lib/Support/MemoryBuffer.cpp

   1 //===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
   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 implements the MemoryBuffer interface.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Support/MemoryBuffer.h"
  15 #include "llvm/ADT/SmallString.h"
  16 #include "llvm/Config/config.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 }
  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 }
 106
 107 template <typename MB>
 108 static ErrorOr<std::unique_ptr<MB>>
 109 getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
 110            uint64_t Offset, 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, int64_t FileSize,
 145                              bool RequiresNullTerminator) {
 146   SmallString<256> NameBuf;
 147   StringRef NameRef = Filename.toStringRef(NameBuf);
 148
 149   if (NameRef == "-")
 150     return getSTDIN();
 151   return getFile(Filename, FileSize, RequiresNullTerminator);
 152 }
 153
 154 ErrorOr<std::unique_ptr<MemoryBuffer>>
 155 MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
 156                            uint64_t Offset, bool IsVolatile) {
 157   return getFileAux<MemoryBuffer>(FilePath, -1, MapSize, Offset, false,
 158                                   IsVolatile);
 159 }
 160
 161 //===----------------------------------------------------------------------===//
 162 // MemoryBuffer::getFile implementation.
 163 //===----------------------------------------------------------------------===//
 164
 165 namespace {
 166 /// Memory maps a file descriptor using sys::fs::mapped_file_region.
 167 ///
 168 /// This handles converting the offset into a legal offset on the platform.
 169 template<typename MB>
 170 class MemoryBufferMMapFile : public MB {
 171   sys::fs::mapped_file_region MFR;
 172
 173   static uint64_t getLegalMapOffset(uint64_t Offset) {
 174     return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
 175   }
 176
 177   static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
 178     return Len + (Offset - getLegalMapOffset(Offset));
 179   }
 180
 181   const char *getStart(uint64_t Len, uint64_t Offset) {
 182     return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
 183   }
 184
 185 public:
 186   MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
 187                        uint64_t Offset, std::error_code &EC)
 188       : MFR(FD, MB::Mapmode, getLegalMapSize(Len, Offset),
 189             getLegalMapOffset(Offset), EC) {
 190     if (!EC) {
 191       const char *Start = getStart(Len, Offset);
 192       MemoryBuffer::init(Start, Start + Len, RequiresNullTerminator);
 193     }
 194   }
 195
 196   /// Disable sized deallocation for MemoryBufferMMapFile, because it has
 197   /// tail-allocated data.
 198   void operator delete(void *p) { ::operator delete(p); }
 199
 200   StringRef getBufferIdentifier() const override {
 201     // The name is stored after the class itself.
 202     return StringRef(reinterpret_cast<const char *>(this + 1));
 203   }
 204
 205   MemoryBuffer::BufferKind getBufferKind() const override {
 206     return MemoryBuffer::MemoryBuffer_MMap;
 207   }
 208 };
 209 }
 210
 211 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
 212 getMemoryBufferForStream(int FD, const Twine &BufferName) {
 213   const ssize_t ChunkSize = 4096*4;
 214   SmallString<ChunkSize> Buffer;
 215   ssize_t ReadBytes;
 216   // Read into Buffer until we hit EOF.
