Home | History | Annotate | Download | only in Support 
      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/Path.h"
     21 #include "llvm/Support/Process.h"
     22 #include "llvm/Support/Program.h"
     23 #include "llvm/Support/system_error.h"
     24 #include <cassert>
     25 #include <cstdio>
     26 #include <cstring>
     27 #include <cerrno>
     28 #include <new>
     29 #include <sys/types.h>
     30 #include <sys/stat.h>
     31 #if !defined(_MSC_VER) && !defined(__MINGW32__)
     32 #include <unistd.h>
     33 #else
     34 #include <io.h>
     35 #endif
     36 #include <fcntl.h>
     37 using namespace llvm;
     38 
     39 //===----------------------------------------------------------------------===//
     40 // MemoryBuffer implementation itself.
     41 //===----------------------------------------------------------------------===//
     42 
     43 MemoryBuffer::~MemoryBuffer() { }
     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                         bool RequiresNullTerminator) {
     49   assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
     50          "Buffer is not null terminated!");
     51   BufferStart = BufStart;
     52   BufferEnd = BufEnd;
     53 }
     54 
     55 //===----------------------------------------------------------------------===//
     56 // MemoryBufferMem implementation.
     57 //===----------------------------------------------------------------------===//
     58 
     59 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
     60 /// null-terminates it.
     61 static void CopyStringRef(char *Memory, StringRef Data) {
     62   memcpy(Memory, Data.data(), Data.size());
     63   Memory[Data.size()] = 0; // Null terminate string.
     64 }
     65 
     66 /// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it.
     67 template <typename T>
     68 static T *GetNamedBuffer(StringRef Buffer, StringRef Name,
     69                          bool RequiresNullTerminator) {
     70   char *Mem = static_cast<char*>(operator new(sizeof(T) + Name.size() + 1));
     71   CopyStringRef(Mem + sizeof(T), Name);
     72   return new (Mem) T(Buffer, RequiresNullTerminator);
     73 }
     74 
     75 namespace {
     76 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
     77 class MemoryBufferMem : public MemoryBuffer {
     78 public:
     79   MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
     80     init(InputData.begin(), InputData.end(), RequiresNullTerminator);
     81   }
     82 
     83   virtual const char *getBufferIdentifier() const {
     84      // The name is stored after the class itself.
     85     return reinterpret_cast<const char*>(this + 1);
     86   }
     87 
     88   virtual BufferKind getBufferKind() const {
     89     return MemoryBuffer_Malloc;
     90   }
     91 };
     92 }
     93 
     94 /// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
     95 /// that InputData must be a null terminated if RequiresNullTerminator is true!
     96 MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
     97                                          StringRef BufferName,
     98                                          bool RequiresNullTerminator) {
     99   return GetNamedBuffer<MemoryBufferMem>(InputData, BufferName,
    100                                          RequiresNullTerminator);
    101 }
    102 
    103 /// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
    104 /// copying the contents and taking ownership of it.  This has no requirements
    105 /// on EndPtr[0].
    106 MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
    107                                              StringRef BufferName) {
    108   MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
    109   if (!Buf) return 0;
    110   memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
    111          InputData.size());
    112   return Buf;
    113 }
    114 
    115 /// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
    116 /// that is not initialized.  Note that the caller should initialize the
    117 /// memory allocated by this method.  The memory is owned by the MemoryBuffer
    118 /// object.
    119 MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
    120                                                   StringRef BufferName) {
    121   // Allocate space for the MemoryBuffer, the data and the name. It is important
    122   // that MemoryBuffer and data are aligned so PointerIntPair works with them.
    123   size_t AlignedStringLen =
    124     RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
    125                        sizeof(void*)); // TODO: Is sizeof(void*) enough?
    126   size_t RealLen = AlignedStringLen + Size + 1;
    127   char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
    128   if (!Mem) return 0;
    129 
    130   // The name is stored after the class itself.
    131   CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
    132 
    133   // The buffer begins after the name and must be aligned.
    134   char *Buf = Mem + AlignedStringLen;
    135   Buf[Size] = 0; // Null terminate buffer.
    136 
    137   return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
    138 }
    139 
    140 /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
    141 /// is completely initialized to zeros.  Note that the caller should
    142 /// initialize the memory allocated by this method.  The memory is owned by
    143 /// the MemoryBuffer object.
    144 MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
    145   MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
    146   if (!SB) return 0;
    147   memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
    148   return SB;
    149 }
    150 
    151 
    152 /// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
    153 /// if the Filename is "-".  If an error occurs, this returns null and fills
    154 /// in *ErrStr with a reason.  If stdin is empty, this API (unlike getSTDIN)
    155 /// returns an empty buffer.
