1 //===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the MemoryBuffer interface.
12 //===----------------------------------------------------------------------===//
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"
31 #include <sys/types.h>
32 #if !defined(_MSC_VER) && !defined(__MINGW32__)
36 // Simplistic definitinos of these macros for use in getOpenFile.
38 #define S_ISREG(x) (1)
41 #define S_ISBLK(x) (0)
46 //===----------------------------------------------------------------------===//
47 // MemoryBuffer implementation itself.
48 //===----------------------------------------------------------------------===//
50 MemoryBuffer::~MemoryBuffer() { }
52 /// init - Initialize this MemoryBuffer as a reference to externally allocated
53 /// memory, memory that we know is already null terminated.
54 void 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;
62 //===----------------------------------------------------------------------===//
63 // MemoryBufferMem implementation.
64 //===----------------------------------------------------------------------===//
66 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
67 /// null-terminates it.
68 static void CopyStringRef(char *Memory, StringRef Data) {
69 memcpy(Memory, Data.data(), Data.size());
70 Memory[Data.size()] = 0; // Null terminate string.
74 struct NamedBufferAlloc {
76 NamedBufferAlloc(StringRef Name) : Name(Name) {}
80 void *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);
87 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
88 class MemoryBufferMem : public MemoryBuffer {
90 MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
91 init(InputData.begin(), InputData.end(), RequiresNullTerminator);
94 virtual const char *getBufferIdentifier() const LLVM_OVERRIDE {
95 // The name is stored after the class itself.
96 return reinterpret_cast<const char*>(this + 1);
99 virtual BufferKind getBufferKind() const LLVM_OVERRIDE {
100 return MemoryBuffer_Malloc;
105 /// getMemBuffer - Open the specified memory range as a MemoryBuffer. Note
106 /// that InputData must be a null terminated if RequiresNullTerminator is true!
107 MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
108 StringRef BufferName,
109 bool RequiresNullTerminator) {
110 return new (NamedBufferAlloc(BufferName))
111 MemoryBufferMem(InputData, RequiresNullTerminator);
114 /// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
115 /// copying the contents and taking ownership of it. This has no requirements
117 MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
118 StringRef BufferName) {
119 MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
121 memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
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
130 MemoryBuffer *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 size_t AlignedStringLen =
135 RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
136 sizeof(void*)); // TODO: Is sizeof(void*) enough?
137 size_t RealLen = AlignedStringLen + Size + 1;
138 char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
141 // The name is stored after the class itself.
142 CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
144 // The buffer begins after the name and must be aligned.
145 char *Buf = Mem + AlignedStringLen;
146 Buf[Size] = 0; // Null terminate buffer.
148 return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
151 /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
152 /// is completely initialized to zeros. Note that the caller should
153 /// initialize the memory allocated by this method. The memory is owned by
154 /// the MemoryBuffer object.
155 MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
156 MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
158 memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
163 /// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
164 /// if the Filename is "-". If an error occurs, this returns null and fills
165 /// in *ErrStr with a reason. If stdin is empty, this API (unlike getSTDIN)
166 /// returns an empty buffer.
167 error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
168 OwningPtr<MemoryBuffer> &result,
171 return getSTDIN(result);
172 return getFile(Filename, result, FileSize);
175 //===----------------------------------------------------------------------===//
176 // MemoryBuffer::getFile implementation.
177 //===----------------------------------------------------------------------===//
180 /// \brief Memorry maps a file descriptor using sys::fs::mapped_file_region.
182 /// This handles converting the offset into a legal offset on the platform.
183 class MemoryBufferMMapFile : public MemoryBuffer {
184 sys::fs::mapped_file_region MFR;
186 static uint64_t getLegalMapOffset(uint64_t Offset) {
187 return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
190 static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
191 return Len + (Offset - getLegalMapOffset(Offset));
194 const char *getStart(uint64_t Len, uint64_t Offset) {
195 return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
199 MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
200 uint64_t Offset, error_code EC)
201 : MFR(FD, false, sys::fs::mapped_file_region::readonly,
202 getLegalMapSize(Len, Offset), getLegalMapOffset(Offset), EC) {
204 const char *Start = getStart(Len, Offset);
205 init(Start, Start + Len, RequiresNullTerminator);
209 virtual const char *getBufferIdentifier() const LLVM_OVERRIDE {
210 // The name is stored after the class itself.
211 return reinterpret_cast<const char *>(this + 1);
214 virtual BufferKind getBufferKind() const LLVM_OVERRIDE {
215 return MemoryBuffer_MMap;
220 static error_code getMemoryBufferForStream(int FD,
221 StringRef BufferName,
222 OwningPtr<MemoryBuffer> &result) {
223 const ssize_t ChunkSize = 4096*4;
224 SmallString<ChunkSize> Buffer;
226 // Read into Buffer until we hit EOF.
