aboutsummaryrefslogtreecommitdiffstats
path: root/lib/Support/MemoryBuffer.cpp
blob: 43eb1813ad6c06575f7dd76590d627e3f665792c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
//===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Chris Lattner and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements the MemoryBuffer interface.
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/MemoryBuffer.h"
#include "llvm/System/MappedFile.h"
#include "llvm/System/Process.h"
#include "llvm/System/Program.h"
#include <cassert>
#include <cstdio>
#include <cstring>
#include <cerrno>
using namespace llvm;

//===----------------------------------------------------------------------===//
// MemoryBuffer implementation itself.
//===----------------------------------------------------------------------===//

MemoryBuffer::~MemoryBuffer() {
  if (MustDeleteBuffer)
    delete [] BufferStart;
}

/// initCopyOf - Initialize this source buffer with a copy of the specified
/// memory range.  We make the copy so that we can null terminate it
/// successfully.
void MemoryBuffer::initCopyOf(const char *BufStart, const char *BufEnd) {
  size_t Size = BufEnd-BufStart;
  BufferStart = new char[Size+1];
  BufferEnd = BufferStart+Size;
  memcpy(const_cast<char*>(BufferStart), BufStart, Size);
  *const_cast<char*>(BufferEnd) = 0;   // Null terminate buffer.
  MustDeleteBuffer = true;
}

/// init - Initialize this MemoryBuffer as a reference to externally allocated
/// memory, memory that we know is already null terminated.
void MemoryBuffer::init(const char *BufStart, const char *BufEnd) {
  assert(BufEnd[0] == 0 && "Buffer is not null terminated!");
  BufferStart = BufStart;
  BufferEnd = BufEnd;
  MustDeleteBuffer = false;
}

//===----------------------------------------------------------------------===//
// MemoryBufferMem implementation.
//===----------------------------------------------------------------------===//

namespace {
class MemoryBufferMem : public MemoryBuffer {
  std::string FileID;
public:
  MemoryBufferMem(const char *Start, const char *End, const char *FID)
  : FileID(FID) {
    init(Start, End);
  }
  
  virtual const char *getBufferIdentifier() const {
    return FileID.c_str();
  }
};
}

/// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
/// that EndPtr[0] must be a null byte and be accessible!
MemoryBuffer *MemoryBuffer::getMemBuffer(const char *StartPtr, 
                                         const char *EndPtr,
                                         const char *BufferName) {
  return new MemoryBufferMem(StartPtr, EndPtr, BufferName);
}

/// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
/// that is completely initialized to zeros.  Note that the caller should
/// initialize the memory allocated by this method.  The memory is owned by
/// the MemoryBuffer object.
MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(unsigned Size,
                                                  const char *BufferName) {
  char *Buf = new char[Size+1];
  Buf[Size] = 0;
  MemoryBufferMem *SB = new MemoryBufferMem(Buf, Buf+Size, BufferName);
  // The memory for this buffer is owned by the MemoryBuffer.
  SB->MustDeleteBuffer = true;
  return SB;
}

/// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
/// is completely initialized to zeros.  Note that the caller should
/// initialize the memory allocated by this method.  The memory is owned by
/// the MemoryBuffer object.
MemoryBuffer *MemoryBuffer::getNewMemBuffer(unsigned Size,
                                            const char *BufferName) {
  MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
  memset(const_cast<char*>(SB->getBufferStart()), 0, Size+1);
  return SB;
}


//===----------------------------------------------------------------------===//
// MemoryBufferMMapFile implementation.
//===----------------------------------------------------------------------===//

namespace {
class MemoryBufferMMapFile : public MemoryBuffer {
  sys::MappedFile File;
public:
  MemoryBufferMMapFile() {}
  
  bool open(const sys::Path &Filename, std::string *ErrStr);
  
  virtual const char *getBufferIdentifier() const {
    return File.path().c_str();
  }
    
