MemoryBuffer.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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/Errno.h"
19#include "llvm/Support/FileSystem.h"
20#include "llvm/Support/MathExtras.h"
21#include "llvm/Support/Path.h"
22#include "llvm/Support/Process.h"
23#include "llvm/Support/Program.h"
24#include "llvm/Support/system_error.h"
25#include <cassert>
26#include <cerrno>
27#include <cstdio>
28#include <cstring>
29#include <new>
30#include <sys/stat.h>
31#include <sys/types.h>
32#if !defined(_MSC_VER) && !defined(__MINGW32__)
33#include <unistd.h>
34#else
35#include <io.h>
36// Simplistic definitinos of these macros for use in getOpenFile.
37#ifndef S_ISREG
38#define S_ISREG(x) (1)
39#endif
40#ifndef S_ISBLK
41#define S_ISBLK(x) (0)
42#endif
43#endif
44using namespace llvm;
45
46//===----------------------------------------------------------------------===//
47// MemoryBuffer implementation itself.
48//===----------------------------------------------------------------------===//
49
50MemoryBuffer::~MemoryBuffer() { }
51
52/// init - Initialize this MemoryBuffer as a reference to externally allocated
53/// memory, memory that we know is already null terminated.
54void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
55                        bool RequiresNullTerminator) {
56  assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
57         "Buffer is not null terminated!");
58  BufferStart = BufStart;
59  BufferEnd = BufEnd;
60}
61
62//===----------------------------------------------------------------------===//
63// MemoryBufferMem implementation.
64//===----------------------------------------------------------------------===//
65
66/// CopyStringRef - Copies contents of a StringRef into a block of memory and
67/// null-terminates it.
68static void CopyStringRef(char *Memory, StringRef Data) {
69  memcpy(Memory, Data.data(), Data.size());
70  Memory[Data.size()] = 0; // Null terminate string.
71}
72
73namespace {
74struct NamedBufferAlloc {
75  StringRef Name;
76  NamedBufferAlloc(StringRef Name) : Name(Name) {}
77};
78}
79
80void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
81  char *Mem = static_cast<char *>(operator new(N + Alloc.Name.size() + 1));
82  CopyStringRef(Mem + N, Alloc.Name);
83  return Mem;
84}
85
86namespace {
87/// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
88class MemoryBufferMem : public MemoryBuffer {
89public:
90  MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
91    init(InputData.begin(), InputData.end(), RequiresNullTerminator);
92  }
93
94  const char *getBufferIdentifier() const override {
95     // The name is stored after the class itself.
96    return reinterpret_cast<const char*>(this + 1);
97  }
98
99  BufferKind getBufferKind() const override {
100    return MemoryBuffer_Malloc;
101  }
102};
103}
104
105/// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
106/// that InputData must be a null terminated if RequiresNullTerminator is true!
107MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
108                                         StringRef BufferName,
109                                         bool RequiresNullTerminator) {
110  return new (NamedBufferAlloc(BufferName))
111      MemoryBufferMem(InputData, RequiresNullTerminator);
112}
113
114/// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
115/// copying the contents and taking ownership of it.  This has no requirements
116/// on EndPtr[0].
117MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
118                                             StringRef BufferName) {
119  MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
120  if (!Buf) return 0;
121  memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
122         InputData.size());
123  return Buf;
124}
125
126/// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
127/// that is not initialized.  Note that the caller should initialize the
128/// memory allocated by this method.  The memory is owned by the MemoryBuffer
129/// object.
130MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
131                                                  StringRef BufferName) {
132  // Allocate space for the MemoryBuffer, the data and the name. It is important
133  // that MemoryBuffer and data are aligned so PointerIntPair works with them.
134  // TODO: Is 16-byte alignment enough?  We copy small object files with large
135  // alignment expectations into this buffer.
136  size_t AlignedStringLen =
137      RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1, 16);
138  size_t RealLen = AlignedStringLen + Size + 1;
139  char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
140  if (!Mem) return 0;
141
142  // The name is stored after the class itself.