 217   do {
 218     Buffer.reserve(Buffer.size() + ChunkSize);
 219     ReadBytes = sys::RetryAfterSignal(-1, ::read, FD, Buffer.end(), ChunkSize);
 220     if (ReadBytes == -1)
 221       return std::error_code(errno, std::generic_category());
 222     Buffer.set_size(Buffer.size() + ReadBytes);
 223   } while (ReadBytes != 0);
 224
 225   return getMemBufferCopyImpl(Buffer, BufferName);
 226 }
 227
 228
 229 ErrorOr<std::unique_ptr<MemoryBuffer>>
 230 MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
 231                       bool RequiresNullTerminator, bool IsVolatile) {
 232   return getFileAux<MemoryBuffer>(Filename, FileSize, FileSize, 0,
 233                                   RequiresNullTerminator, IsVolatile);
 234 }
 235
 236 template <typename MB>
 237 static ErrorOr<std::unique_ptr<MB>>
 238 getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
 239                 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
 240                 bool IsVolatile);
 241
 242 template <typename MB>
 243 static ErrorOr<std::unique_ptr<MB>>
 244 getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
 245            uint64_t Offset, bool RequiresNullTerminator, bool IsVolatile) {
 246   int FD;
 247   std::error_code EC = sys::fs::openFileForRead(Filename, FD, sys::fs::OF_None);
 248
 249   if (EC)
 250     return EC;
 251
 252   auto Ret = getOpenFileImpl<MB>(FD, Filename, FileSize, MapSize, Offset,
 253                                  RequiresNullTerminator, IsVolatile);
 254   close(FD);
 255   return Ret;
 256 }
 257
 258 ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
 259 WritableMemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
 260                               bool IsVolatile) {
 261   return getFileAux<WritableMemoryBuffer>(Filename, FileSize, FileSize, 0,
 262                                           /*RequiresNullTerminator*/ false,
 263                                           IsVolatile);
 264 }
 265
 266 ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
 267 WritableMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
 268                                    uint64_t Offset, bool IsVolatile) {
 269   return getFileAux<WritableMemoryBuffer>(Filename, -1, MapSize, Offset, false,
 270                                           IsVolatile);
 271 }
 272
 273 std::unique_ptr<WritableMemoryBuffer>
 274 WritableMemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {
 275   using MemBuffer = MemoryBufferMem<WritableMemoryBuffer>;
 276   // Allocate space for the MemoryBuffer, the data and the name. It is important
 277   // that MemoryBuffer and data are aligned so PointerIntPair works with them.
 278   // TODO: Is 16-byte alignment enough?  We copy small object files with large
 279   // alignment expectations into this buffer.
 280   SmallString<256> NameBuf;
 281   StringRef NameRef = BufferName.toStringRef(NameBuf);
 282   size_t AlignedStringLen = alignTo(sizeof(MemBuffer) + NameRef.size() + 1, 16);
 283   size_t RealLen = AlignedStringLen + Size + 1;
 284   char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
 285   if (!Mem)
 286     return nullptr;
 287
 288   // The name is stored after the class itself.
 289   CopyStringRef(Mem + sizeof(MemBuffer), NameRef);
 290
 291   // The buffer begins after the name and must be aligned.
 292   char *Buf = Mem + AlignedStringLen;
 293   Buf[Size] = 0; // Null terminate buffer.
 294
 295   auto *Ret = new (Mem) MemBuffer(StringRef(Buf, Size), true);
 296   return std::unique_ptr<WritableMemoryBuffer>(Ret);
 297 }
 298
 299 std::unique_ptr<WritableMemoryBuffer>
 300 WritableMemoryBuffer::getNewMemBuffer(size_t Size, const Twine &BufferName) {
 301   auto SB = WritableMemoryBuffer::getNewUninitMemBuffer(Size, BufferName);
 302   if (!SB)
 303     return nullptr;
 304   memset(SB->getBufferStart(), 0, Size);
 305   return SB;
 306 }
 307
 308 static bool shouldUseMmap(int FD,
 309                           size_t FileSize,
 310                           size_t MapSize,
 311                           off_t Offset,
 312                           bool RequiresNullTerminator,
 313                           int PageSize,
 314                           bool IsVolatile) {
 315   // mmap may leave the buffer without null terminator if the file size changed
 316   // by the time the last page is mapped in, so avoid it if the file size is
 317   // likely to change.
 318   if (IsVolatile)
 319     return false;
 320
 321   // We don't use mmap for small files because this can severely fragment our
 322   // address space.
 323   if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
 324     return false;
 325
 326   if (!RequiresNullTerminator)
 327     return true;
 328
 329   // If we don't know the file size, use fstat to find out.  fstat on an open
 330   // file descriptor is cheaper than stat on a random path.
 331   // FIXME: this chunk of code is duplicated, but it avoids a fstat when
 332   // RequiresNullTerminator = false and MapSize != -1.
