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/SmallString.h"
16 #include "llvm/Config/config.h"
17 #include "llvm/Support/Errc.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"
29 #include <sys/types.h>
30 #include <system_error>
31 #if !defined(_MSC_VER) && !defined(__MINGW32__)
38 //===----------------------------------------------------------------------===//
39 // MemoryBuffer implementation itself.
40 //===----------------------------------------------------------------------===//
42 MemoryBuffer::~MemoryBuffer() { }
44 /// init - Initialize this MemoryBuffer as a reference to externally allocated
45 /// memory, memory that we know is already null terminated.
46 void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
47 bool RequiresNullTerminator) {
48 assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
49 "Buffer is not null terminated!");
50 BufferStart = BufStart;
54 //===----------------------------------------------------------------------===//
55 // MemoryBufferMem implementation.
56 //===----------------------------------------------------------------------===//
58 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
59 /// null-terminates it.
60 static void CopyStringRef(char *Memory, StringRef Data) {
61 memcpy(Memory, Data.data(), Data.size());
62 Memory[Data.size()] = 0; // Null terminate string.
66 struct NamedBufferAlloc {
68 NamedBufferAlloc(const Twine &Name) : Name(Name) {}
72 void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
73 SmallString<256> NameBuf;
74 StringRef NameRef = Alloc.Name.toStringRef(NameBuf);
76 char *Mem = static_cast<char *>(operator new(N + NameRef.size() + 1));
77 CopyStringRef(Mem + N, NameRef);
82 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
83 class MemoryBufferMem : public MemoryBuffer {
85 MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
86 init(InputData.begin(), InputData.end(), RequiresNullTerminator);
89 const char *getBufferIdentifier() const override {
90 // The name is stored after the class itself.
91 return reinterpret_cast<const char*>(this + 1);
94 BufferKind getBufferKind() const override {
95 return MemoryBuffer_Malloc;
100 static ErrorOr<std::unique_ptr<MemoryBuffer>>
101 getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
102 uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize);
104 std::unique_ptr<MemoryBuffer>
105 MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,
106 bool RequiresNullTerminator) {
107 auto *Ret = new (NamedBufferAlloc(BufferName))
108 MemoryBufferMem(InputData, RequiresNullTerminator);
109 return std::unique_ptr<MemoryBuffer>(Ret);
112 std::unique_ptr<MemoryBuffer>
113 MemoryBuffer::getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator) {
114 return std::unique_ptr<MemoryBuffer>(getMemBuffer(
115 Ref.getBuffer(), Ref.getBufferIdentifier(), RequiresNullTerminator));
118 std::unique_ptr<MemoryBuffer>
119 MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {
120 std::unique_ptr<MemoryBuffer> Buf =
121 getNewUninitMemBuffer(InputData.size(), BufferName);
124 memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
129 std::unique_ptr<MemoryBuffer>
130 MemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {
131 // Allocate space for the MemoryBuffer, the data and the name. It is important
132 // that MemoryBuffer and data are aligned so PointerIntPair works with them.
133 // TODO: Is 16-byte alignment enough? We copy small object files with large
134 // alignment expectations into this buffer.
135 SmallString<256> NameBuf;
136 StringRef NameRef = BufferName.toStringRef(NameBuf);
137 size_t AlignedStringLen =
138 RoundUpToAlignment(sizeof(MemoryBufferMem) + NameRef.size() + 1, 16);
139 size_t RealLen = AlignedStringLen + Size + 1;
140 char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
144 // The name is stored after the class itself.
145 CopyStringRef(Mem + sizeof(MemoryBufferMem), NameRef);
147 // The buffer begins after the name and must be aligned.
