src/llvm/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/OwningPtr.h"
  16 #include "llvm/ADT/SmallString.h"
  17 #include "llvm/Config/config.h"
  18 #include "llvm/Support/MathExtras.h"
  19 #include "llvm/Support/Errno.h"
  20 #include "llvm/Support/FileSystem.h"
  21 #include "llvm/Support/Path.h"
  22 #include "llvm/Support/Process.h"
  23 #include "llvm/Support/Program.h"
  24 #include "llvm/Support/system_error.h"
  25 #include <cassert>
  26 #include <cstdio>
  27 #include <cstring>
  28 #include <cerrno>
  29 #include <new>
  30 #include <sys/types.h>
  31 #include <sys/stat.h>
  32 #if !defined(_MSC_VER) && !defined(__MINGW32__)
  33 #include <unistd.h>
  34 #else
  35 #include <io.h>
  36 #endif
  37 #include <fcntl.h>
  38 using namespace llvm;
  39
  40 //===----------------------------------------------------------------------===//
  41 // MemoryBuffer implementation itself.
  42 //===----------------------------------------------------------------------===//
  43
  44 MemoryBuffer::~MemoryBuffer() { }
  45
  46 /// init - Initialize this MemoryBuffer as a reference to externally allocated
  47 /// memory, memory that we know is already null terminated.
  48 void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
  49                         bool RequiresNullTerminator) {
  50   assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
  51          "Buffer is not null terminated!");
  52   BufferStart = BufStart;
  53   BufferEnd = BufEnd;
  54 }
  55
  56 //===----------------------------------------------------------------------===//
  57 // MemoryBufferMem implementation.
  58 //===----------------------------------------------------------------------===//
  59
  60 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
  61 /// null-terminates it.
  62 static void CopyStringRef(char *Memory, StringRef Data) {
  63   memcpy(Memory, Data.data(), Data.size());
  64   Memory[Data.size()] = 0; // Null terminate string.
  65 }
  66
  67 /// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it.
  68 template <typename T>
  69 static T *GetNamedBuffer(StringRef Buffer, StringRef Name,
  70                          bool RequiresNullTerminator) {
  71   char *Mem = static_cast<char*>(operator new(sizeof(T) + Name.size() + 1));
  72   CopyStringRef(Mem + sizeof(T), Name);
  73   return new (Mem) T(Buffer, RequiresNullTerminator);
  74 }
  75
  76 namespace {
  77 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
  78 class MemoryBufferMem : public MemoryBuffer {
  79 public:
  80   MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
  81     init(InputData.begin(), InputData.end(), RequiresNullTerminator);
  82   }
  83
  84   virtual const char *getBufferIdentifier() const LLVM_OVERRIDE {
  85      // The name is stored after the class itself.
  86     return reinterpret_cast<const char*>(this + 1);
  87   }
  88
  89   virtual BufferKind getBufferKind() const LLVM_OVERRIDE {
  90     return MemoryBuffer_Malloc;
  91   }
  92 };
  93 }
  94
  95 /// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
  96 /// that InputData must be a null terminated if RequiresNullTerminator is true!
  97 MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
  98                                          StringRef BufferName,
  99                                          bool RequiresNullTerminator) {
 100   return GetNamedBuffer<MemoryBufferMem>(InputData, BufferName,
 101                                          RequiresNullTerminator);
 102 }
 103
 104 /// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
 105 /// copying the contents and taking ownership of it.  This has no requirements
 106 /// on EndPtr[0].
 107 MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
 108                                              StringRef BufferName) {
 109   MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
 110   if (!Buf) return 0;
 111   memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
 112          InputData.size());
 113   return Buf;
 114 }
 115
 116 /// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
 117 /// that is not initialized.  Note that the caller should initialize the
 118 /// memory allocated by this method.  The memory is owned by the MemoryBuffer
 119 /// object.
 120 MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
 121                                                   StringRef BufferName) {
 122   // Allocate space for the MemoryBuffer, the data and the name. It is important
 123   // that MemoryBuffer and data are aligned so PointerIntPair works with them.
 124   size_t AlignedStringLen =
 125     RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
 126                        sizeof(void*)); // TODO: Is sizeof(void*) enough?
 127   size_t RealLen = AlignedStringLen + Size + 1;
 128   char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
 129   if (!Mem) return 0;
 130
 131   // The name is stored after the class itself.
 132   CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
 133
 134   // The buffer begins after the name and must be aligned.
 135   char *Buf = Mem + AlignedStringLen;
 136   Buf[Size] = 0; // Null terminate buffer.
 137
 138   return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
 139 }
 140
 141 /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
 142 /// is completely initialized to zeros.  Note that the caller should
 143 /// initialize the memory allocated by this method.  The memory is owned by
 144 /// the MemoryBuffer object.
