
88 getFileAsStream(const Twine &Filename);
89
90 /// Given an already-open file descriptor, map some slice of it into a
91 /// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
92 /// Since this is in the middle of a file, the buffer is not null terminated.
93 static ErrorOr<std::unique_ptr<MemoryBuffer>>
94 getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,
95 int64_t Offset, bool IsVolatile = false);
96
97 /// Given an already-open file descriptor, read the file and return a
98 /// MemoryBuffer.
99 ///
100 /// \param IsVolatile Set to true to indicate that the contents of the file
101 /// can change outside the user's control, e.g. when libclang tries to parse
102 /// while the user is editing/updating the file or if the file is on an NFS.
103 static ErrorOr<std::unique_ptr<MemoryBuffer>>
104 getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,
105 bool RequiresNullTerminator = true, bool IsVolatile = false);
106
107 /// Open the specified memory range as a MemoryBuffer. Note that InputData
108 /// must be null terminated if RequiresNullTerminator is true.
109 static std::unique_ptr<MemoryBuffer>
110 getMemBuffer(StringRef InputData, StringRef BufferName = "",
111 bool RequiresNullTerminator = true);
112
113 static std::unique_ptr<MemoryBuffer>
114 getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
115
116 /// Open the specified memory range as a MemoryBuffer, copying the contents
117 /// and taking ownership of it. InputData does not have to be null terminated.
118 static std::unique_ptr<MemoryBuffer>
119 getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
120
121 /// Read all of stdin into a file buffer, and return it.
122 static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
123
124 /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
125 /// is "-".
126 static ErrorOr<std::unique_ptr<MemoryBuffer>>
127 getFileOrSTDIN(const Twine &Filename, int64_t FileSize = -1,
128 bool RequiresNullTerminator = true);
129
130 /// Map a subrange of the specified file as a MemoryBuffer.
131 static ErrorOr<std::unique_ptr<MemoryBuffer>>
132 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
133 bool IsVolatile = false);
134
135 //===--------------------------------------------------------------------===//
136 // Provided for performance analysis.
137 //===--------------------------------------------------------------------===//
138
139 /// The kind of memory backing used to support the MemoryBuffer.
140 enum BufferKind {
141 MemoryBuffer_Malloc,
142 MemoryBuffer_MMap
143 };
144
145 /// Return information on the memory mechanism used to support the
146 /// MemoryBuffer.
147 virtual BufferKind getBufferKind() const = 0;
148
149 MemoryBufferRef getMemBufferRef() const;
150};
151
152/// This class is an extension of MemoryBuffer, which allows copy-on-write
153/// access to the underlying contents. It only supports creation methods that
154/// are guaranteed to produce a writable buffer. For example, mapping a file
155/// read-only is not supported.
156class WritableMemoryBuffer : public MemoryBuffer {
157protected:
158 WritableMemoryBuffer() = default;
159
160 static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
161 sys::fs::mapped_file_region::priv;
162
163public:
164 using MemoryBuffer::getBuffer;
165 using MemoryBuffer::getBufferEnd;
166 using MemoryBuffer::getBufferStart;
167
168 // const_cast is well-defined here, because the underlying buffer is
169 // guaranteed to have been initialized with a mutable buffer.
170 char *getBufferStart() {
171 return const_cast<char *>(MemoryBuffer::getBufferStart());
172 }
173 char *getBufferEnd() {
174 return const_cast<char *>(MemoryBuffer::getBufferEnd());
175 }
176 MutableArrayRef<char> getBuffer() {
177 return {getBufferStart(), getBufferEnd()};
178 }
179
180 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
181 getFile(const Twine &Filename, int64_t FileSize = -1,
182 bool IsVolatile = false);
183
184 /// Map a subrange of the specified file as a WritableMemoryBuffer.
185 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
186 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
187 bool IsVolatile = false);
188
189 /// Allocate a new MemoryBuffer of the specified size that is not initialized.
