X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FSupport%2FMemoryBuffer.cpp;h=ea72720b7f01c53e0cb7c799391cb0ab2c6b521a;hb=1af394766fe4e725d5af2fe82c2ad9cfcbc7dd34;hp=a0c650d6820b0ed859a5f7f9c62b45f717dd8f8d;hpb=b4cc031a3e1306fea74c9211d50c5cde6d9a8cd5;p=oota-llvm.git diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp index a0c650d6820..ea72720b7f0 100644 --- a/lib/Support/MemoryBuffer.cpp +++ b/lib/Support/MemoryBuffer.cpp @@ -46,8 +46,10 @@ MemoryBuffer::~MemoryBuffer() { } /// init - Initialize this MemoryBuffer as a reference to externally allocated /// memory, memory that we know is already null terminated. -void MemoryBuffer::init(const char *BufStart, const char *BufEnd) { - assert(BufEnd[0] == 0 && "Buffer is not null terminated!"); +void MemoryBuffer::init(const char *BufStart, const char *BufEnd, + bool RequiresNullTerminator) { + assert((!RequiresNullTerminator || BufEnd[0] == 0) && + "Buffer is not null terminated!"); BufferStart = BufStart; BufferEnd = BufEnd; } @@ -65,18 +67,19 @@ static void CopyStringRef(char *Memory, StringRef Data) { /// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it. template -static T* GetNamedBuffer(StringRef Buffer, StringRef Name) { +static T* GetNamedBuffer(StringRef Buffer, StringRef Name, + bool RequiresNullTerminator) { char *Mem = static_cast(operator new(sizeof(T) + Name.size() + 1)); CopyStringRef(Mem + sizeof(T), Name); - return new (Mem) T(Buffer); + return new (Mem) T(Buffer, RequiresNullTerminator); } namespace { /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory. class MemoryBufferMem : public MemoryBuffer { public: - MemoryBufferMem(StringRef InputData) { - init(InputData.begin(), InputData.end()); + MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) { + init(InputData.begin(), InputData.end(), RequiresNullTerminator); } virtual const char *getBufferIdentifier() const { @@ -89,8 +92,10 @@ public: /// getMemBuffer - Open the specified memory range as a MemoryBuffer. Note /// that EndPtr[0] must be a null byte and be accessible! MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData, - StringRef BufferName) { - return GetNamedBuffer(InputData, BufferName); + StringRef BufferName, + bool RequiresNullTerminator) { + return GetNamedBuffer(InputData, BufferName, + RequiresNullTerminator); } /// getMemBufferCopy - Open the specified memory range as a MemoryBuffer, @@ -127,7 +132,7 @@ MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size, char *Buf = Mem + AlignedStringLen; Buf[Size] = 0; // Null terminate buffer. - return new (Mem) MemoryBufferMem(StringRef(Buf, Size)); + return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true); } /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that @@ -172,26 +177,37 @@ namespace { /// sys::Path::UnMapFilePages method. class MemoryBufferMMapFile : public MemoryBufferMem { public: - MemoryBufferMMapFile(StringRef Buffer) - : MemoryBufferMem(Buffer) { } + MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator) + : MemoryBufferMem(Buffer, RequiresNullTerminator) { } ~MemoryBufferMMapFile() { - sys::Path::UnMapFilePages(getBufferStart(), getBufferSize()); + static int PageSize = sys::Process::GetPageSize(); + + uintptr_t Start = reinterpret_cast(getBufferStart()); + size_t Size = getBufferSize(); + uintptr_t RealStart = Start & ~(PageSize - 1); + size_t RealSize = Size + (Start - RealStart); + + sys::Path::UnMapFilePages(reinterpret_cast(RealStart), + RealSize); } }; } error_code MemoryBuffer::getFile(StringRef Filename, OwningPtr &result, - int64_t FileSize) { + int64_t FileSize, + bool RequiresNullTerminator) { // Ensure the path is null terminated. SmallString<256> PathBuf(Filename.begin(), Filename.end()); - return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize); + return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize, + RequiresNullTerminator); } error_code MemoryBuffer::getFile(const char *Filename, OwningPtr &result, - int64_t FileSize) { + int64_t FileSize, + bool RequiresNullTerminator) { int OpenFlags = O_RDONLY; #ifdef