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/System/Path.h"
18 #include "llvm/System/Process.h"
19 #include "llvm/System/Program.h"
20 #include <cassert>
21 #include <cstdio>
22 #include <cstring>
23 #include <cerrno>
24 #include <sys/types.h>
25 #include <sys/stat.h>
26 #if !defined(_MSC_VER) && !defined(__MINGW32__)
27 #include <unistd.h>
28 #include <sys/uio.h>
29 #else
30 #include <io.h>
31 #endif
32 #include <fcntl.h>
33 using namespace llvm;
34 
35 //===----------------------------------------------------------------------===//
36 // MemoryBuffer implementation itself.
37 //===----------------------------------------------------------------------===//
38 
39 MemoryBuffer::~MemoryBuffer() {
40   if (MustDeleteBuffer)
41     free((void*)BufferStart);
42 }
43 
44 /// initCopyOf - Initialize this source buffer with a copy of the specified
45 /// memory range.  We make the copy so that we can null terminate it
46 /// successfully.
47 void MemoryBuffer::initCopyOf(const char *BufStart, const char *BufEnd) {
48   size_t Size = BufEnd-BufStart;
49   BufferStart = (char *)malloc(Size+1);
50   BufferEnd = BufferStart+Size;
51   memcpy(const_cast<char*>(BufferStart), BufStart, Size);
52   *const_cast<char*>(BufferEnd) = 0;   // Null terminate buffer.
53   MustDeleteBuffer = true;
54 }
55 
56 /// init - Initialize this MemoryBuffer as a reference to externally allocated
57 /// memory, memory that we know is already null terminated.
58 void MemoryBuffer::init(const char *BufStart, const char *BufEnd) {
59   assert(BufEnd[0] == 0 && "Buffer is not null terminated!");
60   BufferStart = BufStart;
61   BufferEnd = BufEnd;
62   MustDeleteBuffer = false;
63 }
64 
65 //===----------------------------------------------------------------------===//
66 // MemoryBufferMem implementation.
67 //===----------------------------------------------------------------------===//
68 
69 namespace {
70 class MemoryBufferMem : public MemoryBuffer {
71   std::string FileID;
72 public:
73   MemoryBufferMem(const char *Start, const char *End, StringRef FID,
74                   bool Copy = false)
75   : FileID(FID) {
76     if (!Copy)
77       init(Start, End);
78     else
79       initCopyOf(Start, End);
80   }
81 
82   virtual const char *getBufferIdentifier() const {
83     return FileID.c_str();
84   }
85 };
86 }
87 
88 /// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
89 /// that EndPtr[0] must be a null byte and be accessible!
90 MemoryBuffer *MemoryBuffer::getMemBuffer(const char *StartPtr,
91                                          const char *EndPtr,
92                                          const char *BufferName) {
93   return new MemoryBufferMem(StartPtr, EndPtr, BufferName);
94 }
95 
96 /// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
97 /// copying the contents and taking ownership of it.  This has no requirements
98 /// on EndPtr[0].
99 MemoryBuffer *MemoryBuffer::getMemBufferCopy(const char *StartPtr,
100                                              const char *EndPtr,
101                                              const char *BufferName) {
102   return new MemoryBufferMem(StartPtr, EndPtr, BufferName, true);
103 }
104 
105 /// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
106 /// that is completely initialized to zeros.  Note that the caller should
107 /// initialize the memory allocated by this method.  The memory is owned by
108 /// the MemoryBuffer object.
109 MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
110                                                   StringRef BufferName) {
111   char *Buf = (char *)malloc(Size+1);
112   if (!Buf) return 0;
113   Buf[Size] = 0;
114   MemoryBufferMem *SB = new MemoryBufferMem(Buf, Buf+Size, BufferName);
115   // The memory for this buffer is owned by the MemoryBuffer.
116   SB->MustDeleteBuffer = true;
117   return SB;
118 }
119 
120 /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
121 /// is completely initialized to zeros.  Note that the caller should
122 /// initialize the memory allocated by this method.  The memory is owned by
123 /// the MemoryBuffer object.
124 MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size,
125                                             const char *BufferName) {
126   MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
127   if (!SB) return 0;
128   memset(const_cast<char*>(SB->getBufferStart()), 0, Size+1);
129   return SB;
130 }
131 
132 
133 /// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
134 /// if the Filename is "-".  If an error occurs, this returns null and fills
135 /// in *ErrStr with a reason.  If stdin is empty, this API (unlike getSTDIN)
136 /// returns an empty buffer.
137 MemoryBuffer *MemoryBuffer::getFileOrSTDIN(StringRef Filename,
138                                            std::string *ErrStr,
139                                            int64_t FileSize) {
140   if (Filename == "-")
141     return getSTDIN();
142   return getFile(Filename, ErrStr, FileSize);
143 }
144 
145 //===----------------------------------------------------------------------===//
146 // MemoryBuffer::getFile implementation.
