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/Support/MathExtras.h"
  18 #include "llvm/System/Errno.h"
  19 #include "llvm/System/Path.h"
  20 #include "llvm/System/Process.h"
  21 #include "llvm/System/Program.h"
  22 #include <cassert>
  23 #include <cstdio>
  24 #include <cstring>
  25 #include <cerrno>
  26 #include <sys/types.h>
  27 #include <sys/stat.h>
  28 #if !defined(_MSC_VER) && !defined(__MINGW32__)
  29 #include <unistd.h>
  30 #include <sys/uio.h>
  31 #else
  32 #include <io.h>
  33 #endif
  34 #include <fcntl.h>
  35 using namespace llvm;
  36
  37 //===----------------------------------------------------------------------===//
  38 // MemoryBuffer implementation itself.
  39 //===----------------------------------------------------------------------===//
  40
  41 MemoryBuffer::~MemoryBuffer() { }
  42
  43 /// init - Initialize this MemoryBuffer as a reference to externally allocated
  44 /// memory, memory that we know is already null terminated.
  45 void MemoryBuffer::init(const char *BufStart, const char *BufEnd) {
  46   assert(BufEnd[0] == 0 && "Buffer is not null terminated!");
  47   BufferStart = BufStart;
  48   BufferEnd = BufEnd;
  49 }
  50
  51 //===----------------------------------------------------------------------===//
  52 // MemoryBufferMem implementation.
  53 //===----------------------------------------------------------------------===//
  54
  55 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
  56 /// null-terminates it.
  57 static void CopyStringRef(char *Memory, StringRef Data) {
  58   memcpy(Memory, Data.data(), Data.size());
  59   Memory[Data.size()] = 0; // Null terminate string.
  60 }
  61
  62 /// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it.
  63 template <typename T>
  64 static T* GetNamedBuffer(StringRef Buffer, StringRef Name) {
  65   char *Mem = static_cast<char*>(operator new(sizeof(T) + Name.size() + 1));
  66   CopyStringRef(Mem + sizeof(T), Name);
  67   return new (Mem) T(Buffer);
  68 }
  69
  70 namespace {
  71 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
  72 class MemoryBufferMem : public MemoryBuffer {
  73 public:
  74   MemoryBufferMem(StringRef InputData) {
  75     init(InputData.begin(), InputData.end());
  76   }
  77
  78   virtual const char *getBufferIdentifier() const {
  79      // The name is stored after the class itself.
  80     return reinterpret_cast<const char*>(this + 1);
  81   }
  82 };
  83 }
  84
  85 /// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
  86 /// that EndPtr[0] must be a null byte and be accessible!
  87 MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
  88                                          StringRef BufferName) {
  89   return GetNamedBuffer<MemoryBufferMem>(InputData, BufferName);
  90 }
  91
  92 /// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
  93 /// copying the contents and taking ownership of it.  This has no requirements
  94 /// on EndPtr[0].
  95 MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
  96                                              StringRef BufferName) {
  97   MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
  98   if (!Buf) return 0;
  99   memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
 100          InputData.size());
 101   return Buf;
 102 }
 103
 104 /// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
 105 /// that is not initialized.  Note that the caller should initialize the
 106 /// memory allocated by this method.  The memory is owned by the MemoryBuffer
 107 /// object.
 108 MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
 109                                                   StringRef BufferName) {
 110   // Allocate space for the MemoryBuffer, the data and the name. It is important
 111   // that MemoryBuffer and data are aligned so PointerIntPair works with them.
 112   size_t AlignedStringLen =
 113     RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
 114                        sizeof(void*)); // TODO: Is sizeof(void*) enough?
 115   size_t RealLen = AlignedStringLen + Size + 1;
 116   char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
 117   if (!Mem) return 0;
 118
 119   // The name is stored after the class itself.
 120   CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
 121
 122   // The buffer begins after the name and must be aligned.
 123   char *Buf = Mem + AlignedStringLen;
 124   Buf[Size] = 0; // Null terminate buffer.
 125
 126   return new (Mem) MemoryBufferMem(StringRef(Buf, Size));
 127 }
 128
 129 /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
 130 /// is completely initialized to zeros.  Note that the caller should
 131 /// initialize the memory allocated by this method.  The memory is owned by
 132 /// the MemoryBuffer object.
 133 MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
 134   MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
 135   if (!SB) return 0;
 136   memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
 137   return SB;
 138 }
 139
 140
 141 /// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
 142 /// if the Filename is "-".  If an error occurs, this returns null and fills
 143 /// in *ErrStr with a reason.  If stdin is empty, this API (unlike getSTDIN)
 144 /// returns an empty buffer.
 145 MemoryBuffer *MemoryBuffer::getFileOrSTDIN(StringRef Filename,
 146                                            std::string *ErrStr,
 147                                            int64_t FileSize,
 148                                            struct stat *FileInfo) {
 149   if (Filename == "-")
 150     return getSTDIN(ErrStr);
 151   return getFile(Filename, ErrStr, FileSize, FileInfo);
 152 }
 153
 154 MemoryBuffer *MemoryBuffer::getFileOrSTDIN(const char *Filename,
 155                                            std::string *ErrStr,
 156                                            int64_t FileSize,
 157                                            struct stat *FileInfo) {
 158   if (strcmp(Filename, "-") == 0)
 159     return getSTDIN(ErrStr);
 160   return getFile(Filename, ErrStr, FileSize, FileInfo);
 161 }
 162
 163 //===----------------------------------------------------------------------===//
 164 // MemoryBuffer::getFile implementation.
