llvm/lib/Support/MemoryBuffer.cpp

   1 //===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
   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 implements the MemoryBuffer interface.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/MemoryBuffer.h"
  14 #include "llvm/ADT/SmallString.h"
  15 #include "llvm/Config/config.h"
  16 #include "llvm/Support/AutoConvert.h"
  17 #include "llvm/Support/Errc.h"
  18 #include "llvm/Support/Errno.h"
  19 #include "llvm/Support/FileSystem.h"
  20 #include "llvm/Support/MathExtras.h"
  21 #include "llvm/Support/Path.h"
  22 #include "llvm/Support/Process.h"
  23 #include "llvm/Support/Program.h"
  24 #include "llvm/Support/SmallVectorMemoryBuffer.h"
  25 #include <cassert>
  26 #include <cerrno>
  27 #include <cstring>
  28 #include <new>
  29 #include <sys/types.h>
  30 #include <system_error>
  31 #if !defined(_MSC_VER) && !defined(__MINGW32__)
  32 #include <unistd.h>
  33 #else
  34 #include <io.h>
  35 #endif
  36 using namespace llvm;
  37
  38 //===----------------------------------------------------------------------===//
  39 // MemoryBuffer implementation itself.
  40 //===----------------------------------------------------------------------===//
  41
  42 MemoryBuffer::~MemoryBuffer() { }
  43
  44 /// init - Initialize this MemoryBuffer as a reference to externally allocated
  45 /// memory, memory that we know is already null terminated.
  46 void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
  47                         bool RequiresNullTerminator) {
  48   assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
  49          "Buffer is not null terminated!");
  50   BufferStart = BufStart;
  51   BufferEnd = BufEnd;
  52 }
  53
  54 //===----------------------------------------------------------------------===//
  55 // MemoryBufferMem implementation.
  56 //===----------------------------------------------------------------------===//
  57
  58 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
  59 /// null-terminates it.
  60 static void CopyStringRef(char *Memory, StringRef Data) {
  61   if (!Data.empty())
  62     memcpy(Memory, Data.data(), Data.size());
  63   Memory[Data.size()] = 0; // Null terminate string.
  64 }
  65
  66 namespace {
  67 struct NamedBufferAlloc {
  68   const Twine &Name;
  69   NamedBufferAlloc(const Twine &Name) : Name(Name) {}
  70 };
  71 } // namespace
  72
  73 void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
  74   SmallString<256> NameBuf;
  75   StringRef NameRef = Alloc.Name.toStringRef(NameBuf);
  76
  77   char *Mem = static_cast<char *>(operator new(N + NameRef.size() + 1));
  78   CopyStringRef(Mem + N, NameRef);
  79   return Mem;
  80 }
  81
  82 namespace {
  83 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
  84 template<typename MB>
  85 class MemoryBufferMem : public MB {
  86 public:
  87   MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
  88     MemoryBuffer::init(InputData.begin(), InputData.end(),
  89                        RequiresNullTerminator);
  90   }
  91
  92   /// Disable sized deallocation for MemoryBufferMem, because it has
  93   /// tail-allocated data.
  94   void operator delete(void *p) { ::operator delete(p); }
  95
  96   StringRef getBufferIdentifier() const override {
  97     // The name is stored after the class itself.