 145 MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
 146   MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
 147   if (!SB) return 0;
 148   memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
 149   return SB;
 150 }
 151
 152
 153 /// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
 154 /// if the Filename is "-".  If an error occurs, this returns null and fills
 155 /// in *ErrStr with a reason.  If stdin is empty, this API (unlike getSTDIN)
 156 /// returns an empty buffer.
 157 error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
 158                                         OwningPtr<MemoryBuffer> &result,
 159                                         int64_t FileSize) {
 160   if (Filename == "-")
 161     return getSTDIN(result);
 162   return getFile(Filename, result, FileSize);
 163 }
 164
 165 error_code MemoryBuffer::getFileOrSTDIN(const char *Filename,
 166                                         OwningPtr<MemoryBuffer> &result,
 167                                         int64_t FileSize) {
 168   if (strcmp(Filename, "-") == 0)
 169     return getSTDIN(result);
 170   return getFile(Filename, result, FileSize);
 171 }
 172
 173 //===----------------------------------------------------------------------===//
 174 // MemoryBuffer::getFile implementation.
 175 //===----------------------------------------------------------------------===//
 176
 177 namespace {
 178 /// MemoryBufferMMapFile - This represents a file that was mapped in with the
 179 /// sys::Path::MapInFilePages method.  When destroyed, it calls the
 180 /// sys::Path::UnMapFilePages method.
 181 class MemoryBufferMMapFile : public MemoryBufferMem {
 182 public:
 183   MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator)
 184     : MemoryBufferMem(Buffer, RequiresNullTerminator) { }
 185
 186   ~MemoryBufferMMapFile() {
 187     static int PageSize = sys::Process::GetPageSize();
 188
 189     uintptr_t Start = reinterpret_cast<uintptr_t>(getBufferStart());
 190     size_t Size = getBufferSize();
 191     uintptr_t RealStart = Start & ~(PageSize - 1);
 192     size_t RealSize = Size + (Start - RealStart);
 193
 194     sys::Path::UnMapFilePages(reinterpret_cast<const char*>(RealStart),
 195                               RealSize);
 196   }
 197
 198   virtual BufferKind getBufferKind() const LLVM_OVERRIDE {
 199     return MemoryBuffer_MMap;
 200   }
 201 };
 202 }
 203
 204 error_code MemoryBuffer::getFile(StringRef Filename,
 205                                  OwningPtr<MemoryBuffer> &result,
 206                                  int64_t FileSize,
 207                                  bool RequiresNullTerminator) {
 208   // Ensure the path is null terminated.
 209   SmallString<256> PathBuf(Filename.begin(), Filename.end());
 210   return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize,
 211                                RequiresNullTerminator);
 212 }
 213
 214 error_code MemoryBuffer::getFile(const char *Filename,
 215                                  OwningPtr<MemoryBuffer> &result,
 216                                  int64_t FileSize,
 217                                  bool RequiresNullTerminator) {
 218   // First check that the "file" is not a directory
 219   bool is_dir = false;
 220   error_code err = sys::fs::is_directory(Filename, is_dir);
 221   if (err)
 222     return err;
 223   if (is_dir)
 224     return make_error_code(errc::is_a_directory);
 225
 226   int OpenFlags = O_RDONLY;
 227 #ifdef O_BINARY
 228   OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
 229 #endif
 230   int FD = ::open(Filename, OpenFlags);
 231   if (FD == -1)
 232     return error_code(errno, posix_category());
 233
 234   error_code ret = getOpenFile(FD, Filename, result, FileSize, FileSize,
 235                                0, RequiresNullTerminator);
 236   close(FD);
 237   return ret;
 238 }
 239
 240 static bool shouldUseMmap(int FD,
 241                           size_t FileSize,
 242                           size_t MapSize,
 243                           off_t Offset,
 244                           bool RequiresNullTerminator,
 245                           int PageSize) {
 246   // We don't use mmap for small files because this can severely fragment our
 247   // address space.
 248   if (MapSize < 4096*4)
 249     return false;
 250
 251   if (!RequiresNullTerminator)
 252     return true;
 253
 254
 255   // If we don't know the file size, use fstat to find out.  fstat on an open
 256   // file descriptor is cheaper than stat on a random path.
 257   // FIXME: this chunk of code is duplicated, but it avoids a fstat when
 258   // RequiresNullTerminator = false and MapSize != -1.
 259   if (FileSize == size_t(-1)) {
 260     struct stat FileInfo;
 261     // TODO: This should use fstat64 when available.