O_BINARY OpenFlags |= O_BINARY; // Open input file in binary mode on win32. @@ -200,17 +216,32 @@ error_code MemoryBuffer::getFile(const char *Filename, if (FD == -1) { return error_code(errno, posix_category()); } - error_code ret = getOpenFile(FD, Filename, result, FileSize); + error_code ret = getOpenFile(FD, Filename, result, FileSize, FileSize, + 0, RequiresNullTerminator); close(FD); return ret; } -error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, - OwningPtr &result, - int64_t FileSize) { +static bool shouldUseMmap(int FD, + size_t FileSize, + size_t MapSize, + off_t Offset, + bool RequiresNullTerminator, + int PageSize) { + // We don't use mmap for small files because this can severely fragment our + // address space. + if (MapSize < 4096*4) + return false; + + if (!RequiresNullTerminator) + return true; + + // If we don't know the file size, use fstat to find out. fstat on an open // file descriptor is cheaper than stat on a random path. - if (FileSize == -1) { + // FIXME: this chunk of code is duplicated, but it avoids a fstat when + // RequiresNullTerminator = false and MapSize != -1. + if (FileSize == size_t(-1)) { struct stat FileInfo; // TODO: This should use fstat64 when available. if (fstat(FD, &FileInfo) == -1) { @@ -219,23 +250,59 @@ error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, FileSize = FileInfo.st_size; } + // If we need a null terminator and the end of the map is inside the file, + // we cannot use mmap. + size_t End = Offset + MapSize; + assert(End <= FileSize); + if (End != FileSize) + return false; - // If the file is large, try to use mmap to read it in. We don't use mmap - // for small files, because this can severely fragment our address space. Also - // don't try to map files that are exactly a multiple of the system page size, - // as the file would not have the required null terminator. - // - // FIXME: Can we just mmap an extra page in the latter case? - if (FileSize >= 4096*4 && - (FileSize & (sys::Process::GetPageSize()-1)) != 0) { - if (const char *Pages = sys::Path::MapInFilePages(FD, FileSize)) { + // Don't try to map files that are exactly a multiple of the system page size + // if we need a null terminator. + if ((FileSize & (PageSize -1)) == 0) + return false; + + return true; +} + +error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, + OwningPtr &result, + size_t FileSize, size_t MapSize, + off_t Offset, + bool RequiresNullTerminator) { + static int PageSize = sys::Process::GetPageSize(); + + // Default is to map the full file. + if (MapSize == size_t(-1)) { + // If we don't know the file size, use fstat to find out. fstat on an open + // file descriptor is cheaper than stat on a random path. + if (FileSize == size_t(-1)) { + struct stat FileInfo; + // TODO: This should use fstat64 when available. + if (fstat(FD, &FileInfo) == -1) { + return error_code(errno, posix_category()); + } + FileSize = FileInfo.st_size; + } + MapSize = FileSize; + } + + if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator, + PageSize)) { + off_t RealMapOffset = Offset & ~(PageSize - 1); + off_t Delta = Offset - RealMapOffset; + size_t RealMapSize = MapSize + Delta; + + if (const char *Pages = sys::Path::MapInFilePages(FD, + RealMapSize, + RealMapOffset)) { result.reset(GetNamedBuffer( - StringRef(Pages, FileSize), Filename)); + StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator)); return success; } } - MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(FileSize, Filename); + MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename); if (!Buf) { // Failed to create a buffer. The only way it can fail is if // new(std::nothrow) returns 0. @@ -245,7 +312,10 @@ error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, OwningPtr SB(Buf); char *BufPtr = const_cast(SB->getBufferStart()); - size_t BytesLeft = FileSize; + size_t BytesLeft = MapSize; + if (lseek(FD, Offset, SEEK_SET) == -1) + return error_code(errno, posix_category()); + while (BytesLeft) { ssize_t NumRead = ::read(FD, BufPtr, BytesLeft); if (NumRead == -1) {