143  CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
144
145  // The buffer begins after the name and must be aligned.
146  char *Buf = Mem + AlignedStringLen;
147  Buf[Size] = 0; // Null terminate buffer.
148
149  return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
150}
151
152/// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
153/// is completely initialized to zeros.  Note that the caller should
154/// initialize the memory allocated by this method.  The memory is owned by
155/// the MemoryBuffer object.
156MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
157  MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
158  if (!SB) return 0;
159  memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
160  return SB;
161}
162
163
164/// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
165/// if the Filename is "-".  If an error occurs, this returns null and fills
166/// in *ErrStr with a reason.  If stdin is empty, this API (unlike getSTDIN)
167/// returns an empty buffer.
168error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
169                                        std::unique_ptr<MemoryBuffer> &Result,
170                                        int64_t FileSize) {
171  if (Filename == "-")
172    return getSTDIN(Result);
173  return getFile(Filename, Result, FileSize);
174}
175
176error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
177                                        OwningPtr<MemoryBuffer> &Result,
178                                        int64_t FileSize) {
179  std::unique_ptr<MemoryBuffer> MB;
180  error_code ec = getFileOrSTDIN(Filename, MB, FileSize);
181  Result = std::move(MB);
182  return ec;
183}
184
185
186//===----------------------------------------------------------------------===//
187// MemoryBuffer::getFile implementation.
188//===----------------------------------------------------------------------===//
189
190namespace {
191/// \brief Memory maps a file descriptor using sys::fs::mapped_file_region.
192///
193/// This handles converting the offset into a legal offset on the platform.
194class MemoryBufferMMapFile : public MemoryBuffer {
195  sys::fs::mapped_file_region MFR;
196
197  static uint64_t getLegalMapOffset(uint64_t Offset) {
198    return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
199  }
200
201  static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
202    return Len + (Offset - getLegalMapOffset(Offset));
203  }
204
205  const char *getStart(uint64_t Len, uint64_t Offset) {
206    return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
207  }
208
209public:
210  MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
211                       uint64_t Offset, error_code EC)
212      : MFR(FD, false, sys::fs::mapped_file_region::readonly,
213            getLegalMapSize(Len, Offset), getLegalMapOffset(Offset), EC) {
214    if (!EC) {
215      const char *Start = getStart(Len, Offset);
216      init(Start, Start + Len, RequiresNullTerminator);
217    }
218  }
219
220  const char *getBufferIdentifier() const override {
221    // The name is stored after the class itself.
222    return reinterpret_cast<const char *>(this + 1);
223  }
224
225  BufferKind getBufferKind() const override {
226    return MemoryBuffer_MMap;
227  }
228};
229}
230
231static error_code getMemoryBufferForStream(int FD,
232                                           StringRef BufferName,
233                                           std::unique_ptr<MemoryBuffer> &Result) {
234  const ssize_t ChunkSize = 4096*4;
235  SmallString<ChunkSize> Buffer;
236  ssize_t ReadBytes;
237  // Read into Buffer until we hit EOF.
238  do {
239    Buffer.reserve(Buffer.size() + ChunkSize);
240    ReadBytes = read(FD, Buffer.end(), ChunkSize);
241    if (ReadBytes == -1) {
242      if (errno == EINTR) continue;
243      return error_code(errno, posix_category());
244    }
245    Buffer.set_size(Buffer.size() + ReadBytes);
246  } while (ReadBytes != 0);
247
248  Result.reset(MemoryBuffer::getMemBufferCopy(Buffer, BufferName));
249  return error_code::success();
250}
251
252static error_code getFileAux(const char *Filename,
253                             std::unique_ptr<MemoryBuffer> &Result,
254                             int64_t FileSize,
255                             bool RequiresNullTerminator);
256
257error_code MemoryBuffer::getFile(Twine Filename,
258                                 std::unique_ptr<MemoryBuffer> &Result,
259                                 int64_t FileSize,
260                                 bool RequiresNullTerminator) {
261  // Ensure the path is null terminated.