190 /// Note that the caller should initialize the memory allocated by this
191 /// method. The memory is owned by the MemoryBuffer object.
192 static std::unique_ptr<WritableMemoryBuffer>
193 getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "");
194
195 /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
196 /// that the caller need not initialize the memory allocated by this method.
197 /// The memory is owned by the MemoryBuffer object.
198 static std::unique_ptr<WritableMemoryBuffer>
199 getNewMemBuffer(size_t Size, const Twine &BufferName = "");
200
201private:
202 // Hide these base class factory function so one can't write
203 // WritableMemoryBuffer::getXXX()
204 // and be surprised that he got a read-only Buffer.
205 using MemoryBuffer::getFileAsStream;
206 using MemoryBuffer::getFileOrSTDIN;
207 using MemoryBuffer::getMemBuffer;
208 using MemoryBuffer::getMemBufferCopy;
209 using MemoryBuffer::getOpenFile;
210 using MemoryBuffer::getOpenFileSlice;
211 using MemoryBuffer::getSTDIN;
212};
213
214/// This class is an extension of MemoryBuffer, which allows write access to
215/// the underlying contents and committing those changes to the original source.
216/// It only supports creation methods that are guaranteed to produce a writable
217/// buffer. For example, mapping a file read-only is not supported.
218class WriteThroughMemoryBuffer : public MemoryBuffer {
219protected:
220 WriteThroughMemoryBuffer() = default;
221
222 static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
223 sys::fs::mapped_file_region::readwrite;
224
225public:
226 using MemoryBuffer::getBuffer;
227 using MemoryBuffer::getBufferEnd;
228 using MemoryBuffer::getBufferStart;
229
230 // const_cast is well-defined here, because the underlying buffer is
231 // guaranteed to have been initialized with a mutable buffer.
232 char *getBufferStart() {
233 return const_cast<char *>(MemoryBuffer::getBufferStart());
234 }
235 char *getBufferEnd() {
236 return const_cast<char *>(MemoryBuffer::getBufferEnd());
237 }
238 MutableArrayRef<char> getBuffer() {
239 return {getBufferStart(), getBufferEnd()};
240 }
241
242 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
243 getFile(const Twine &Filename, int64_t FileSize = -1);
244
245 /// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
246 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
247 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
248
249private:
250 // Hide these base class factory function so one can't write
251 // WritableMemoryBuffer::getXXX()
252 // and be surprised that he got a read-only Buffer.
253 using MemoryBuffer::getFileAsStream;
254 using MemoryBuffer::getFileOrSTDIN;
255 using MemoryBuffer::getMemBuffer;
256 using MemoryBuffer::getMemBufferCopy;
257 using MemoryBuffer::getOpenFile;
258 using MemoryBuffer::getOpenFileSlice;
259 using MemoryBuffer::getSTDIN;
260};
261
262class MemoryBufferRef {
263 StringRef Buffer;
264 StringRef Identifier;
265
266public:
267 MemoryBufferRef() = default;
268 MemoryBufferRef(MemoryBuffer& Buffer)
269 : Buffer(Buffer.getBuffer()), Identifier(Buffer.getBufferIdentifier()) {}
270 MemoryBufferRef(StringRef Buffer, StringRef Identifier)
271 : Buffer(Buffer), Identifier(Identifier) {}
272
273 StringRef getBuffer() const { return Buffer; }
274
275 StringRef getBufferIdentifier() const { return Identifier; }
276
277 const char *getBufferStart() const { return Buffer.begin(); }
278 const char *getBufferEnd() const { return Buffer.end(); }
279 size_t getBufferSize() const { return Buffer.size(); }
280};
281
282// Create wrappers for C Binding types (see CBindingWrapping.h).
283DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
284
285} // end namespace llvm
286
287#endif // LLVM_SUPPORT_MEMORYBUFFER_H
288