LLVM  6.0.0svn
MemoryBuffer.cpp
Go to the documentation of this file.
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 
15 #include "llvm/ADT/SmallString.h"
16 #include "llvm/Config/config.h"
17 #include "llvm/Support/Errc.h"
18 #include "llvm/Support/Errno.h"
21 #include "llvm/Support/Path.h"
22 #include "llvm/Support/Process.h"
23 #include "llvm/Support/Program.h"
24 #include <cassert>
25 #include <cerrno>
26 #include <cstring>
27 #include <new>
28 #include <sys/types.h>
29 #include <system_error>
30 #if !defined(_MSC_VER) && !defined(__MINGW32__)
31 #include <unistd.h>
32 #else
33 #include <io.h>
34 #endif
35 using namespace llvm;
36 
37 //===----------------------------------------------------------------------===//
38 // MemoryBuffer implementation itself.
39 //===----------------------------------------------------------------------===//
40 
42 
43 /// init - Initialize this MemoryBuffer as a reference to externally allocated
44 /// memory, memory that we know is already null terminated.
45 void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
46  bool RequiresNullTerminator) {
47  assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
48  "Buffer is not null terminated!");
49  BufferStart = BufStart;
50  BufferEnd = BufEnd;
51 }
52 
53 //===----------------------------------------------------------------------===//
54 // MemoryBufferMem implementation.
55 //===----------------------------------------------------------------------===//
56 
57 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
58 /// null-terminates it.
59 static void CopyStringRef(char *Memory, StringRef Data) {
60  if (!Data.empty())
61  memcpy(Memory, Data.data(), Data.size());
62  Memory[Data.size()] = 0; // Null terminate string.
63 }
64 
65 namespace {
66 struct NamedBufferAlloc {
67  const Twine &Name;
68  NamedBufferAlloc(const Twine &Name) : Name(Name) {}
69 };
70 }
71 
72 void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
73  SmallString<256> NameBuf;
74  StringRef NameRef = Alloc.Name.toStringRef(NameBuf);
75 
76  char *Mem = static_cast<char *>(operator new(N + NameRef.size() + 1));
77  CopyStringRef(Mem + N, NameRef);
78  return Mem;
79 }
80 
81 namespace {
82 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
83 class MemoryBufferMem : public MemoryBuffer {
84 public:
85  MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
86  init(InputData.begin(), InputData.end(), RequiresNullTerminator);
87  }
88 
89  /// Disable sized deallocation for MemoryBufferMem, because it has
90  /// tail-allocated data.
91  void operator delete(void *p) { ::operator delete(p); }
92 
93  StringRef getBufferIdentifier() const override {
94  // The name is stored after the class itself.
95  return StringRef(reinterpret_cast<const char *>(this + 1));
96  }
97 
98  BufferKind getBufferKind() const override {
99  return MemoryBuffer_Malloc;
100  }
101 };
102 }
103 
105 getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
106  uint64_t Offset, bool RequiresNullTerminator, bool IsVolatile);
107 
108 std::unique_ptr<MemoryBuffer>
110  bool RequiresNullTerminator) {
111  auto *Ret = new (NamedBufferAlloc(BufferName))
112  MemoryBufferMem(InputData, RequiresNullTerminator);
113  return std::unique_ptr<MemoryBuffer>(Ret);
114 }
115 
116 std::unique_ptr<MemoryBuffer>
117 MemoryBuffer::getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator) {
118  return std::unique_ptr<MemoryBuffer>(getMemBuffer(
119  Ref.getBuffer(), Ref.getBufferIdentifier(), RequiresNullTerminator));
120 }
121 
122 std::unique_ptr<MemoryBuffer>
123 MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {
124  std::unique_ptr<MemoryBuffer> Buf =
125  getNewUninitMemBuffer(InputData.size(), BufferName);
126  if (!Buf)
127  return nullptr;
128  memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
129  InputData.size());
130  return Buf;
131 }
132 
133 std::unique_ptr<MemoryBuffer>
134 MemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {
135  // Allocate space for the MemoryBuffer, the data and the name. It is important
136  // that MemoryBuffer and data are aligned so PointerIntPair works with them.
