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 /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
78 /// if successful, otherwise returning null.
79 ///
80 /// \param IsText Set to true to indicate that the file should be read in
81 /// text mode.
82 ///
83 /// \param IsVolatile Set to true to indicate that the contents of the file
84 /// can change outside the user's control, e.g. when libclang tries to parse
85 /// while the user is editing/updating the file or if the file is on an NFS.
86 static ErrorOr<std::unique_ptr<MemoryBuffer>>
87 getFile(const Twine &Filename, bool IsText = false,
88 bool RequiresNullTerminator = true, bool IsVolatile = false);
89
90 /// Read all of the specified file into a MemoryBuffer as a stream
91 /// (i.e. until EOF reached). This is useful for special files that
92 /// look like a regular file but have 0 size (e.g. /proc/cpuinfo on Linux).
93 static ErrorOr<std::unique_ptr<MemoryBuffer>>
94 getFileAsStream(const Twine &Filename);
95
96 /// Given an already-open file descriptor, map some slice of it into a
97 /// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
98 /// Since this is in the middle of a file, the buffer is not null terminated.
99 static ErrorOr<std::unique_ptr<MemoryBuffer>>
100 getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
101 int64_t Offset, bool IsVolatile = false);
102
103 /// Given an already-open file descriptor, read the file and return a
104 /// MemoryBuffer.
105 ///
106 /// \param IsVolatile Set to true to indicate that the contents of the file
107 /// can change outside the user's control, e.g. when libclang tries to parse
108 /// while the user is editing/updating the file or if the file is on an NFS.
109 static ErrorOr<std::unique_ptr<MemoryBuffer>>
110 getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
111 bool RequiresNullTerminator = true, bool IsVolatile = false);
112
113 /// Open the specified memory range as a MemoryBuffer. Note that InputData
114 /// must be null terminated if RequiresNullTerminator is true.
115 static std::unique_ptr<MemoryBuffer>
116 getMemBuffer(StringRef InputData, StringRef BufferName = "",
117 bool RequiresNullTerminator = true);
118
119 static std::unique_ptr<MemoryBuffer>
120 getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
121
122 /// Open the specified memory range as a MemoryBuffer, copying the contents
123 /// and taking ownership of it. InputData does not have to be null terminated.
124 static std::unique_ptr<MemoryBuffer>
125 getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
126
127 /// Read all of stdin into a file buffer, and return it.
128 static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
129
130 /// Open the specified file as a MemoryBuffer, or open stdin if the Filename
131 /// is "-".
132 static ErrorOr<std::unique_ptr<MemoryBuffer>>
133 getFileOrSTDIN(const Twine &Filename, bool IsText = false,
134 bool RequiresNullTerminator = true);
135
136 /// Map a subrange of the specified file as a MemoryBuffer.
137 static ErrorOr<std::unique_ptr<MemoryBuffer>>
138 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
139 bool IsVolatile = false);
140
141 //===--------------------------------------------------------------------===//
142 // Provided for performance analysis.
143 //===--------------------------------------------------------------------===//
144
145 /// The kind of memory backing used to support the MemoryBuffer.
146 enum BufferKind {
147 MemoryBuffer_Malloc,
148 MemoryBuffer_MMap
149 };
150
151 /// Return information on the memory mechanism used to support the
152 /// MemoryBuffer.
153 virtual BufferKind getBufferKind() const = 0;
154
155 MemoryBufferRef getMemBufferRef() const;
156};
157
158/// This class is an extension of MemoryBuffer, which allows copy-on-write
159/// access to the underlying contents. It only supports creation methods that
160/// are guaranteed to produce a writable buffer. For example, mapping a file
161/// read-only is not supported.
162class WritableMemoryBuffer : public MemoryBuffer {
163protected:
164 WritableMemoryBuffer() = default;
165
166public:
167 using MemoryBuffer::getBuffer;
168 using MemoryBuffer::getBufferEnd;
169 using MemoryBuffer::getBufferStart;
170
171 // const_cast is well-defined here, because the underlying buffer is
172 // guaranteed to have been initialized with a mutable buffer.
173 char *getBufferStart() {
174 return const_cast<char *>(MemoryBuffer::getBufferStart());
175 }
176 char *getBufferEnd() {
177 return const_cast<char *>(MemoryBuffer::getBufferEnd());
178 }
179 MutableArrayRef<char> getBuffer() {
180 return {getBufferStart(), getBufferEnd()};
181 }
182
183 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
184 getFile(const Twine &Filename, bool IsVolatile = false);
185
186 /// Map a subrange of the specified file as a WritableMemoryBuffer.
187 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
188 getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
189 bool IsVolatile = false);
190
191 /// Allocate a new MemoryBuffer of the specified size that is not initialized.
192 /// Note that the caller should initialize the memory allocated by this
193 /// method. The memory is owned by the MemoryBuffer object.
194 static std::unique_ptr<WritableMemoryBuffer>
195 getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "");
196
197 /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
198 /// that the caller need not initialize the memory allocated by this method.
199 /// The memory is owned by the MemoryBuffer object.
200 static std::unique_ptr<WritableMemoryBuffer>
201 getNewMemBuffer(size_t Size, const Twine &BufferName = "");
202
203private:
204 // Hide these base class factory function so one can't write
205 // WritableMemoryBuffer::getXXX()
206 // and be surprised that he got a read-only Buffer.
207 using MemoryBuffer::getFileAsStream;
208 using MemoryBuffer::getFileOrSTDIN;
209 using MemoryBuffer::getMemBuffer;
210 using MemoryBuffer::getMemBufferCopy;
211 using MemoryBuffer::getOpenFile;
212 using MemoryBuffer::getOpenFileSlice;
213 using MemoryBuffer::getSTDIN;
214};
215
216/// This class is an extension of MemoryBuffer, which allows write access to
217/// the underlying contents and committing those changes to the original source.
218/// It only supports creation methods that are guaranteed to produce a writable
219/// buffer. For example, mapping a file read-only is not supported.
220class WriteThroughMemoryBuffer : public MemoryBuffer {
221protected:
222 WriteThroughMemoryBuffer() = default;
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
261// Create wrappers for C Binding types (see CBindingWrapping.h).
262DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
263
264} // end namespace llvm
265
266#endif // LLVM_SUPPORT_MEMORYBUFFER_H
267