    156 error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
    157                                         OwningPtr<MemoryBuffer> &result,
    158                                         int64_t FileSize) {
    159   if (Filename == "-")
    160     return getSTDIN(result);
    161   return getFile(Filename, result, FileSize);
    162 }
    163 
    164 error_code MemoryBuffer::getFileOrSTDIN(const char *Filename,
    165                                         OwningPtr<MemoryBuffer> &result,
    166                                         int64_t FileSize) {
    167   if (strcmp(Filename, "-") == 0)
    168     return getSTDIN(result);
    169   return getFile(Filename, result, FileSize);
    170 }
    171 
    172 //===----------------------------------------------------------------------===//
    173 // MemoryBuffer::getFile implementation.
    174 //===----------------------------------------------------------------------===//
    175 
    176 namespace {
    177 /// MemoryBufferMMapFile - This represents a file that was mapped in with the
    178 /// sys::Path::MapInFilePages method.  When destroyed, it calls the
    179 /// sys::Path::UnMapFilePages method.
    180 class MemoryBufferMMapFile : public MemoryBufferMem {
    181 public:
    182   MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator)
    183     : MemoryBufferMem(Buffer, RequiresNullTerminator) { }
    184 
    185   ~MemoryBufferMMapFile() {
    186     static int PageSize = sys::Process::GetPageSize();
    187 
    188     uintptr_t Start = reinterpret_cast<uintptr_t>(getBufferStart());
    189     size_t Size = getBufferSize();
    190     uintptr_t RealStart = Start & ~(PageSize - 1);
    191     size_t RealSize = Size + (Start - RealStart);
    192 
    193     sys::Path::UnMapFilePages(reinterpret_cast<const char*>(RealStart),
    194                               RealSize);
    195   }
    196 
    197   virtual BufferKind getBufferKind() const {
    198     return MemoryBuffer_MMap;
    199   }
    200 };
    201 }
    202 
    203 error_code MemoryBuffer::getFile(StringRef Filename,
    204                                  OwningPtr<MemoryBuffer> &result,
    205                                  int64_t FileSize,
    206                                  bool RequiresNullTerminator) {
    207   // Ensure the path is null terminated.
    208   SmallString<256> PathBuf(Filename.begin(), Filename.end());
    209   return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize,
    210                                RequiresNullTerminator);
    211 }
    212 
    213 error_code MemoryBuffer::getFile(const char *Filename,
    214                                  OwningPtr<MemoryBuffer> &result,
    215                                  int64_t FileSize,
    216                                  bool RequiresNullTerminator) {
    217   int OpenFlags = O_RDONLY;
    218 #ifdef O_BINARY
    219   OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
    220 #endif
    221   int FD = ::open(Filename, OpenFlags);
    222   if (FD == -1)
    223     return error_code(errno, posix_category());
    224 
    225   error_code ret = getOpenFile(FD, Filename, result, FileSize, FileSize,
    226                                0, RequiresNullTerminator);
    227   close(FD);
    228   return ret;
    229 }
    230 
    231 static bool shouldUseMmap(int FD,
    232                           size_t FileSize,
    233                           size_t MapSize,
    234                           off_t Offset,
    235                           bool RequiresNullTerminator,
    236                           int PageSize) {
    237   // We don't use mmap for small files because this can severely fragment our
    238   // address space.
    239   if (MapSize < 4096*4)
    240     return false;
    241 
    242   if (!RequiresNullTerminator)
    243     return true;
    244 
    245 
    246   // If we don't know the file size, use fstat to find out.  fstat on an open
    247   // file descriptor is cheaper than stat on a random path.
    248   // FIXME: this chunk of code is duplicated, but it avoids a fstat when
    249   // RequiresNullTerminator = false and MapSize != -1.
    250   if (FileSize == size_t(-1)) {
    251     struct stat FileInfo;
    252     // TODO: This should use fstat64 when available.
    253     if (fstat(FD, &FileInfo) == -1) {
    254       return error_code(errno, posix_category());
    255     }
    256     FileSize = FileInfo.st_size;
    257   }
    258 
    259   // If we need a null terminator and the end of the map is inside the file,
    260   // we cannot use mmap.
    261   size_t End = Offset + MapSize;
    262   assert(End <= FileSize);
    263   if (End != FileSize)
    264     return false;
    265 
    266   // Don't try to map files that are exactly a multiple of the system page size
    267   // if we need a null terminator.