  98     return StringRef(reinterpret_cast<const char *>(this + 1));
  99   }
 100
 101   MemoryBuffer::BufferKind getBufferKind() const override {
 102     return MemoryBuffer::MemoryBuffer_Malloc;
 103   }
 104 };
 105 } // namespace
 106
 107 template <typename MB>
 108 static ErrorOr<std::unique_ptr<MB>>
 109 getFileAux(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
 110            bool IsText, bool RequiresNullTerminator, bool IsVolatile);
 111
 112 std::unique_ptr<MemoryBuffer>
 113 MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,
 114                            bool RequiresNullTerminator) {
 115   auto *Ret = new (NamedBufferAlloc(BufferName))
 116       MemoryBufferMem<MemoryBuffer>(InputData, RequiresNullTerminator);
 117   return std::unique_ptr<MemoryBuffer>(Ret);
 118 }
 119
 120 std::unique_ptr<MemoryBuffer>
 121 MemoryBuffer::getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator) {
 122   return std::unique_ptr<MemoryBuffer>(getMemBuffer(
 123       Ref.getBuffer(), Ref.getBufferIdentifier(), RequiresNullTerminator));
 124 }
 125
 126 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
 127 getMemBufferCopyImpl(StringRef InputData, const Twine &BufferName) {
 128   auto Buf = WritableMemoryBuffer::getNewUninitMemBuffer(InputData.size(), BufferName);
 129   if (!Buf)
 130     return make_error_code(errc::not_enough_memory);
 131   memcpy(Buf->getBufferStart(), InputData.data(), InputData.size());
 132   return std::move(Buf);
 133 }
 134
 135 std::unique_ptr<MemoryBuffer>
 136 MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {
 137   auto Buf = getMemBufferCopyImpl(InputData, BufferName);
 138   if (Buf)
 139     return std::move(*Buf);
 140   return nullptr;
 141 }
 142
 143 ErrorOr<std::unique_ptr<MemoryBuffer>>
 144 MemoryBuffer::getFileOrSTDIN(const Twine &Filename, bool IsText,
 145                              bool RequiresNullTerminator) {
 146   SmallString<256> NameBuf;
 147   StringRef NameRef = Filename.toStringRef(NameBuf);
 148
 149   if (NameRef == "-")
 150     return getSTDIN();
 151   return getFile(Filename, IsText, RequiresNullTerminator,
 152                  /*IsVolatile=*/false);
 153 }
 154
 155 ErrorOr<std::unique_ptr<MemoryBuffer>>
 156 MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
 157                            uint64_t Offset, bool IsVolatile) {
 158   return getFileAux<MemoryBuffer>(FilePath, MapSize, Offset, /*IsText=*/false,
 159                                   /*RequiresNullTerminator=*/false, IsVolatile);
 160 }
 161
 162 //===----------------------------------------------------------------------===//
 163 // MemoryBuffer::getFile implementation.
 164 //===----------------------------------------------------------------------===//
 165
 166 namespace {
 167
 168 template <typename MB>
 169 constexpr sys::fs::mapped_file_region::mapmode Mapmode =
 170     sys::fs::mapped_file_region::readonly;
 171 template <>
 172 constexpr sys::fs::mapped_file_region::mapmode Mapmode<MemoryBuffer> =
 173     sys::fs::mapped_file_region::readonly;
 174 template <>
 175 constexpr sys::fs::mapped_file_region::mapmode Mapmode<WritableMemoryBuffer> =
 176     sys::fs::mapped_file_region::priv;
 177 template <>
 178 constexpr sys::fs::mapped_file_region::mapmode
 179     Mapmode<WriteThroughMemoryBuffer> = sys::fs::mapped_file_region::readwrite;
 180
 181 /// Memory maps a file descriptor using sys::fs::mapped_file_region.
 182 ///
 183 /// This handles converting the offset into a legal offset on the platform.
 184 template<typename MB>
 185 class MemoryBufferMMapFile : public MB {
 186   sys::fs::mapped_file_region MFR;
 187
 188   static uint64_t getLegalMapOffset(uint64_t Offset) {
 189     return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
 190   }
 191
 192   static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
 193     return Len + (Offset - getLegalMapOffset(Offset));
 194   }
 195
 196   const char *getStart(uint64_t Len, uint64_t Offset) {
 197     return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
 198   }
 199
 200 public:
 201   MemoryBufferMMapFile(bool RequiresNullTerminator, sys::fs::file_t FD, uint64_t Len,
 202                        uint64_t Offset, std::error_code &EC)
 203       : MFR(FD, Mapmode<MB>, getLegalMapSize(Len, Offset),
 204             getLegalMapOffset(Offset), EC) {
 205     if (!EC) {
 206       const char *Start = getStart(Len, Offset);
 207       MemoryBuffer::init(Start, Start + Len, RequiresNullTerminator);
 208     }
 209   }
 210
 211   /// Disable sized deallocation for MemoryBufferMMapFile, because it has
 212   /// tail-allocated data.
 213   void operator delete(void *p) { ::operator delete(p); }
 214
 215   StringRef getBufferIdentifier() const override {
 216     // The name is stored after the class itself.
 217     return StringRef(reinterpret_cast<const char *>(this + 1));
 218   }
 219
 220   MemoryBuffer::BufferKind getBufferKind() const override {
 221     return MemoryBuffer::MemoryBuffer_MMap;
 222   }
 223 };
 224 } // namespace
 225
 226 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
 227 getMemoryBufferForStream(sys::fs::file_t FD, const Twine &BufferName) {
 228   const ssize_t ChunkSize = 4096*4;
 229   SmallString<ChunkSize> Buffer;
 230   // Read into Buffer until we hit EOF.