148 char *Buf = Mem + AlignedStringLen;
149 Buf[Size] = 0; // Null terminate buffer.
151 auto *Ret = new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
152 return std::unique_ptr<MemoryBuffer>(Ret);
155 std::unique_ptr<MemoryBuffer>
156 MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
157 std::unique_ptr<MemoryBuffer> SB = getNewUninitMemBuffer(Size, BufferName);
160 memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
164 ErrorOr<std::unique_ptr<MemoryBuffer>>
165 MemoryBuffer::getFileOrSTDIN(const Twine &Filename, int64_t FileSize) {
166 SmallString<256> NameBuf;
167 StringRef NameRef = Filename.toStringRef(NameBuf);
171 return getFile(Filename, FileSize);
174 ErrorOr<std::unique_ptr<MemoryBuffer>>
175 MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
177 return getFileAux(FilePath, -1, MapSize, Offset, false, false);
181 //===----------------------------------------------------------------------===//
182 // MemoryBuffer::getFile implementation.
183 //===----------------------------------------------------------------------===//
186 /// \brief Memory maps a file descriptor using sys::fs::mapped_file_region.
188 /// This handles converting the offset into a legal offset on the platform.
189 class MemoryBufferMMapFile : public MemoryBuffer {
190 sys::fs::mapped_file_region MFR;
192 static uint64_t getLegalMapOffset(uint64_t Offset) {
193 return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
196 static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
197 return Len + (Offset - getLegalMapOffset(Offset));
200 const char *getStart(uint64_t Len, uint64_t Offset) {
201 return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
205 MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
206 uint64_t Offset, std::error_code &EC)
207 : MFR(FD, sys::fs::mapped_file_region::readonly,
208 getLegalMapSize(Len, Offset), getLegalMapOffset(Offset), EC) {
210 const char *Start = getStart(Len, Offset);
211 init(Start, Start + Len, RequiresNullTerminator);
215 const char *getBufferIdentifier() const override {
216 // The name is stored after the class itself.
217 return reinterpret_cast<const char *>(this + 1);
220 BufferKind getBufferKind() const override {
221 return MemoryBuffer_MMap;
226 static ErrorOr<std::unique_ptr<MemoryBuffer>>
227 getMemoryBufferForStream(int FD, const Twine &BufferName) {
228 const ssize_t ChunkSize = 4096*4;
229 SmallString<ChunkSize> Buffer;
231 // Read into Buffer until we hit EOF.
233 Buffer.reserve(Buffer.size() + ChunkSize);
234 ReadBytes = read(FD, Buffer.end(), ChunkSize);
235 if (ReadBytes == -1) {
236 if (errno == EINTR) continue;
237 return std::error_code(errno, std::generic_category());
239 Buffer.set_size(Buffer.size() + ReadBytes);
240 } while (ReadBytes != 0);
242 return MemoryBuffer::getMemBufferCopy(Buffer, BufferName);
246 ErrorOr<std::unique_ptr<MemoryBuffer>>
247 MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
248 bool RequiresNullTerminator, bool IsVolatileSize) {
249 return getFileAux(Filename, FileSize, FileSize, 0,
250 RequiresNullTerminator, IsVolatileSize);
253 static ErrorOr<std::unique_ptr<MemoryBuffer>>
254 getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
255 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
256 bool IsVolatileSize);
258 static ErrorOr<std::unique_ptr<MemoryBuffer>>
259 getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
260 uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize) {
262 std::error_code EC = sys::fs::openFileForRead(Filename, FD);
266 ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =
267 getOpenFileImpl(FD, Filename, FileSize, MapSize, Offset,
268 RequiresNullTerminator, IsVolatileSize);
273 static bool shouldUseMmap(int FD,
277 bool RequiresNullTerminator,
279 bool IsVolatileSize) {
280 // mmap may leave the buffer without null terminator if the file size changed
281 // by the time the last page is mapped in, so avoid it if the file size is
286 // We don't use mmap for small files because this can severely fragment our
288 if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
291 if (!RequiresNullTerminator)
295 // If we don't know the file size, use fstat to find out. fstat on an open
296 // file descriptor is cheaper than stat on a random path.