137  // TODO: Is 16-byte alignment enough? We copy small object files with large
138  // alignment expectations into this buffer.
139  SmallString<256> NameBuf;
140  StringRef NameRef = BufferName.toStringRef(NameBuf);
141  size_t AlignedStringLen =
142  alignTo(sizeof(MemoryBufferMem) + NameRef.size() + 1, 16);
143  size_t RealLen = AlignedStringLen + Size + 1;
144  char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
145  if (!Mem)
146  return nullptr;
147 
148  // The name is stored after the class itself.
149  CopyStringRef(Mem + sizeof(MemoryBufferMem), NameRef);
150 
151  // The buffer begins after the name and must be aligned.
152  char *Buf = Mem + AlignedStringLen;
153  Buf[Size] = 0; // Null terminate buffer.
154 
155  auto *Ret = new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
156  return std::unique_ptr<MemoryBuffer>(Ret);
157 }
158 
159 std::unique_ptr<MemoryBuffer>
161  std::unique_ptr<MemoryBuffer> SB = getNewUninitMemBuffer(Size, BufferName);
162  if (!SB)
163  return nullptr;
164  memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
165  return SB;
166 }
167 
169 MemoryBuffer::getFileOrSTDIN(const Twine &Filename, int64_t FileSize,
170  bool RequiresNullTerminator) {
171  SmallString<256> NameBuf;
172  StringRef NameRef = Filename.toStringRef(NameBuf);
173 
174  if (NameRef == "-")
175  return getSTDIN();
176  return getFile(Filename, FileSize, RequiresNullTerminator);
177 }
178 
180 MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
181  uint64_t Offset, bool IsVolatile) {
182  return getFileAux(FilePath, -1, MapSize, Offset, false, IsVolatile);
183 }
184 
185 
186 //===----------------------------------------------------------------------===//
187 // MemoryBuffer::getFile implementation.
188 //===----------------------------------------------------------------------===//
189 
190 namespace {
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.
194 class MemoryBufferMMapFile : public MemoryBuffer {
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 
209 public:
210  MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
211  uint64_t Offset, std::error_code &EC)
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  /// Disable sized deallocation for MemoryBufferMMapFile, because it has
221  /// tail-allocated data.
222  void operator delete(void *p) { ::operator delete(p); }
223 
224  StringRef getBufferIdentifier() const override {
225  // The name is stored after the class itself.
226  return StringRef(reinterpret_cast<const char *>(this + 1));
227  }
228 
229  BufferKind getBufferKind() const override {
230  return MemoryBuffer_MMap;
231  }
232 };
233 }
234 
236 getMemoryBufferForStream(int FD, const Twine &BufferName) {
237  const ssize_t ChunkSize = 4096*4;
238  SmallString<ChunkSize> Buffer;
239  ssize_t ReadBytes;
240  // Read into Buffer until we hit EOF.
241  do {
242  Buffer.reserve(Buffer.size() + ChunkSize);
243  ReadBytes = sys::RetryAfterSignal(-1, read, FD, Buffer.end(), ChunkSize);
244  if (ReadBytes == -1)
245  return std::error_code(errno, std::generic_category());
246  Buffer.set_size(Buffer.size() + ReadBytes);
247  } while (ReadBytes != 0);
248 
249  return MemoryBuffer::getMemBufferCopy(Buffer, BufferName);
250 }
251 
252 
254 MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
255  bool RequiresNullTerminator, bool IsVolatile) {
256  return getFileAux(Filename, FileSize, FileSize, 0,
257  RequiresNullTerminator, IsVolatile);
258 }
259 
261 getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
262  uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
263  bool IsVolatile);
264 
266 getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
267  uint64_t Offset, bool RequiresNullTerminator, bool IsVolatile) {
268  int FD;
269  std::error_code EC = sys::fs::openFileForRead(Filename, FD);
270  if (EC)
271  return EC;
272 
274  getOpenFileImpl(FD, Filename, FileSize, MapSize, Offset,
275  RequiresNullTerminator, IsVolatile);
276  close(FD);
277  return Ret;
278 }
279 
280 static bool shouldUseMmap(int FD,
281  size_t FileSize,
282  size_t MapSize,
283  off_t Offset,
284  bool RequiresNullTerminator,
285  int PageSize,
286  bool IsVolatile) {
287  // mmap may leave the buffer without null terminator if the file size changed
288  // by the time the last page is mapped in, so avoid it if the file size is
289  // likely to change.
