include/llvm/Support/MemoryBuffer.h

   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
  27 namespace llvm {
  28
  29 class 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.
  41 class MemoryBuffer {
  42   const char *BufferStart; // Start of the buffer.
  43   const char *BufferEnd;   // End of the buffer.
  44
  45 protected:
  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
  54 public:
  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(sys::fs::file_t 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(sys::fs::file_t 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.
 155 class WritableMemoryBuffer : public MemoryBuffer {
 156 protected:
 157   WritableMemoryBuffer() = default;
 158
 159   static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
 160       sys::fs::mapped_file_region::priv;
 161
 162 public:
 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
 200 private:
 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.
 217 class WriteThroughMemoryBuffer : public MemoryBuffer {
 218 protected:
 219   WriteThroughMemoryBuffer() = default;
 220
 221   static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
 222       sys::fs::mapped_file_region::readwrite;
 223
 224 public:
 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
 248 private:
 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 class MemoryBufferRef {
 262   StringRef Buffer;
 263   StringRef Identifier;
 264
 265 public:
 266   MemoryBufferRef() = default;
 267   MemoryBufferRef(const 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).
 282 DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
 283
 284 } // end namespace llvm
 285
 286 #endif // LLVM_SUPPORT_MEMORYBUFFER_H