262  SmallString<256> PathBuf;
263  StringRef NullTerminatedName = Filename.toNullTerminatedStringRef(PathBuf);
264  return getFileAux(NullTerminatedName.data(), Result, FileSize,
265                    RequiresNullTerminator);
266}
267
268error_code MemoryBuffer::getFile(Twine Filename,
269                                 OwningPtr<MemoryBuffer> &Result,
270                                 int64_t FileSize,
271                                 bool RequiresNullTerminator) {
272  std::unique_ptr<MemoryBuffer> MB;
273  error_code ec = getFile(Filename, MB, FileSize, RequiresNullTerminator);
274  Result = std::move(MB);
275  return ec;
276}
277
278static error_code getOpenFileImpl(int FD, const char *Filename,
279                                  std::unique_ptr<MemoryBuffer> &Result,
280                                  uint64_t FileSize, uint64_t MapSize,
281                                  int64_t Offset, bool RequiresNullTerminator);
282
283static error_code getFileAux(const char *Filename,
284                             std::unique_ptr<MemoryBuffer> &Result, int64_t FileSize,
285                             bool RequiresNullTerminator) {
286  int FD;
287  error_code EC = sys::fs::openFileForRead(Filename, FD);
288  if (EC)
289    return EC;
290
291  error_code ret = getOpenFileImpl(FD, Filename, Result, FileSize, FileSize, 0,
292                                   RequiresNullTerminator);
293  close(FD);
294  return ret;
295}
296
297static bool shouldUseMmap(int FD,
298                          size_t FileSize,
299                          size_t MapSize,
300                          off_t Offset,
301                          bool RequiresNullTerminator,
302                          int PageSize) {
303  // We don't use mmap for small files because this can severely fragment our
304  // address space.
305  if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
306    return false;
307
308  if (!RequiresNullTerminator)
309    return true;
310
311
312  // If we don't know the file size, use fstat to find out.  fstat on an open
313  // file descriptor is cheaper than stat on a random path.
314  // FIXME: this chunk of code is duplicated, but it avoids a fstat when
315  // RequiresNullTerminator = false and MapSize != -1.
316  if (FileSize == size_t(-1)) {
317    sys::fs::file_status Status;
318    error_code EC = sys::fs::status(FD, Status);
319    if (EC)
320      return EC;
321    FileSize = Status.getSize();
322  }
323
324  // If we need a null terminator and the end of the map is inside the file,
325  // we cannot use mmap.
326  size_t End = Offset + MapSize;
327  assert(End <= FileSize);
328  if (End != FileSize)
329    return false;
330
331#if defined(_WIN32) || defined(__CYGWIN__)
332  // Don't peek the next page if file is multiple of *physical* pagesize(4k)
333  // but is not multiple of AllocationGranularity(64k),
334  // when a null terminator is required.
335  // FIXME: It's not good to hardcode 4096 here. dwPageSize shows 4096.
336  if ((FileSize & (4096 - 1)) == 0)
337    return false;
338#endif
339
340  // Don't try to map files that are exactly a multiple of the system page size
341  // if we need a null terminator.
342  if ((FileSize & (PageSize -1)) == 0)
343    return false;
344
345  return true;
346}
347
348static error_code getOpenFileImpl(int FD, const char *Filename,
349                                  std::unique_ptr<MemoryBuffer> &Result,
350                                  uint64_t FileSize, uint64_t MapSize,
351                                  int64_t Offset, bool RequiresNullTerminator) {
352  static int PageSize = sys::process::get_self()->page_size();
353
354  // Default is to map the full file.
355  if (MapSize == uint64_t(-1)) {
356    // If we don't know the file size, use fstat to find out.  fstat on an open
357    // file descriptor is cheaper than stat on a random path.
358    if (FileSize == uint64_t(-1)) {
359      sys::fs::file_status Status;
360      error_code EC = sys::fs::status(FD, Status);
361      if (EC)
362        return EC;
363
364      // If this not a file or a block device (e.g. it's a named pipe
365      // or character device), we can't trust the size. Create the memory
366      // buffer by copying off the stream.
