lib/Support/MemoryBuffer.cpp

   1 //===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file was developed by Chris Lattner and is distributed under
   6 // the University of Illinois Open Source 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/System/MappedFile.h"
  16 #include "llvm/System/Process.h"
  17 #include "llvm/System/Program.h"
  18 #include <cassert>
  19 #include <cstdio>
  20 #include <cstring>
  21 #include <cerrno>
  22 using namespace llvm;
  23
  24 //===----------------------------------------------------------------------===//
  25 // MemoryBuffer implementation itself.
  26 //===----------------------------------------------------------------------===//
  27
  28 MemoryBuffer::~MemoryBuffer() {
  29   if (MustDeleteBuffer)
  30     delete [] BufferStart;
  31 }
  32
  33 /// initCopyOf - Initialize this source buffer with a copy of the specified
  34 /// memory range.  We make the copy so that we can null terminate it
  35 /// successfully.
  36 void MemoryBuffer::initCopyOf(const char *BufStart, const char *BufEnd) {
  37   size_t Size = BufEnd-BufStart;
  38   BufferStart = new char[Size+1];
  39   BufferEnd = BufferStart+Size;
  40   memcpy(const_cast<char*>(BufferStart), BufStart, Size);
  41   *const_cast<char*>(BufferEnd) = 0;   // Null terminate buffer.
  42   MustDeleteBuffer = true;
  43 }
  44
  45 /// init - Initialize this MemoryBuffer as a reference to externally allocated
  46 /// memory, memory that we know is already null terminated.
  47 void MemoryBuffer::init(const char *BufStart, const char *BufEnd) {
  48   assert(BufEnd[0] == 0 && "Buffer is not null terminated!");
  49   BufferStart = BufStart;
  50   BufferEnd = BufEnd;
  51   MustDeleteBuffer = false;
  52 }
  53
  54 //===----------------------------------------------------------------------===//
  55 // MemoryBufferMem implementation.
  56 //===----------------------------------------------------------------------===//
  57
  58 namespace {
  59 class MemoryBufferMem : public MemoryBuffer {
  60   std::string FileID;
  61 public:
  62   MemoryBufferMem(const char *Start, const char *End, const char *FID)
  63   : FileID(FID) {
  64     init(Start, End);
  65   }
  66
  67   virtual const char *getBufferIdentifier() const {
  68     return FileID.c_str();
  69   }
  70 };
  71 }
  72
  73 /// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
  74 /// that EndPtr[0] must be a null byte and be accessible!
  75 MemoryBuffer *MemoryBuffer::getMemBuffer(const char *StartPtr,
  76                                          const char *EndPtr,
  77                                          const char *BufferName) {
  78   return new MemoryBufferMem(StartPtr, EndPtr, BufferName);
  79 }
  80
  81 /// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
  82 /// that is completely initialized to zeros.  Note that the caller should
  83 /// initialize the memory allocated by this method.  The memory is owned by
  84 /// the MemoryBuffer object.
  85 MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(unsigned Size,
  86                                                   const char *BufferName) {
  87   char *Buf = new char[Size+1];
  88   Buf[Size] = 0;
  89   MemoryBufferMem *SB = new MemoryBufferMem(Buf, Buf+Size, BufferName);
  90   // The memory for this buffer is owned by the MemoryBuffer.
  91   SB->MustDeleteBuffer = true;
  92   return SB;
  93 }
  94
  95 /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
  96 /// is completely initialized to zeros.  Note that the caller should
  97 /// initialize the memory allocated by this method.  The memory is owned by
  98 /// the MemoryBuffer object.
  99 MemoryBuffer *MemoryBuffer::getNewMemBuffer(unsigned Size,
 100                                             const char *BufferName) {
 101   MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
 102   memset(const_cast<char*>(SB->getBufferStart()), 0, Size+1);
 103   return SB;
 104 }
 105
 106
 107 //===----------------------------------------------------------------------===//
 108 // MemoryBufferMMapFile implementation.
 109 //===----------------------------------------------------------------------===//
 110
 111 namespace {
 112 class MemoryBufferMMapFile : public MemoryBuffer {
 113   sys::MappedFile File;
 114 public:
 115   MemoryBufferMMapFile() {}
 116
 117   bool open(const sys::Path &Filename, std::string *ErrStr);
 118
 119   virtual const char *getBufferIdentifier() const {
 120     return File.path().c_str();
 121   }
 122
 123   ~MemoryBufferMMapFile();
 124 };
 125 }
 126
 127 bool MemoryBufferMMapFile::open(const sys::Path &Filename,
 128                                 std::string *ErrStr) {
 129   // FIXME: This does an extra stat syscall to figure out the size, but we
 130   // already know the size!