290  if (IsVolatile)
291  return false;
292 
293  // We don't use mmap for small files because this can severely fragment our
294  // address space.
295  if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
296  return false;
297 
298  if (!RequiresNullTerminator)
299  return true;
300 
301  // If we don't know the file size, use fstat to find out. fstat on an open
302  // file descriptor is cheaper than stat on a random path.
303  // FIXME: this chunk of code is duplicated, but it avoids a fstat when
304  // RequiresNullTerminator = false and MapSize != -1.
305  if (FileSize == size_t(-1)) {
306  sys::fs::file_status Status;
307  if (sys::fs::status(FD, Status))
308  return false;
309  FileSize = Status.getSize();
310  }
311 
312  // If we need a null terminator and the end of the map is inside the file,
313  // we cannot use mmap.
314  size_t End = Offset + MapSize;
315  assert(End <= FileSize);
316  if (End != FileSize)
317  return false;
318 
319  // Don't try to map files that are exactly a multiple of the system page size
320  // if we need a null terminator.
321  if ((FileSize & (PageSize -1)) == 0)
322  return false;
323 
324 #if defined(__CYGWIN__)
325  // Don't try to map files that are exactly a multiple of the physical page size
326  // if we need a null terminator.
327  // FIXME: We should reorganize again getPageSize() on Win32.
328  if ((FileSize & (4096 - 1)) == 0)
329  return false;
330 #endif
331 
332  return true;
333 }
334 
336 getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
337  uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
338  bool IsVolatile) {
339  static int PageSize = sys::Process::getPageSize();
340 
341  // Default is to map the full file.
342  if (MapSize == uint64_t(-1)) {
343  // If we don't know the file size, use fstat to find out. fstat on an open
344  // file descriptor is cheaper than stat on a random path.
345  if (FileSize == uint64_t(-1)) {
346  sys::fs::file_status Status;
347  std::error_code EC = sys::fs::status(FD, Status);
348  if (EC)
349  return EC;
350 
351  // If this not a file or a block device (e.g. it's a named pipe
352  // or character device), we can't trust the size. Create the memory
353  // buffer by copying off the stream.
354  sys::fs::file_type Type = Status.type();
355  if (Type != sys::fs::file_type::regular_file &&
357  return getMemoryBufferForStream(FD, Filename);
358 
359  FileSize = Status.getSize();
360  }
361  MapSize = FileSize;
362  }
363 
364  if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
365  PageSize, IsVolatile)) {
366  std::error_code EC;
367  std::unique_ptr<MemoryBuffer> Result(
368  new (NamedBufferAlloc(Filename))
369  MemoryBufferMMapFile(RequiresNullTerminator, FD, MapSize, Offset, EC));
370  if (!EC)
371  return std::move(Result);
372  }
373 
374  std::unique_ptr<MemoryBuffer> Buf =
375  MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
376  if (!Buf) {
377  // Failed to create a buffer. The only way it can fail is if
378  // new(std::nothrow) returns 0.
380  }
381 
382  char *BufPtr = const_cast<char *>(Buf->getBufferStart());
383 
384  size_t BytesLeft = MapSize;
385 #ifndef HAVE_PREAD
386  if (lseek(FD, Offset, SEEK_SET) == -1)
387  return std::error_code(errno, std::generic_category());
388 #endif
389 
390  while (BytesLeft) {
391 #ifdef HAVE_PREAD
392  ssize_t NumRead = sys::RetryAfterSignal(-1, ::pread, FD, BufPtr, BytesLeft,
393  MapSize - BytesLeft + Offset);
394 #else
395  ssize_t NumRead = sys::RetryAfterSignal(-1, ::read, FD, BufPtr, BytesLeft);
396 #endif
397  if (NumRead == -1) {
398  // Error while reading.