367      sys::fs::file_type Type = Status.type();
368      if (Type != sys::fs::file_type::regular_file &&
369          Type != sys::fs::file_type::block_file)
370        return getMemoryBufferForStream(FD, Filename, Result);
371
372      FileSize = Status.getSize();
373    }
374    MapSize = FileSize;
375  }
376
377  if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
378                    PageSize)) {
379    error_code EC;
380    Result.reset(new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile(
381        RequiresNullTerminator, FD, MapSize, Offset, EC));
382    if (!EC)
383      return error_code::success();
384  }
385
386  MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
387  if (!Buf) {
388    // Failed to create a buffer. The only way it can fail is if
389    // new(std::nothrow) returns 0.
390    return make_error_code(errc::not_enough_memory);
391  }
392
393  std::unique_ptr<MemoryBuffer> SB(Buf);
394  char *BufPtr = const_cast<char*>(SB->getBufferStart());
395
396  size_t BytesLeft = MapSize;
397#ifndef HAVE_PREAD
398  if (lseek(FD, Offset, SEEK_SET) == -1)
399    return error_code(errno, posix_category());
400#endif
401
402  while (BytesLeft) {
403#ifdef HAVE_PREAD
404    ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
405#else
406    ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
407#endif
408    if (NumRead == -1) {
409      if (errno == EINTR)
410        continue;
411      // Error while reading.
412      return error_code(errno, posix_category());
413    }
414    if (NumRead == 0) {
415      assert(0 && "We got inaccurate FileSize value or fstat reported an "
416                   "invalid file size.");
417      *BufPtr = '\0'; // null-terminate at the actual size.
418      break;
419    }
420    BytesLeft -= NumRead;
421    BufPtr += NumRead;
422  }
423
424  Result.swap(SB);
425  return error_code::success();
426}
427
428error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
429                                     std::unique_ptr<MemoryBuffer> &Result,
430                                     uint64_t FileSize,
431                                     bool RequiresNullTerminator) {
432  return getOpenFileImpl(FD, Filename, Result, FileSize, FileSize, 0,
433                         RequiresNullTerminator);
434}
435
436error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
437                                     OwningPtr<MemoryBuffer> &Result,
438                                     uint64_t FileSize,
439                                     bool RequiresNullTerminator) {
440  std::unique_ptr<MemoryBuffer> MB;
441  error_code ec = getOpenFileImpl(FD, Filename, MB, FileSize, FileSize, 0,
442                                  RequiresNullTerminator);
443  Result = std::move(MB);
444  return ec;
445}
446
447error_code MemoryBuffer::getOpenFileSlice(int FD, const char *Filename,
448                                          std::unique_ptr<MemoryBuffer> &Result,
449                                          uint64_t MapSize, int64_t Offset) {
450  return getOpenFileImpl(FD, Filename, Result, -1, MapSize, Offset, false);
451}
452
453error_code MemoryBuffer::getOpenFileSlice(int FD, const char *Filename,
454                                          OwningPtr<MemoryBuffer> &Result,
455                                          uint64_t MapSize, int64_t Offset) {
456  std::unique_ptr<MemoryBuffer> MB;
457  error_code ec = getOpenFileImpl(FD, Filename, MB, -1, MapSize, Offset, false);
458  Result = std::move(MB);
459  return ec;
460}
461
462//===----------------------------------------------------------------------===//
463// MemoryBuffer::getSTDIN implementation.
464//===----------------------------------------------------------------------===//
465
466error_code MemoryBuffer::getSTDIN(std::unique_ptr<MemoryBuffer> &Result) {
467  // Read in all of the data from stdin, we cannot mmap stdin.
468  //
469  // FIXME: That isn't necessarily true, we should try to mmap stdin and
470  // fallback if it fails.
471  sys::ChangeStdinToBinary();
472
473  return getMemoryBufferForStream(0, "<stdin>", Result);
474}
475
476error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &Result) {
477  std::unique_ptr<MemoryBuffer> MB;
478  error_code ec = getSTDIN(MB);
479  Result = std::move(MB);
480  return ec;
481}
482