 165 //===----------------------------------------------------------------------===//
 166
 167 namespace {
 168 /// MemoryBufferMMapFile - This represents a file that was mapped in with the
 169 /// sys::Path::MapInFilePages method.  When destroyed, it calls the
 170 /// sys::Path::UnMapFilePages method.
 171 class MemoryBufferMMapFile : public MemoryBufferMem {
 172 public:
 173   MemoryBufferMMapFile(StringRef Buffer)
 174     : MemoryBufferMem(Buffer) { }
 175
 176   ~MemoryBufferMMapFile() {
 177     sys::Path::UnMapFilePages(getBufferStart(), getBufferSize());
 178   }
 179 };
 180
 181 /// FileCloser - RAII object to make sure an FD gets closed properly.
 182 class FileCloser {
 183   int FD;
 184 public:
 185   explicit FileCloser(int FD) : FD(FD) {}
 186   ~FileCloser() { ::close(FD); }
 187 };
 188 }
 189
 190 MemoryBuffer *MemoryBuffer::getFile(StringRef Filename, std::string *ErrStr,
 191                                     int64_t FileSize, struct stat *FileInfo) {
 192   SmallString<256> PathBuf(Filename.begin(), Filename.end());
 193   return MemoryBuffer::getFile(PathBuf.c_str(), ErrStr, FileSize, FileInfo);
 194 }
 195
 196 MemoryBuffer *MemoryBuffer::getFile(const char *Filename, std::string *ErrStr,
 197                                     int64_t FileSize, struct stat *FileInfo) {
 198   int OpenFlags = O_RDONLY;
 199 #ifdef O_BINARY
 200   OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
 201 #endif
 202   int FD = ::open(Filename, OpenFlags);
 203   if (FD == -1) {
 204     if (ErrStr) *ErrStr = sys::StrError();
 205     return 0;
 206   }
 207   FileCloser FC(FD); // Close FD on return.
 208
 209   // If we don't know the file size, use fstat to find out.  fstat on an open
 210   // file descriptor is cheaper than stat on a random path.
 211   if (FileSize == -1 || FileInfo) {
 212     struct stat MyFileInfo;
 213     struct stat *FileInfoPtr = FileInfo? FileInfo : &MyFileInfo;
 214
 215     // TODO: This should use fstat64 when available.
 216     if (fstat(FD, FileInfoPtr) == -1) {
 217       if (ErrStr) *ErrStr = sys::StrError();
 218       return 0;
 219     }
 220     FileSize = FileInfoPtr->st_size;
 221   }
 222
 223
 224   // If the file is large, try to use mmap to read it in.  We don't use mmap
 225   // for small files, because this can severely fragment our address space. Also
 226   // don't try to map files that are exactly a multiple of the system page size,
 227   // as the file would not have the required null terminator.
 228   //
 229   // FIXME: Can we just mmap an extra page in the latter case?
 230   if (FileSize >= 4096*4 &&
 231       (FileSize & (sys::Process::GetPageSize()-1)) != 0) {
 232     if (const char *Pages = sys::Path::MapInFilePages(FD, FileSize)) {
 233       return GetNamedBuffer<MemoryBufferMMapFile>(StringRef(Pages, FileSize),
 234                                                   Filename);
 235     }
 236   }
 237
 238   MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(FileSize, Filename);
 239   if (!Buf) {
 240     // Failed to create a buffer.
 241     if (ErrStr) *ErrStr = "could not allocate buffer";
 242     return 0;
 243   }
 244
 245   OwningPtr<MemoryBuffer> SB(Buf);
 246   char *BufPtr = const_cast<char*>(SB->getBufferStart());
 247
 248   size_t BytesLeft = FileSize;
 249   while (BytesLeft) {
 250     ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
 251     if (NumRead == -1) {
 252       if (errno == EINTR)
 253         continue;
 254       // Error while reading.
 255       if (ErrStr) *ErrStr = sys::StrError();
 256       return 0;
 257     } else if (NumRead == 0) {
 258       // We hit EOF early, truncate and terminate buffer.
 259       Buf->BufferEnd = BufPtr;
 260       *BufPtr = 0;
 261       return SB.take();
 262     }
 263     BytesLeft -= NumRead;
 264     BufPtr += NumRead;
 265   }
 266
 267   return SB.take();
 268 }
 269
 270 //===----------------------------------------------------------------------===//
 271 // MemoryBuffer::getSTDIN implementation.
 272 //===----------------------------------------------------------------------===//
 273
 274 MemoryBuffer *MemoryBuffer::getSTDIN(std::string *ErrStr) {
 275   // Read in all of the data from stdin, we cannot mmap stdin.
 276   //
 277   // FIXME: That isn't necessarily true, we should try to mmap stdin and
 278   // fallback if it fails.
 279   sys::Program::ChangeStdinToBinary();
 280
 281   const ssize_t ChunkSize = 4096*4;
 282   SmallString<ChunkSize> Buffer;
 283   ssize_t ReadBytes;
 284   // Read into Buffer until we hit EOF.
 285   do {
 286     Buffer.reserve(Buffer.size() + ChunkSize);
 287     ReadBytes = read(0, Buffer.end(), ChunkSize);
 288     if (ReadBytes == -1) {
 289       if (errno == EINTR) continue;
 290       if (ErrStr) *ErrStr = sys::StrError();
 291       return 0;
 292     }
 293     Buffer.set_size(Buffer.size() + ReadBytes);
 294   } while (ReadBytes != 0);
 295
 296   return getMemBufferCopy(Buffer, "<stdin>");
 297 }