399  return std::error_code(errno, std::generic_category());
400  }
401  if (NumRead == 0) {
402  memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.
403  break;
404  }
405  BytesLeft -= NumRead;
406  BufPtr += NumRead;
407  }
408 
409  return std::move(Buf);
410 }
411 
413 MemoryBuffer::getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,
414  bool RequiresNullTerminator, bool IsVolatile) {
415  return getOpenFileImpl(FD, Filename, FileSize, FileSize, 0,
416  RequiresNullTerminator, IsVolatile);
417 }
418 
420 MemoryBuffer::getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,
421  int64_t Offset, bool IsVolatile) {
422  assert(MapSize != uint64_t(-1));
423  return getOpenFileImpl(FD, Filename, -1, MapSize, Offset, false, IsVolatile);
424 }
425 
427  // Read in all of the data from stdin, we cannot mmap stdin.
428  //
429  // FIXME: That isn't necessarily true, we should try to mmap stdin and
430  // fallback if it fails.
432 
433  return getMemoryBufferForStream(0, "<stdin>");
434 }
435 
438  int FD;
439  std::error_code EC = sys::fs::openFileForRead(Filename, FD);
440  if (EC)
441  return EC;
443  getMemoryBufferForStream(FD, Filename);
444  close(FD);
445  return Ret;
446 }
447 
451  return MemoryBufferRef(Data, Identifier);
452 }
virtual StringRef getBufferIdentifier() const
Return an identifier for this buffer, typically the filename it was read from.
Definition: MemoryBuffer.h:65
void init(const char *BufStart, const char *BufEnd, bool RequiresNullTerminator)
init - Initialize this MemoryBuffer as a reference to externally allocated memory, memory that we know is already null terminated.
static ErrorOr< std::unique_ptr< MemoryBuffer > > getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize, int64_t Offset, bool IsVolatile=false)
Given an already-open file descriptor, map some slice of it into a MemoryBuffer.
Represents either an error or a value T.
Definition: ErrorOr.h:69
StringRef getBuffer() const
Definition: MemoryBuffer.h:59
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
constexpr char IsVolatile[]
Key for Kernel::Arg::Metadata::mIsVolatile.
std::error_code openFileForRead(const Twine &Name, int &ResultFD, SmallVectorImpl< char > *RealPath=nullptr)
This class provides various memory handling functions that manipulate MemoryBlock instances...
Definition: Memory.h:46
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE size_t size() const
size - Get the string size.
Definition: StringRef.h:138
static std::unique_ptr< MemoryBuffer > getMemBuffer(StringRef InputData, StringRef BufferName="", bool RequiresNullTerminator=true)
Open the specified memory range as a MemoryBuffer.
StringRef toStringRef(SmallVectorImpl< char > &Out) const
This returns the twine as a single StringRef if it can be represented as such.
Definition: Twine.h:453
static ErrorOr< std::unique_ptr< MemoryBuffer > > getMemoryBufferForStream(int FD, const Twine &BufferName)
This class represents a memory mapped file.
Definition: FileSystem.h:805
static std::unique_ptr< MemoryBuffer > getNewUninitMemBuffer(size_t Size, const Twine &BufferName="")
Allocate a new MemoryBuffer of the specified size that is not initialized.
uint64_t alignTo(uint64_t Value, uint64_t Align, uint64_t Skew=0)
Returns the next integer (mod 2**64) that is greater than or equal to Value and is a multiple of Alig...
Definition: MathExtras.h:677
void reserve(size_type N)
Definition: SmallVector.h:380
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize, uint64_t Offset, bool RequiresNullTerminator, bool IsVolatile)
static std::unique_ptr< MemoryBuffer > getNewMemBuffer(size_t Size, StringRef BufferName="")
Allocate a new zero-initialized MemoryBuffer of the specified size.