    268   if ((FileSize & (PageSize -1)) == 0)
    269     return false;
    270 
    271   return true;
    272 }
    273 
    274 error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
    275                                      OwningPtr<MemoryBuffer> &result,
    276                                      uint64_t FileSize, uint64_t MapSize,
    277                                      int64_t Offset,
    278                                      bool RequiresNullTerminator) {
    279   static int PageSize = sys::Process::GetPageSize();
    280 
    281   // Default is to map the full file.
    282   if (MapSize == uint64_t(-1)) {
    283     // If we don't know the file size, use fstat to find out.  fstat on an open
    284     // file descriptor is cheaper than stat on a random path.
    285     if (FileSize == uint64_t(-1)) {
    286       struct stat FileInfo;
    287       // TODO: This should use fstat64 when available.
    288       if (fstat(FD, &FileInfo) == -1) {
    289         return error_code(errno, posix_category());
    290       }
    291       FileSize = FileInfo.st_size;
    292     }
    293     MapSize = FileSize;
    294   }
    295 
    296   if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
    297                     PageSize)) {
    298     off_t RealMapOffset = Offset & ~(PageSize - 1);
    299     off_t Delta = Offset - RealMapOffset;
    300     size_t RealMapSize = MapSize + Delta;
    301 
    302     if (const char *Pages = sys::Path::MapInFilePages(FD,
    303                                                       RealMapSize,
    304                                                       RealMapOffset)) {
    305       result.reset(GetNamedBuffer<MemoryBufferMMapFile>(
    306           StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator));
    307 
    308       if (RequiresNullTerminator && result->getBufferEnd()[0] != '\0') {
    309         // There could be a racing issue that resulted in the file being larger
    310         // than the FileSize passed by the caller. We already have an assertion
    311         // for this in MemoryBuffer::init() but have a runtime guarantee that
    312         // the buffer will be null-terminated here, so do a copy that adds a
    313         // null-terminator.
    314         result.reset(MemoryBuffer::getMemBufferCopy(result->getBuffer(),
    315                                                     Filename));
    316       }
    317       return error_code::success();
    318     }
    319   }
    320 
    321   MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
    322   if (!Buf) {
    323     // Failed to create a buffer. The only way it can fail is if
    324     // new(std::nothrow) returns 0.
    325     return make_error_code(errc::not_enough_memory);
    326   }
    327 
    328   OwningPtr<MemoryBuffer> SB(Buf);
    329   char *BufPtr = const_cast<char*>(SB->getBufferStart());
    330 
    331   size_t BytesLeft = MapSize;
    332 #ifndef HAVE_PREAD
    333   if (lseek(FD, Offset, SEEK_SET) == -1)
    334     return error_code(errno, posix_category());
    335 #endif
    336 
    337   while (BytesLeft) {
    338 #ifdef HAVE_PREAD
    339     ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
    340 #else
    341     ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
    342 #endif
    343     if (NumRead == -1) {
    344       if (errno == EINTR)
    345         continue;
    346       // Error while reading.
    347       return error_code(errno, posix_category());
    348     }
    349     if (NumRead == 0) {
    350       assert(0 && "We got inaccurate FileSize value or fstat reported an "
    351                    "invalid file size.");
    352       *BufPtr = '\0'; // null-terminate at the actual size.
    353       break;
    354     }
    355     BytesLeft -= NumRead;
    356     BufPtr += NumRead;
    357   }
    358 
    359   result.swap(SB);
    360   return error_code::success();
    361 }
    362 
    363 //===----------------------------------------------------------------------===//
    364 // MemoryBuffer::getSTDIN implementation.
    365 //===----------------------------------------------------------------------===//
    366 
    367 error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
    368   // Read in all of the data from stdin, we cannot mmap stdin.
    369   //
    370   // FIXME: That isn't necessarily true, we should try to mmap stdin and
    371   // fallback if it fails.
    372   sys::Program::ChangeStdinToBinary();
    373 
    374   const ssize_t ChunkSize = 4096*4;
    375   SmallString<ChunkSize> Buffer;
    376   ssize_t ReadBytes;
    377   // Read into Buffer until we hit EOF.
    378   do {
    379     Buffer.reserve(Buffer.size() + ChunkSize);
    380     ReadBytes = read(0, Buffer.end(), ChunkSize);
    381     if (ReadBytes == -1) {
    382       if (errno == EINTR) continue;
    383       return error_code(errno, posix_category());
    384     }
    385     Buffer.set_size(Buffer.size() + ReadBytes);
    386   } while (ReadBytes != 0);
    387 
    388   result.reset(getMemBufferCopy(Buffer, "<stdin>"));
    389   return error_code::success();
    390 }
    391