 231   for (;;) {
 232     Buffer.reserve(Buffer.size() + ChunkSize);
 233     Expected<size_t> ReadBytes = sys::fs::readNativeFile(
 234         FD, makeMutableArrayRef(Buffer.end(), ChunkSize));
 235     if (!ReadBytes)
 236       return errorToErrorCode(ReadBytes.takeError());
 237     if (*ReadBytes == 0)
 238       break;
 239     Buffer.set_size(Buffer.size() + *ReadBytes);
 240   }
 241
 242   return getMemBufferCopyImpl(Buffer, BufferName);
 243 }
 244
 245 ErrorOr<std::unique_ptr<MemoryBuffer>>
 246 MemoryBuffer::getFile(const Twine &Filename, bool IsText,
 247                       bool RequiresNullTerminator, bool IsVolatile) {
 248   return getFileAux<MemoryBuffer>(Filename, /*MapSize=*/-1, /*Offset=*/0,
 249                                   IsText, RequiresNullTerminator, IsVolatile);
 250 }
 251
 252 template <typename MB>
 253 static ErrorOr<std::unique_ptr<MB>>
 254 getOpenFileImpl(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
 255                 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
 256                 bool IsVolatile);
 257
 258 template <typename MB>
 259 static ErrorOr<std::unique_ptr<MB>>
 260 getFileAux(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
 261            bool IsText, bool RequiresNullTerminator, bool IsVolatile) {
 262   Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead(
 263       Filename, IsText ? sys::fs::OF_TextWithCRLF : sys::fs::OF_None);
 264   if (!FDOrErr)
 265     return errorToErrorCode(FDOrErr.takeError());
 266   sys::fs::file_t FD = *FDOrErr;
 267   auto Ret = getOpenFileImpl<MB>(FD, Filename, /*FileSize=*/-1, MapSize, Offset,
 268                                  RequiresNullTerminator, IsVolatile);
 269   sys::fs::closeFile(FD);
 270   return Ret;
 271 }
 272
 273 ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
 274 WritableMemoryBuffer::getFile(const Twine &Filename, bool IsVolatile) {
 275   return getFileAux<WritableMemoryBuffer>(
 276       Filename, /*MapSize=*/-1, /*Offset=*/0, /*IsText=*/false,
 277       /*RequiresNullTerminator=*/false, IsVolatile);
 278 }
 279
 280 ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
 281 WritableMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
 282                                    uint64_t Offset, bool IsVolatile) {
 283   return getFileAux<WritableMemoryBuffer>(
 284       Filename, MapSize, Offset, /*IsText=*/false,
 285       /*RequiresNullTerminator=*/false, IsVolatile);
 286 }
 287
 288 std::unique_ptr<WritableMemoryBuffer>
 289 WritableMemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {
 290   using MemBuffer = MemoryBufferMem<WritableMemoryBuffer>;
 291   // Allocate space for the MemoryBuffer, the data and the name. It is important
 292   // that MemoryBuffer and data are aligned so PointerIntPair works with them.
 293   // TODO: Is 16-byte alignment enough?  We copy small object files with large
 294   // alignment expectations into this buffer.
 295   SmallString<256> NameBuf;
 296   StringRef NameRef = BufferName.toStringRef(NameBuf);
 297   size_t AlignedStringLen = alignTo(sizeof(MemBuffer) + NameRef.size() + 1, 16);
 298   size_t RealLen = AlignedStringLen + Size + 1;
 299   char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
 300   if (!Mem)
 301     return nullptr;
 302
 303   // The name is stored after the class itself.
 304   CopyStringRef(Mem + sizeof(MemBuffer), NameRef);
 305
 306   // The buffer begins after the name and must be aligned.
 307   char *Buf = Mem + AlignedStringLen;
 308   Buf[Size] = 0; // Null terminate buffer.
 309
 310   auto *Ret = new (Mem) MemBuffer(StringRef(Buf, Size), true);
 311   return std::unique_ptr<WritableMemoryBuffer>(Ret);
 312 }
 313
 314 std::unique_ptr<WritableMemoryBuffer>
 315 WritableMemoryBuffer::getNewMemBuffer(size_t Size, const Twine &BufferName) {
 316   auto SB = WritableMemoryBuffer::getNewUninitMemBuffer(Size, BufferName);
 317   if (!SB)
 318     return nullptr;
 319   memset(SB->getBufferStart(), 0, Size);
 320   return SB;
 321 }
 322
 323 static bool shouldUseMmap(sys::fs::file_t FD,
 324                           size_t FileSize,
 325                           size_t MapSize,
 326                           off_t Offset,
 327                           bool RequiresNullTerminator,
 328                           int PageSize,
 329                           bool IsVolatile) {
 330   // mmap may leave the buffer without null terminator if the file size changed
 331   // by the time the last page is mapped in, so avoid it if the file size is
 332   // likely to change.