228 Buffer.reserve(Buffer.size() + ChunkSize);
229 ReadBytes = read(FD, Buffer.end(), ChunkSize);
230 if (ReadBytes == -1) {
231 if (errno == EINTR) continue;
232 return error_code(errno, posix_category());
234 Buffer.set_size(Buffer.size() + ReadBytes);
235 } while (ReadBytes != 0);
237 result.reset(MemoryBuffer::getMemBufferCopy(Buffer, BufferName));
238 return error_code::success();
241 error_code MemoryBuffer::getFile(StringRef Filename,
242 OwningPtr<MemoryBuffer> &result,
244 bool RequiresNullTerminator) {
245 // Ensure the path is null terminated.
246 SmallString<256> PathBuf(Filename.begin(), Filename.end());
247 return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize,
248 RequiresNullTerminator);
251 static error_code getOpenFileImpl(int FD, const char *Filename,
252 OwningPtr<MemoryBuffer> &Result,
253 uint64_t FileSize, uint64_t MapSize,
254 int64_t Offset, bool RequiresNullTerminator);
256 error_code MemoryBuffer::getFile(const char *Filename,
257 OwningPtr<MemoryBuffer> &result,
259 bool RequiresNullTerminator) {
261 error_code EC = sys::fs::openFileForRead(Filename, FD);
265 error_code ret = getOpenFileImpl(FD, Filename, result, FileSize, FileSize, 0,
266 RequiresNullTerminator);
271 static bool shouldUseMmap(int FD,
275 bool RequiresNullTerminator,
277 // We don't use mmap for small files because this can severely fragment our
279 if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
282 if (!RequiresNullTerminator)
286 // If we don't know the file size, use fstat to find out. fstat on an open
287 // file descriptor is cheaper than stat on a random path.
288 // FIXME: this chunk of code is duplicated, but it avoids a fstat when
289 // RequiresNullTerminator = false and MapSize != -1.
290 if (FileSize == size_t(-1)) {
291 sys::fs::file_status Status;
292 error_code EC = sys::fs::status(FD, Status);
295 FileSize = Status.getSize();
298 // If we need a null terminator and the end of the map is inside the file,
299 // we cannot use mmap.
300 size_t End = Offset + MapSize;
301 assert(End <= FileSize);
305 // Don't try to map files that are exactly a multiple of the system page size
306 // if we need a null terminator.
307 if ((FileSize & (PageSize -1)) == 0)
313 static error_code getOpenFileImpl(int FD, const char *Filename,
314 OwningPtr<MemoryBuffer> &result,
315 uint64_t FileSize, uint64_t MapSize,
316 int64_t Offset, bool RequiresNullTerminator) {
317 static int PageSize = sys::process::get_self()->page_size();
319 // Default is to map the full file.
320 if (MapSize == uint64_t(-1)) {
321 // If we don't know the file size, use fstat to find out. fstat on an open
322 // file descriptor is cheaper than stat on a random path.
323 if (FileSize == uint64_t(-1)) {
324 sys::fs::file_status Status;
325 error_code EC = sys::fs::status(FD, Status);
329 // If this not a file or a block device (e.g. it's a named pipe
330 // or character device), we can't trust the size. Create the memory
331 // buffer by copying off the stream.
332 sys::fs::file_type Type = Status.type();
333 if (Type != sys::fs::file_type::regular_file &&
334 Type != sys::fs::file_type::block_file)
335 return getMemoryBufferForStream(FD, Filename, result);
337 FileSize = Status.getSize();
342 if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
345 result.reset(new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile(
346 RequiresNullTerminator, FD, MapSize, Offset, EC));
348 return error_code::success();
351 MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
353 // Failed to create a buffer. The only way it can fail is if
354 // new(std::nothrow) returns 0.
355 return make_error_code(errc::not_enough_memory);
358 OwningPtr<MemoryBuffer> SB(Buf);
359 char *BufPtr = const_cast<char*>(SB->getBufferStart());
361 size_t BytesLeft = MapSize;
363 if (lseek(FD, Offset, SEEK_SET) == -1)
364 return error_code(errno, posix_category());
369 ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
371 ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
376 // Error while reading.
377 return error_code(errno, posix_category());
380 assert(0 && "We got inaccurate FileSize value or fstat reported an "
381 "invalid file size.");
382 *BufPtr = '\0'; // null-terminate at the actual size.
385 BytesLeft -= NumRead;
390 return error_code::success();
393 error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
394 OwningPtr<MemoryBuffer> &Result,
396 bool RequiresNullTerminator) {
397 return getOpenFileImpl(FD, Filename, Result, FileSize, FileSize, 0,
398 RequiresNullTerminator);
401 error_code MemoryBuffer::getOpenFileSlice(int FD, const char *Filename,
402 OwningPtr<MemoryBuffer> &Result,
403 uint64_t MapSize, int64_t Offset) {
404 return getOpenFileImpl(FD, Filename, Result, -1, MapSize, Offset, false);
407 //===----------------------------------------------------------------------===//
408 // MemoryBuffer::getSTDIN implementation.
409 //===----------------------------------------------------------------------===//
411 error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
412 // Read in all of the data from stdin, we cannot mmap stdin.
414 // FIXME: That isn't necessarily true, we should try to mmap stdin and
415 // fallback if it fails.
416 sys::ChangeStdinToBinary();
418 return getMemoryBufferForStream(0, "<stdin>", result);