 333   if (FileSize == size_t(-1)) {
 334     sys::fs::file_status Status;
 335     if (sys::fs::status(FD, Status))
 336       return false;
 337     FileSize = Status.getSize();
 338   }
 339
 340   // If we need a null terminator and the end of the map is inside the file,
 341   // we cannot use mmap.
 342   size_t End = Offset + MapSize;
 343   assert(End <= FileSize);
 344   if (End != FileSize)
 345     return false;
 346
 347   // Don't try to map files that are exactly a multiple of the system page size
 348   // if we need a null terminator.
 349   if ((FileSize & (PageSize -1)) == 0)
 350     return false;
 351
 352 #if defined(__CYGWIN__)
 353   // Don't try to map files that are exactly a multiple of the physical page size
 354   // if we need a null terminator.
 355   // FIXME: We should reorganize again getPageSize() on Win32.
 356   if ((FileSize & (4096 - 1)) == 0)
 357     return false;
 358 #endif
 359
 360   return true;
 361 }
 362
 363 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
 364 getReadWriteFile(const Twine &Filename, uint64_t FileSize, uint64_t MapSize,
 365                  uint64_t Offset) {
 366   int FD;
 367   std::error_code EC = sys::fs::openFileForReadWrite(
 368       Filename, FD, sys::fs::CD_OpenExisting, sys::fs::OF_None);
 369
 370   if (EC)
 371     return EC;
 372
 373   // Default is to map the full file.
 374   if (MapSize == uint64_t(-1)) {
 375     // If we don't know the file size, use fstat to find out.  fstat on an open
 376     // file descriptor is cheaper than stat on a random path.
 377     if (FileSize == uint64_t(-1)) {
 378       sys::fs::file_status Status;
 379       std::error_code EC = sys::fs::status(FD, Status);
 380       if (EC)
 381         return EC;
 382
 383       // If this not a file or a block device (e.g. it's a named pipe
 384       // or character device), we can't mmap it, so error out.
 385       sys::fs::file_type Type = Status.type();
 386       if (Type != sys::fs::file_type::regular_file &&
 387           Type != sys::fs::file_type::block_file)
 388         return make_error_code(errc::invalid_argument);
 389
 390       FileSize = Status.getSize();
 391     }
 392     MapSize = FileSize;
 393   }
 394
 395   std::unique_ptr<WriteThroughMemoryBuffer> Result(
 396       new (NamedBufferAlloc(Filename))
 397           MemoryBufferMMapFile<WriteThroughMemoryBuffer>(false, FD, MapSize,
 398                                                          Offset, EC));
 399   if (EC)
 400     return EC;
 401   return std::move(Result);
 402 }
 403
 404 ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
 405 WriteThroughMemoryBuffer::getFile(const Twine &Filename, int64_t FileSize) {
 406   return getReadWriteFile(Filename, FileSize, FileSize, 0);
 407 }
 408
 409 /// Map a subrange of the specified file as a WritableMemoryBuffer.
 410 ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
 411 WriteThroughMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
 412                                        uint64_t Offset) {
 413   return getReadWriteFile(Filename, -1, MapSize, Offset);
 414 }
 415
 416 template <typename MB>
 417 static ErrorOr<std::unique_ptr<MB>>
 418 getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
 419                 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
 420                 bool IsVolatile) {
 421   static int PageSize = sys::Process::getPageSize();
 422
 423   // Default is to map the full file.
 424   if (MapSize == uint64_t(-1)) {
 425     // If we don't know the file size, use fstat to find out.  fstat on an open
 426     // file descriptor is cheaper than stat on a random path.
 427     if (FileSize == uint64_t(-1)) {
 428       sys::fs::file_status Status;
 429       std::error_code EC = sys::fs::status(FD, Status);
 430       if (EC)
 431         return EC;
 432
 433       // If this not a file or a block device (e.g. it's a named pipe
 434       // or character device), we can't trust the size. Create the memory
 435       // buffer by copying off the stream.