 131   bool Failure = File.open(Filename, sys::MappedFile::READ_ACCESS, ErrStr);
 132   if (Failure) return true;
 133
 134   if (!File.map(ErrStr))
 135     return true;
 136
 137   size_t Size = File.size();
 138
 139   static unsigned PageSize = sys::Process::GetPageSize();
 140   assert(((PageSize & (PageSize-1)) == 0) && PageSize &&
 141          "Page size is not a power of 2!");
 142
 143   // If this file is not an exact multiple of the system page size (common
 144   // case), then the OS has zero terminated the buffer for us.
 145   if ((Size & (PageSize-1))) {
 146     init(File.charBase(), File.charBase()+Size);
 147   } else {
 148     // Otherwise, we allocate a new memory buffer and copy the data over
 149     initCopyOf(File.charBase(), File.charBase()+Size);
 150
 151     // No need to keep the file mapped any longer.
 152     File.unmap();
 153   }
 154   return false;
 155 }
 156
 157 MemoryBufferMMapFile::~MemoryBufferMMapFile() {
 158   if (File.isMapped())
 159     File.unmap();
 160 }
 161
 162 //===----------------------------------------------------------------------===//
 163 // MemoryBuffer::getFile implementation.
 164 //===----------------------------------------------------------------------===//
 165
 166 MemoryBuffer *MemoryBuffer::getFile(const char *FilenameStart, unsigned FnSize,
 167                                     std::string *ErrStr, int64_t FileSize){
 168   // FIXME: it would be nice if PathWithStatus didn't copy the filename into a
 169   // temporary string. :(
 170   sys::PathWithStatus P(FilenameStart, FnSize);
 171 #if 1
 172   MemoryBufferMMapFile *M = new MemoryBufferMMapFile();
 173   if (!M->open(P, ErrStr))
 174     return M;
 175   delete M;
 176   return 0;
 177 #else
 178   // FIXME: We need an efficient and portable method to open a file and then use
 179   // 'read' to copy the bits out.  The unix implementation is below.  This is
 180   // an important optimization for clients that want to open large numbers of
 181   // small files (using mmap on everything can easily exhaust address space!).
 182
 183   // If the user didn't specify a filesize, do a stat to find it.
 184   if (FileSize == -1) {
 185     const sys::FileStatus *FS = P.getFileStatus();
 186     if (FS == 0) return 0;  // Error stat'ing file.
 187
 188     FileSize = FS->fileSize;
 189   }
 190
 191   // If the file is larger than some threshold, use mmap, otherwise use 'read'.
 192   if (FileSize >= 4096*4) {
 193     MemoryBufferMMapFile *M = new MemoryBufferMMapFile();
 194     if (!M->open(P, ErrStr))
 195       return M;
 196     delete M;
 197     return 0;
 198   }
 199
 200   MemoryBuffer *SB = getNewUninitMemBuffer(FileSize, FilenameStart);
 201   char *BufPtr = const_cast<char*>(SB->getBufferStart());
 202
 203   int FD = ::open(FilenameStart, O_RDONLY);
 204   if (FD == -1) {
 205     delete SB;
 206     return 0;
 207   }
 208
 209   unsigned BytesLeft = FileSize;
 210   while (BytesLeft) {
 211     ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
 212     if (NumRead != -1) {
 213       BytesLeft -= NumRead;
 214       BufPtr += NumRead;
 215     } else if (errno == EINTR) {
 216       // try again
 217     } else {
 218       // error reading.
 219       close(FD);
 220       delete SB;
 221       return 0;
 222     }
 223   }
 224   close(FD);
 225
 226   return SB;
 227 #endif
 228 }
 229
 230
 231 //===----------------------------------------------------------------------===//
 232 // MemoryBuffer::getSTDIN implementation.
 233 //===----------------------------------------------------------------------===//
 234
 235 namespace {
 236 class STDINBufferFile : public MemoryBuffer {
 237 public:
 238   virtual const char *getBufferIdentifier() const {
 239     return "<stdin>";
 240   }
 241 };
 242 }
 243
 244 MemoryBuffer *MemoryBuffer::getSTDIN() {
 245   char Buffer[4096*4];
 246
 247   std::vector<char> FileData;
 248
 249   // Read in all of the data from stdin, we cannot mmap stdin.
 250   sys::Program::ChangeStdinToBinary();
 251   while (size_t ReadBytes = fread(Buffer, 1, 4096*4, stdin))
 252     FileData.insert(FileData.end(), Buffer, Buffer+ReadBytes);
 253
 254   size_t Size = FileData.size();
 255   MemoryBuffer *B = new STDINBufferFile();
 256   B->initCopyOf(&FileData[0], &FileData[Size]);
 257   return B;
 258 }