Represents the result of a call to sys::fs::status().
Definition: FileSystem.h:219
static ErrorOr< std::unique_ptr< MemoryBuffer > > getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize, uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator, bool IsVolatile)
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE const char * data() const
data - Get a pointer to the start of the string (which may not be null terminated).
Definition: StringRef.h:128
const char * const_data() const
Get a const view of the data.
virtual BufferKind getBufferKind() const =0
Return information on the memory mechanism used to support the MemoryBuffer.
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
StringRef getBuffer() const
Definition: MemoryBuffer.h:170
std::error_code make_error_code(BitcodeError E)
May only access map via const_data as read only.
Definition: FileSystem.h:808
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool empty() const
empty - Check if the string is empty.
Definition: StringRef.h:133
static cl::opt< int > PageSize("imp-null-check-page-size", cl::desc("The page size of the target in bytes"), cl::init(4096))
static void CopyStringRef(char *Memory, StringRef Data)
CopyStringRef - Copies contents of a StringRef into a block of memory and null-terminates it...
static ErrorOr< std::unique_ptr< MemoryBuffer > > getSTDIN()
Read all of stdin into a file buffer, and return it.
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
std::error_code status(const Twine &path, file_status &result, bool follow=true)
Get file status as if by POSIX stat().
static const unsigned End
auto RetryAfterSignal(const FailT &Fail, const Fun &F, const Args &... As) -> decltype(F(As...))
Definition: Errno.h:34
static unsigned getPageSize()
MemoryBufferRef getMemBufferRef() const
This interface provides simple read-only access to a block of memory, and provides simple methods for...
Definition: MemoryBuffer.h:40
static std::unique_ptr< MemoryBuffer > getMemBufferCopy(StringRef InputData, const Twine &BufferName="")
Open the specified memory range as a MemoryBuffer, copying the contents and taking ownership of it...
static bool shouldUseMmap(int FD, size_t FileSize, size_t MapSize, off_t Offset, bool RequiresNullTerminator, int PageSize, bool IsVolatile)
StringRef getBufferIdentifier() const
Definition: MemoryBuffer.h:172
iterator begin() const
Definition: StringRef.h:106
std::error_code ChangeStdinToBinary()
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset, bool IsVolatile=false)
Map a subrange of the specified file as a MemoryBuffer.
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFileOrSTDIN(const Twine &Filename, int64_t FileSize=-1, bool RequiresNullTerminator=true)
Open the specified file as a MemoryBuffer, or open stdin if the Filename is "-".
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:120
void set_size(size_type N)
Set the array size to N, which the current array must have enough capacity for.
Definition: SmallVector.h:689
Provides a library for accessing information about this process and other processes on the operating ...
file_type
An enumeration for the file system&#39;s view of the type.
Definition: FileSystem.h:57
virtual ~MemoryBuffer()
value_type read(const void *memory, endianness endian)
Read a value of a particular endianness from memory.
Definition: Endian.h:66
#define N
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFileAsStream(const Twine &Filename)
Read all of the specified file into a MemoryBuffer as a stream (i.e.
BufferKind
The kind of memory backing used to support the MemoryBuffer.
Definition: MemoryBuffer.h:147
static ErrorOr< std::unique_ptr< MemoryBuffer > > getFile(const Twine &Filename, int64_t FileSize=-1, bool RequiresNullTerminator=true, bool IsVolatile=false)
Open the specified file as a MemoryBuffer, returning a new MemoryBuffer if successful, otherwise returning null.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
static ErrorOr< std::unique_ptr< MemoryBuffer > > getOpenFile(int FD, const Twine &Filename, uint64_t FileSize, bool RequiresNullTerminator=true, bool IsVolatile=false)
Given an already-open file descriptor, read the file and return a MemoryBuffer.
iterator end() const
Definition: StringRef.h:108