MemoryBuffer.cpp revision 5d86759e0ff44e07ead4982673fe10abec50f765 
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/Support/Errno.h"
19#include "llvm/Support/Path.h"
20#include "llvm/Support/Process.h"
21#include "llvm/Support/Program.h"
22#include "llvm/Support/system_error.h"
23#include <cassert>
24#include <cstdio>
25#include <cstring>
26#include <cerrno>
27#include <new>
28#include <sys/types.h>
29#include <sys/stat.h>
30#if !defined(_MSC_VER) && !defined(__MINGW32__)
31#include <unistd.h>
32#include <sys/uio.h>
33#else
34#include <io.h>
35#endif
36#include <fcntl.h>
37using namespace llvm;
38
39namespace { const llvm::error_code success; }
40
41//===----------------------------------------------------------------------===//
42// MemoryBuffer implementation itself.
43//===----------------------------------------------------------------------===//
44
45MemoryBuffer::~MemoryBuffer() { }
46
47/// init - Initialize this MemoryBuffer as a reference to externally allocated
48/// memory, memory that we know is already null terminated.
49void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
50                        bool RequiresNullTerminator) {
51  assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
52         "Buffer is not null terminated!");
53  BufferStart = BufStart;
54  BufferEnd = BufEnd;
55}
56
57//===----------------------------------------------------------------------===//
58// MemoryBufferMem implementation.
59//===----------------------------------------------------------------------===//
60
61/// CopyStringRef - Copies contents of a StringRef into a block of memory and
62/// null-terminates it.
63static void CopyStringRef(char *Memory, StringRef Data) {
64  memcpy(Memory, Data.data(), Data.size());
65  Memory[Data.size()] = 0; // Null terminate string.
66}
67
68/// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it.
69template <typename T>
70static T* GetNamedBuffer(StringRef Buffer, StringRef Name,
71                         bool RequiresNullTerminator) {
72  char *Mem = static_cast<char*>(operator new(sizeof(T) + Name.size() + 1));
73  CopyStringRef(Mem + sizeof(T), Name);
74  return new (Mem) T(Buffer, RequiresNullTerminator);
75}
76
77namespace {
78/// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
79class MemoryBufferMem : public MemoryBuffer {
80public:
81  MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
82    init(InputData.begin(), InputData.end(), RequiresNullTerminator);
83  }
84
85  virtual const char *getBufferIdentifier() const {
86     // The name is stored after the class itself.
87    return reinterpret_cast<const char*>(this + 1);
88  }
89
90  virtual BufferKind getBufferKind() const {
91    return MemoryBuffer_Malloc;
92  }
93};
94}
95
96/// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
97/// that EndPtr[0] must be a null byte and be accessible!
98MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
99                                         StringRef BufferName,
100                                         bool RequiresNullTerminator) {
101  return GetNamedBuffer<MemoryBufferMem>(InputData, BufferName,
102                                         RequiresNullTerminator);
103}
104
105/// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
106/// copying the contents and taking ownership of it.  This has no requirements
107/// on EndPtr[0].
108MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
109                                             StringRef BufferName) {
110  MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
111  if (!Buf) return 0;
112  memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
113         InputData.size());
114  return Buf;
115}
116
117/// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
118/// that is not initialized.  Note that the caller should initialize the
119/// memory allocated by this method.  The memory is owned by the MemoryBuffer
120/// object.
121MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
122                                                  StringRef BufferName) {
123  // Allocate space for the MemoryBuffer, the data and the name. It is important
124  // that MemoryBuffer and data are aligned so PointerIntPair works with them.
125  size_t AlignedStringLen =
126    RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
127                       sizeof(void*)); // TODO: Is sizeof(void*) enough?
128  size_t RealLen = AlignedStringLen + Size + 1;
129  char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
130  if (!Mem) return 0;
131
132  // The name is stored after the class itself.
133  CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
134
135  // The buffer begins after the name and must be aligned.
136  char *Buf = Mem + AlignedStringLen;
137  Buf[Size] = 0; // Null terminate buffer.
138
139  return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
140}
141
142/// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
143/// is completely initialized to zeros.  Note that the caller should
144/// initialize the memory allocated by this method.  The memory is owned by
145/// the MemoryBuffer object.
146MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
147  MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
148  if (!SB) return 0;
149  memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
150  return SB;
151}
152
153
154/// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
155/// if the Filename is "-".  If an error occurs, this returns null and fills
156/// in *ErrStr with a reason.  If stdin is empty, this API (unlike getSTDIN)
157/// returns an empty buffer.
158error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
159                                        OwningPtr<MemoryBuffer> &result,
160                                        int64_t FileSize) {
161  if (Filename == "-")
162    return getSTDIN(result);
163  return getFile(Filename, result, FileSize);
164}
165
166error_code MemoryBuffer::getFileOrSTDIN(const char *Filename,
167                                        OwningPtr<MemoryBuffer> &result,
168                                        int64_t FileSize) {
169  if (strcmp(Filename, "-") == 0)
170    return getSTDIN(result);
171  return getFile(Filename, result, FileSize);
172}
173
174//===----------------------------------------------------------------------===//
175// MemoryBuffer::getFile implementation.
176//===----------------------------------------------------------------------===//
177
178namespace {
179/// MemoryBufferMMapFile - This represents a file that was mapped in with the
180/// sys::Path::MapInFilePages method.  When destroyed, it calls the
181/// sys::Path::UnMapFilePages method.
182class MemoryBufferMMapFile : public MemoryBufferMem {
183public:
184  MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator)
185    : MemoryBufferMem(Buffer, RequiresNullTerminator) { }
186
187  ~MemoryBufferMMapFile() {
188    static int PageSize = sys::Process::GetPageSize();
189
190    uintptr_t Start = reinterpret_cast<uintptr_t>(getBufferStart());
191    size_t Size = getBufferSize();
192    uintptr_t RealStart = Start & ~(PageSize - 1);
193    size_t RealSize = Size + (Start - RealStart);
194
195    sys::Path::UnMapFilePages(reinterpret_cast<const char*>(RealStart),
196                              RealSize);
197  }
198
199  virtual BufferKind getBufferKind() const {
200    return MemoryBuffer_MMap;
201  }
202};
203}
204
205error_code MemoryBuffer::getFile(StringRef Filename,
206                                 OwningPtr<MemoryBuffer> &result,
207                                 int64_t FileSize,
208                                 bool RequiresNullTerminator) {
209  // Ensure the path is null terminated.
210  SmallString<256> PathBuf(Filename.begin(), Filename.end());
211  return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize,
212                               RequiresNullTerminator);
213}
214
215error_code MemoryBuffer::getFile(const char *Filename,
216                                 OwningPtr<MemoryBuffer> &result,
217                                 int64_t FileSize,
218                                 bool RequiresNullTerminator) {
219  int OpenFlags = O_RDONLY;
220#ifdef O_BINARY
221  OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
222#endif
223  int FD = ::open(Filename, OpenFlags);
224  if (FD == -1) {
225    return error_code(errno, posix_category());
226  }
227  error_code ret = getOpenFile(FD, Filename, result, FileSize, FileSize,
228                               0, RequiresNullTerminator);
229  close(FD);
230  return ret;
231}
232
233static bool shouldUseMmap(int FD,
234                          size_t FileSize,
235                          size_t MapSize,
236                          off_t Offset,
237                          bool RequiresNullTerminator,
238                          int PageSize) {
239  // We don't use mmap for small files because this can severely fragment our
240  // address space.
241  if (MapSize < 4096*4)
242    return false;
243
244  if (!RequiresNullTerminator)
245    return true;
246
247
248  // If we don't know the file size, use fstat to find out.  fstat on an open
249  // file descriptor is cheaper than stat on a random path.
250  // FIXME: this chunk of code is duplicated, but it avoids a fstat when
251  // RequiresNullTerminator = false and MapSize != -1.
252  if (FileSize == size_t(-1)) {
253    struct stat FileInfo;
254    // TODO: This should use fstat64 when available.