 333   if (IsVolatile && RequiresNullTerminator)
 334     return false;
 335
 336   // We don't use mmap for small files because this can severely fragment our
 337   // address space.
 338   if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
 339     return false;
 340
 341   if (!RequiresNullTerminator)
 342     return true;
 343
 344   // If we don't know the file size, use fstat to find out.  fstat on an open
 345   // file descriptor is cheaper than stat on a random path.
 346   // FIXME: this chunk of code is duplicated, but it avoids a fstat when
 347   // RequiresNullTerminator = false and MapSize != -1.
 348   if (FileSize == size_t(-1)) {
 349     sys::fs::file_status Status;
 350     if (sys::fs::status(FD, Status))
 351       return false;
 352     FileSize = Status.getSize();
 353   }
 354
 355   // If we need a null terminator and the end of the map is inside the file,
 356   // we cannot use mmap.
 357   size_t End = Offset + MapSize;
 358   assert(End <= FileSize);
 359   if (End != FileSize)
 360     return false;
 361
 362   // Don't try to map files that are exactly a multiple of the system page size
 363   // if we need a null terminator.
 364   if ((FileSize & (PageSize -1)) == 0)
 365     return false;
 366
 367 #if defined(__CYGWIN__)
 368   // Don't try to map files that are exactly a multiple of the physical page size
 369   // if we need a null terminator.
 370   // FIXME: We should reorganize again getPageSize() on Win32.
 371   if ((FileSize & (4096 - 1)) == 0)
 372     return false;
 373 #endif
 374
 375   return true;
 376 }
 377
 378 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
 379 getReadWriteFile(const Twine &Filename, uint64_t FileSize, uint64_t MapSize,
 380                  uint64_t Offset) {
 381   Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForReadWrite(
 382       Filename, sys::fs::CD_OpenExisting, sys::fs::OF_None);
 383   if (!FDOrErr)
 384     return errorToErrorCode(FDOrErr.takeError());
 385   sys::fs::file_t FD = *FDOrErr;
 386
 387   // Default is to map the full file.
 388   if (MapSize == uint64_t(-1)) {
 389     // If we don't know the file size, use fstat to find out.  fstat on an open
 390     // file descriptor is cheaper than stat on a random path.
 391     if (FileSize == uint64_t(-1)) {
 392       sys::fs::file_status Status;
 393       std::error_code EC = sys::fs::status(FD, Status);
 394       if (EC)
 395         return EC;
 396
 397       // If this not a file or a block device (e.g. it's a named pipe
 398       // or character device), we can't mmap it, so error out.
 399       sys::fs::file_type Type = Status.type();
 400       if (Type != sys::fs::file_type::regular_file &&
 401           Type != sys::fs::file_type::block_file)
 402         return make_error_code(errc::invalid_argument);
 403
 404       FileSize = Status.getSize();
 405     }
 406     MapSize = FileSize;
 407   }
 408
 409   std::error_code EC;
 410   std::unique_ptr<WriteThroughMemoryBuffer> Result(
 411       new (NamedBufferAlloc(Filename))
 412           MemoryBufferMMapFile<WriteThroughMemoryBuffer>(false, FD, MapSize,
 413                                                          Offset, EC));
 414   if (EC)
 415     return EC;
 416   return std::move(Result);
 417 }
 418
 419 ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
 420 WriteThroughMemoryBuffer::getFile(const Twine &Filename, int64_t FileSize) {
 421   return getReadWriteFile(Filename, FileSize, FileSize, 0);
 422 }
 423
 424 /// Map a subrange of the specified file as a WritableMemoryBuffer.
 425 ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
 426 WriteThroughMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
 427                                        uint64_t Offset) {
 428   return getReadWriteFile(Filename, -1, MapSize, Offset);
 429 }
 430
 431 template <typename MB>
 432 static ErrorOr<std::unique_ptr<MB>>
 433 getOpenFileImpl(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
 434                 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
 435                 bool IsVolatile) {
 436   static int PageSize = sys::Process::getPageSizeEstimate();
 437
 438   // Default is to map the full file.