 262     if (fstat(FD, &FileInfo) == -1) {
 263       return error_code(errno, posix_category());
 264     }
 265     FileSize = FileInfo.st_size;
 266   }
 267
 268   // If we need a null terminator and the end of the map is inside the file,
 269   // we cannot use mmap.
 270   size_t End = Offset + MapSize;
 271   assert(End <= FileSize);
 272   if (End != FileSize)
 273     return false;
 274
 275   // Don't try to map files that are exactly a multiple of the system page size
 276   // if we need a null terminator.
 277   if ((FileSize & (PageSize -1)) == 0)
 278     return false;
 279
 280   return true;
 281 }
 282
 283 error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
 284                                      OwningPtr<MemoryBuffer> &result,
 285                                      uint64_t FileSize, uint64_t MapSize,
 286                                      int64_t Offset,
 287                                      bool RequiresNullTerminator) {
 288   static int PageSize = sys::Process::GetPageSize();
 289
 290   // Default is to map the full file.
 291   if (MapSize == uint64_t(-1)) {
 292     // If we don't know the file size, use fstat to find out.  fstat on an open
 293     // file descriptor is cheaper than stat on a random path.
 294     if (FileSize == uint64_t(-1)) {
 295       struct stat FileInfo;
 296       // TODO: This should use fstat64 when available.
 297       if (fstat(FD, &FileInfo) == -1) {
 298         return error_code(errno, posix_category());
 299       }
 300       FileSize = FileInfo.st_size;
 301     }
 302     MapSize = FileSize;
 303   }
 304
 305   if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
 306                     PageSize)) {
 307     off_t RealMapOffset = Offset & ~(PageSize - 1);
 308     off_t Delta = Offset - RealMapOffset;
 309     size_t RealMapSize = MapSize + Delta;
 310
 311     if (const char *Pages = sys::Path::MapInFilePages(FD,
 312                                                       RealMapSize,
 313                                                       RealMapOffset)) {
 314       result.reset(GetNamedBuffer<MemoryBufferMMapFile>(
 315           StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator));
 316       return error_code::success();
 317     }
 318   }
 319
 320   MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
 321   if (!Buf) {
 322     // Failed to create a buffer. The only way it can fail is if
 323     // new(std::nothrow) returns 0.
 324     return make_error_code(errc::not_enough_memory);
 325   }
 326
 327   OwningPtr<MemoryBuffer> SB(Buf);
 328   char *BufPtr = const_cast<char*>(SB->getBufferStart());
 329
 330   size_t BytesLeft = MapSize;
 331 #ifndef HAVE_PREAD
 332   if (lseek(FD, Offset, SEEK_SET) == -1)
 333     return error_code(errno, posix_category());
 334 #endif
 335
 336   while (BytesLeft) {
 337 #ifdef HAVE_PREAD
 338     ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
 339 #else
 340     ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
 341 #endif
 342     if (NumRead == -1) {
 343       if (errno == EINTR)
 344         continue;
 345       // Error while reading.
 346       return error_code(errno, posix_category());
 347     }
 348     if (NumRead == 0) {
 349       assert(0 && "We got inaccurate FileSize value or fstat reported an "
 350                    "invalid file size.");
 351       *BufPtr = '\0'; // null-terminate at the actual size.
 352       break;
 353     }
 354     BytesLeft -= NumRead;
 355     BufPtr += NumRead;
 356   }
 357
 358   result.swap(SB);
 359   return error_code::success();
 360 }
 361
 362 //===----------------------------------------------------------------------===//
 363 // MemoryBuffer::getSTDIN implementation.
 364 //===----------------------------------------------------------------------===//
 365
 366 error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
 367   // Read in all of the data from stdin, we cannot mmap stdin.
 368   //
 369   // FIXME: That isn't necessarily true, we should try to mmap stdin and
 370   // fallback if it fails.
 371   sys::Program::ChangeStdinToBinary();
 372
 373   const ssize_t ChunkSize = 4096*4;
 374   SmallString<ChunkSize> Buffer;
 375   ssize_t ReadBytes;
 376   // Read into Buffer until we hit EOF.
 377   do {
 378     Buffer.reserve(Buffer.size() + ChunkSize);
 379     ReadBytes = read(0, Buffer.end(), ChunkSize);
 380     if (ReadBytes == -1) {
 381       if (errno == EINTR) continue;
 382       return error_code(errno, posix_category());
 383     }
 384     Buffer.set_size(Buffer.size() + ReadBytes);
 385   } while (ReadBytes != 0);
 386
 387   result.reset(getMemBufferCopy(Buffer, "<stdin>"));
 388   return error_code::success();
 389 }