 436       sys::fs::file_type Type = Status.type();
 437       if (Type != sys::fs::file_type::regular_file &&
 438           Type != sys::fs::file_type::block_file)
 439         return getMemoryBufferForStream(FD, Filename);
 440
 441       FileSize = Status.getSize();
 442     }
 443     MapSize = FileSize;
 444   }
 445
 446   if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
 447                     PageSize, IsVolatile)) {
 448     std::error_code EC;
 449     std::unique_ptr<MB> Result(
 450         new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile<MB>(
 451             RequiresNullTerminator, FD, MapSize, Offset, EC));
 452     if (!EC)
 453       return std::move(Result);
 454   }
 455
 456   auto Buf = WritableMemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
 457   if (!Buf) {
 458     // Failed to create a buffer. The only way it can fail is if
 459     // new(std::nothrow) returns 0.
 460     return make_error_code(errc::not_enough_memory);
 461   }
 462
 463   char *BufPtr = Buf.get()->getBufferStart();
 464
 465   size_t BytesLeft = MapSize;
 466 #ifndef HAVE_PREAD
 467   if (lseek(FD, Offset, SEEK_SET) == -1)
 468     return std::error_code(errno, std::generic_category());
 469 #endif
 470
 471   while (BytesLeft) {
 472 #ifdef HAVE_PREAD
 473     ssize_t NumRead = sys::RetryAfterSignal(-1, ::pread, FD, BufPtr, BytesLeft,
 474                                             MapSize - BytesLeft + Offset);
 475 #else
 476     ssize_t NumRead = sys::RetryAfterSignal(-1, ::read, FD, BufPtr, BytesLeft);
 477 #endif
 478     if (NumRead == -1) {
 479       // Error while reading.
 480       return std::error_code(errno, std::generic_category());
 481     }
 482     if (NumRead == 0) {
 483       memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.
 484       break;
 485     }
 486     BytesLeft -= NumRead;
 487     BufPtr += NumRead;
 488   }
 489
 490   return std::move(Buf);
 491 }
 492
 493 ErrorOr<std::unique_ptr<MemoryBuffer>>
 494 MemoryBuffer::getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,
 495                           bool RequiresNullTerminator, bool IsVolatile) {
 496   return getOpenFileImpl<MemoryBuffer>(FD, Filename, FileSize, FileSize, 0,
 497                          RequiresNullTerminator, IsVolatile);
 498 }
 499
 500 ErrorOr<std::unique_ptr<MemoryBuffer>>
 501 MemoryBuffer::getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,
 502                                int64_t Offset, bool IsVolatile) {
 503   assert(MapSize != uint64_t(-1));
 504   return getOpenFileImpl<MemoryBuffer>(FD, Filename, -1, MapSize, Offset, false,
 505                                        IsVolatile);
 506 }
 507
 508 ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {
 509   // Read in all of the data from stdin, we cannot mmap stdin.
 510   //
 511   // FIXME: That isn't necessarily true, we should try to mmap stdin and
 512   // fallback if it fails.
 513   sys::ChangeStdinToBinary();
 514
 515   return getMemoryBufferForStream(0, "<stdin>");
 516 }
 517
 518 ErrorOr<std::unique_ptr<MemoryBuffer>>
 519 MemoryBuffer::getFileAsStream(const Twine &Filename) {
 520   int FD;
 521   std::error_code EC = sys::fs::openFileForRead(Filename, FD, sys::fs::OF_None);
 522   if (EC)
 523     return EC;
 524   ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =
 525       getMemoryBufferForStream(FD, Filename);
 526   close(FD);
 527   return Ret;
 528 }
 529
 530 MemoryBufferRef MemoryBuffer::getMemBufferRef() const {
 531   StringRef Data = getBuffer();
 532   StringRef Identifier = getBufferIdentifier();
 533   return MemoryBufferRef(Data, Identifier);
 534 }
 535
 536 void MemoryBuffer::anchor() {}
 537 void SmallVectorMemoryBuffer::anchor() {}