 439   if (MapSize == uint64_t(-1)) {
 440     // If we don't know the file size, use fstat to find out.  fstat on an open
 441     // file descriptor is cheaper than stat on a random path.
 442     if (FileSize == uint64_t(-1)) {
 443       sys::fs::file_status Status;
 444       std::error_code EC = sys::fs::status(FD, Status);
 445       if (EC)
 446         return EC;
 447
 448       // If this not a file or a block device (e.g. it's a named pipe
 449       // or character device), we can't trust the size. Create the memory
 450       // buffer by copying off the stream.
 451       sys::fs::file_type Type = Status.type();
 452       if (Type != sys::fs::file_type::regular_file &&
 453           Type != sys::fs::file_type::block_file)
 454         return getMemoryBufferForStream(FD, Filename);
 455
 456       FileSize = Status.getSize();
 457     }
 458     MapSize = FileSize;
 459   }
 460
 461   if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
 462                     PageSize, IsVolatile)) {
 463     std::error_code EC;
 464     std::unique_ptr<MB> Result(
 465         new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile<MB>(
 466             RequiresNullTerminator, FD, MapSize, Offset, EC));
 467     if (!EC)
 468       return std::move(Result);
 469   }
 470
 471 #ifdef __MVS__
 472   // Set codepage auto-conversion for z/OS.
 473   if (auto EC = llvm::enableAutoConversion(FD))
 474     return EC;
 475 #endif
 476
 477   auto Buf = WritableMemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
 478   if (!Buf) {
 479     // Failed to create a buffer. The only way it can fail is if
 480     // new(std::nothrow) returns 0.
 481     return make_error_code(errc::not_enough_memory);
 482   }
 483
 484   // Read until EOF, zero-initialize the rest.
 485   MutableArrayRef<char> ToRead = Buf->getBuffer();
 486   while (!ToRead.empty()) {
 487     Expected<size_t> ReadBytes =
 488         sys::fs::readNativeFileSlice(FD, ToRead, Offset);
 489     if (!ReadBytes)
 490       return errorToErrorCode(ReadBytes.takeError());
 491     if (*ReadBytes == 0) {
 492       std::memset(ToRead.data(), 0, ToRead.size());
 493       break;
 494     }
 495     ToRead = ToRead.drop_front(*ReadBytes);
 496     Offset += *ReadBytes;
 497   }
 498
 499   return std::move(Buf);
 500 }
 501
 502 ErrorOr<std::unique_ptr<MemoryBuffer>>
 503 MemoryBuffer::getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
 504                           bool RequiresNullTerminator, bool IsVolatile) {
 505   return getOpenFileImpl<MemoryBuffer>(FD, Filename, FileSize, FileSize, 0,
 506                          RequiresNullTerminator, IsVolatile);
 507 }
 508
 509 ErrorOr<std::unique_ptr<MemoryBuffer>>
 510 MemoryBuffer::getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
 511                                int64_t Offset, bool IsVolatile) {
 512   assert(MapSize != uint64_t(-1));
 513   return getOpenFileImpl<MemoryBuffer>(FD, Filename, -1, MapSize, Offset, false,
 514                                        IsVolatile);
 515 }
 516
 517 ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {
 518   // Read in all of the data from stdin, we cannot mmap stdin.
 519   //
 520   // FIXME: That isn't necessarily true, we should try to mmap stdin and
 521   // fallback if it fails.
 522   sys::ChangeStdinMode(sys::fs::OF_Text);
 523
 524   return getMemoryBufferForStream(sys::fs::getStdinHandle(), "<stdin>");
 525 }
 526
 527 ErrorOr<std::unique_ptr<MemoryBuffer>>
 528 MemoryBuffer::getFileAsStream(const Twine &Filename) {
 529   Expected<sys::fs::file_t> FDOrErr =
 530       sys::fs::openNativeFileForRead(Filename, sys::fs::OF_None);
 531   if (!FDOrErr)
 532     return errorToErrorCode(FDOrErr.takeError());
 533   sys::fs::file_t FD = *FDOrErr;
 534   ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =
 535       getMemoryBufferForStream(FD, Filename);
 536   sys::fs::closeFile(FD);
 537   return Ret;
 538 }
 539
 540 MemoryBufferRef MemoryBuffer::getMemBufferRef() const {
 541   StringRef Data = getBuffer();
 542   StringRef Identifier = getBufferIdentifier();
 543   return MemoryBufferRef(Data, Identifier);
 544 }
 545
 546 SmallVectorMemoryBuffer::~SmallVectorMemoryBuffer() {}