  ~MemoryBufferMMapFile();
};
}

bool MemoryBufferMMapFile::open(const sys::Path &Filename,
                                std::string *ErrStr) {
  // FIXME: This does an extra stat syscall to figure out the size, but we
  // already know the size!
  bool Failure = File.open(Filename, sys::MappedFile::READ_ACCESS, ErrStr);
  if (Failure) return true;
  
  if (!File.map(ErrStr))
    return true;
  
  size_t Size = File.size();
  
  static unsigned PageSize = sys::Process::GetPageSize();
  assert(((PageSize & (PageSize-1)) == 0) && PageSize &&
         "Page size is not a power of 2!");
  
  // If this file is not an exact multiple of the system page size (common
  // case), then the OS has zero terminated the buffer for us.
  if ((Size & (PageSize-1))) {
    init(File.charBase(), File.charBase()+Size);
  } else {
    // Otherwise, we allocate a new memory buffer and copy the data over
    initCopyOf(File.charBase(), File.charBase()+Size);
    
    // No need to keep the file mapped any longer.
    File.unmap();
  }
  return false;
}

MemoryBufferMMapFile::~MemoryBufferMMapFile() {
  if (File.isMapped())
    File.unmap();
}

//===----------------------------------------------------------------------===//
// MemoryBuffer::getFile implementation.
//===----------------------------------------------------------------------===//

MemoryBuffer *MemoryBuffer::getFile(const char *FilenameStart, unsigned FnSize,
                                    std::string *ErrStr, int64_t FileSize){
  // FIXME: it would be nice if PathWithStatus didn't copy the filename into a
  // temporary string. :(
  sys::PathWithStatus P(FilenameStart, FnSize);
#if 1
  MemoryBufferMMapFile *M = new MemoryBufferMMapFile();
  if (!M->open(P, ErrStr))
    return M;
  delete M;
  return 0;
#else
  // FIXME: We need an efficient and portable method to open a file and then use
  // 'read' to copy the bits out.  The unix implementation is below.  This is
  // an important optimization for clients that want to open large numbers of
  // small files (using mmap on everything can easily exhaust address space!).
  
  // If the user didn't specify a filesize, do a stat to find it.
  if (FileSize == -1) {
    const sys::FileStatus *FS = P.getFileStatus();
    if (FS == 0) return 0;  // Error stat'ing file.
   
    FileSize = FS->fileSize;
  }
  
  // If the file is larger than some threshold, use mmap, otherwise use 'read'.
  if (FileSize >= 4096*4) {
    MemoryBufferMMapFile *M = new MemoryBufferMMapFile();
    if (!M->open(P, ErrStr))
      return M;
    delete M;
    return 0;
  }
  
  MemoryBuffer *SB = getNewUninitMemBuffer(FileSize, FilenameStart);
  char *BufPtr = const_cast<char*>(SB->getBufferStart());
  
  int FD = ::open(FilenameStart, O_RDONLY);
  if (FD == -1) {
    delete SB;
    return 0;
  }
  
  unsigned BytesLeft = FileSize;
  while (BytesLeft) {
    ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
    if (NumRead != -1) {
      BytesLeft -= NumRead;
      BufPtr += NumRead;
    } else if (errno == EINTR) {
      // try again
    } else {
      // error reading.
      close(FD);
      delete SB;
      return 0;
    }
  }
  close(FD);
  
  return SB;
#endif
}


//===----------------------------------------------------------------------===//
// MemoryBuffer::getSTDIN implementation.
//===----------------------------------------------------------------------===//

namespace {
class STDINBufferFile : public MemoryBuffer {
public:
  virtual const char *getBufferIdentifier() const {
    return "<stdin>";
  }
};
}

MemoryBuffer *MemoryBuffer::getSTDIN() {
  char Buffer[4096*4];
  
  std::vector<char> FileData;
  
  // Read in all of the data from stdin, we cannot mmap stdin.
  sys::Program::ChangeStdinToBinary();
  while (size_t ReadBytes = fread(Buffer, 1, 4096*4, stdin))
    FileData.insert(FileData.end(), Buffer, Buffer+ReadBytes);
  
  FileData.push_back(0); // &FileData[Size] is invalid. So is &*FileData.end().
  size_t Size = FileData.size();
  MemoryBuffer *B = new STDINBufferFile();
  B->initCopyOf(&FileData[0], &FileData[Size-1]);
  return B;
}