summaryrefslogtreecommitdiff
path: root/lib/Support/MemoryBuffer.cpp
blob: 0771af5fee0748333a6f1f15f567eafeee87c48c (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
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
//===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file 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/ADT/OwningPtr.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Errno.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/system_error.h"
#include <cassert>
#include <cstdio>
#include <cstring>
#include <cerrno>
#include <new>
#include <sys/types.h>
#include <sys/stat.h>
#if !defined(_MSC_VER) && !defined(__MINGW32__)
#include <unistd.h>
#include <sys/uio.h>
#else
#include <io.h>
#endif
#include <fcntl.h>
using namespace llvm;

namespace { const llvm::error_code success; }

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

MemoryBuffer::~MemoryBuffer() { }

/// 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,
                        bool RequiresNullTerminator) {
  assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
         "Buffer is not null terminated!");
  BufferStart = BufStart;
  BufferEnd = BufEnd;
}

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

/// CopyStringRef - Copies contents of a StringRef into a block of memory and
/// null-terminates it.
static void CopyStringRef(char *Memory, StringRef Data) {
  memcpy(Memory, Data.data(), Data.size());
  Memory[Data.size()] = 0; // Null terminate string.
}

/// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it.
template <typename T>
static T *GetNamedBuffer(StringRef Buffer, StringRef Name,
                         bool RequiresNullTerminator) {
  char *Mem = static_cast<char*>(operator new(sizeof(T) + Name.size() + 1));
  CopyStringRef(Mem + sizeof(T), Name);
  return new (Mem) T(Buffer, RequiresNullTerminator);
}

namespace {
/// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
class MemoryBufferMem : public MemoryBuffer {
public:
  MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
    init(InputData.begin(), InputData.end(), RequiresNullTerminator);
  }

  virtual const char *getBufferIdentifier() const {
     // The name is stored after the class itself.
    return reinterpret_cast<const char*>(this + 1);
  }
  
  virtual BufferKind getBufferKind() const {
    return MemoryBuffer_Malloc;
  }
};
}

/// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
/// that InputData must be a null terminated if RequiresNullTerminator is true!
MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
                                         StringRef BufferName,
                                         bool RequiresNullTerminator) {
  return GetNamedBuffer<MemoryBufferMem>(InputData, BufferName,
                                         RequiresNullTerminator);
}

/// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
/// copying the contents and taking ownership of it.  This has no requirements
/// on EndPtr[0].
MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
                                             StringRef BufferName) {
  MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
  if (!Buf) return 0;
  memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
         InputData.size());
  return Buf;
}

/// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
/// that is not initialized.  Note that the caller should initialize the
/// memory allocated by this method.  The memory is owned by the MemoryBuffer
/// object.
MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
                                                  StringRef BufferName) {
  // Allocate space for the MemoryBuffer, the data and the name. It is important
  // that MemoryBuffer and data are aligned so PointerIntPair works with them.
  size_t AlignedStringLen =
    RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
                       sizeof(void*)); // TODO: Is sizeof(void*) enough?
  size_t RealLen = AlignedStringLen + Size + 1;
  char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
  if (!Mem) return 0;

  // The name is stored after the class itself.
  CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);

  // The buffer begins after the name and must be aligned.
  char *Buf = Mem + AlignedStringLen;
  Buf[Size] = 0; // Null terminate buffer.

  return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
}

/// 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(size_t Size, StringRef BufferName) {
  MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
  if (!SB) return 0;
  memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
  return SB;
}


/// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
/// if the Filename is "-".  If an error occurs, this returns null and fills
/// in *ErrStr with a reason.  If stdin is empty, this API (unlike getSTDIN)
/// returns an empty buffer.
error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
                                        OwningPtr<MemoryBuffer> &result,
                                        int64_t FileSize) {
  if (Filename == "-")
    return getSTDIN(result);
  return getFile(Filename, result, FileSize);
}

error_code MemoryBuffer::getFileOrSTDIN(const char *Filename,
                                        OwningPtr<MemoryBuffer> &result,
                                        int64_t FileSize) {
  if (strcmp(Filename, "-") == 0)
    return getSTDIN(result);
  return getFile(Filename, result, FileSize);
}

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

namespace {
/// MemoryBufferMMapFile - This represents a file that was mapped in with the
/// sys::Path::MapInFilePages method.  When destroyed, it calls the
/// sys::Path::UnMapFilePages method.
class MemoryBufferMMapFile : public MemoryBufferMem {
public:
  MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator)
    : MemoryBufferMem(Buffer, RequiresNullTerminator) { }

