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 27 namespace llvm { 28 namespace sys { 29 namespace fs { 30 // Duplicated from FileSystem.h to avoid a dependency. 31 #if defined(_WIN32) 32 // A Win32 HANDLE is a typedef of void* 33 using file_t = void *; 34 #else 35 using 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. 50 class MemoryBuffer { 51 const char *BufferStart; // Start of the buffer. 52 const char *BufferEnd; // End of the buffer. 53 54 protected: 55 MemoryBuffer() = default; 56 57 void init(const char *BufStart, const char *BufEnd, 58 bool RequiresNullTerminator); 59 60 public: 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. 169 class WritableMemoryBuffer : public MemoryBuffer { 170 protected: 171 WritableMemoryBuffer() = default; 172 173 public: 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 = ""); 209 210 private: 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. 227 class WriteThroughMemoryBuffer : public MemoryBuffer { 228 protected: 229 WriteThroughMemoryBuffer() = default; 230 231 public: 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); 254 255 private: 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). 269 DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef) 270 271 } // end namespace llvm 272 273 #endif // LLVM_SUPPORT_MEMORYBUFFER_H 274