147 //===----------------------------------------------------------------------===//
148 
149 namespace {
150 /// MemoryBufferMMapFile - This represents a file that was mapped in with the
151 /// sys::Path::MapInFilePages method.  When destroyed, it calls the
152 /// sys::Path::UnMapFilePages method.
153 class MemoryBufferMMapFile : public MemoryBuffer {
154   std::string Filename;
155 public:
156   MemoryBufferMMapFile(StringRef filename, const char *Pages, uint64_t Size)
157     : Filename(filename) {
158     init(Pages, Pages+Size);
159   }
160 
161   virtual const char *getBufferIdentifier() const {
162     return Filename.c_str();
163   }
164 
165   ~MemoryBufferMMapFile() {
166     sys::Path::UnMapFilePages(getBufferStart(), getBufferSize());
167   }
168 };
169 }
170 
171 MemoryBuffer *MemoryBuffer::getFile(StringRef Filename, std::string *ErrStr,
172                                     int64_t FileSize) {
173   int OpenFlags = 0;
174 #ifdef O_BINARY
175   OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
176 #endif
177   int FD = ::open(Filename.str().c_str(), O_RDONLY|OpenFlags);
178   if (FD == -1) {
179     if (ErrStr) *ErrStr = strerror(errno);
180     return 0;
181   }
182 
183   // If we don't know the file size, use fstat to find out.  fstat on an open
184   // file descriptor is cheaper than stat on a random path.
185   if (FileSize == -1) {
186     struct stat FileInfo;
187     // TODO: This should use fstat64 when available.
188     if (fstat(FD, &FileInfo) == -1) {
189       if (ErrStr) *ErrStr = strerror(errno);
190       ::close(FD);
191       return 0;
192     }
193     FileSize = FileInfo.st_size;
194   }
195 
196 
197   // If the file is large, try to use mmap to read it in.  We don't use mmap
198   // for small files, because this can severely fragment our address space. Also
199   // don't try to map files that are exactly a multiple of the system page size,
200   // as the file would not have the required null terminator.
201   //
202   // FIXME: Can we just mmap an extra page in the latter case?
203   if (FileSize >= 4096*4 &&
204       (FileSize & (sys::Process::GetPageSize()-1)) != 0) {
205     if (const char *Pages = sys::Path::MapInFilePages(FD, FileSize)) {
206       // Close the file descriptor, now that the whole file is in memory.
207       ::close(FD);
208       return new MemoryBufferMMapFile(Filename, Pages, FileSize);
209     }
210   }
211 
212   MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(FileSize, Filename);
213   if (!Buf) {
214     // Failed to create a buffer.
215     if (ErrStr) *ErrStr = "could not allocate buffer";
216     ::close(FD);
217     return 0;
218   }
219 
220   OwningPtr<MemoryBuffer> SB(Buf);
221   char *BufPtr = const_cast<char*>(SB->getBufferStart());
222 
223   size_t BytesLeft = FileSize;
224   while (BytesLeft) {
225     ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
226     if (NumRead > 0) {
227       BytesLeft -= NumRead;
228       BufPtr += NumRead;
229     } else if (NumRead == -1 && errno == EINTR) {
230       // try again
231     } else {
232       // error reading.
233       if (ErrStr) *ErrStr = strerror(errno);
234       close(FD);
235       return 0;
236     }
237   }
238   close(FD);
239 
240   return SB.take();
241 }
242 
243 //===----------------------------------------------------------------------===//
244 // MemoryBuffer::getSTDIN implementation.
245 //===----------------------------------------------------------------------===//
246 
247 namespace {
248 class STDINBufferFile : public MemoryBuffer {
249 public:
250   virtual const char *getBufferIdentifier() const {
251     return "<stdin>";
252   }
253 };
254 }
255 
256 MemoryBuffer *MemoryBuffer::getSTDIN() {
257   char Buffer[4096*4];
258 
259   std::vector<char> FileData;
260 
261   // Read in all of the data from stdin, we cannot mmap stdin.
262   //
263   // FIXME: That isn't necessarily true, we should try to mmap stdin and
264   // fallback if it fails.
265   sys::Program::ChangeStdinToBinary();
266   size_t ReadBytes;
267   do {
268     ReadBytes = fread(Buffer, sizeof(char), sizeof(Buffer), stdin);
269     FileData.insert(FileData.end(), Buffer, Buffer+ReadBytes);
270   } while (ReadBytes == sizeof(Buffer));
271 
272   FileData.push_back(0); // &FileData[Size] is invalid. So is &*FileData.end().
273   size_t Size = FileData.size();
274   MemoryBuffer *B = new STDINBufferFile();
275   B->initCopyOf(&FileData[0], &FileData[Size-1]);
276   return B;
277 }
278