255    if (fstat(FD, &FileInfo) == -1) {
256      return error_code(errno, posix_category());
257    }
258    FileSize = FileInfo.st_size;
259  }
260
261  // If we need a null terminator and the end of the map is inside the file,
262  // we cannot use mmap.
263  size_t End = Offset + MapSize;
264  assert(End <= FileSize);
265  if (End != FileSize)
266    return false;
267
268  // Don't try to map files that are exactly a multiple of the system page size
269  // if we need a null terminator.
270  if ((FileSize & (PageSize -1)) == 0)
271    return false;
272
273  return true;
274}
275
276error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
277                                     OwningPtr<MemoryBuffer> &result,
278                                     size_t FileSize, size_t MapSize,
279                                     off_t Offset,
280                                     bool RequiresNullTerminator) {
281  static int PageSize = sys::Process::GetPageSize();
282
283  // Default is to map the full file.
284  if (MapSize == size_t(-1)) {
285    // If we don't know the file size, use fstat to find out.  fstat on an open
286    // file descriptor is cheaper than stat on a random path.
287    if (FileSize == size_t(-1)) {
288      struct stat FileInfo;
289      // TODO: This should use fstat64 when available.
290      if (fstat(FD, &FileInfo) == -1) {
291        return error_code(errno, posix_category());
292      }
293      FileSize = FileInfo.st_size;
294    }
295    MapSize = FileSize;
296  }
297
298  if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
299                    PageSize)) {
300    off_t RealMapOffset = Offset & ~(PageSize - 1);
301    off_t Delta = Offset - RealMapOffset;
302    size_t RealMapSize = MapSize + Delta;
303
304    if (const char *Pages = sys::Path::MapInFilePages(FD,
305                                                      RealMapSize,
306                                                      RealMapOffset)) {
307      result.reset(GetNamedBuffer<MemoryBufferMMapFile>(
308          StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator));
309      return success;
310    }
311  }
312
313  MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
314  if (!Buf) {
315    // Failed to create a buffer. The only way it can fail is if
316    // new(std::nothrow) returns 0.
317    return make_error_code(errc::not_enough_memory);
318  }
319
320  OwningPtr<MemoryBuffer> SB(Buf);
321  char *BufPtr = const_cast<char*>(SB->getBufferStart());
322
323  size_t BytesLeft = MapSize;
324  if (lseek(FD, Offset, SEEK_SET) == -1)
325    return error_code(errno, posix_category());
326
327  while (BytesLeft) {
328    ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
329    if (NumRead == -1) {
330      if (errno == EINTR)
331        continue;
332      // Error while reading.
333      return error_code(errno, posix_category());
334    } else if (NumRead == 0) {
335      // We hit EOF early, truncate and terminate buffer.
336      Buf->BufferEnd = BufPtr;
337      *BufPtr = 0;
338      result.swap(SB);
339      return success;
340    }
341    BytesLeft -= NumRead;
342    BufPtr += NumRead;
343  }
344
345  result.swap(SB);
346  return success;
347}
348
349//===----------------------------------------------------------------------===//
350// MemoryBuffer::getSTDIN implementation.
351//===----------------------------------------------------------------------===//
352
353error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
354  // Read in all of the data from stdin, we cannot mmap stdin.
355  //
356  // FIXME: That isn't necessarily true, we should try to mmap stdin and
357  // fallback if it fails.
358  sys::Program::ChangeStdinToBinary();
359
360  const ssize_t ChunkSize = 4096*4;
361  SmallString<ChunkSize> Buffer;
362  ssize_t ReadBytes;
363  // Read into Buffer until we hit EOF.
364  do {
365    Buffer.reserve(Buffer.size() + ChunkSize);
366    ReadBytes = read(0, Buffer.end(), ChunkSize);
367    if (ReadBytes == -1) {
368      if (errno == EINTR) continue;
369      return error_code(errno, posix_category());
370    }
371    Buffer.set_size(Buffer.size() + ReadBytes);
372  } while (ReadBytes != 0);
373
374  result.reset(getMemBufferCopy(Buffer, "<stdin>"));
375  return success;
376}
377