  ~MemoryBufferMMapFile() {
    static int PageSize = sys::Process::GetPageSize();

    uintptr_t Start = reinterpret_cast<uintptr_t>(getBufferStart());
    size_t Size = getBufferSize();
    uintptr_t RealStart = Start & ~(PageSize - 1);
    size_t RealSize = Size + (Start - RealStart);

    sys::Path::UnMapFilePages(reinterpret_cast<const char*>(RealStart),
                              RealSize);
  }
  
  virtual BufferKind getBufferKind() const {
    return MemoryBuffer_MMap;
  }
};
}

error_code MemoryBuffer::getFile(StringRef Filename,
                                 OwningPtr<MemoryBuffer> &result,
                                 int64_t FileSize,
                                 bool RequiresNullTerminator) {
  // Ensure the path is null terminated.
  SmallString<256> PathBuf(Filename.begin(), Filename.end());
  return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize,
                               RequiresNullTerminator);
}

error_code MemoryBuffer::getFile(const char *Filename,
                                 OwningPtr<MemoryBuffer> &result,
                                 int64_t FileSize,
                                 bool RequiresNullTerminator) {
  int OpenFlags = O_RDONLY;
#ifdef O_BINARY
  OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
#endif
  int FD = ::open(Filename, OpenFlags);
  if (FD == -1)
    return error_code(errno, posix_category());

  error_code ret = getOpenFile(FD, Filename, result, FileSize, FileSize,
                               0, RequiresNullTerminator);
  close(FD);
  return ret;
}

static bool shouldUseMmap(int FD,
                          size_t FileSize,
                          size_t MapSize,
                          off_t Offset,
                          bool RequiresNullTerminator,
                          int PageSize) {
  // We don't use mmap for small files because this can severely fragment our
  // address space.
  if (MapSize < 4096*4)
    return false;

  if (!RequiresNullTerminator)
    return true;


  // If we don't know the file size, use fstat to find out.  fstat on an open
  // file descriptor is cheaper than stat on a random path.
  // FIXME: this chunk of code is duplicated, but it avoids a fstat when
  // RequiresNullTerminator = false and MapSize != -1.
  if (FileSize == size_t(-1)) {
    struct stat FileInfo;
    // TODO: This should use fstat64 when available.
    if (fstat(FD, &FileInfo) == -1) {
      return error_code(errno, posix_category());
    }
    FileSize = FileInfo.st_size;
  }

  // If we need a null terminator and the end of the map is inside the file,
  // we cannot use mmap.
  size_t End = Offset + MapSize;
  assert(End <= FileSize);
  if (End != FileSize)
    return false;

  // Don't try to map files that are exactly a multiple of the system page size
  // if we need a null terminator.
  if ((FileSize & (PageSize -1)) == 0)
    return false;

  return true;
}

error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
                                     OwningPtr<MemoryBuffer> &result,
                                     uint64_t FileSize, uint64_t MapSize,
                                     int64_t Offset,
                                     bool RequiresNullTerminator) {
  static int PageSize = sys::Process::GetPageSize();

  // Default is to map the full file.
  if (MapSize == uint64_t(-1)) {
    // If we don't know the file size, use fstat to find out.  fstat on an open
    // file descriptor is cheaper than stat on a random path.
    if (FileSize == uint64_t(-1)) {
      struct stat FileInfo;
      // TODO: This should use fstat64 when available.
      if (fstat(FD, &FileInfo) == -1) {
        return error_code(errno, posix_category());
      }
      FileSize = FileInfo.st_size;
    }
    MapSize = FileSize;
  }

  if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
                    PageSize)) {
    off_t RealMapOffset = Offset & ~(PageSize - 1);
    off_t Delta = Offset - RealMapOffset;
    size_t RealMapSize = MapSize + Delta;

    if (const char *Pages = sys::Path::MapInFilePages(FD,
                                                      RealMapSize,
                                                      RealMapOffset)) {
      result.reset(GetNamedBuffer<MemoryBufferMMapFile>(
          StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator));
      return success;
    }
  }

  MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
  if (!Buf) {
    // Failed to create a buffer. The only way it can fail is if
    // new(std::nothrow) returns 0.
    return make_error_code(errc::not_enough_memory);
  }

  OwningPtr<MemoryBuffer> SB(Buf);
  char *BufPtr = const_cast<char*>(SB->getBufferStart());

  size_t BytesLeft = MapSize;
  if (lseek(FD, Offset, SEEK_SET) == -1)
    return error_code(errno, posix_category());

  while (BytesLeft) {
    ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
    if (NumRead == -1) {
      if (errno == EINTR)
        continue;
      // Error while reading.
      return error_code(errno, posix_category());
    } else if (NumRead == 0) {
      // We hit EOF early, truncate and terminate buffer.
      Buf->BufferEnd = BufPtr;
      *BufPtr = 0;
      result.swap(SB);
      return success;
    }
    BytesLeft -= NumRead;
    BufPtr += NumRead;
  }

  result.swap(SB);
  return success;
}

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

error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
  // Read in all of the data from stdin, we cannot mmap stdin.
  //
  // FIXME: That isn't necessarily true, we should try to mmap stdin and
  // fallback if it fails.
  sys::Program::ChangeStdinToBinary();

  const ssize_t ChunkSize = 4096*4;
  SmallString<ChunkSize> Buffer;
  ssize_t ReadBytes;
  // Read into Buffer until we hit EOF.
  do {
    Buffer.reserve(Buffer.size() + ChunkSize);
    ReadBytes = read(0, Buffer.end(), ChunkSize);
    if (ReadBytes == -1) {
      if (errno == EINTR) continue;
      return error_code(errno, posix_category());
    }
    Buffer.set_size(Buffer.size() + ReadBytes);
  } while (ReadBytes != 0);

  result.reset(getMemBufferCopy(Buffer, "<stdin>"));
  return success;
}