297 // FIXME: this chunk of code is duplicated, but it avoids a fstat when
298 // RequiresNullTerminator = false and MapSize != -1.
299 if (FileSize == size_t(-1)) {
300 sys::fs::file_status Status;
301 if (sys::fs::status(FD, Status))
303 FileSize = Status.getSize();
306 // If we need a null terminator and the end of the map is inside the file,
307 // we cannot use mmap.
308 size_t End = Offset + MapSize;
309 assert(End <= FileSize);
313 // Don't try to map files that are exactly a multiple of the system page size
314 // if we need a null terminator.
315 if ((FileSize & (PageSize -1)) == 0)
318 #if defined(__CYGWIN__)
319 // Don't try to map files that are exactly a multiple of the physical page size
320 // if we need a null terminator.
321 // FIXME: We should reorganize again getPageSize() on Win32.
322 if ((FileSize & (4096 - 1)) == 0)
329 static ErrorOr<std::unique_ptr<MemoryBuffer>>
330 getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
331 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
332 bool IsVolatileSize) {
333 static int PageSize = sys::Process::getPageSize();
335 // Default is to map the full file.
336 if (MapSize == uint64_t(-1)) {
337 // If we don't know the file size, use fstat to find out. fstat on an open
338 // file descriptor is cheaper than stat on a random path.
339 if (FileSize == uint64_t(-1)) {
340 sys::fs::file_status Status;
341 std::error_code EC = sys::fs::status(FD, Status);
345 // If this not a file or a block device (e.g. it's a named pipe
346 // or character device), we can't trust the size. Create the memory
347 // buffer by copying off the stream.
348 sys::fs::file_type Type = Status.type();
349 if (Type != sys::fs::file_type::regular_file &&
350 Type != sys::fs::file_type::block_file)
351 return getMemoryBufferForStream(FD, Filename);
353 FileSize = Status.getSize();
358 if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
359 PageSize, IsVolatileSize)) {
361 std::unique_ptr<MemoryBuffer> Result(
362 new (NamedBufferAlloc(Filename))
363 MemoryBufferMMapFile(RequiresNullTerminator, FD, MapSize, Offset, EC));
365 return std::move(Result);
368 std::unique_ptr<MemoryBuffer> Buf =
369 MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
371 // Failed to create a buffer. The only way it can fail is if
372 // new(std::nothrow) returns 0.
373 return make_error_code(errc::not_enough_memory);
376 char *BufPtr = const_cast<char *>(Buf->getBufferStart());
378 size_t BytesLeft = MapSize;
380 if (lseek(FD, Offset, SEEK_SET) == -1)
381 return std::error_code(errno, std::generic_category());
386 ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
388 ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
393 // Error while reading.
394 return std::error_code(errno, std::generic_category());
397 memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.
400 BytesLeft -= NumRead;
404 return std::move(Buf);
407 ErrorOr<std::unique_ptr<MemoryBuffer>>
408 MemoryBuffer::getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,
409 bool RequiresNullTerminator, bool IsVolatileSize) {
410 return getOpenFileImpl(FD, Filename, FileSize, FileSize, 0,
411 RequiresNullTerminator, IsVolatileSize);
414 ErrorOr<std::unique_ptr<MemoryBuffer>>
415 MemoryBuffer::getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,
417 assert(MapSize != uint64_t(-1));
418 return getOpenFileImpl(FD, Filename, -1, MapSize, Offset, false,
419 /*IsVolatileSize*/ false);
422 ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {
423 // Read in all of the data from stdin, we cannot mmap stdin.
425 // FIXME: That isn't necessarily true, we should try to mmap stdin and
426 // fallback if it fails.
427 sys::ChangeStdinToBinary();
429 return getMemoryBufferForStream(0, "<stdin>");
432 MemoryBufferRef MemoryBuffer::getMemBufferRef() const {
433 StringRef Data = getBuffer();
434 StringRef Identifier = getBufferIdentifier();
435 return MemoryBufferRef(Data, Identifier);